POST-EARTHQUAKE BUILDING SAFETY EVALUATIONS in KATHMANDU VALLEY Observations & Recommendations

POST-EARTHQUAKE BUILDING SAFETY EVALUATIONS IN KATHMANDU VALLEY Observations & Recommendations

June 2015 REPORT

M7.8 Gorkha Earthquake Post-Earthquake Building Safety Evaluations in the Kathmandu Valley Observations and Recommendations

Kathmandu, Nepal

June 2015

Prepared for

Homraj Acharya, Country Director Global Fairness Initiative Kathmandu, Nepal

Prepared by Sabina S. Surana, P.E.

728 134th Street SW Suite 200 Everett, WA 98204 U.S.A. 425/741-3800 Fax 425/741-3900 www.reidmiddleton.com

Table of Contents Page No. ACKNOWLEDGEMENTS ...... 3 1.0 INTRODUCTION ...... 1 2.0 BUILDING CONSTRUCTION TYPES ...... 2 3.0 STRUCTURAL ASSESSMENT OBSERVATIONS ...... 6 4.0 RECOMMENDATIONS ...... 19

Appendix List

Appendix A: Checklists Used in Nepal Appendix B: Damaged Assessment Guidelines provided by GFI Appendix C: Indian Standard - Repair and Seismic Strengthening of Buildings - Guidelines Appendix D: Tip 12: How do Brick Masonry Houses behave during Earthquake? Appendix E: Tip 13: Why Masonry Building should have Simple Structural Configuration? Appendix F: Tip14: Why Horizontal Bands are required in Masonry Buildings? Appendix G: Tip 15: Why is Vertical Reinforcement required in Masonry Buildings? Appendix H: Tip 16: How to make Stone Masonry Buildings Earthquake Resistant? Appendix I: Tip 17: How do Earthquakes Affect Reinforced Concrete Building? Appendix J: Tip 18: How do Beams in RC Building Resist Earthquakes? Appendix K: Tip 19: How do Columns in RC Building Resist Earthquakes? Appendix L: Tip 20: How do Beam-Column Joints in RC Building Resist Earthquakes? Appendix M: Tip 21: Why are Open-Ground Storey Buildings Vulnerable in Earthquakes? Appendix N: Seismic Safety for Adobe Homes Appendix O: Boundary Wall Construction Guide Appendix P: American Society of Civil Engineers Code of Ethics Appendix Q: References

List of Figures

FIGURE 1. BUILDING SAFETY ASSESSMENT PERFORMANCE AREA (REID MIDDLETON)...... 1 FIGURE 2. TYPICAL RC FRAME BUILDING WITH BRICK INFILL CONSTRUCTION (SURANA)...... 2 FIGURE 3. UNREINFORCED LOAD BEARING BRICK BUILDING IN PHUTUNG, KATHMANDU (SURANA)...... 3 FIGURE 4. UNREINFORCED LOAD BEARING BRICK WITH MUD MORTAR BUILDING IN PHUTUNG, KATHMANDU (SURANA)...... 4 FIGURE 5. UNREINFORCED LOAD BEARING ADOBE BUILDING IN PHUTUNG, KATHMANDU (SURANA)...... 4 FIGURE 6. BAMBOO FLOOR SYSTEM IN UNREINFORCED LOAD BEARING BUILDING, KATHMANDU (SURANA)...... 5 FIGURE 7. RC FRAME BUILDING BEHAVIOUR DURING EARTHQUAKE (IITK-BMTPC EARTHQUAKE TIP 17)...... 7 FIGURE 8. BEAM-COLUMN JOINT BEHAVIOUR DURING EARTHQUAKE (IITK-BMTPC EARTHQUAKE TIP 20)...... 7 FIGURE 9. SOFT STOREY BUILDING BEHAVIOUR DURING EARTHQUAKE (IITK-BMTPC EARTHQUAKE TIP 21)...... 7 FIGURE 10. SOFT STOREY FAILURE ON RC FRAME STRUCTURE IN LUBHU, KATHMANDU (SURANA)...... 8

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FIGURE 11. COLUMN BASE DAMAGE ON RC FRAME BUILDING IN DHARMASTHALI, KATHMANDU (SURANA)...... 8 FIGURE 12. FAILURE AT COLUMN JOINT ON RC FRAME BUILDING IN KANTIPUR PUBLICATION BUILDING, KATHMANDU (SURANA)...... 9 FIGURE 13. BRICK INFILL WALL DAMAGE ON RC FRAME BUILDING IN HATTIBAN, KATHMANDU (SURANA)...... 10 FIGURE 14. POORLY CONSTRUCTED BRICK INFILL WALL IN PHUTUNG, KATHMANDU (SURANA)...... 10 FIGURE 15. BRICK MASONRY BUILDING BEHAVIOR DURING EARTHQUAKE (IITK-BMTPC EARTHQUAKE TIP 12). . 11 FIGURE 16. PARTIAL OR COMPLETE COLLAPSE OF UNREINFORCED LOAD BEARING BRICK STRUCTURES IN DHARMASTHALI, KATHMANDU (SURANA)...... 12 FIGURE 17. DIAGONAL SHEAR CRACKS AND CORNER SEPARATION IN UNREINFORCED LOAD BEARING BRICK STRUCTURE IN KATHMANDU (SURANA)...... 12 FIGURE 18. OUT-OF-PLANE WALL FAILURE IN UNREINFORCED LOAD BEARING BRICK STRUCTURES IN DURBAR HIGH SCHOOL, KATHMANDU (SURANA)...... 13 FIGURE 19. ROOFTOP WATER TANK SUPPORT FAILURE IN JORPATI, KATHMANDU (SURANA)...... 14 FIGURE 20. ROOFTOP WATER HEATER SUPPORT FAILURE IN JORPATI, KATHMANDU (SURANA)...... 15 FIGURE 21. DAMAGE AT CONSTRUCTION JOINT IN ASIAN INSTITUTE OF TECHNOLOGY AND MANAGEMENT, KATHMANDU (SURANA)...... 16 FIGURE 22. COLLAPSED UNREINFORCED BRICK BOUNDARY WALL IN ASIAN INSTITUTE OF TECHNOLOGY AND MANAGEMENT, KATHMANDU (SURANA)...... 17 FIGURE 23. TYPICAL SEISMIC JOINT IN NEPAL MEDICAL COLLEGE BUILDING, KATHMANDU (SURANA)...... 17 FIGURE 24. BOOK SHELVES IN LIBRARY OF MINISTRY OF GENERAL ADMINISTRATION, KATHMANDU (SURANA). ... 18 FIGURE 25. STRENGTHENING RC COLUMN BY JACKETING (IS 13935, 1993)...... 19 FIGURE 26. STRENGTHENING RC BEAMS BY JACKETING (IS 13935, 1993)...... 20 FIGURE 27. INCREASING RC COLUMN FLEXURAL STRENGTH BY CONTINUING LONGITUDINAL REINFORCEMENT THROUGH EXISTING CONCRETE SLAB (UNIDO MANUAL)...... 20 FIGURE 28. FRP APPLICATION ON EXISTING RC FRAME BUILDING (THE SHAKEOUT SCENARIO, SUPPLEMENTAL STUDY)...... 21 FIGURE 29. STRUCTURAL RESTORATION OF CRACKED MASONRY WALLS (IS 13935, 1993)...... 22 FIGURE 30. GROUT OR EPOXY INJECTION IN EXISTING WEAK WALLS (IS 13935, 1993)...... 23 FIGURE 31. SEWING TRANSVERSE WALLS WITH INCLINED BARS TO REINFORCE CORNERS (IS 13935, 1993) ...... 23 FIGURE 32. STRENGTHENING WITH WIRE-MESH AND MORTAR (IS 13935, 1993) ...... 24 FIGURE 33. SECURE ROOFTOP WATER TANK AND PROVIDE FRAMING CONNECTION TO ROOF SLAB (NSET) ...... 25 FIGURE 34. BOOKSHELVES CONNECTIONS TO WALL AND FLOOR (NSET) ...... 25 FIGURE 35. SUSPENDED CEILING SYSTEM -- GENERAL BRACING ASSEMBLY (FEMA E-74) ...... 26 FIGURE 36. VERTICAL TANK CONNECTION (FEMA E-74) ...... 26

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Acknowledgements

The author would like to thank David B. Swanson, P.E., S.E., Structural Group Director at Reid Middleton, Inc., who dedicated his time and expertise to provide suggestions as a reviewer; her firm Reid Middleton, Inc., for funding her time; and her colleagues for allowing her time away from her design practice to work as a volunteer in her home country of Nepal.

The author is especially thankful to Global Fairness Initiative for organizing, deploying, and funding travel costs for volunteer structural engineers to conduct safety assessments of damaged buildings in Nepal and to International Masonry Institute for publishing the call for volunteers.

Special thanks to Lenny Anderson of Reid Middleton, Inc., for his assistance with the report cover and graphics.

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1.0 Introduction

The purpose of this report is to present the author’s observations, findings, and recommendations at the request of Homraj Acharya, Country Director for Global Fairness Initiative (GFI) and as a follow up to volunteer service performing rapid post-earthquake safety evaluations of damaged buildings in the Kathmandu valley in Nepal. In May 2015, following the magnitude M7.8 Gorkha Earthquake that struck Nepal on April 25, 2015, GFI deployed volunteer structural engineers from the United States to provide rapid post-earthquake safety evaluations of damaged buildings.

The team travelled to Nepal at the request of the Nepalese government and in collaboration with GFI’s local partners Brick Clean Nepal and MinErgy. The primary mission of the team was to perform rapid post-earthquake safety evaluations of damaged buildings in the Kathmandu valley and to assist local authorities and residents in determining whether their structures were safe to occupy. The team performed building safety evaluation assessments alongside volunteer Nepalese engineers deployed by the Nepal Engineering Association (NEA).

This report summarizes the observations, findings, and recommendations from the author only, not the entire team. The author, a native of Nepal who trained as an architect in Nepal and a structural engineer in the United States, spent nine days in Nepal performing building safety assessments. The opinions expressed in this report are based on only visual observations of the structures. No destructive testing was performed to verify the quality of materials and workmanship. No calculations have been made to determine the adequacy of the structural system or its compliance with accepted local building code requirements. No other warranty is made as to the professional advice included in this report. This report has been prepared for the exclusive use of GFI and is not intended for use by other parties, nor may it contain sufficient information for purposes of other parties or their uses.

Figure 1. Building Safety Assessment Performance Area (Reid Middleton).

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2.0 Building Construction Types

There were two prevalent types of building construction found in the Kathmandu valley.

1. Reinforced Concrete (RC) frames with brick infill

The majority of newer buildings in the Kathmandu valley are constructed of RC frames with cast-in-place reinforced concrete slabs on shallow concrete spread footings with brick masonry infill walls. The Lateral Force Resisting Systems (LFRS) of the RC frame buildings were designed as concrete moment frames. However, the stiffness of the brick masonry walls was often not taken into account while designing the concrete moment frames. The infill walls are mostly designed as non-load-bearing partition walls only.

Figure 2. Typical RC Frame Building with Brick Infill Construction (Surana).

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2. Unreinforced load bearing masonry walls

Some of the newer buildings are constructed of unreinforced load bearing brick masonry walls with cement mortar on shallow continuous wall footings. The diaphragms of these buildings are constructed of cast-in-place reinforced concrete slabs. In some buildings, the roof diaphragms consist of wood roof joists with corrugated metal panels.

The majority of historic and older construction is comprised of either brick with mud mortar or adobe construction. The floor systems of brick houses are constructed of unreinforced mud or cement plaster (if the building had been remodeled) over wooden planks and floor joists. The floor systems of adobe houses are made of locally available mud plaster on a bamboo floor system. The roof systems consist of either fired clay tiles overlain on wooden planks over wood roof joists with mud mortar or corrugated metal deck over wood joists.

Figure 3. Unreinforced Load Bearing Brick Building in Phutung, Kathmandu (Surana).

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Figure 4. Unreinforced Load Bearing Brick with Mud Mortar Building in Phutung, Kathmandu (Surana).

Figure 5. Unreinforced Load Bearing Adobe Building in Phutung, Kathmandu (Surana).

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Figure 6. Bamboo Floor System in Unreinforced Load Bearing Building, Kathmandu (Surana).

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3.0 Structural Assessment Observations

Based on safety assessments performed on a number of residential, commercial, and institutional buildings, the following observations were made on the earthquake performance relative to the types of construction.

1. RC Frames with Brick Infill Buildings

RC frames with brick infill buildings performed reasonably well in this earthquake. The most common damage observed was diagonal cracks on brick infill walls and plaster. The stiffness of infill walls was typically not taken into account while designing the RC moment frames as the LFRS. Due to the stiffness of the brick masonry material, the lateral loads were transferred to the infill walls, causing damage. However, the most significant damage to buildings appeared to be mostly due to poor construction and the soft-storey phenomenon where a lower level floor is significantly weaker and more flexible than the upper floors of the building. Some of the structural damage observed were corner column crushing from overturning forces, shear failure at beam-column joints, and severe diagonal shear cracks within the relatively weak and non-ductile brick masonry infill walls.

Most of the RC frame buildings in the Kathmandu valley appeared to have an open floor architectural layout with fewer infill walls for stores or other commercial purposes at the ground floor level. This significantly reduced the stiffness of the lower floor level compared to upper levels with more infill walls, creating a soft storey. Soft storey buildings were particularly susceptible to earthquake damage as has been observed in many other earthquakes around the world. To avoid soft storey failures, the LFRS at that storey should be designed for adequate lateral strength, stiffness, and ductility.

Furthermore, the stiffness of brick infill walls was usually not considered on RC frame building design in Nepal. The lack of consideration for this design element caused these unreinforced brick masonry infill walls to experience significant diagonal cracking from horizontal shear and in many cases, out-of-plane failure of the infill wall system. Due to the stiffness of the brick wall, the lateral load is transferred to the infill walls, resulting in severe damage in some cases. To avoid damage to the infill, the wall stiffness should be considered while designing RC frames as a LFRS. See Figure 7 and the Earthquake Tips publications in the appendices for more explanation of the consequences of this flawed design assumption.

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Figure 7. RC Frame Building Behaviour during Earthquake (IITK-BMTPC Earthquake Tip 17).

Figure 8. Beam-Column Joint Behaviour during Earthquake (IITK-BMTPC Earthquake Tip 20).

Figure 9. Soft Storey Building Behaviour during Earthquake (IITK-BMTPC Earthquake Tip 21).

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Figure 10. Soft Storey Failure on RC Frame Structure in Lubhu, Kathmandu (Surana).

Figure 11. Column Base Damage on RC Frame Building in Dharmasthali, Kathmandu (Surana).

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Figure 12. Failure at Column Joint on RC Frame Building in Kantipur Publication Building, Kathmandu (Surana).

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Figure 13. Brick Infill Wall Damage on RC Frame Building in Hattiban, Kathmandu (Surana).

Figure 14. Poorly Constructed Brick Infill Wall in Phutung, Kathmandu (Surana)

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2. Unreinforced Load Bearing Brick Wall Buildings

Well known for their poor earthquake performance, the unreinforced load bearing brick masonry and cement mortar buildings performed poorly as expected. The common damage observed in these buildings was diagonal shear failure on mortar, including horizontal bed and vertical head joints and out-of-plane wall collapses. Most of the unreinforced load bearing wall buildings lacked positive wall-to-diaphragm structural connections, causing out- of-plane wall failure. The performance of unreinforced brick buildings can be increased significantly by providing a horizontal cast-in-place reinforced concrete lintel band over openings and below flexible diaphragms to tie the walls together.

The adobe and brick with mud mortar buildings were severely damaged. The common damage observed was diagonal shear failure on brick and mortar, corner wall separation, and out-of-plane wall failure. To increase the performance of adobe construction, care must be taken in proper design, construction material use, and the use of skilled construction workers.

Figure 15. Brick Masonry Building Behavior during Earthquake (IITK-BMTPC Earthquake Tip 12).

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Figure 16. Partial or Complete Collapse of Unreinforced Load Bearing Brick Structures in Dharmasthali, Kathmandu (Surana).

Figure 17. Diagonal Shear Cracks and Corner Separation in Unreinforced Load Bearing Brick Structure in Kathmandu (Surana).

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Figure 18. Out-of-Plane Wall Failure in Unreinforced Load Bearing Brick Structures in Durbar High School, Kathmandu (Surana).

3. Nonstructural Damage

While the safety assessments were mostly focused on building structures, the nonstructural performance of the building components was also deemed important from the life-safety aspect. Following are some of the nonstructural damages that were observed during the building assessments:

Rooftop Unit Failure

The most common nonstructural failure observed was rooftop unit collapses such as water tanks, water heaters, and solar panels. Roof top unit supports and their connections to roof slabs should be designed for appropriate gravity and lateral forces.

Seismic Joint Failure

Inappropriate seismic joint material or the lack of it between the buildings led to significant structural damage and failures. The lack of seismic joints between structures or properly detailed seismic joints typically result in pounding of two structures with different seismic vibration characteristics. The seismic joints, where used, appeared to be filled with non- ductile and brittle materials that transfer seismic forces in undesirable ways. Seismic joint cover materials should be flexible enough to dissipate inertial forces from the seismic event to avoid earthquake damage between the buildings.

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Boundary Wall Failure

The majority of boundary walls around the perimeter of buildings constructed with unreinforced brick walls were collapsed due to out-of-plane failure. See appendix for seismic resisting boundary wall construction configuration details.

Suspended Ceiling Failure

Suspended ceiling failures were also observed in various cinema theaters and office buildings.

These types of internal architectural features and systems should be adequately braced to avoid damage that could cause disruption to business as well as injuries to people.

Figure 19. Rooftop Water Tank Support Failure in Jorpati, Kathmandu (Surana).

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Figure 20. Rooftop Water Heater Support Failure in Jorpati, Kathmandu (Surana).

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Figure 21. Damage at Construction Joint in Asian Institute of Technology and Management, Kathmandu (Surana).

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Figure 22. Collapsed Unreinforced Brick Boundary Wall in Asian Institute of Technology and Management, Kathmandu (Surana).

Figure 23. Typical Seismic Joint in Nepal Medical College Building, Kathmandu (Surana).

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Figure 24. Book Shelves in Library of Ministry of General Administration, Kathmandu (Surana).

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4.0 Recommendations

4.1 Recommendation for Repair and Strengthening

The following are generalized types of common repairs that may be appropriate for many of these earthquake-damaged structures. These repair concepts are being provided based on the damage observed during the post-earthquake building safety evaluations. The recommendations represented here are based on long-standing earthquake risk reduction research done by various academic institutions and professional organizations. Final analysis and design of seismic rehabilitation must consider all aspects of the building structure and use in its present or future configuration.

RC Frame Repair

Minor crack repairs on the RC frame buildings are often performed by injecting epoxy into the cracks to provide a structural bond within the gap of the crack and to close the crack for weatherproofing. Major structural deficiencies in structural members can also be strengthened by jacketing the existing columns and beams. The jacket may consist of steel, fiber wrap, or most commonly of additional cast-in-place concrete with longitudinal and transverse reinforcements around the perimeter of existing beam and columns. The improvement to the strength of columns and beams will vary depending on the type of strengthening employed. To increase the flexural strength of columns, it is recommended to provide continuous longitudinal reinforcements through holes drilled in the slab and filled with new concrete. It is important to note that jacketing may only improve the strength and stiffness of members but may not provide significant improvement on ductility. The specific details of the existing frame, column, or beam to be strengthened will determine the level of improvement that can be achieved by jacketing.

The RC Frame members and the connections can also be repaired or strengthened by overlaying Fiber Reinforced Polymer (FRP) wrapping. FRP is a high-strength, reinforced polymer product containing aramid, glass, or carbon-based fibers.

Figure 25. Strengthening RC Column by Jacketing (IS 13935, 1993).

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Figure 26. Strengthening RC Beams by Jacketing (IS 13935, 1993).

Figure 27. Increasing RC Column Flexural Strength by continuing Longitudinal Reinforcement through Existing Concrete Slab (UNIDO Manual).

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Figure 28. FRP Application on Existing RC Frame Building (The Shakeout Scenario, Supplemental Study).

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Unreinforced Brick Wall Repair:

Following are some of the recommendations for repairing damage to and strengthening of unreinforced brick walls:

Figure 29. Structural Restoration of Cracked Masonry Walls (IS 13935, 1993).

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Figure 30. Grout or Epoxy Injection in Existing Weak Walls (IS 13935, 1993).

Figure 31. Sewing Transverse Walls with Inclined Bars to reinforce Corners (IS 13935, 1993)

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Figure 32. Strengthening with Wire-mesh and Mortar (IS 13935, 1993)

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Nonstructural Hazard Mitigation:

Following are some of the recommendations for mitigating nonstructural hazards during an earthquake:

Figure 33. Secure Rooftop Water Tank and Provide Framing connection to Roof Slab (NSET)

Figure 34. Bookshelves Connections to Wall and Floor (NSET)

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Figure 35. Suspended Ceiling System -- General Bracing Assembly (FEMA E-74)

Figure 36. Vertical Tank Connection (FEMA E-74)

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4.2 Recommendations for Immediate Action

Based on the field observations, the following steps are recommended to be prioritized as immediate action items.

• The priority should be to complete the building safety assessments of damaged buildings throughout the impacted area to inform the public of the safety risks of re-occupying their buildings. • The building safety assessments should be prioritized to essential facilities like hospitals and schools and to the hard hit areas similar to Dharmasthali and Phutung, where residents are still afraid to occupy their houses, even with minor damage to the structures. Their fear is caused by the numerous building collapses and the large number of casualties resulting from it. • Establish guidelines for demolishing, barricading, shoring, and emergency stabilization of the structures with significant structural damage. • Establish safety programs and guidelines to train workers to demolish damaged high-rise structures. • Designate and regulate the sites for discarding construction debris.

4.3 Recommendations for Future Long-Term Action

The following guideline documents and training programs are considered to be important to prepare for the potential seismic event in the future. It is recommended that these steps be developed as long-term action items. There is no particular order of priority in this list.

• Prepare emergency management plans for future disasters. • Establish guidelines for repair and retrofit of damaged structures and train local engineers. • Enforce stricter provisions of the building codes compliance. • Provide independent review of construction documents by local authorities having jurisdiction to ensure the compliance with building codes before issuance of building permit. • Provide construction inspections by qualified inspectors from municipalities or qualified agencies during construction, especially during the construction of Lateral Force Resisting Systems. • Establish and enforce provisions for alteration or addition to existing building structures. • Encourage coordination between the design team and the construction team during construction. • Require design team involvement during construction such as providing review of shop drawings and onsite filed investigations during construction to ensure the contractor is following the construction documents. • Establish accountability for design teams and contractors.

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• Establish a code of ethics for both design professionals and contractors. The American Society of Civil Engineers (ASCE) has a well-documented and long-standing code of ethics for civil and structural engineers. A copy of this is provided in the appendix of this report. • Establish and mandate contractor training and certifications to avoid poor construction practices. • Mandate material testing or certifications for construction materials to maintain the quality of construction before construction. • Require the prime general contractor to be responsible for coordinating between various subcontractors during construction and to be responsible for the construction quality and workmanship of the overall construction project. • In areas of steep slopes or soft ground, require that a qualified geotechnical engineer be retained during design and construction to ensure appropriate soil bearing capacity to design foundation and to help ensure appropriate soil compaction is met to achieve required foundation bearing capacities during construction.

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Appendix A Checklists Used in Nepal

REPORT June 2015 Nepal Post-Earthquake Building Safety Evaluations Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Annex III: Rapid Evaluation Form

Rapid Evaluation Safety Assessment Form Inspection Inspector ID: Inspection date and time: AM PM Organization: Areas inspected: Exterior only Exterior and interior

Building Description Address: Building Name: District: Building contact/phone: Municipality/VDC : Approx. “Footprint area” (sq. ft): Ward No: Tole: Type of Construction Adobe Stone in mud Stone in cement Brick in cement Wood frame Bamboo Brick in mud Brick in cement R.C frame Others: Type of Floor Primary Occupancy: Flexible Rigid Residential HospitalGovernment office Police station Type of Roof Educational IndustryOffice Institute Mix Flexible Rigid Commercial Club Hotel/Restaurant Others:

Evaluation Estimated Building Minor/None Moderate Severe Observed Conditions: Damage ¾Collapsed, partially collapsed, or moved off its foundation (excluding contents) ¾Building or any story is out of plumb None

¾Damage to primary structural members, cracking of walls, or 0-1% other signs of distress present ¾Parapet, chimney, or other falling hazard 1-10% ¾ Large fissures in ground, massive ground movement, or slope 10-30% displacement present ¾Other hazard (Specify) e.g tree, power line etc: 30-60% 60-100%

Comments: 100%

Posting Choose a posting based on the evaluation and team judgment. Severe conditions endangering the overall building are grounds for an Unsafe posting. Localized Severe and overall Moderate conditions may allow a Restricted Use posting. Post INSPECTED placed at main entrance. Post RESTRICTED USE and UNSAFE placards at all entrances. INSPECTED (Green placard) RESTRICTED USE (Yellow placard) UNSAFE (Red placard) Record any use and entry restrictions exactly as written on placard:

Further Actions Check the boxes below only if further actions are needed. Barricades needed in the following areas: Detailed evaluation recommended: Structural Geotechnical Other

Comments:

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Annex IV: Detail Evaluation Form

Detailed Evaluation Safety Assessment Form Inspection Inspector ID: Inspection date and time: AM PM Organization: Areas inspected: Exterior only Exterior and interior

Sketch (Optional) Provide a sketch of the building or damage portions, Indicate damage points. Estimated Building Damage

If requested by the jurisdiction, estimate building damage (repair cost ÷replacement cost, excluding contents).

None

0‐1%

1‐10%

10‐30%

30‐60%

60‐100%

100%

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Detailed Evaluation Safety Assessment Form Page 2

Evaluation Investigate the building for the condition below and check the appropriate column. Damage Levels Extreme Moderate‐Heavy Insignificant‐Light Comments >2/3 1/3‐2/3 <1/3 >2/3 1/3‐2/3 <1/3 >2/3 1/3‐2/3 <1/3 Overall hazards: ¾Collapse or partial collapse ¾Building or storey leaning ¾Others Structural hazards: ¾Foundation ¾Roofs, floors (vertical loads) For Masonry Buildings: ¾Corner separation ¾Diagonal cracking ¾Out of plane failure ¾In‐plane flexural failure ¾Delamination For Reinforced Concrete Buildings: ¾Joint ¾Lap splice ¾Columns ¾Beams ¾Infill Nonstructural hazards: ¾Parapets ¾Cladding, glazing ¾Ceilings, light fixtures ¾Interior walls, partitions ¾Life lines (electric, water, etc) ¾Other Geotechnical hazards: ¾Slope failure, debris ¾Ground movement ¾Other General Comments:

Recommendations: Damage Grade Grade 1 Grade 2 Grade 3 Grade 4 Grade 5

Retrofit / Demolition Repair Retrofit Demolish

Further Actions Check the boxes below only if further actions are needed. Barricades needed in the following areas: Detailed evaluation recommended: Structural Geotechnical Other

Comments:

Appendix B Damaged Assessment Guidelines provided by GFI

REPORT June 2015 Nepal Post-Earthquake Building Safety Evaluations Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings

(Part II: Post-disaster damage assessment)

93 Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Table of Contents

1. Introduction ...... 1

1.1 Purpose ...... 1

1.2 Basis and Scope ...... 1

1.3 Guideline Dissemination ...... 1

2. Damage Assessment Process ...... 2

2.1 General ...... 2

2.2 Human Resources ...... 3

3. Rapid Evaluation ...... 4

3.1 General ...... 4

3.2 Safety Precaution ...... 4

3.3 Steps for Rapid Evaluation ...... 5

3.4 Posting Safety Status ...... 7

3.4.1 Inspected ...... 7

3.4.2 Limited Entry or Restricted Use ...... 8

3.4.3 Unsafe ...... 9

3.5 Limitations of Rapid Evaluation ...... 10

4. Detail Evaluation ...... 10

4.1 Understanding the Characteristics of Damaging Earthquake ...... 10

4.2 Review of Existing Building Data ...... 11

4.3 Assessing the Consequences of the Damaging Earthquake ...... 11

4.4 Assessing Pre-existing Conditions ...... 11

4.5 Survey the Building from Outside ...... 12

4.6 Examine the site for Geotechnical Hazards ...... 12

4.7 Inspect the structural system from inside the building ...... 12

4.8 Inspect the Buildings in Critical Locations ...... 13

4.8.1 Earthquake Damage Patterns in Masonry Buildings ...... 13

94 Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

4.8.1.1 Corner Separation ...... 13

4.8.1.2 Diagonal Cracking ...... 13

4.8.1.3 Out of Plane Failure flexural failure ...... 16

4.8.1.4 In-plane flexural failure ...... 18

4.8.1.5 Delamination of Walls ...... 21

4.8.2 Earthquake Damage Patterns in Reinforced Concrete Frame Buildings ...... 22

4.8.2.1 Beam-Column Joint Failure ...... 22

4.8.2.2 Lap-splice Damage ...... 23

4.8.2.3 Short Column Damage ...... 24

4.8.2.4 Soft-story damage ...... 25

4.8.2.5 Shear/flexure cracks in column and beam members ...... 27

4.8.2.6 Damage to Infill-Wall ...... 28

4.9 Conduct Test ...... 29

4.9.1 Sounding Test ...... 29

4.9.2 Rebar Detection Test ...... 31

4.9.3 In-Situ Testing In-Place Shear ...... 33

4.10 Detail Evaluation ...... 34

4.11 Identification of Damage Levels ...... 35

4.11.1.1 Earthquake damage grades of Masonry buildings with flexible floor and roof ...... 35

4.11.1.2 Earthquake damage grades of Masonry buildings with rigid floor and roof ...... 37

4.11.1.3 Earthquake damage grades of Reinforced Concrete Buildings ...... 39

5. References ...... 42

ANNEXES ...... 44

Annex I: Examples of Rapid Evaluation ...... 44

Annex II: Examples of Detailed Evaluated Buildings ...... 46

Annex III: Rapid Evaluation Form ...... 47

Annex IV: Detail Evaluation Form ...... 48

95 Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

1. Introduction

1.1 Purpose

The purpose of this document is to provide practical criteria and guidance for evaluating earthquake damage to buildings with primary lateral-force-resisting systems consisting of reinforced concrete frame and masonry buildings which are prevalent in Nepal. The procedures in this manual are intended to characterize the observed damage caused by the earthquake in terms of the loss in building performance capability. The intended users of this document are primarily practicing engineers with experience in concrete and masonry design and construction with basic understanding of earthquake resistant design and construction. Information in this document also may be useful to building owners, and government agencies. However the users should consult with a qualified engineer for interpretation or specific application of this document.

1.2 Basis and Scope

The evaluation procedure assumes that when an earthquake causes damage to a building, a competent engineer can assess the effects, at least partially, through visual inspection augmented by investigative tests, structural analysis, and knowledge of the building construction. By determining how the structural damage has changed structural properties, it is feasible to develop potential actions (performance restoration measures) that, if implemented, would restore the damaged building to a condition such that its future earthquake performance would be essentially equivalent to that of the building in its pre-event condition. The costs associated with these conceptual performance restoration measures quantify the loss associated with the earthquake damage.

The theoretical basis of this guideline is based on different documents from Federal Emergency Management Agency (FEMA) and Applied Technology Council (ATC) namely ATC 20, FEMA 154, FEMA 273, FEMA 274, FEMA 306, FEMA 307, FEMA 308, FEMA 356, ATC 40 etc and the experience of damage assessment of the buildings after Kashmir earthquake in Pakistan.

There are four levels of damage assessment: • Windshield: Overall scope of damage • Rapid : Assessment sufficient for most buildings • Detailed: Closer assessment of difficult or complex buildings • Engineering : Consultant engaged by owner

This guideline covers the rapid and detailed assessment procedures. Process for windshield will be different as it is the overall damage assessment from air i.e. helicopter survey, the last one needs quantitative assessment of individual buildings.

The damage assessment methodology suggested in this guideline is not for grant distribution but different grades of damage identified after detail evaluation can be utilized as a basis for grant dispersion also.

1.3 Guideline Dissemination

The guideline has the potential to improve the situation of earthquake disaster affected area through proper planning if appropriately implemented by concerned authorities. This guideline should reach to engineers and practitioners who are working in the field of construction and disaster and make use of the document effectively and efficiently.

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

However, distribution of printed guidelines alone has been shown to be ineffective in achieving change in practice. Guidelines are more likely to be effective if they are disseminated by means of an active education. Hence, training for guideline users should be carried out in parallel so that they are in a position to better understand the issue and make best use of the guidelines.

Guidelines must obviously be made as widely available as possible in order to facilitate implementation. It is necessary to have wide circulations among engineers and practitioners working in the field of earthquake engineering. It thus requires an integrated effort by the concerned authorities like local government, municipalities, NGO's, INGO's and other related organisations towards dissemination of publication in wider range.

Further dissemination and implementation of a guideline should be monitored and evaluated. The guideline also needs thorough review by experts in the field. This should undergo mandatory updating procedure to transform it into pre-standard and then to building standard.

2. Damage Assessment Process

2.1 General

This system of overall safety evaluation of earthquake damaged buildings is based on experience of such assessment in Pakistan after Kashmir earthquake. The purpose of rapid evaluation is similar to ATC-20.

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Structures Identified for Evaluation

Rapid Evaluation

Obviously Apparently OK Questionable Unsafe Post INSPECTED Post Post UNSAFE (Suggest for Repair) LIMITED ENTRY (Suggest for Demolition)

Detail Evaluation

Possibility to Safe, Repairs is Restore/Retrofit Unsafe, Demolish Required and Reconstruction MODERATE/HEAVY SLIGHT /MODERATE HEAVY/VERY HEAVY DAMAGE (Suggest for DAMAGE (Suggest for DAMAGE Major Restoration and Repair/Retrofit) (Suggest for Demolition) Retrofit)

Detail Quantitative Analysis

Figure 1: Flowchart showing damage assessment process

The purpose of rapid evaluation is rapid assessment for safety. It is to identify quickly which buildings are obviously unsafe, apparently safe and questionable.

In detailed Evaluation, buildings are inspected more thoroughly, with more investigation into the vertical and lateral load resisting systems. The purpose of detailed evaluations is not only to identify the level of safety but also to identify the buildings that can be restored and retrofitted or need to demolish. Only limited buildings that are difficult to recommend for retrofit or demolition will be recommended for detailed quantitative assessment. However, after detail retrofit design and cost estimation, if the retrofitting cost is higher, it might be suggested for reconstruction. General recommendation for feasibility of retrofitting is up to 30% of the reconstruction cost of the same size building. Rapid evaluation methodology is described in chapter 3 and the detail evaluation in chapter 4 of this guideline.

2.2 Human Resources

All engineers, architects, sub-engineers can conduct the rapid evaluation once trained on rapid evaluation process and methodology. It is recommended that they are trained during normal time now and conduct refresher course after the earthquake again just before going to the field. Concerned

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment) department needs to prepare the roster of trained professionals and their experience so that a right team is sent for different type of evaluation.

Engineers with structural engineering background and trained on detail evaluation methodology can conduct the detail evaluation for buildings. Engineers with lifelines background and trained on detail evaluation of lifelines can conduct the detail evaluation of lifelines.

Engineers/ Architect Engineers with Engineers with Sub-engineers Structures Lifeline (Building Inspectors) Background Background

Rapid Detailed Evaluation of Evaluation of Bridges, Roads, Rapid All Occupancies Airports, Treatment Evaluation of Plants, Pipelines, All Occupancies Detail Evaluation Reservoirs, Water of All Occupancies Tanks and Dams

3. Rapid Evaluation

3.1 General

The objective of the Rapid Evaluation is to quickly inspect and evaluate buildings in the damaged area with a minimum manpower available at the time of emergency. The rapid evaluation can be done by civil, structural, geotechnical engineers and architects with experience on building construction and trained on rapid evaluation methodology.

General situation during emergency is:

• Usually a scarcity of skilled manpower available to conduct building- by- building inspections

• Utilization of the talents and experiences of professionals involved in building construction

• Once all buildings in a given area have been inspected and those that are apparently unsafe have been posted, the remaining structures, the so called gray-area buildings are left for a detailed assessment by a structural engineer

Rapid evaluation is done just after the earthquake to assess the safety of buildings to judge whether people can enter the building or not. It can be done by visual inspection.

3.2 Safety Precaution

All possible safety precautions should be exercised as building under study could be in dilapidated condition and could loss its stability in whole or in parts causing casualty. The team must comprise at least two personnel, both trained in assessment works. The team personnel must wear safety hats when assessing the buildings. Before entering a house, its condition should be well assessed as the

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

house could be in dangerous state. Wherever the uncertainty exists and team is in doubt, it is better to be conservative.

3.3 Steps for Rapid Evaluation

The initial steps in the visual observation of earthquake damage are to identify the location of the wall in the building and to determine the dimensions of the wall (height, length, and thickness). A tape measure is used for quantifying the overall dimensions of the wall. A sketch of the wall elevation should then be prepared. The sketch should include sufficient detail to depict the dimensions of the wall, it should be roughly to scale, and it should be marked with the wall location. Observable damage such as cracks, spalling and exposed reinforcing bars should be indicated on the sketches. Sketches should be made in sufficient detail to indicate the approximate orientation and width of cracks. Crack width is measured using the crack comparator or tape measure at representative locations along significant cracks. Avoid holes and edge spalls when measuring crack widths. Crack widths typically do not change abruptly over the length of a crack. If the wall is accessible from both sides, the opposite side of the wall should be checked to evaluate whether the cracks extend through the thickness of the wall and to verify that the crack widths are consistent.

Photographs can be used to supplement the sketches. If the cracks are small, they may not show up in the photographs, except in extreme close-up shots. Paint, markers, or chalk can be used to highlight the location of cracks in photographs. However, photographs with highlighted crack should always be presented with a written disclaimer that the cracks have been highlighted and that the size of the cracks cannot be inferred from the photograph.

During a visual inspection, the engineer should carefully examine the wall for the type of damage and possible causes. Indications that the cracks or spalls may be recent or that the damage may have occurred prior to the earthquake should be noted. Visual observation of the nonstructural elements in the building can also be very useful in assessing the overall severity of the earthquake, the inter-story displacements experienced by the building, and the story accelerations. Full-height nonstructural items such as partitions and facades should be inspected for evidence of inter-story movement such as recent scrapes, cracked windows, or crushed wallboard.

Following steps are recommended for conducting rapid evaluation of earthquake damaged building.

I. Study the house from outside, take a walk around the house and do visual inspection Visual inspection from outside and inside of the building is the only method applicable for rapid evaluation of buildings. Generally, earthquake damage to concrete and masonry walls (common building types in Nepal) is visible on the exposed surface. Observable types of damage include cracks, spalls and delaminations, permanent lateral displacement, and buckling or fracture of reinforcements. II. Enter the house to do assessment inside if it is safe to do so Enter the building if entering the house is safe. Inspect the house from inside as done from outside. Identify cracks, spalls and delaminations, joints opening, permanent lateral displacement, and buckling or fracture of reinforcements. Come out of the houses as soon as possible. III. Fill-up the form, note the observations Rapid evaluation form is given in Annex III of this guideline. The key information to be collected is: 1) Information about evaluator

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

2) Building Description: Owners’ name, Address, contact no, total plinth area, type of construction, Type of floor, type of roof, primary occupancy etc. 3) Damage conditions 4) Estimated building damage ratio 5) Safety status (Posting) 6) Further Actions When filling the form, the evaluators must use: General knowledge of construction - the evaluator must be able to look at any particular load carrying system and rapidly identify the system, know how it works, and the corresponding load path. For the frame buildings, beam-column system is the primary load carrying system while as for masonry structures, the walls are the main elements of the system. Professional experience - the evaluator must have practical experience working with the various types of buildings and their load carrying systems. This experience may come from designing and detailing systems, reviewing the designs and details prepared by others, or inspecting the actual construction of the systems. Good judgment - above all, evaluators must be able to look at a damaged or potentially damaged system and, based on their knowledge and experience, make a judgment on the ability of that system to withstand another event of approximately equal magnitude.

IV. Rapid Evaluation Six main parameters are evaluated during rapid evaluation process. Safety of the building is judged primarily based on these six parameters. If the building has any of condition 1, 2, 3 or 5 as per the Table 1, the building is categorized as unsafe. If the building has condition 4 or 6, it can be termed as unsafe or area unsafe. Table 1: Criteria for building being unsafe S.N. Conditions Posting 1 Building has collapsed, partially collapsed, or moved off its foundation Unsafe 2 Building or any story is significantly out of plumb Unsafe Obvious severe damage to primary structural members, severe cracking of 3 walls, severe cracking of columns, beam-column joints, buckling of Unsafe reinforcement bars, or other signs of severe distress present 4 Obvious parapet, chimney, or other falling hazard present Area Unsafe Large fissures in ground, massive ground movement, or slope displacement 5 Unsafe present Unsafe or 6 Other hazard present (e.g. fallen power line, fallen tree) Area Unsafe If these entire six factors give positive result the building is obviously safe. The remaining buildings with damage but do not fall under these six factors are questionable buildings and based on conditions limited entry or restricted use. As the purpose of the rapid assessment is to identify the buildings’ safety rapidly, all the buildings that are done rapid assessment should undergo detail assessment explained in Section 4 of this guideline. Photo 1-4 below show different types of damage resulting to unsafe building.

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Photo 1: Building Partially Collapsed Photo 2: Building with a story out of plumb

Photo 3: Photo 4: Severe Damage to Primary Structural System Severe Damage to Primary Structural System

3.4 Posting Safety Status

Three kinds of posting similar to ATC-20 are recommended in this guideline also. Posting classifications, colour and description of the posting is given in Table 2 below.

Table 2: Posting Classifications

Posting Classification Color Description

INSPECTED Green No apparent hazard found, although repairs may be required. Original lateral load capacity not significantly decreased. No restriction on use or occupancy

LIMITED Yellow Dangerous condition believed to be present. Entry by owner ENTRY/Restricted permitted only for emergency purposes and only at own risk. Use No usage on continuous basis. Entry by public not permitted. Possible major aftershock hazard

UNSAFE Red Extreme hazard may collapse. Imminent danger of collapse from an aftershock. Unsafe for occupancy or entry, except by authorities.

3.4.1 Inspected

Inspected posting means habitable, minor or no damage - this green placard is used to identify buildings that have been inspected but in which no serious damage has been found. These structures are in a condition that allows them to be lawfully reoccupied; however, repairs may be necessary

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Following are the main criteria for posting this classification: • Observed damage, if any, does not appear to pose a safety risk • Vertical or lateral capacity not significantly decreased • Repairs may be required • Lawful entry, occupancy and use permitted

3.4.2 Limited Entry or Restricted Use

Limited entry or restricted use means damage which represents some degree of threat to occupants. Restricted Use is intended for buildings that have been damaged; yet the damage does not totally preclude occupying the structure. It can mean that parts of a structure could be occupied, or it could be used to denote those buildings that can be entered for a brief period of time only to remove possessions. The use of a Restricted Use placard will minimize the number of buildings which will require additional safety assessments because restrictions can be placed on the use and occupancy of the structure until such a time as the owner can retain an architect or engineer to develop the necessary repair program.

8 Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Following are the main criteria for posting this classification: • Some risk from damage in all or part of building • Restricted on o duration of occupancy o areas of occupancy o Usage • Restrictions enforced by owner / manager

3.4.3 Unsafe

UNSAFE posting means not habitable, significant threat to life safety. The red ATC-20 Unsafe placard is used on those structures with the most serious damage. Typically, these are structures that represent a threat to life-safety should they be occupied. It is important to note that this category does not mean the building must be demolished. This placard carries the statement, "THIS IS NOT A DEMOLITION ORDER" to clarify that the building simply is not safe enough to occupy. In the vast majority of cases, structures posted unsafe can be repaired to a safe and usable condition.

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Following are the main criteria for posting this classification: • Falling, collapse, or other hazard • Does not necessarily indicate that demollition is required • Owner must mitigate hazards to satisfaction of jurisdiction to gain entry

3.5 Limitations of Rapid Evaluation

The rapid evaluation is carried out just after an earthquake for the purpose of safety evaluation of the buildings so that people can decide to occupy or not enter the building following an earthquake. The result whatever comes from the rapid evaluation MUST NOT BE USED FOR DEMOLITION as many buildings that are assigned as UNSAFE might be possible to restore and retrofit.

4. Detail Evaluation

Detailed assessment is conducted after some time of an earthquake to assess level of damage in detail. Main purpose of this assessment is to assess compensation to household, planning for reconstruction activity or to assess level of intervention required for repair and retrofitting.

4.1 Understanding the Characteristics of Damaging Earthquake

During the evaluation of damage to concrete or masonry wall buildings, information on the characteristics of the damaging earthquake can lead to valuable insight on the performance characteristics of the structure. For example, if the ground motion caused by the earthquake can be estimated quantitatively, the analysis techniques can provide an estimate of the resulting maximum displacement of the structure. This displacement, in conjunction with the theoretical capacity curve, indicates an expected level of component damage. If the observed component damage is similar to that predicted, the validity of the theoretical model is verified in an approximate manner. If the damage differs, informed adjustments can be made to the model.

10 Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

4.2 Review of Existing Building Data

The data collection process begins with the acquisition of documents describing the pertinent conditions of the building. Review of construction drawings simplifies field work and leads to a more complete understanding of the building. Original architectural and structural construction drawings are central to an effective and efficient evaluation of damage. Potential sources of these and other documents include the current and previous building owners, building departments, and the original architects or engineers. Drawings may also be available from architects or engineers who have performed prior evaluations for the building. In addition to construction drawings, it is helpful to assemble the following documents if possible:

• Site seismicity/geotechnical reports • Structural calculations • Construction specifications • As Built Drawings • Foundation reports • Prior building assessments

Review of the existing building information serves several purposes. If reviewed before field investigations, the information facilitates the analytical identification of structural components. This preliminary analysis also helps to guide the field investigation to components that are likely to be damaged. Existing information can also help to distinguish between damage caused by the earthquake and pre-existing damage. Finally, the scope of the field inspection and testing program depends on the accuracy and availability of existing structural information. For example, if structural drawings reliably detail the size and placement of reinforcing, expensive and intrusive tests to verify conditions in critical locations may be unnecessary.

4.3 Assessing the Consequences of the Damaging Earthquake

Methods for inspecting and testing concrete and masonry wall buildings for earthquake damage fall into two general categories, nondestructive and intrusive. Nondestructive techniques do not require any removal of the integral portions of the components. In some cases, however, it may be necessary to remove finishes in order to conduct the procedure. In contrast, intrusive techniques involve extraction of structural materials for the purpose of testing or for access to allow inspection of portions of a component.

4.4 Assessing Pre-existing Conditions

Interpretation of the findings of damage observations requires care and diligence. When evaluating damage to a concrete or masonry wall, an engineer should consider all possible causes in an effort to distinguish between that attributable to the damaging earthquake and that which occurred earlier (pre- existing conditions).

Since the evaluation of earthquake damaged buildings is typically conducted within weeks or months of the event, cracking and spalling caused by earthquakes is normally relatively recent damage. Cracks associated with drying shrinkage or a previous earthquake, on the other hand, would be relatively old. General guidance for assessing the relative age of cracks based on visual observations is as follows.

Recent cracks typically have the following characteristics:

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

• Small, loose edge spalls • Light, uniform color of concrete or mortar within crack • Sharp, uneroded edges • Little or no evidence of carbonation Older cracks typically have the following characteristics: • Paint or soot inside crack • Water, corrosion, or other stains seeping from crack • Previous, undisturbed patches over crack • Rounded, eroded edges • Deep carbonation

Evaluating the significance of damage requires an understanding of the structural behavior of the wall during the earthquake. The evaluating engineer must consider the implications of the observations with respect to the overall behavior of the building and the results of analytical calculations. The behavior must be correlated with the damage. If the observed damage is not reasonably consistent with the overall seismic behavior of the structure, the crack may have been caused by an action other than the earthquake.

4.5 Survey the Building from Outside

• Begin the survey by walking around the exterior of the building • Try to determine the structural system • Examine the structure for vertical discontinuities • Examine the structure for irregular configuration in plan • Look for cracking of exterior walls, glass frames etc., which are symptoms of excessive drift • Examine non-structural elements • Look for new fractures in the foundation or exposed lower wall of buildings • Different Inspection and test required to conduct.

4.6 Examine the site for Geotechnical Hazards

• Examine the site for fissures, bulged ground, and vertical movements • In hillside areas, examine the area for landslide displacement and debris encroaching onto the site • Since geotechnical hazards can extend in area to include several or more buildings, undamaged buildings in an unstable area may be posted limited entry or unsafe

4.7 Inspect the structural system from inside the building

• Before entering the building, look for falling hazards and consider the danger of collapse • Enter building • Check the structural system

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

• Look in stairwells, basements, mechanical rooms etc. to view the structural system • Examine the vertical load carrying system • Examine the lateral load carrying system • Check the different types of buildings using checklist

4.8 Inspect the Buildings in Critical Locations

Different types of buildings may suffer different types of damage. Masonry buildings have certain types of damage patterns and reinforced concrete buildings have other types. The buildings need to evaluate in detail with those identified damage patterns from past earthquakes. Different types of damage patters for masonry and reinforced concrete buildings are given in this section for the reference.

4.8.1 Earthquake Damage Patterns in Masonry Buildings

4.8.1.1 Corner Separation

Separation of orthogonal walls due to in-plane and out-of-plane stresses at corners is one of the most common damage patterns in masonry buildings. Separations in both sides of a wall result to an unstable condition leading to out-of-plane failure. The failure is due to lack of lateral support at two ends of the wall during out of plane loading.

This type of failure significantly reduces the lateral load carrying system of the building if all the corners are separated. The decision for restoration/retrofitting and demolition depends on extent of such damage. If only limited numbers or portion of the walls is separated, the buildings can be restored and retrofitted. If all/most of the corners are separated it is difficult to restore the original capacity by restoration and retrofitting.

Photo 5: Heavy corner separation Photo 6: Moderate corner separation

4.8.1.2 Diagonal Cracking

Diagonal cracking of piers either starting from corners of openings or in solid walls is another common type of damage to unreinforced masonry walls. The major reasons of the failure are either bed joint sliding or diagonal tension.

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Bed joint sliding: In this type of behavior, sliding occurs on bed joints. In this type of damage, sliding on a horizontal plane, and a stair-stepped diagonal crack where the head joints open and close to allow for movement on the bed joint. Pure bed joint sliding is a ductile mode with significant hysteretic energy absorption capability. If sliding continues without leading to a more brittle mode such as toe crushing, then gradual degradation of the cracking region occurs until instability is reached.

Diagonal Tension: Typical diagonal tension cracking—resulting from strong mortar, weak units, and high compressive stress—can be identified by diagonal cracks (“X” cracks) that propagate through the units. In many cases, the cracking is sudden, brittle, and vertical load capacity drops quickly. The cracks may then extend to the toe and the triangles above and below the crack separate.

Significance of diagonal cracking for these two types of cases is given in Table 3 and Table 4 respectively (Ref: FEMA 306, Chapter 7).

Table 3: Level and description of damage to masonry wall pier in diagonal cracking on bed joint sliding mode

LEVEL OF TYPICAL PERFORMANCE DESCRIPION OF DAMAGE DAMAGE RESTORATION MEASURES Insignificant- 1. Hairline cracks/spalled mortar in head Not necessary for restoration of Slight and bed joints either on a horizontal structural performance. (Measures may plane or in a stair stepped fashion has be necessary for restoration of nonstructural characteristics.) been initiated, but no offset along the crack has occurred and the crack plane or stair-stepping is not continuous across the pier. 2. No cracks in masonry units. Moderate 1. Horizontal cracks/spalled mortar at bed • Replacement or enhancement is joints indicating that in-plane offset required for full restoration of along the crack has occurred and/or seismic performance. opening of the head joints up to • For partial restoration of approximately 1/4”, creating a stair- performance: stepped crack pattern. Repoint spalled mortar and open 2. 5% of courses or fewer have cracks in head joints. masonry units. Heavy 1. Horizontal cracks/spalled mortar on Replacement or enhancement is bed joints indicating that in-plane offset required for full restoration of along the crack has occurred and/or seismic performance. opening of the head joints up to For partial restoration of approximately 1/2”, creating a stair- stepped crack pattern. performance: 2. 5% of courses or fewer have cracks in o Repoint spalled mortar and open masonry units. head joints. o Inject cracks and open head joints. Extreme Vertical load-carrying ability is Replacement or enhancement required. threatened.

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

• Stair-stepped movement is so significant that upper bricks have slid off their supporting brick. • Cracks have propagated into a significant number of courses of units. • Residual set is so significant that portions of masonry at the edges of the pier have begun or are about to fall.

Table 4: Level and description of damage to masonry wall pier in diagonal cracking on Diagonal Tension mode

LEVEL OF TYPICAL PERFORMANCE DESCRIPION OF DAMAGE DAMAGE RESTORATION MEASURES Insignificant- Hairline diagonal cracks in masonry units Not necessary for restoration of Slight in fewer than 5% of courses. structural performance. (Measures may be necessary for Restoration of nonstructural characteristics.) Moderate 1. Diagonal cracks in pier, many of • Repoint spalled mortar. which go through masonry units, with • Inject cracks. crack widths below 1/4”. 2. Diagonal cracks reach or nearly reach corners. 3. No crushing/spalling of pier corners. Heavy 1. Diagonal cracks in pier, many of Replacement or enhancement is which go through masonry units, with required for full restoration of seismic crack widths over 1/4”. Damage may performance. For partial restoration of performance: also include: • Replace/drypack damaged • Some minor crushing/spalling of units. pier corners and/or • Repoint spalled mortar. • Minor movement along or across • Inject cracks. crack plane.

Extreme Vertical load-carrying ability is Replacement or enhancement is threatened required • Significant movement or rotation along crack plane. • Residual set is so significant that portions of masonry at the edges of the pier have begun or are about to fall.

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Photo7: Diagonal cracking of masonry piers Photo 8: Diagonal cracking of solid wall starting from corner of openings

Photo 9: Diagonal cracking of solid wall (Bed joint sliding mode)

4.8.1.3 Out of Plane Failure flexural failure

Out-of-plane failures are common in URM buildings. Usually they occur due to the lack of adequate wall ties, bands or cross walls. When ties are adequate, the wall may fail due to out-of- plane bending between floor levels. In case of long walls, without cross walls, the failure mode is out of plane bending horizontally. One mode of is rigid-body rocking motion occurring on three cracks: one at the top of the wall, one at the bottom, and one at mid-height. As rocking increases, the mortar and masonry units at the crack locations can be degraded, and residual offsets can occur at the crack planes. The ultimate limit state is that the walls rock too far and overturn. Important variables are the vertical stress on the wall and the height-to-thickness ratio of the wall. Thus, walls at the top of buildings and slender walls are more likely to suffer damage.

Table 5 compares different level of damages for out-of-plane flexural mode of failure (Ref: FEMA 306, Chapter 7). Photos 10 to 11 show the out of plane failure of masonry walls.

Table 5: Out-of-plane flexural failure of masonry wall

LEVEL OF TYPICAL PERFORMANCE DESCRIPION OF DAMAGE DAMAGE RESTORATION MEASURES

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Insignificant- 1. Hairline cracks at floor/roof lines and Not necessary for restoration of Slight mid-height of stories. structural performance. 2. No out-of-plane offset or spalling of (Measures may be necessary for mortar along cracks. restoration of nonstructural characteristics.)

Moderate 1. Cracks at floor/roof lines and mid- Repoint spalled mortar: height of stories may have mortar spalls up to full depth of joint and possibly: • Out-of-plane offsets along cracks of up to 1/8”.

Heavy 1. Cracks at floor/roof lines and mid- Replacement or enhancement is height of stories may have mortar required for full restoration of seismic spalls up to full depth of joint. performance. 2. Spalling and rounding at edges of units For partial restoration of out-of-plane along crack plane. performance: 3. Out-of-plane offsets along cracks of up • Replace/dry pack damaged to 1/2”. units • Re-point spalled mortar

Extreme 1. Vertical-load-carrying ability is Replacement or enhancement required. threatened: • Significant out-of-plane or in-plane movement at top and bottom of piers “walking”). • Significant crushing/spalling of bricks at crack locations.

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Photo 10: Out of plane failure of stone wall Photo11: Out of plane failure of block wall

4.8.1.4 In-plane flexural failure

There are two types of failure mode for in-plane flexural failure. One with “Flexural Cracking/Toe Crushing/Bed Joint Sliding” and another with “Flexural Cracking/Toe Crushing” (Ref: FEMA 306)

Flexural Cracking/Toe Crushing/Bed Joint Sliding: This type of moderately ductile behavior has occurred in relatively short walls with L/heff ratio of about 1.7, in which bed joint sliding and toe crushing strength capacities are similar. Damage occurs in the following sequence. First, flexural cracking occurs at the heel of the wall. Then diagonally-oriented cracks appear at the toe of the wall, typically accompanied by spalling and crushing of the units. In some cases, toe crushing is immediately followed by a steep inclined crack propagating upward from the toe. Next, sliding occurs along a horizontal bed joint near the base of the wall, accompanied in some cases by stair stepped bed joint sliding at upper portions of the wall. With repeated cycles of loading, diagonal cracks increase. Finally, crushing of the toes or excessive sliding, leads to failure.

Flexural Cracking/Toe Crushing: This type of behavior typically occurs in stockier walls with L/heff > 1.25. Based on laboratory testing, four steps can usually be identified. First, flexural cracking happens at the base of the wall, but it does not propagate all the way across the wall. This can also cause a series of horizontal cracks to form above the heel. Second, sliding occurs on bed joints in the central portion of the pier. Third, diagonal cracks form at the toe of the wall. Finally, large cracks form at the upper corners of the wall. Failure occurs when the triangular portion of wall above the crack rotates off the crack or the toe crushes so significantly that vertical load is compromised. Note that, for simplicity, the figures below only show a single crack, but under cyclic loading, multiple cracks stepping in each direction are possible.

Significance of in-plane flexural cracking for these two types of cases is given in Table 6 and Table 7 respectively.

Table 6: In-plane flexural failure of masonry wall (Flexural Cracking/Toe Crushing/Bed Joint Sliding Case)

LEVEL OF TYPICAL PERFORMANCE DESCRIPION OF DAMAGE DAMAGE RESTORATION MEASURES Insignificant- 1. Horizontal hairline cracks in bed joints Not necessary for restoration of Slight at the heel of the wall. structural performance. (Measures may 2. Possibly diagonally-oriented cracks be necessary for restoration of nonstructural characteristics.) and minor spalling at the toe of the

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

wall.

Moderate 1. Horizontal cracks/spalled mortar at bed • Replace/dry pack damaged units. joints at or near the base of the wall • Repoint spalled mortar and open indicating that in-plane offset along the head joints. crack has occurred up to approximately • Inject cracks and open head joints. 1/4”. • Install pins and drilled dowels in 2. Possibly diagonally-oriented cracks toe regions. and spalling at the toe of the wall. Cracks extend upward several courses. 3. Possibly diagonally-oriented cracks at upper portions of the wall which may be in the units.

Heavy 1. Horizontal bed joint cracks near the • Replace/dry pack damaged units. base of the wall similar to Moderate, • Repoint spalled mortar and open except width is up to approximately head joints. 1/2”. • Inject cracks and open head joints. 2. Possibly extensive diagonally-oriented • Install pins and drilled dowels in cracks and spalling at the toe of the toe regions. wall. Cracks extend upward several courses. 3. Possibly diagonally-oriented cracks up to 1/2” at upper portions of the wall.

Extreme Vertical load-carrying ability is Replacement or enhancement required. threatened • Stair-stepped movement is so significant that upper bricks have slid off their supporting brick. • Toes have begun to disintegrate. • Residual set is so significant that portions of masonry at the edges of the pier have begun or are about to fall.

Table 7: In-plane flexural failure of masonry wall (Flexural Cracking/Toe Crushing/)

LEVEL OF TYPICAL PERFORMANCE DESCRIPION OF DAMAGE DAMAGE RESTORATION MEASURES Insignificant- 1. Horizontal hairline cracks in bed joints Not necessary for restoration of Moderate at the heel of the wall. structural performance. (Measures may 2. Horizontal cracking on 1-3 cracks in be necessary for restoration of nonstructural characteristics.) the central portion of the wall. No

offset along the crack has occurred and the crack plane is not continuous

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across the pier. 3. No cracks in masonry units. Heavy 1. Horizontal hairline cracks in bed joints at the heel of the wall. Replacement or enhancement is 2. Horizontal cracking on 1-3 cracks in required for full restoration of seismic performance. the central portion of the wall. Some offset along the crack may have For partial restoration of performance: occurred. 3. Diagonal cracking at the toe of the • Repoint spalled mortar. wall, likely to be through the units, and some of units may be spalled. • Inject cracks

Extreme 1. Horizontal hairline cracks in bed joints Replacement or enhancement is at the heel of the wall. required for full restoration of seismic 2. Horizontal cracking on 1 or more performance. For partial restoration of performance: cracks in the central portion of the • Replace/dry pack damaged units. wall. Offset along the crack will have • Repoint spalled mortar. occurred. 3. Diagonal cracking at the toe of the • Inject cracks. wall, likely to be through the units, and • Install pins and drilled dowels in some of units may be spalled. toe regions. 4. Large cracks have formed at upper portions of the wall. In walls with aspect ratios of L/heff >1.5, these cracks will be diagonally oriented; for more slender piers, cracks will be more vertical and will go through units.

Insignificant to Slight Damage Moderate Damage

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Heavy Damage

Figure 2: Illustrations on in-plane flexural failure of masonry wall (Flexural Cracking/Toe Crushing/Bed Joint Sliding Case)

Insignificant to Moderate Damage Heavy Damage

Extreme Damage

Fig 3: Illustrations on in-plane flexural failure of masonry wall (Flexural Cracking/Toe Crushing)

4.8.1.5 Delamination of Walls

Delamination of two wyths of masonry walls is another type of damage. This type of damage can be tested by sounding test described in section 4.9.1. At the last stage of this type of damage one wyth of the wall get collapsed. Phot 11 and 12 show the delamination of walls during earthquakes.

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Photo 11: Delamination of outer stone masonry Photo 12: Delamination of outer and inner stone wall masonry walls

4.8.2 Earthquake Damage Patterns in Reinforced Concrete Frame Buildings

4.8.2.1 Beam-Column Joint Failure

This type of failure is caused by weak connections of the framing elements. Distress is caused by over-strength of the members framing into the connection, leading to very high principal tension stresses. Table 8 gives different level of connection damage.

Table 8: Beam-column joint damage

LEVEL OF TYPICAL PERFORMANCE DESCRIPION OF DAMAGE DAMAGE RESTORATION MEASURES Insignificant- Slight X hairline cracks in joint Inject Cracks Slight Moderate X-cracks in joint become more extensive and widen to about 1/8”. Inject Cracks

Heavy • Extensive X-cracks in joint widen to • Remove spalled and loose concrete. about 1/4”. Remove and replace buckled or • Exterior joints show cover concrete fractured reinforcing. spalling off from back of joint. Some • Provide additional ties over the length side cover may also spall off. of the replaced bars. Patch concrete. Inject cracks. Extreme Significant loss of load carrying capacity Restore/replacement • Ties broken • Concrete came out • Bars Buckled

Illustrations and photographs of Beam-Column Joint damage are given below. Illustrations are from FEMA 306.

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Typical appearance of Insignificant-light Typical appearance of Moderate Damage Daamage

Typical appearance of Heavy Damage

Photo 13: Extreme Damage of Beam-Column Joint

4.8.2.2 Lap-splice Damage

Lack of sufficient lap length, in hinge zones, leads to eventual slippage of splice bars. The cover spalls off due to high compression stresses, exposing the core concrete and damaged lap splice zone. Table 9 gives different level of connection damagge.

Table 9: Lap Splice Damage LEVEL OF TYPICAL PERFORMANCE DESCRIPION OF DAMAGE DAMAGE RESTORATION MEASURES Insignificant- Flexural cracks at lap level. Slight hairline Inject cracks in frame. Slight vertical cracks. Moderate Tensile flexural cracks at floor slab level with some evidence of toe crushing over Inject cracks in frame. the bottom 1/2”. Longitudinal splitting cracks loosen the cover concrete. Heavy Significant spalling of the cover concrete Remove spalled and loose concrete. over the length of the lap splice, exposing Provide additional ties over the length the core and reinforcing of the exposed bars. Patch concrete. steel Apply composite overlay to damaged region of column. Extreme Significant loss of load carrying capacity Restore/replacement • Cover spalled • Core concrete cracked • Ties Broken • Reinforced bars slipped

Illustrations and photographs of lap-splice damage are given below. Illustrations are from FEMA 306.

23 Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Typical appearance of Insignificant-light Typical appearance of Moderate Damage Damage

Typical appearance of Heavy Damage Photo 14: Extreme Damage of Lap splice in column

4.8.2.3 Short Column Damagee

Short columns tend to attract seismic forces because of high stiffness relative to other columns in a story. Short column behavior may also occur in buildings with clerestory windows, or in buildings with partial height masonry infill panels.

If not adequately detailed, the columns may suffer a non-ductile shear failure which may result in partial collapse of the structure. A short column that can develop the shear capacity to develop the flexural strength over the clear height will have some ductility to prevent sudden non-ductile failure of the vertical support system.

Photos 15, 16 and 17 show the short column damage of the columns.

24 Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Photo 15: Slight-moderate damage Photo 16: Heavy Damage

Photo 17: Extreme Damage

4.8.2.4 Soft-story damage

This condition commonly occurs in buildings in urban areas where ground floor is usually open for parking or shops for commercial purposes. Soft stories usually are revealed by an abrupt change in inter-story drift. Although a comparison of the stiffness in adjacent stories is the direct approach, a simple first step might be to plot and compare the inter-story drifts.

The photos 18 show the soft story damage of the columns.

25 Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

drift drift

normal Soft story

Figure 4: Soft-story failure mechanism

Brick infill

Weak columns

Open floor Open floor

Ground shaking Ground shaking

Figure 5: Soft-story failure in a building with masonry infill

Photo 18: Earthquake damage due to soft story

26 Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

4.8.2.5 Shear/flexure cracks in column and beam members

Column and beam members of reinforced concrete buildings sustain two basic types of failure, namely: a) Flexure/Bending Failure: As the column/beam deform under increased loading, it can fail in two possible ways. If relatively more steel is present on the tension face, concrete crushes in compression; this is a brittle failure and is therefore undesirable. If less steel is present on the tension face, the steel yields first and redistribution occurs in the beam and eventually the concrete crushes in compression; this is a ductile failure. b) Shear Failure: A column/beam may also fail due to shearing action. A shear crack is inclined at 450 to the horizontal. Closed loops stirrups and ties are provided to avoid such shearing action. Shear damage occurs when the area of these stirrups is insufficient. Shear failure is brittle, and therefore, has larger impact if this type of damage observed.

Photo 19: Shear cracks in beam near to support Photo 20: Shear crack in beam near to support and at mid span

Photo 21: Shear crack in column Photo 22: Buckling of column bars

27 Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

4.8.2.6 Damage to Infill-Wall

Masonry infill panel in between concrete frames get damaged in in-plane and out-of plane. The out- of-plane failure pattern is discussed here.

Table 10 gives different level of infill wall damage (Ref: FEMA 306).

Table 10: Infill panel damage

LEVEL OF DESCRIPION OF DAMAGE TYPICAL PERFORMANCE DAMAGE RESTORATION MEASURES

Insignificant- Flexural cracking in the mortar beds around Re-point spalled mortar. Slight the perimeter, with hairline cracking in

mortar bed at mid-height of panel.

Moderate Crushing and loss of mortar along top, mid- Apply shotcrete, ferro-cement, or height, bottom and side mortar beds. composite overlay to the infill. Possibly some in-plane damage, as evidenced by hair-line X-cracks in the central panel area.

Heavy Severe corner-to-corner cracking with some Remove and replace infill. out-of plane dislodgment of masonry. Top,

bottom and mid height mortar bed is completely crushed and/or missing. There is some out-of-plane dislodgment of masonry. Concurrent in-plane damage should also be expected, as evidenced by extensive X- cracking

Extreme The infill panel has failed in out of plane Rebuilt infill wall

Moderate damage to Infill panel Heavy damage to infill panel

Figure 6: Illustration of infill panel damage.

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Photo 23: Moderate-Heavy Damage to Infill wall Photo 24: Extreme Damage to Infill wall

4.9 Conduct Test

4.9.1 Rebound Hammer Test

Description

A rebound hammer provides a method for assessing the in-situ compressive strength of concrete. In this test, a calibrated hammer impact is applied to the surface of the concrete. The amount of rebound of the hammer is measured and correlated with the manufacturer's data to estimate the strength of the concrete. The method has also been used to evaluate the strength of masonry.

Equipment

A calibrated rebound hammer is a single piece of equipment that is hand operated

Execution

The person operating the equipment places the impact plunger of the hammer against the concrete and then presses the hammer until the hammer releases. The operator then records the value on the scale of the hammer. Typically three or more tests are conducted at a location. If the values from the tests are consistent, record the average value. If the values vary significantly, additional readings should be taken until a consistent pattern of results is obtained.

Since the test is relatively rapid, a number of test locations can be chosen for each wall. The values from the tests are converted into compressive strength using tables prepared by the manufacturer of the rebound hammer.

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Photo 25: Use of Rebound hammer Photo 26: Rebound hammer

Personal Qualification

A technician with minimal training can operate the rebound hammer. An engineer experienced with rebound hammer data should be available to supervise to verify that any anomalous values can be explained.

Reporting Requirements

The personnel conducting the tests should provide sketches of the wall, indicating the location of the tests and the findings. The sketch should include the following information:

• Mark the location of the test marked on either a floor plan or wall elevation.

• Record the number of tests conducted at a given location.

• Report either the average of actual readings or the average values converted into compressive strength along with the method used to convert the values into compressive strength.

• Report the type of rebound hammer used along with the date of last calibration.

• Record the date of the test.

• List the responsible engineer overseeing the test and the name of the company conducting the test.

Limitations

The rebound hammer does not give a precise value of compressive strength, but rather an estimate of strength that can be used for comparison. Frequent calibration of the unit is required (ACI, 1994). Although manufacturers’ tables can be used to estimate the concrete strength, better estimates can be obtained by removing core samples at selected locations where the rebound testing has been performed. The core samples are then subjected to compression tests. The rebound values from other

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment) areas can be compared with the rebound values that correspond to the measured core compressive strength.

The results of the rebound hammer tests are sensitive to the quality of the concrete on the outer several inches of the wall. More reproducible results can be obtained from formed surfaces rather than from finished surfaces. Surface moisture and roughness can also affect the readings. The impact from the rebound hammer can produce a slight dimple in the surface of the wall. Do not take more than one reading at the same spot, since the first impact can affect the surface, and thus affect the results of a subsequent test.

When using the rebound hammer on masonry, the hammer should be placed at the centre of the masonry unit. The values of the tests on masonry reflect the strength of the masonry unit and the mortar. This method is only useful in assessing the strength of the outer wythe of a multi-wythe wall. Rebound Hammer Test

4.9.2 Rebar Detection Test

Description

Cover-meter is the general term for a rebar detector used to determine the location and size of reinforcing steel in a concrete or masonry wall. The basic principle of most rebar detectors is the interaction between the reinforcing bar and a low frequency magnetic field. If used properly, many types of rebar detectors can also identify the amount of cover for the bar and/or the size of the bar. Rebar detection is useful for verifying the construction of the wall, if drawings are available, and in preparing as-built data if no previous construction information is available.

Equipment

Several types and brands of rebar detectors are commercially available. The two general classes are those based on the principle of magnetic reluctance and those based on the principle of eddy. The various models can have a variety of features including analogue or digital readout, audible signal, one handed operation, and readings for reinforcing bars and prestressing tendons. Some models can store the data on floppy disks to be imported into computer programs for plotting results.

Conducting Test

The unit is held away from metallic objects and calibrated to zero reading. After calibration, the unit is placed against the surface of the wall. The orientation of the probe should be in the direction of the rebar that is being detected. The probe is slid slowly along the wall, perpendicular to the orientation of the probe, until an audible or visual spike in the readout is encountered.

The probe is passed back and forth over the region of the spike to find the location of the maximum reading, which should correspond to the location of the rebar. This location is then marked on the wall. The procedure is repeated for the perpendicular direction of reinforcing.

If size of the bar is known, the cover-meter readout can be used to determine the depth of the reinforcing bar. If the depth of the bar is known, the readout can be used to determine the size of the bar. If neither quantity is known, most rebar detectors can be used to determine both the size and the depth using a spacer technique.

The process involves recording the peak reading at a bar and then introducing a spacer of known thickness between the probe and the surface of the wall. A second reading is then taken. The two readings are compared to estimate the bar size and depth. Intrusive testing can be used to help

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment) interpret the data from the detector readings. Selective removal of portions of the wall can be performed to expose the reinforcing bars. The rebar detector can be used adjacent to the area of removal to verify the accuracy of the readings.

Photo 27: Use of rebar detector for verification of Photo 28: Ferro-scan detector reinforcement details

Personnel Qualifications

The personnel operating the equipment should be trained and experienced with the use of the particular model of cover-meter being used and should understand the limitations of the unit.

Reporting Requirements

The personnel conducting the tests should provide a sketch of the wall indicating the location of the testing and the findings. The sketch should include the following information:

• Mark the locations of the test on either a floor plan or wall elevation.

• Report the results of the test, including bar size and spacing and whether the size was verified.

• List the type of rebar detector used.

• Report the date of the test.

• List the responsible engineer overseeing the test and the name of the company conducting the test.

Limitations

Pulse-velocity measurements require access to both sides of the wall. The wall surfaces need to be relatively smooth. Rough areas can be ground smooth to improve the acoustic coupling. Couplant must be used to fill the air space between the transducer and the surface of the wall. If air voids exist between the transducer and the surface, the travel time of the pulse will increase, causing incorrect readings.

Some couplant materials can stain the wall surface. Non-staining gels are available, but should be checked in an inconspicuous area to verify that it will not disturb the appearance.

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Embedded reinforcing bars, oriented in the direction of travel of the pulse, can affect the results, since the ultrasonic pulses travel through steel at a faster rate than will significantly affect the results. The moisture content of the concrete also has a slight effect (up to about 2 percent) on the pulse velocity.

Pulse-velocity measurements can detect the presence of voids or discontinuities within a wall; however, these measurements cannot determine the depth of the voids.

4.9.3 In-Situ Testing In-Place Shear

Description

The shear strength of unreinforced masonry construction depends largely on the strength of the mortar used in the wall. An in-place shear test is the preferred method for determining the strength of existing mortar. The results of these tests are used to determine the shear strength of the wall.

Equipment

• Chisels and grinders are needed to remove the bricks and mortar adjacent to the test area. • A hydraulic ram, calibrated and capable of displaying the applied load. • A dial gauge, calibrated to 0.001 inch.

Execution

Prepare the test location by removing the brick, including the mortar, on one side of the brick to be tested. The head joint on the opposite side of the brick to be tested is also removed. Care must be exercised so that the mortar joint above or below the brick to be tested is not damaged.

The hydraulic ram is inserted in the space where the brick was removed. A steel loading block is placed between the ram and the brick to be tested so that the ram will distribute its load over the end face of the brick. The dial gauge can also be inserted in the space.

The brick is then loaded with the ram until the first indication of cracking or movement of the brick. The ram force and associated deflection on the dial gage are recorded to develop a force-deflection plot on which the first cracking or movement should be indicated. A dial gauge can be used to calculate a rough estimate of shear stiffness.

Inspect the collar joint and estimate the percentage of the collar joint that was effective in resisting the force from the ram. The brick that was removed should then be replaced and the joints repointed.

Photo 29-30: Test set up for In-situ Shear test

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Personnel Qualifications

The technician conducting this test should have previous experience with the technique and should be familiar with the operation of the equipment. Having a second technician at the site is useful for recording the data and watching for the first indication of cracking or movement. The structural engineer or designee should choose test locations that provide a representative sampling of conditions.

Reporting Results

The personnel conducting the tests should provide a written report of the findings to the evaluating engineer. The results for the in-place shear tests should contain, at a minimum, the following information for each test location:

• Describe test location or give the identification number provided by the engineer. • Specify the length and width of the brick that was tested, and its cross-sectional area. • Give the maximum mortar strength value measured during the test, in terms of force and stress. • Estimate the effective area of the bond between the brick and the grout at the collar joint. • Record the deflection of the brick at the point of peak applied force. • Record the date of the test. • List the responsible engineer overseeing the test and the name of the company conducting the test.

Limitations

This test procedure is only capable of measuring the shear strength of the mortar in the outer wythe of a multi-wythe wall. The engineer should verify that the exterior wythe being tested is a part of the structural wall, by checking for the presence of header courses. This test should not be conducted on veneer wythes.

Test values from exterior wythes may produce lower values when compared with tests conducted on inner wythes. The difference can be due to weathering of the mortar on the exterior wythes. The exterior brick may also have a reduced depth of mortar for aesthetic purposes.

The test results can only be qualitatively adjusted to account for the presence of mortar in the collar joints. If mortar is present in the collar joint, the engineer or technician conducting the test is not able to discern how much of that mortar actually resisted the force from the ram.

The personnel conducting the tests must carefully watch the brick during the test to accurately determine the ram force at which first cracking or movement occurs. First cracking or movement indicates the maximum force, and thus the maximum shear strength. If this peak is missed, the values obtained will be based only on the sliding friction contribution of the mortar, which will be less than the bond strength contribution.

4.10 Detail Evaluation

Detail evaluation form is given in Annex IV of this guideline. Form should be filled in reference with section 4.1 to 4.9 mentioned above. The detail evaluation should also recommend different grade of damage. The damage grade goes from damage grade 1 to damage grade 5. Different level of damage grades with photographs for masonry and reinforced concrete buildings are given in section 4.11 of this guideline.

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

4.11 Identification of Damage Levels

4.11.1.1 Earthquake damage grades of Masonry buildings with flexible floor and roof

Damage Grade 1

Thin cracks in plaster, falling of plaster bits in Building need not be vacated, only architectural limited parts, fall of loose stone from upper part repairs needed, Seismic strengthening advised of building in rare cases

Damage Grade 2

Thin cracks in many walls, falling of plaster in Architecture repairs needed, Seismic last bits over large area, damage to non-structural strengthening advised. parts like chimney, projecting cornices; The load carrying capacity s not reduced appreciably.

35 Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Damage Grade 3

Large and extensive cracks in most walls, roof Cracks in wall need grouting, architectural repairs tiles detach, tilting or falling of chimneys, failure required, Seismic strengthening advised of individual non-structural elements such as partition/ gable walls. Load carrying capacity of structure is partially reduced.

Damage Grade 4

Gaps occur in walls, walls collapse, partial Vacate the building, demolish and construct or structural failure of floor/ roof, Building takes a extensive restoration and strengthening dangers state.

36 Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Damage Grade 5

Total or near total collapse Clear the site and reconstruction

4.11.1.2 Earthquake damage grades of Masonry buildings with rigid floor and roof

Damage Grade 1

Damage Grade 2

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Damage Grade 3

Damage Grade 4

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Gaps occur in walls, walls collapse, partial Vacate the building, demolish and construct or structural failure of floor/ roof, Building takes a extensive restoration and strengthening dangers state.

Damage Grade 5

Total or near total collapse Clear the site and reconstruction

4.11.1.3

4.11.1.4 Earthquake damage grades of Reinforced Concrete Buildings

Damage Grade 1

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Fine cracks in plaster over frame members or in Building need not be vacated, only architectural walls at the base, Fine cracks in partitions and repairs needed, Seismic strengthening advised. infill

Damage Grade 2

Cracks in columns and beams of frame and in Architecture repairs needed, Seismic structural walls, Cracks in partition and infill strengthening advised. walls, fall of brittle plaster and cladding, falling mortar from joints of wall panel

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Damage Grade 3

Cracks in column and beam at the base, spalling Cracks in wall need grouting, architectural repairs of concrete covers, buckling of steel bars, Large required, Seismic strengthening advised cracks in partitions and infill walls, failure of individual infill panels

Damage Grade 4

Large cracks in structural elements with Vacate the building, demolish and construct or compression failure of concrete and fracture of extensive restoration and strengthening rebars, bond failure of beam bars, tilting of columns, collapse of few columns or single upper floor

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Damage Grade 5

Collapse of ground floor or parts of the building Clear the site and reconstruction

5. References 18. Arya, A. S. et al; 1986, Guidelines for Earthquake Resistant Non-engineered Construction, International Association for Earthquake Engineering. 19. Bothara, J. K., Pandey, B. H., Guragain, R., 2004, Retrofitting of Low Strength Masonry School Buildings, NZSEE, 20. Building Construction under Seismic conditions in Balkan Region, 1983, Repair and Strengthening of Reinforced Concrete, Stone, Brick-masonry Buildings, UNDP/ UNIDO/RER 79/015, Vienna. 21. Central Public Works Department, Indian Building Congress in association with Indian Institute of Technology Madras, Handbook on “Seismic Retrofit of Buildings”, 2008 22. EMS, 1998, European Macro-seismic Scale, ONLINE, http://www.gfz-potsdam.de/pb5/pb53/projekt/ems/core/emsa_cor.htm 23. Federal Emergency Management Agency, (FEMA 273), NEHRP Guidelines For The Seismic Rehabilitation Of Buildings, Building Seismic Safety Council, Washington D. C., 1988. 24. Federal Emergency Management Agency, (FEMA 274), NEHRP Commentary On the Guidelines For The Seismic Rehabilitation Of Buildings, Building Seismic Safety Council, Washington D. C., 1988. 25. Federal Emergency Management Agency, (FEMA 356), Pre-standard and Commentary for the Seismic Rehabilitation of Buildings, Building Seismic Safety Council, Washington D. C., 2000. 26. IS 1893:2002; Criteria for earthquake resistant design of structures, Bureau of Indian Standard. 27. JICA, 2002, The Study on Earthquake Disaster Mitigation in the Kathmandu Valley, Kingdom of Nepal, Japan International Corporation Agency and Ministry of Home Affairs, GoN.

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

28. NBC 105-1994, Seismic Design of Buildings in Nepal, Govt. of Nepal, Ministry of Housing and Physical Planning, Department of Buildings, Nepal, 1995. 29. NBC 203-1994, Guidelines for Earthquake Resistant Building Construction: Low Strength Masonry, Govt. of Nepal, Ministry of Housing and Physical Planning, Department of Buildings, Nepal, 1995. 30. New Zealand National Society for Earthquake Engineering, 1995, Guidelines for Assessing and Strengthening Earthquake Risk Building: Unreinforced Masonry (Draft Copy), New Zealand National Society for Earthquake Engineering. 31. Procedure for post-earthquake safety evaluation of buildings, (ATC 20), Applied technology council, 3 Twin Dolphin Drive, Suite 275 Redwood City, California 94065 32. Federal Emergency Management Agency, (FEMA 154), Rapid Visual Screening of Buildings for Potential Seismic Hazards: A Handbook. Second Edition, Building Seismic Safety Council, Washington D. C., 1988. 33. Federal Emergency Management Agency, (FEMA 306), Evaluation of Earthquake Damaged Concrete and Masonry Wall Buildings: Basic Procedures Manual, Building Seismic Safety Council, Washington D. C., 1988. 34. Federal Emergency Management Agency, (FEMA 307), Evaluation of Earthquake Damaged Concrete and Masonry Wall Buildings: Technical Resources, Building Seismic Safety Council, Washington D. C., 1988.

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

35.

ANNEXES

Annex I: Examples of Rapid Evaluation

Red Green

Yellow Red

Green Red

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Yellow Red

Green Red

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Annex II: Examples of Detailed Evaluated Buildings

Red Red

Green Yellow

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Annex III: Rapid Evaluation Form

Rapid Evaluation Safety Assessment Form Inspection Inspector ID: Inspection date and time: AM PM Organization: Areas inspected: Exterior only Exterior and interior

Comments: 100%

Further Actions Check the boxes below only if further actions are needed. Barricades needed in the following areas: Detailed evaluation recommended: Structural Geotechnical Other

Comments:

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Annex IV: Detail Evaluation Form

Detailed Evaluation Safety Assessment Form Inspection Inspector ID: Inspection date and time: AM PM Organization: Areas inspected: Exterior only Exterior and interior

Sketch (Optional) Provide a sketch of the building or damage portions, Indicate damage points. Estimated Building Damage

If requested by the jurisdiction, estimate building damage (repair cost ÷replacement cost, excluding contents).

None

0‐1%

1‐10%

10‐30%

30‐60%

60‐100%

100%

Seismic Vulnerability Evaluation Guideline for Private and Public Buildings (Part II: post-disaster damage assessment)

Detailed Evaluation Safety Assessment Form Page 2

Recommendations: Damage Grade Grade 1 Grade 2 Grade 3 Grade 4 Grade 5

Retrofit / Demolition Repair Retrofit Demolish

Further Actions Check the boxes below only if further actions are needed. Barricades needed in the following areas: Detailed evaluation recommended: Structural Geotechnical Other

Comments:

Appendix C Indian Standard - Repair and Seismic Strengthening of Buildings - Guidelines

REPORT June 2015 Nepal Post-Earthquake Building Safety Evaluations

Appendix D Tip 12: How do Brick Masonry Houses behave during Earthquake?

REPORT June 2015 Nepal Post-Earthquake Building Safety Evaluations Learning

Earthquake Design and Earthquake Tip 12 Construction

How do brick masonry houses behave during earthquakes?

Behaviour of Brick Masonry Walls by horizontal forces due to earthquake. A wall topples Masonry buildings are brittle structures and one of down easily if pushed horizontally at the top in a the most vulnerable of the entire building stock under direction perpendicular to its plane (termed weak strong earthquake shaking. The large number of direction), but offers much greater resistance if pushed human fatalities in such constructions during the past along its length (termed strong direction) (Figure 1b). earthquakes in India corroborates this. Thus, it is very The ground shakes simultaneously in the vertical important to improve the seismic behaviour of and two horizontal directions during earthquakes masonry buildings. A number of earthquake-resistant (IITK-BMTPC Earthquake Tip 5). However, the features can be introduced to achieve this objective. horizontal vibrations are the most damaging to normal Ground vibrations during earthquakes cause masonry buildings. Horizontal inertia force developed inertia forces at locations of mass in the building. at the roof transfers to the walls acting either in the These forces travel through the roof and walls to the weak or in the strong direction. If all the walls are not foundation. The main emphasis is on ensuring that tied together like a box, the walls loaded in their weak these forces reach the ground without causing major direction tend to topple (Figure 2a). damage or collapse. Of the three components of a To ensure good seismic performance, all walls masonry building (roof, wall and foundation) (Figure must be joined properly to the adjacent walls. In this 1a), the walls are most vulnerable to damage caused way, walls loaded in their weak direction can take advantage of the good lateral resistance offered by walls loaded in their strong direction (Figure 2b). Further, walls also need to be tied to the roof and Walls foundation to preserve their overall integrity. Roof Toppling A

Foundation B (a) Basic components of a masonry building

Pushed in the plane of the wall

A Direction of earthquake shaking A Weak Direction (a) For the direction of earthquake shaking shown, wall B tends to fail Toothed joints in masonry A courses B or L-shaped Direction of B dowel bars earthquake shaking

Strong Toppling B Direction A

Pushed perpendicular to the plane of the wall Direction of earthquake Direction of shaking earthquake shaking (b) Direction of force on a wall critically determines (b) Wall B properly connected to Wall A (Note: roof its earthquake performance is not shown): Walls A (loaded in strong direction)

support Walls B (loaded in weak direction) Figure 1: Basic components of a masonry building – walls are sensitive to direction of Figure 2: Advantage sharing between walls –

earthquake forces. only possible if walls are well connected.

IITK-BMTPC Earthquake Tip 12

How do brick masonry houses behave during earthquakes? page 2 How to Improve Behaviour of Masonry Walls Choice and Quality of Building Materials Masonry walls are slender because of their small Earthquake performance of a masonry wall is very thickness compared to their height and length. A sensitive to the properties of its constituents, namely simple way of making these walls behave well during masonry units and mortar. The properties of these earthquake shaking is by making them act together as materials vary across India due to variation in raw a box along with the roof at the top and with the materials and construction methods. A variety of foundation at the bottom. A number of construction masonry units are used in the country, e.g., clay bricks aspects are required to ensure this box action. Firstly, (burnt and unburnt), concrete blocks (solid and connections between the walls should be good. This hollow), stone blocks. Burnt clay bricks are most can be achieved by (a) ensuring good interlocking of commonly used. These bricks are inherently porous, the masonry courses at the junctions, and (b) and so they absorb water. Excessive porosity is employing horizontal bands at various levels, detrimental to good masonry behaviour because the particularly at the lintel level. Secondly, the sizes of bricks suck away water from the adjoining mortar, door and window openings need to be kept small. The which results in poor bond between brick and mortar, smaller the openings, the larger is the resistance and in difficulty in positioning masonry units. For this offered by the wall. Thirdly, the tendency of a wall to reason, bricks with low porosity are to be used, and topple when pushed in the weak direction can be they must be soaked in water before use to minimise reduced by limiting its length-to-thickness and height- the amount of water drawn away from the mortar. to-thickness ratios (Figure 3). Design codes specify Various mortars are used, e.g., mud, cement-sand, limits for these ratios. A wall that is too tall or too long or cement-sand-lime. Of these, mud mortar is the in comparison to its thickness, is particularly weakest; it crushes easily when dry, flows outward vulnerable to shaking in its weak direction (Figure 3). and has very low earthquake resistance. Cement-sand mortar with lime is the most suitable. This mortar mix provides excellent workability for laying bricks, stretches without crumbling at low earthquake shaking, and bonds well with bricks. The earthquake response of masonry walls depends on the relative Overturning strengths of brick and mortar. Bricks must be stronger than mortar. Excessive thickness of mortar is not Overturning desirable. A 10mm thick mortar layer is generally satisfactory from practical and aesthetic considerations. Indian Standards prescribe the preferred types and grades of bricks and mortars to be used in buildings in each seismic zone. Soil Soil Related Earthquake Tip Thick Wall (1½ brick) Short Wall (1 brick) Tip 5: What are the seismic effects on structures? versus versus Resource Material Thin Wall (1 brick) Tall Wall (1 brick) IS 1905, (1987), Indian Standard Code of Practice for Structural Use of Unreinforced Masonry, Bureau of Indian Standards, New Delhi. IS 4326, (1993), Indian Standard Code of Practice for Earthquake Resistant Design and Construction of Buildings, Bureau of Indian Standards, Inertia force Large portion of wall New Delhi. from roof not supported by IS 13828, (1993), Indian Standard Guidelines for Improving Earthquake cross walls Resistance of Low-strength Masonry Buildings, Bureau of Indian Standards, New Delhi.

Cross Wall Paulay,T., and Priestley,M.J.N., (1992), Seismic Design of Reinforced Concrete and Masonry Buildings, John Wiley & Sons, New York. Cross Wall Long Wall Next Upcoming Tip Why should masonry houses have simple structural configuration?

Authored by:

C.V.R.Murty Indian Institute of Technology Kanpur Kanpur, India

Sponsored by: Short Wall Building Materials and Technology Promotion Good support offered Council, New Delhi, India by cross walls This release is a property of IIT Kanpur and BMTPC New Figure 3: Slender walls are vulnerable – height Delhi. It may be reproduced without changing its contents and length to be kept within limits. Note: In this and with due acknowledgement. Suggestions/comments figure, the effect of roof on walls is not shown. may be sent to: [email protected]. Visit www.nicee.org or www.bmtpc.org, to see previous IITK-BMTPC Earthquake Tips. March 2003

Appendix E Tip 13: Why Masonry Building should have Simple Structural Configuration?

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Earthquake Design and Earthquake Tip 13 Construction

Why should masonry buildings have simple structural configuration?

Box Action in Masonry Buildings consider a four-wall system of a single storey masonry Brick masonry buildings have large mass and building (Figure 2). During earthquake shaking, inertia hence attract large horizontal forces during earthquake forces act in the strong direction of some walls and in shaking. They develop numerous cracks under both the weak direction of others (See IITK-BMTPC compressive and tensile forces caused by earthquake Earthquake Tip 12). Walls shaken in the weak direction shaking. The focus of earthquake resistant masonry seek support from the other walls, i.e., walls B1 and B2 building construction is to ensure that these effects are seek support from walls A1 and A2 for shaking in the sustained without major damage or collapse. direction shown in Figure 2. To be more specific, wall Appropriate choice of structural configuration can B1 pulls walls A1 and A2, while wall B2 pushes help achieve this. against them. At the next instance, the direction of The structural configuration of masonry buildings shaking could change to the horizontal direction includes aspects like (a) overall shape and size of the perpendicular to that shown in Figure 2. Then, walls A building, and (b) distribution of mass and (horizontal) and B change their roles; Walls B1 and B2 become the lateral load resisting elements across the building. strong ones and A1 and A2 weak. Large, tall, long and unsymmetric buildings perform Thus, walls transfer loads to each other at their poorly during earthquakes (IITK-BMTPC Earthquake junctions (and through the lintel bands and roof). Tip 6). A strategy used in making them earthquake- Hence, the masonry courses from the walls meeting at resistant is developing good box action between all the corners must have good interlocking. For this reason, elements of the building, i.e., between roof, walls and openings near the wall corners are detrimental to good foundation (Figure 1). Loosely connected roof or seismic performance. Openings too close to wall unduly slender walls are threats to good seismic corners hamper the flow of forces from one wall to behaviour. For example, a horizontal band introduced another (Figure 3). Further, large openings weaken at the lintel level ties the walls together and helps to walls from carrying the inertia forces in their own make them behave as a single unit. plane. Thus, it is best to keep all openings as small as possible and as far away from the corners as possible. Roof that stays together as a single Good integral unit during earthquakes Inertia force connection from roof between roof and walls Walls with Inertia force from roof small openings A1

Lintel Band B2 B1

Good Stiff Foundation connection between walls and Good connection foundation Regions at wall corners where load Direction of transfer Figure 1: Essential requirements to ensure box earthquake takes place action in a masonry building. shaking from one

wall to Influence of Openings another

Openings are functional necessities in buildings. Figure 2: Regions of force transfer from weak walls to strong walls in a masonry building – However, location and size of openings in walls wall B1 pulls walls A1 and A2, while wall B2 assume significance in deciding the performance of pushes walls A1 and A2. masonry buildings in earthquakes. To understand this,

IITK-BMTPC Earthquake Tip 13

Why should masonry buildings have simple structural configuration? page 2

Large window opening Tall reduces the slender wall wall strength in its strong direction Inertia force of roof mass Damage

Damage Diagonal bracing effect Door opening close to wall corner weakens the connection between walls Damage

Figure 3: Openings weaken walls in a masonry

building –a single closed horizontal band must (a) Damage in building with rigidly built-in staircase be provided above all of them.

Reinforced Concrete Earthquake-Resistant Features Stair Case Tower Indian Standards suggest a number of earthquake- (or Mumty) resistant measures to develop good box-type action in masonry buildings and improve their seismic performance. For instance, it is suggested that a Gap building having horizontal projections when seen from the top, e.g., like a building with plan shapes L, T, E and Y, be separated into (almost) simple rectangular blocks in plan, each of which has simple and good earthquake behaviour (IITK-BMTPC Earthquake Tip 6). During earthquakes, separated blocks can oscillate independently and even hammer each other if they are too close. Thus, adequate gap is necessary between these different blocks of the building. The Indian Standards suggest minimum seismic separations between blocks of buildings. However, it may not be (b) Building with separated staircase necessary to provide such separations between blocks, Figure 4: Earthquake-resistant detailing of if horizontal projections in buildings are small, say up to ~15-20% of the length of building in that direction. staircase in masonry building – must be carefully designed and constructed. Inclined staircase slabs in masonry buildings offer another concern. An integrally connected staircase slab acts like a cross-brace between floors and transfers Related Earthquake Tip large horizontal forces at the roof and lower levels Tip 5: What are the seismic effects on structures? (Figure 4a). These are areas of potential damage in Tip 6: How architectural features affect buildings during earthquakes? masonry buildings, if not accounted for in staircase Tip12: How brick masonry houses behave during earthquakes? design and construction. To overcome this, sometimes, Next Upcoming Tip staircases are completely separated (Figure 4b) and Why are horizontal bands necessary in masonry buildings? built on a separate reinforced concrete structure.

Adequate gap is provided between the staircase tower Authored by: and the masonry building to ensure that they do not C.V.R.Murty pound each other during strong earthquake shaking. Indian Institute of Technology Kanpur Resource Material Kanpur, India IS 1905, (1987), Indian Standard Code of Practice for Structural Use of Sponsored by: Unreinforced Masonry, Bureau of Indian Standards, New Delhi. IS 42326, (1993), Indian Standard Code of Practice for Earthquake Building Materials and Technology Promotion Resistant Design and Construction of Buildings, Bureau of Indian Council, New Delhi, India Standards, New Delhi.

IS 13828, (1993), Indian Standard Guidelines for Improving Earthquake This release is a property of IIT Kanpur and BMTPC New

Resistance of Low-strength Masonry Buildings, Bureau of Indian Delhi. It may be reproduced without changing its contents and with due acknowledgement. Suggestions/comments Standards, New Delhi. Tomazevic,M., (1999), Earthquake Resistant Design of Masonry may be sent to: [email protected]. Visit www.nicee.org or Buildings, Imperial College Press, London, UK. www.bmtpc.org, to see previous IITK-BMTPC Earthquake Tips. April 2003

Appendix F Tip14: Why Horizontal Bands are required in Masonry Buildings?

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Earthquake Design and Earthquake Tip 14 Construction

Why are horizontal bands necessary in masonry buildings?

Role of Horizontal Bands flat timber or CGI sheet roof, roof band needs to be Horizontal bands are the most important provided. In buildings with pitched or sloped roof, the earthquake-resistant feature in masonry buildings. The roof band is very important. Plinth bands are bands are provided to hold a masonry building as a primarily used when there is concern about uneven single unit by tying all the walls together, and are settlement of foundation soil. similar to a closed belt provided around cardboard The lintel band ties the walls together and creates boxes. There are four types of bands in a typical a support for walls loaded along weak direction from masonry building, namely gable band, roof band, lintel walls loaded in strong direction. This band also band and plinth band (Figure 1), named after their reduces the unsupported height of the walls and location in the building. The lintel band is the most thereby improves their stability in the weak direction. important of all, and needs to be provided in almost all During the 1993 Latur earthquake (Central India), the buildings. The gable band is employed only in intensity of shaking in Killari village was IX on MSK buildings with pitched or sloped roofs. In buildings scale. Most masonry houses sustained partial or with flat reinforced concrete or reinforced brick roofs, the complete collapse (Figure 2a). On the other hand, there roof band is not required, because the roof slab also was one masonry building in the village, which had a plays the role of a band. However, in buildings with lintel band and it sustained the shaking very well with hardly any damage (Figure 2b). Roof Masonry above lintel Lintel Band

Masonry below lintel

Wall Plinth Band

Foundation

Soil

(a) Building with Flat Roof

(a) Building with no horizontal lintel band: collapse of roof and walls Gable-roof connection

Gable Roof Band Band Truss-wall connection

Floor-walls Lintel connection Band

Lintel Band

Plinth Cross wall (b) A building with horizontal lintel band in Killari connection Band village: no damage Peripheral wall connection Figure 2: The 1993 Latur Earthquake (Central (b) Two-storey Building with Pitched Roof India) - one masonry house in Killari village had Figure 1: Horizontal Bands in masonry building – horizontal lintel band and sustained the shaking

Improve earthquake-resistance. without damage.

IITK-BMTPC Earthquake Tip 14

Why are horizontal bands necessary in masonry buildings? page 2 Design of Lintel Bands Wood Spacers During earthquake shaking, the lintel band undergoes bending and pulling actions (Figure 3). To resist these actions, the construction of lintel band Wood requires special attention. Bands can be made of wood Runners (including bamboo splits) or of reinforced concrete A

(RC) (Figure 4); the RC bands are the best. The straight B lengths of the band must be properly connected at the wall corners. This will allow the band to support walls loaded in their weak direction by walls loaded in their (a) Wooden Band strong direction. Small lengths of wood spacers (in wooden bands) or steel links (in RC bands) are used to make the straight lengths of wood runners or steel bars act together. In wooden bands, proper nailing of Steel Links straight lengths with spacers is important. Likewise, in A RC bands, adequate anchoring of steel links with steel Steel Bars bars is necessary. B Correct Bending of Pulling of Practices Lintel Band Lintel Band

Lintel Band

Direction of Inertia Force

Incorrect Practice

(b) RC Band

Figure 4: Horizontal Bands in masonry buildings – RC bands are the best.

Direction of Related Earthquake Tip earthquake Tip 5: What are the seismic effects on structures? shaking Tip12: How brick masonry houses behave during earthquakes? Tip13: Why masonry buildings should have simple structural configuration?

Resource Material 150 75 mm mm IAEE, (1986), Guidelines for Earthquake Resistant Non-Engineered Construction, International Association for Earthquake Engineering, Tokyo, available on www.nicee.org. IS 4326, (1993), Indian Standard Code of Practice for Earthquake Resistant Design and Construction of Buildings, Bureau of Indian Standards, New Delhi. Small Large IS 13828, (1993), Indian Standard Guidelines for Improving Earthquake Resistance of Low-strength Masonry Buildings, Bureau of Indian Cross-section of Standards, New Delhi.

Lintel Bands Next Upcoming Tip Why is vertical reinforcement required in masonry buildings?

Figure 3: Bending and pulling in lintel bands – Bands must be capable of resisting these. Authored by:

C.V.R.Murty

Indian Institute of Technology Kanpur Indian Standards Kanpur, India The Indian Standards IS:4326-1993 and IS:13828 Sponsored by: (1993) provide sizes and details of the bands. When Building Materials and Technology Promotion wooden bands are used, the cross-section of runners is Council, New Delhi, India to be at least 75mm×38mm and of spacers at least 50mm×30mm. When RC bands are used, the minimum This release is a property of IIT Kanpur and BMTPC New Delhi. It may be reproduced without changing its contents thickness is 75mm, and at least two bars of 8mm and with due acknowledgement. Suggestions/comments diameter are required, tied across with steel links of at may be sent to: [email protected]. Visit www.nicee.org or least 6mm diameter at a spacing of 150 mm centers. www.bmtpc.org, to see previous IITK-BMTPC Earthquake Tips. May 2003

Appendix G Tip 15: Why is Vertical Reinforcement required in Masonry Buildings?

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Earthquake Design and Earthquake Tip 15 Construction

Why is vertical reinforcement required in masonry buildings?

Response of Masonry Walls Horizontal bands are provided in masonry Roof buildings to improve their earthquake performance. These bands include plinth band, lintel band and roof Roof Band band. Even if horizontal bands are provided, masonry Lintel buildings are weakened by the openings in their walls Band Door Window Opening Opening (Figure 1). During earthquake shaking, the masonry walls get grouped into three sub-units, namely spandrel masonry, wall pier masonry and sill masonry. Foundation Plinth Roof SoilMasonry Band (a) Building Components Pier

Spandrel Masonry Lintel Level Wall Pier Rocking Masonry of Pier Sill Level Crushing Sill Masonry Plinth Level Foundation

Soil Uplifting of masonry (b) Rocking of Masonry Piers

Figure 1: Sub-units in masonry building – walls behave as discrete units during earthquakes.

Consider a hipped roof building with two window X-Cracking of Masonry openings and one door opening in a wall (Figure 2a). It Piers has lintel and plinth bands. Since the roof is a hipped one, a roof band is also provided. When the ground shakes, the inertia force causes the small-sized Foundation masonry wall piers to disconnect from the masonry Soil above and below. These masonry sub-units rock back (c) X-Cracking of Masonry Piers and forth, developing contact only at the opposite diagonals (Figure 2b). The rocking of a masonry pier Figure 2: Earthquake response of a hipped roof

can crush the masonry at the corners. Rocking is masonry building – no vertical reinforcement is provided in walls. possible when masonry piers are slender, and when weight of the structure above is small. Otherwise, the piers are more likely to develop diagonal (X-type) Roof Earthquake- shear cracking (Figure 2c); this is the most common induced inertia failure type in masonry buildings. force In un-reinforced masonry buildings (Figure 3), the Sliding cross-section area of the masonry wall reduces at the opening. During strong earthquake shaking, the building may slide just under the roof, below the lintel band or at the sill level. Sometimes, the building may also slide at the plinth level. The exact location of Foundation

sliding depends on numerous factors including building weight, the earthquake-induced inertia force, Figure 3: Horizontal sliding at sill level in a the area of openings, and type of doorframes used. masonry building – no vertical reinforcement.

IITK-BMTPC Earthquake Tip 15

Why is vertical reinforcement required in masonry buildings? page 2

How Vertical Reinforcement Helps Earthquake-induced inertia force Embedding vertical reinforcement bars in the edges of the wall piers and anchoring them in the foundation at the bottom and in the roof band at the Cracking top (Figure 4), forces the slender masonry piers to undergo bending instead of rocking. In wider wall piers, the vertical bars enhance their capability to resist horizontal earthquake forces and delay the X-cracking. Adequate cross-sectional area of these vertical bars prevents the bar from yielding in tension. Further, the vertical bars also help protect the wall from sliding as well as from collapsing in the weak direction. (a) Cracking in building with no corner reinforcement

Lintel Band Bending Reinforcement of Pier Bars

Sill Band (Similar to Lintel Band, but discontinued at door openings)

Vertical steel bars anchored in

foundation and roof band (b) No cracks in building with vertical reinforcement (a) Vertical reinforcement causes bending of

masonry piers in place of rocking (See Figure 2). Figure 5: Cracks at corners of openings in a masonry building – reinforcement around them

helps.

Related - Earthquake Tip

Tip 5: What are the seismic effects on structures? Tip12: How brick masonry houses behave during earthquakes? Tip13: Why masonry buildings should have simple structural configuration? Tip14: Why horizontal bands are required in masonry buildings?

Resource Material Amrose,J., (1991), Simplified Design of Masonry Structures, John Wiley (b) Vertical reinforcement prevents sliding in walls & Sons, Inc., New York, USA. (See Figure 3). BMTPC, (2000), Guidelines: Improving Earthquake Resistance of Housing, Building Materials and Technology Promotion Council, Figure 4: Vertical reinforcement in masonry walls New Delhi. – wall behaviour is modified. IS 4326, (1993), Indian Standard Code of Practice for Earthquake Resistant Design and Construction of Buildings, Bureau of Indian Standards, New Delhi. Protection of Openings in Walls IS 13828, (1993), Indian Standard Guidelines for Improving Earthquake Sliding failure mentioned above is rare, even in Resistance of Low-strength Masonry Buildings, Bureau of Indian unconfined masonry buildings. However, the most Standards, New Delhi. common damage, observed after an earthquake, is Next Upcoming Tip diagonal X-cracking of wall piers, and also inclined How to improve seismic behaviour of stone masonry buildings? cracks at the corners of door and window openings. When a wall with an opening deforms during Authored by: earthquake shaking, the shape of the opening distorts C.V.R.Murty and becomes more like a rhombus - two opposite Indian Institute of Technology Kanpur corners move away and the other two come closer. Kanpur, India Under this type of deformation, the corners that come Sponsored by: closer develop cracks (Figure 5a). The cracks are bigger Building Materials and Technology Promotion when the opening sizes are larger. Steel bars provided Council, New Delhi, India in the wall masonry all around the openings restrict This release is a property of IIT Kanpur and BMTPC New these cracks at the corners (Figure 5b). In summary, Delhi. It may be reproduced without changing its contents lintel and sill bands above and below openings, and and with due acknowledgement. Suggestions/comments vertical reinforcement adjacent to vertical edges, may be sent to: [email protected]. Visit www.nicee.org or provide protection against this type of damage. www.bmtpc.org, to see previous IITK-BMTPC Earthquake Tips. June 2003

Appendix H Tip 16: How to make Stone Masonry Buildings Earthquake Resistant?

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Earthquake Design and Earthquake Tip 16 Construction

How to make Stone Masonry Buildings Earthquake Resistant?

Behaviour during Past India Earthquakes masonry dwellings. Likewise, a majority of the over Stone has been used in building construction in 13,800 deaths during 2001 Bhuj (Gujarat) earthquake is India since ancient times since it is durable and locally attributed to the collapse of this type of construction. available. There are huge numbers of stone buildings The main patterns of earthquake damage include: in the country, ranging from rural houses to royal (a) bulging/separation of walls in the horizontal palaces and temples. In a typical rural stone house, direction into two distinct wythes (Figure 2a), (b) there are thick stone masonry walls (thickness ranges separation of walls at corners and T-junctions (Figure from 600 to 1200 mm) built using rounded stones from 2b), (c) separation of poorly constructed roof from riverbeds bound with mud mortar. These walls are walls, and eventual collapse of roof, and (d) constructed with stones placed in a random manner, disintegration of walls and eventual collapse of the and hence do not have the usual layers (or courses) whole dwelling. seen in brick walls. These uncoursed walls have two exterior vertical layers (called wythes) of large stones, filled in between with loose stone rubble and mud mortar. A typical uncoursed random (UCR) stone masonry wall is illustrated in Figure 1. In many cases, these walls support heavy roofs (for example, timber roof with thick mud overlay).

Vertically split Vertical gap (a) Separation of a thick wall into two layers layer of wall Vertically split layer of wall

Mud mortar

Outward bulging of vertical wall layer Half-dressed oblong stones

(b) Separation of unconnected adjacent walls at junctions

Figure 2: Major concerns in a traditional stone Figure 1: Schematic of the wall section of a house – deficiencies in walls, roof and in their traditional stone house – thick walls without connections have been prime causes for failure. stones that go across split into 2 vertical layers. Earthquake Resistant Features Laypersons may consider such stone masonry Low strength stone masonry buildings are weak buildings robust due to the large wall thickness and against earthquakes, and should be avoided in high robust appearance of stone construction. But, these seismic zones. The Indian Standard IS:13828-1993 buildings are one of the most deficient building states that inclusion of special earthquake-resistant systems from earthquake-resistance point of view. The design and construction features may raise the main deficiencies include excessive wall thickness, earthquake resistance of these buildings and reduce absence of any connection between the two wythes of the loss of life. However, in spite of the seismic the wall, and use of round stones (instead of shaped features these buildings may not become totally free ones). Such dwellings have shown very poor from heavy damage and even collapse in case of a performance during past earthquakes in India and major earthquake. The contribution of the each of other countries (e.g., Greece, Iran, Turkey, former these features is difficult to quantify, but qualitatively Yugoslavia). In the 1993 Killari (Maharashtra) these features have been observed to improve the earthquake alone, over 8,000 people died, most of performance of stone masonry dwellings during past them buried under the rubble of traditional stone earthquakes. These features include:

IITK-BMTPC Earthquake Tip 16

How to make Stone Masonry Buildings Earthquake Resistant? page 2 (a) Ensure proper wall construction The wall thickness resistance, its extensive use is likely to continue due to should not exceed 450mm. Round stone boulders tradition and low cost. But, to protect human lives and should not be used in the construction! Instead, the property in future earthquakes, it is necessary to stones should be shaped using chisels and follow proper stone masonry construction as described hammers. Use of mud mortar should be avoided in above (especially features (a) and (b) in seismic zones higher seismic zones. Instead, cement-sand mortar III and higher). Also, the use of seismic bands is highly should be 1:6 (or richer) and lime-sand mortar 1:3 (or recommended (as described in feature (c) above and in richer) should be used. IITK-BMTPC Earthquake Tip 14). (b) Ensure proper bond in masonry courses: The masonry Discontinuities in lintel walls should be built in construction lifts not Horizontal band should be avoided

exceeding 600mm. Through-stones (each extending Lintel Band over full thickness of wall) or a pair of overlapping

bond-stones (each extending over at least ¾ths thickness of wall) must be used at every 600mm along the height and at a maximum spacing of 1.2m along the length (Figure 3).

Wall Alternatives to Section Through Stones

Wood plank < 600mm Hooked steel link S-shaped steel tie

< 600mm <450mm

Floor Wall Plan Level Figure 4: Horizontal lintel band is essential in random rubble stone masonry walls – provides integrity to the dwelling, and holds the

Pair of overlapping stones <1200mm walls together to resist horizontal earthquake

(each of length at least Bond effects. ¾ths the wall thickness) stone

Related - Earthquake Tip Tip14: Why horizontal bands are required in masonry buildings? Resource Material Brzev,S., Greene,M. and Sinha,R. (2001), “Rubble stone masonry <1200mm <1200mm <400mm walls with timber walls and timber roof,” World Housing Figure 3: Use of “through stones” or “bond Encyclopedia (www.world-housing.net), India/Report 18, stones” in stone masonry walls – vital in published by EERI and IAEE. IAEE, (1986), Guidelines for Earthquake Resistant Non-Engineered preventing the wall from separating into wythes. Construction, The ACC Limited, Thane, 2001 (See www.niceee.org). IS 13828, (1993), Indian Standard Guidelines - Improving Earthquake (c) Provide horizontal reinforcing elements: The stone Resistance of Low-Strength Masonry Buildings, Bureau of Indian masonry dwellings must have horizontal bands Standards, New Delhi. Publications of Building Materials and Technology Promotion Council, (See IITK-BMTPC Earthquake Tip 14 for plinth, lintel, New Delhi (www.bmtpc.org): roof and gable bands). These bands can be (a) Retrofitting of Stone Houses in Marathwada Area of Maharashtra constructed out of wood or reinforced concrete, and (b) Guidelines For Improving Earthquake Resistance of Housing chosen based on economy. It is important to (c) Manual for Repair and Reconstruction of Houses Damaged in Earthquake in October 1991 in the Garhwal Region of UP provide at least one band (either lintel band or roof band) in stone masonry construction (Figure 4). Next Upcoming Tip What are the seismic effects on RC frame buildings? : The (d) Control on overall dimensions and heights unsupported length of walls between cross-walls Authored by: should be limited to 5m; for longer walls, cross C.V.R.Murty supports raised from the ground level called Indian Institute of Technology Kanpur buttresses should be provided at spacing not more Kanpur, India than 4m. The height of each storey should not Sponsored by: exceed 3.0m. In general, stone masonry buildings Building Materials and Technology Promotion should not be taller than 2 storeys when built in Council, New Delhi, India cement mortar, and 1 storey when built in lime or mud mortar. The wall should have a thickness of at This release is a property of IIT Kanpur and BMTPC New Delhi. It may be reproduced without changing its contents least one-sixth its height. and with due acknowledgement. Suggestions/comments Although, this type of stone masonry construction may be sent to: [email protected]. Visit www.nicee.org or practice is deficient with regards to earthquake www.bmtpc.org, to see previous IITK-BMTPC Earthquake Tips. July 2003

Appendix I Tip 17: How do Earthquakes Affect Reinforced Concrete Building?

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Earthquake Design and Earthquake Tip 17 Construction

How do Earthquakes Affect Reinforced Concrete Buildings?

Reinforced Concrete Buildings In most buildings, the geometric distortion of the slab In recent times, reinforced concrete buildings have is negligible in the horizontal plane; this behaviour is become common in India, particularly in towns and known as the rigid diaphragm action (Figure 2b). cities. Reinforced concrete (or simply RC ) consists of Structural engineers must consider this during design. two primary materials, namely concrete with reinforcing steel bars. Concrete is made of sand, crushed stone (called aggregates) and cement, all mixed with pre-determined amount of water. Concrete can be molded into any desired shape, and steel bars can be bent into many shapes. Thus, structures of complex shapes are (a) Out-of-plane Vertical Movement possible with RC. A typical RC building is made of horizontal (b) In-plane Horizontal Movement Figure 2: Floor bends with the beam but moves members (beams and slabs ) and vertical members all columns at that level together. (columns and walls), and supported by foundations that rest on ground. The system comprising of RC columns After columns and floors in a RC building are cast and connecting beams is called a RC Frame. The RC and the concrete hardens, vertical spaces between frame participates in resisting the earthquake forces. columns and floors are usually filled-in with masonry Earthquake shaking generates inertia forces in the walls to demarcate a floor area into functional spaces building, which are proportional to the building mass. (rooms). Normally, these masonry walls, also called Since most of the building mass is present at floor infill walls, are not connected to surrounding RC levels, earthquake-induced inertia forces primarily columns and beams. When columns receive horizontal develop at the floor levels. These forces travel forces at floor levels, they try to move in the horizontal downwards - through slab and beams to columns and direction, but masonry walls tend to resist this walls, and then to the foundations from where they are movement. Due to their heavy weight and thickness, dispersed to the ground. As inertia forces accumulate these walls attract rather large horizontal forces downwards from the top of the building, the columns (Figure 3). However, since masonry is a brittle and walls at lower storeys experience higher material, these walls develop cracks once their ability earthquake-induced forces (Figure 1) and are therefore to carry horizontal load is exceeded. Thus, infill walls designed to be stronger than those in storeys above. act like sacrificial fuses in buildings; they develop cracks under severe ground shaking but help share the 5 load of the beams and columns until cracking.

4 Earthquake performance of infill walls is enhanced by mortars of good strength, making proper masonry 3 courses, and proper packing of gaps between RC frame and masonry infill walls. However, an infill wall 2 that is unduly tall or long in comparison to its Floor Level 1 thickness can fall out -of-plane (i.e., along its thin direction), which can be life threatening. Also, placing

Total Force infills irregularly in the building causes ill effects like Figure 1: Total horizontal earthquake force in a short-column effect and torsion (these will be discussed building increases downwards along its height. in subsequent IITK-BMTPC Earthquake Tips).

Roles of Floor Slabs and Masonry Walls Floor slabs are horizontal plate-like elements, which facilitate functional use of buildings. Usually, beams and slabs at one storey level are cast together. Gap In residential multi-storey buildings, thickness of slabs Compression is only about 110-150mm. When beams bend in the vertical direction during earthquakes, these thin slabs Cracks bend along with them (Figure 2a). And, when beams move with columns in the horizontal direction, the Figure 3: Infill walls move together with the slab usually forces the beams to move together with it. columns under earthquake shaking.

IITK-BMTPC Earthquake Tip 17

How do Earthquakes Affect Reinforced Concrete Buildings? page 2 Horizontal Earthquake Effects are Different (which receive forces from columns) should be Gravity loading (due to self weight and contents) on stronger than columns. Further, connections between buildings causes RC frames to bend resulting in beams & columns and columns & foundations should stretching and shortening at various locations. Tension not fail so that beams can safely transfer forces to is generated at surfaces that stretch and compression columns and columns to foundations. at those that shorten (Figure 4b). Under gravity loads, When this strategy is adopted in design, damage is tension in the beams is at the bottom surface of the likely to occur first in beams (Figure 5a). When beams beam in the central location and is at the top surface at are detailed properly to have large ductility, the the ends. On the other hand, earthquake loading causes building as a whole can deform by large amounts tension on beam and column faces at locations despite progressive damage caused due to consequent different from those under gravity loading (Figure 4c); yielding of beams. In contrast, if columns are made the relative levels of this tension (in technical terms, weaker, they suffer severe local damage, at the top and bending moment) generated in members are shown in bottom of a particular storey (Figure 5b). This localized Figure 4d. The level of bending moment due to damage can lead to collapse of a building, although earthquake loading depends on severity of shaking columns at storeys above remain almost undamaged. and can exceed that due to gravity loading. Thus, Damage under strong earthquake shaking, the beam ends can Large Small displacement displacement develop tension on either of the top and bottom faces. at collapse at collapse Since concrete cannot carry this tension, steel bars are required on both faces of beams to resist reversals of Damage distributed All damage bending moment. Similarly, steel bars are required on in all in one all faces of columns too. storeys storey Strength Hierarchy

For a building to remain safe during earthquake shaking, columns (which receive forces from beams) (a) Strong Columns, (b) Weak Columns, should be stronger than beams, and foundations Weak Beams Strong Beams

Figure 5: Two distinct designs of buildings that

result in different earthquake performances œ

Gravity Earthquake columns should be stronger than beams.

Load Load Relevant Indian Standards The Bureau of Indian Standards, New Delhi, (a) published the following Indian standards pertaining to design of RC frame buildings: (a) Indian Seismic Code (IS 1893 (Part 1), 2002) – for calculating earthquake forces, Stretching of member (b) Indian Concrete Code (IS 456, 2000) – for design of and locations of tension Tension RC members, and (c) Ductile Detailing Code for RC Structures (IS 13920, 1993) – for detailing requirements in seismic regions. Related - Earthquake Tip Tip 5: What are the seismic effects on structures? Resource Material Tension Englekirk,R.E., Seismic Design of Reinforced and Precast Concrete Buildings, John Wiley & Sons, Inc., USA, 2003. Penelis,G.G., and Kappos,A.J., Earthquake Resistant Concrete (b) (c) Structures, E&FN SPON, UK, 1997. Next Upcoming Tip Amount of How do Beams in RC Buildings Resist Earthquakes?

tension

Authored by: C.V.R.Murty

Indian Institute of Technology Kanpur

Kanpur, India Sponsored by:

Building Materials and Technology Promotion

Council, New Delhi, India

(d) This release is a property of IIT Kanpur and BMTPC New Delhi. It may be reproduced without changing its contents Figure 4: Earthquake shaking reverses tension and with due acknowledgement. Suggestions/comments and compression in members œ reinforcement is may be sent to: [email protected] . Visit www.nicee.org or required on both faces of members. www.bmtpc.org, to see previous IITK-BMTPC Earthquake Tips. August 2003

Appendix J Tip 18: How do Beams in RC Building Resist Earthquakes?

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Earthquake Design and Earthquake Tip 18 Construction

How do Beams in RC Buildings Resist Earthquakes?

Reinforcement and Seismic Damage (b) Shear Failure: A beam may also fail due to shearing In RC buildings, the vertical and horizontal action. A shear crack is inclined at 45° to the members (i.e., the columns and beams) are built horizontal; it develops at mid-depth near the integrally with each other. Thus, under the action of support and grows towards the top and bottom loads, they act together as a frame transferring forces faces (Figure 2b). Closed loop stirrups are provided from one to another. This Tip is meant for beams that to avoid such shearing action. Shear damage occurs are part of a building frame and carry earthquake- when the area of these stirrups is insufficient. induced forces. Shear failure is brittle, and therefore, shear failure Beams in RC buildings have two sets of steel must be avoided in the design of RC beams. reinforcement, namely: (a) long straight bars (called Design Strategy longitudinal bars) placed along its length, and (b) closed Designing a beam involves the selection of its loops of small diameter steel bars (called stirrups) material properties (i.e, grades of steel bars and concrete) placed vertically at regular intervals along its full and shape and size; these are usually selected as a part length (Figure 1). of an overall design strategy of the whole building. And, the amount and distribution of steel to be provided Vertical Stirrup Smaller diameter steel in the beam must be determined by performing design bars that are made into Beam calculations as per is:456-2000 and IS13920-1993. closed loops and are placed at regular Column Column intervals along the full length of the beam Beam

Bottom face stretches in tension and vertical cracks develop (a) Flexure Failure

Column Inclined crack Longitudinal Bar

Larger diameter steel bars that go through the full length of the

beam

Figure 1: Steel reinforcement in beams - stirrups Beam 45° prevent longitudinal bars from bending outwards. (b) Shear Failure Beams sustain two basic types of failures, namely: Figure 2: Two types of damage in a beam: (a) Flexural (or Bending) Failure: As the beam sags under flexure damage is preferred. Longitudinal bars increased loading, it can fail in two possible ways. resist the tension forces due to bending while If relatively more steel is present on the tension vertical stirrups resist shear forces. face, concrete crushes in compression; this is a brittle failure and is therefore undesirable. If relatively Longitudinal bars are provided to resist flexural less steel is present on the tension face, the steel cracking on the side of the beam that stretches. Since yields first (it keeps elongating but does not snap, as both top and bottom faces stretch during strong steel has ability to stretch large amounts before it earthquake shaking (IITK-BMTPC Earthquake Tip 17), snaps; see IITK-BMTPC Earthquake Tip 9) and longitudinal steel bars are required on both faces at the redistribution occurs in the beam until eventually ends and on the bottom face at mid-length (Figure 3). the concrete crushes in compression; this is a ductile The Indian Ductile Detailing Code IS13920-1993 failure and hence is desirable. Thus, more steel on prescribes that: tension face is not necessarily desirable! The ductile (a) At least two bars go through the full length of the failure is characterized with many vertical cracks beam at the top as well as the bottom of the beam. starting from the stretched beam face, and going (b) At the ends of beams, the amount of steel provided towards its mid-depth (Figure 2a). at the bottom is at least half that at top.

35 IITK-BMTPC Earthquake Tip 18

How do Beams in RC Buildings Resist Earthquakes? page 2 bars are (a) made away from the face of the column, Bottom steel at supports At least 2 bars should go and (b) not made at locations where they are likely to at least half of that at top full length of beam stretch by large amounts and yield (e.g., bottom bars at mid-length of the beam). Moreover, at the locations of laps, vertical stirrups should be provided at a closer spacing (Figure 6). Beam Spacing of stirrups Spacing of stirrups

Total amount of steel as calculated as calculated

Column from calculation Column (but not more than d/4 (but not more than d/4 and 8 times beam bar and 8 times beam bar Spacing of stirrups Figure 3: Location and amount of longitudinal diameter) diameter) as per calculations steel bars in beams – these resist tension due to (but not more than 2d 2d flexure . d/2)

Stirrups in RC beams help in three ways, namely d (i) they carry the vertical shear force and thereby resist 2d Beam 2d diagonal shear cracks (Figure 2b), (ii) they protect the concrete from bulging outwards due to flexure, and Column Column (iii) they prevent the buckling of the compressed Figure 5: Location and amount of vertical stirrups longitudinal bars due to flexure. In moderate to severe in beams – IS:13920-1993 limit on maximum seismic zones, the Indian Standard IS13920-1993 spacing ensures good earthquake behaviour. prescribes the following requirements related to stirrups in reinforced concrete beams:

(a) The diameter of stirrup must be at least 6mm; in Lapping of longitudinal bars beams more than 5m long, it must be at least 8mm. Spacing of stirrups (b) Both ends of the vertical stirrups should be bent not more than 150mm into a 135° hook (Figure 4) and extended Beam

sufficiently beyond this hook to ensure that the

stirrup does not open out in an earthquake.

(b) The spacing of vertical stirrups in any portion of Lapping prohibited in the beam should be determined from calculations regions where Column longitudinal bars can Column (c) The maximum spacing of stirrups is less than half yield in tension the depth of the beam (Figure 5).

(d) For a length of twice the depth of the beam from Figure 6: Details of lapping steel reinforcement the face of the column, an even more stringent in seismic beams – as per IS13920-1993. spacing of stirrups is specified, namely half the spacing mentioned in (c) above (Figure 5). Related - Earthquake Tip 135° The ends of stirrups Tip 9: How to Make Buildings Ductile for Good Seismic Performance? are bent at 135°. Such stirrups do not Tip 17: How do Earthquakes Affect Reinforced Concrete Buildings? open during strong Resource Material earthquake shaking. IS 13920, (1993), “Indian Standard Code of Practice for Ductile Detailing of Reinforced Concrete Structures Subjected to Seismic Forces,” Bureau of Indian Standards, New Delhi Preferred: Paulay,T., and Priestley,M.J.N., (1997), “Seismic Design of Masonry

135° hooks in Horizontal ≥10 times and Reinforced Concrete Buildings,” John Wiley & Sons, USA adjacent Spacing diameter of McGregor,J.M., (1997), “Reinforced Concrete Mechanics and Design,“ stirrup stirrups on Third Edition, Prentice Hall, USA alternate sides 135º Next Upcoming Tip

How do Columns in RC Buildings Resist Earthquakes?

Authored by:

C.V.R.Murty

Figure 4: Steel reinforcement in seismic beams Indian Institute of Technology Kanpur

- stirrups with 135° hooks at ends required as per Kanpur, India

IS:13920-1993. Sponsored by: Building Materials and Technology Promotion Steel reinforcement bars are available usually in Council, New Delhi, India lengths of 12-14m. Thus, it becomes necessary to overlap bars when beams of longer lengths are to be This release is a property of IIT Kanpur and BMTPC New Delhi. It may be reproduced without changing its contents made. At the location of the lap, the bars transfer large and with due acknowledgement. Suggestions/comments forces from one to another. Thus, the Indian Standard may be sent to: [email protected] Visit www.nicee.org or IS:13920-1993 prescribes that such laps of longitudinal www.bmtpc.org, to see previous IITK-BMTPC Earthquake Tips. September 2003 36

Appendix K Tip 19: How do Columns in RC Building Resist Earthquakes?

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Earthquake Design and Earthquake Tip 19 Construction

How do Columns in RC Buildings Resist Earthquakes?

Possible Earthquake Damage Vertical Bars tied together with Closed Ties Columns, the vertical members in RC buildings, Closely spaced horizontal closed ties help in three contain two types of steel reinforcement, namely: (a) ways, namely (i) they carry the horizontal shear forces long straight bars (called longitudinal bars) placed induced by earthquakes, and thereby resist diagonal vertically along the length, and (b) closed loops of shear cracks, (ii) they hold together the vertical bars smaller diameter steel bars (called transverse ties) and prevent them from excessively bending outwards placed horizontally at regular intervals along its full (in technical terms, this bending phenomenon is called length (Figure 1). Columns can sustain two types of buckling), and (iii) they contain the concrete in the damage, namely axial-flexural (or combined compression- column within the closed loops. The ends of the ties bending) failure and shear failure. Shear damage is brittle must be bent as 135° hooks (Figure 2). Such hook ends and must be avoided in columns by providing prevent opening of loops and consequently bulging transverse ties at close spacing (Figure 2b). of concrete and buckling of vertical bars. Closed Ties Vertical bars The ends of ties are Smaller diameter steel bars Larger diameter steel bent at 135°. Such ties that are made into closed bars that go through do not open during loops and are placed at Ties with the full height of the strong earthquake regular intervals along the 10 times column ends bent at 135° shaking. full height of the column diameter of tie

135° Vertical Spacing (a)

Column Figure 1: Steel reinforcement in columns – closed Shear Failure Large spacing of ties at close spacing improve the performance of ties and lack of columns under strong earthquake shaking. 135° hook ends in them causes brittle failure of during Design Strategy 2001 Bhuj Designing a column involves selection of materials earthquake to be used (i.e, grades of concrete and steel bars), (b) choosing shape and size of the cross-section, and calculating amount and distribution of steel reinforcement. Figure 2: Steel reinforcement in seismic columns The first two aspects are part of the overall design – closed ties with 135° hooks are required as per strategy of the whole building. The Indian Ductile Indian Ductile Detailing Code IS:13920-1993. Detailing Code IS:13920-1993 requires columns to be at least 300mm wide. A column width of up to 200mm is The Indian Standard IS13920-1993 prescribes allowed if unsupported length is less than 4m and following details for earthquake-resistant columns: beam length is less than 5m. Columns that are required (a) Closely spaced ties must be provided at the two to resist earthquake forces must be designed to ends of the column over a length not less than prevent shear failure by a skillful selection of larger dimension of the column, one-sixth the reinforcement. column height or 450mm.

IITK-BMTPC Earthquake Tip 19

How do Columns in RC Buildings Resist Earthquakes? page 2 (b) Over the distance specified in item (a) above and below a beam-column junction, the vertical spacing of ties in columns should not exceed D/4 for where Spacing of ties not more than D/4, but need D is the smallest dimension of the column (e.g., in a At least larger of not be less than 75mm nor rectangular column, D is the length of the small D, h c/6 and 450 mm more than 100 mm side). This spacing need not be less than 75mm nor more than 100mm. At other locations, ties are Beam spaced as per calculations but not more than D/2. (c) The length of tie beyond the 135° bends must be at least 10 times diameter of steel bar used to make hc/4 the closed tie; this extension beyond the bend should not be less than 75mm. Spacing of ties Construction drawings with clear details of closed not more than D/2 ties are helpful in the effective implementation at h construction site. In columns where the spacing c Spacing of ties in lap length Lapping of between the corner bars exceeds 300mm, the Indian not more than smaller of vertical bars D/2 and 150 mm Standard prescribes additional links with 180° hook in middle-half ends for ties to be effective in holding the concrete in of column its place and to prevent the buckling of vertical bars. These links need to go around both vertical bars and Spacing of ties horizontal closed ties (Figure 3); special care is not more than D/2 required to implement this properly at site. h /4 c Extra Links

Beam

At least larger of Spacing of ties D, hc/6 and 450 mm not more than D/4, but need not be less than 75mm nor more than 100 mm

180° links around BOTH vertical bars Figure 4: Placing vertical bars and closed ties in

and 135° ties columns – column ends and lap lengths are to be protected with closely spaced ties.

Column Related - Earthquake Tip Figure 3: Extra links are required to keep the Tip17: How do Earthquakes Affect Reinforced Concrete Buildings?

concrete in place – 180° links are necessary to Tip18: How do Beams in RC Buildings Resist Earthquakes?

prevent the 135° tie from bulging outwards. Resource Material IS 13920, (1993), Indian Standard Code of Practice for Ductile Detailing of Reinforced Concrete Structures Subjected to Seismic Forces, Bureau of Lapping Vertical Bars Indian Standards, New Delhi. In the construction of RC buildings, due to the Paulay,T., and Priestley,M.J.N., Seismic Design of Masonry and Reinforced Concrete Buildings, John Wiley & Sons, USA, 1992. limitations in available length of bars and due to Next Upcoming Tip constraints in construction, there are numerous How do Beam-Column Joints in RC Buildings Resist Earthquakes?

occasions when column bars have to be joined. A simple way of achieving this is by overlapping the two Authored by: bars over at least a minimum specified length, called C.V.R.Murty lap length. The lap length depends on types of Indian Institute of Technology Kanpur reinforcement and concrete. For ordinary situations, it Kanpur, India is about 50 times bar diameter. Further, IS:13920-1993 Sponsored by: prescribes that the lap length be provided ONLY in the Building Materials and Technology Promotion middle half of column and not near its top or bottom Council, New Delhi, India ends (Figure 4). Also, only half the vertical bars in the

column are to be lapped at a time in any storey. This release is a property of IIT Kanpur and BMTPC New Delhi. It may be reproduced without changing its contents Further, when laps are provided, ties must be and with due acknowledgement. Suggestions/comments provided along the length of the lap at a spacing not may be sent to: [email protected]. Visit www.nicee.org or more than 150mm. www.bmtpc.org, to see previous IITK-BMTPC Earthquake Tips. October 2003

Appendix L Tip 20: How do Beam-Column Joints in RC Building Resist Earthquakes?

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Earthquake Design and Earthquake Tip 20 Construction

How do Beam-Column Joints in RC Buildings resist Earthquakes?

Why Beam-Column Joints are Special Further, under the action of the above pull-push In RC buildings, portions of columns that are forces at top and bottom ends, joints undergo common to beams at their intersections are called beam- geometric distortion; one diagonal length of the joint column joints (Figure 1). Since their constituent elongates and the other compresses (Figure 2b). If the materials have limited strengths, the joints have limited column cross-sectional size is insufficient, the concrete force carrying capacity. When forces larger than these in the joint develops diagonal cracks. are applied during earthquakes, joints are severely Reinforcing the Beam-Column Joint damaged. Repairing damaged joints is difficult, and so Diagonal cracking & crushing of concrete in joint damage must be avoided. Thus, beam-column joints region should be prevented to ensure good earthquake must be designed to resist earthquake effects. performance of RC frame buildings. Using large column sizes is the most effective way of achieving this. In Beam-Column Joint addition, closely spaced closed-loop steel ties are required Overlap volume common to beams around column bars (Figure 3) to hold together and columns concrete in joint region and to resist shear forces. Intermediate column bars also are effective in confining the joint concrete and resisting horizontal shear forces.

Closed ties

10 times diameter of tie Beam Figure 1: Beam-Column Joints are critical parts of a building – they need to be designed. 135º

Column Earthquake Behaviour of Joints Intermediate Under earthquake shaking, the beams adjoining a Column Bars joint are subjected to moments in the same (clockwise Figure 3: Closed loop steel ties in beam-column

joints – such ties with 135° hooks resist the ill or counter-clockwise) direction (Figure 1). Under these effects of distortion of joints. moments, the top bars in the beam-column joint are pulled in one direction and the bottom ones in the Providing closed-loop ties in the joint requires opposite direction (Figure 2a). These forces are some extra effort. Indian Standard IS:13920-1993 balanced by bond stress developed between concrete recommends continuing the transverse loops around and steel in the joint region. If the column is not wide the column bars through the joint region. In practice, enough or if the strength of concrete in the joint is low, this is achieved by preparing the cage of the there is insufficient grip of concrete on the steel bars. reinforcement (both longitudinal bars and stirrups) of all In such circumstances, the bar slips inside the joint beams at a floor level to be prepared on top of the region, and beams loose their capacity to carry load. beam formwork of that level and lowered into the cage

(Figures 4a and 4b). However, this may not always be

possible particularly when the beams are long and the Compression entire reinforcement cage becomes heavy. Gripping of bar inside Anchoring Beam Bars joint region Tension The gripping of beam bars in the joint region is improved first by using columns of reasonably large cross-sectional size. As explained in Earthquake Tip 19, the Indian Standard IS:13920-1993 requires building (a) Loss of grip on beam bars (b) Distortion of joint: in joint region: causes diagonal columns in seismic zones III, IV and V to be at least Large column width and good cracking and crushing 300mm wide in each direction of the cross-section concrete help in holding the of concrete beam bars when they support beams that are longer than 5m or when these columns are taller than 4m between floors Figure 2: Pull-push forces on joints cause two (or beams). The American Concrete Institute problems – these result in irreparable damage in recommends a column width of at least 20 times the joints under strong seismic shaking. diameter of largest longitudinal bar used in adjoining beam. 39 IITK-BMTPC Earthquake Tip 20

How do Beam-Column Joints in RC Buildings resist Earthquakes? page 2 beam top bar in position while casting the column up Temporary (a) Stage I : prop to the soffit of the beam. Moreover, the vertical Beam top bars are not placed, but horizontal distance beyond the 90º bend in beam bars is not very ties in the joint region effective in providing anchorage. On the other hand, if are stacked up. column width is large, beam bars may not extend below soffit of the beam (Figure 5b). Thus, it is preferable to have columns with sufficient width. Such an approach is used in many codes [e.g., ACI318, 2005]. In interior joints, the beam bars (both top and bottom) need to go through the joint without any cut in the joint region. Also, these bars must be placed within the column bars and with no bends (Figure 6).

Beam bars bent in joint region overstress the core concrete adjoining the bends

Column (a) Poor Practice

(b) Beam

Stage II : Beam Beam bars are within column Top bars of the beam bars and also straight are inserted in the Column (b) Good Practice beam stirrups, and beam reinforcement cage is lowered into Shear failure of RC the formwork beam-column joint during the 1985 (c) Mexico City Stage III : Earthquake, Ties in the joint region are when beam bars raised to their final locations, CA, USA Oakland, EERI, are passed outside tied with binding wire, and the column cross- column ties are continued CD, Slide Annotated EERI The section Figure 4: Providing horizontal ties in the joints – three-stage procedure is required. (c) Photo from: Photo 98-2,

In exterior joints where beams terminate at Figure 6: Anchorage of beam bars in interior joints – diagrams (a) and (b) show cross- columns (Figure 5), longitudinal beam bars need to be sectional views in plan of joint region. anchored into the column to ensure proper gripping of bar in joint. The length of anchorage for a bar of grade Fe415 (characteristic tensile strength of 415MPa) is Related - Earthquake Tip about 50 times its diameter. This length is measured Tip17: How do Earthquakes Affect Reinforced Concrete Buildings? from the face of the column to the end of the bar Tip18: How do Beams in RC Buildings Resist Earthquakes? anchored in the column. In columns of small widths Tip19: How do Columns in RC Buildings Resist Earthquakes? and when beam bars are of large diameter (Figure 5a), Reading Material a portion of beam top bar is embedded in the column ACI 318, (2005), “Building Code Requirements for Structural Concrete that is cast up to the soffit of the beam, and a part of it and Commentary,” American Concrete Institute, USA overhangs. It is difficult to hold such an overhanging IS 13920, (1993), “Indian Standard Code of Practice for Ductile Detailing of Reinforced Concrete Structures Subjected to Seismic Forces,” Bureau Narrow Column Wide Column of Indian Standards, New Delhi SP 123, (1991), “Design of Beam-Column Joints for Seismic Resistance,” Special Publication, American Concrete Institute, USA L-shaped bar ends ACI 318-2005 Practice Authored by: C.V.R.Murty Indian Institute of Technology Kanpur Kanpur, India Sponsored by: Approximately 50 times bar diameter diameter bar times 50 Approximately Portion of top beam Building Materials and Technology Promotion bar below soffit of the Portion of column already cast Council, New Delhi, India beam (a) Poor (b) Good This release is a property of IIT Kanpur and BMTPC New Figure 5: Anchorage of beam bars in exterior Delhi. It may be reproduced without changing its contents and with due acknowledgement. Suggestions/comments joints – diagrams show elevation of joint region. may be sent to: [email protected] Visit www.nicee.org or www.bmtpc.org, to see previous IITK-BMTPC Earthquake Tips. 40

Appendix M Tip 21: Why are Open-Ground Storey Buildings Vulnerable in Earthquakes?

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Earthquake Design and Earthquake Tip 21 Construction

Why are Open-Ground Storey Buildings Vulnerable in Earthquakes?

Basic Features Ahmedabad alone has about 25,000 five-storey Reinforced concrete (RC) frame buildings are buildings and about 1,500 eleven-storey buildings; becoming increasingly common in urban India. Many majority of them have open ground storeys. Further, a such buildings constructed in recent times have a huge number of similarly designed and constructed special feature – the ground storey is left open for the buildings exist in the various towns and cities situated purpose of parking (Figure 1), i.e., columns in the in moderate to severe seismic zones (namely III, IV ground storey do not have any partition walls (of and V) of the country. The collapse of more than a either masonry or RC) between them. Such buildings hundred RC frame buildings with open ground are often called open ground storey buildings or buildings storeys at Ahmedabad (~225km away from epicenter) on stilts. during the 2001 Bhuj earthquake has emphasised that such buildings are extremely vulnerable under earthquake shaking. The presence of walls in upper storeys makes them much stiffer than the open ground storey. Thus, the upper storeys move almost together as a single block, and most of the horizontal displacement of the building occurs in the soft ground storey itself. In common language, this type of buildings can be explained as a building on chopsticks. Thus, such buildings swing back-and-forth like inverted pendulums during earthquake shaking (Figure 2a), and the columns in the open ground storey are severely Figure 1: Ground storeys of reinforced concrete stressed (Figure 2b). If the columns are weak (do not buildings are left open to facilitate parking – have the required strength to resist these high stresses) this is common in urban areas in India. or if they do not have adequate ductility (See IIT- An open ground storey building, having only BMTPC Earthquake Tip 9), they may be severely columns in the ground storey and both partition walls damaged (Figure 3a) which may even lead to collapse and columns in the upper storeys, have two distinct of the building (Figure 3b). characteristics, namely: (a) It is relatively flexible in the ground storey, i.e., the

relative horizontal displacement it undergoes in the Earthquake ground storey is much larger than what each of the oscillations storeys above it does. This flexible ground storey is also called soft storey. (b) It is relatively weak in ground storey, i.e., the total horizontal earthquake force it can carry in the ground storey is significantly smaller than what each of the storeys above it can carry. Thus, the open ground storey may also be a weak storey. Inverted Often, open ground storey buildings are called soft (a) storey buildings, even though their ground storey may Pendulum be soft and weak. Generally, the soft or weak storey usually exists at the ground storey level, but it could Stiff upper storeys: be at any other storey level too. Small displacement between Earthquake Behaviour adjacent floors

Open ground storey buildings have consistently Soft ground storey: shown poor performance during past earthquakes Large displacement between foundation and first floor across the world (for example during 1999 Turkey, 1999

Taiwan and 2003 Algeria earthquakes); a significant (b) Ground storey columns severely stressed number of them have collapsed. A large number of Figure 2: Upper storeys of open ground storey buildings with open ground storey have been built in buildings move together as a single block –

India in recent years. For instance, the city of such buildings are like inverted pendulums.

IITK-BMTPC Earthquake Tip 21

Why are Open-Ground Storey Buildings Vulnerable in Earthquakes? page 2 structure. The Code suggests that the forces in the columns, beams and shear walls (if any) under the action of seismic loads specified in the code, may be obtained by considering the bare frame building (without any infills) (Figure 4b). However, beams and columns in the open ground storey are required to be designed for 2.5 times the forces obtained from this bare frame analysis. For all new RC frame buildings, the best option is to avoid such sudden and large decrease in stiffness and/or strength in any storey; it would be ideal to build walls (either masonry or RC walls) in the ground storey also (Figure 5). Designers can avoid dangerous Photo Courtesy: The EERI Annotated Slide Set CD, Earthquake Engineering Research Institute, Oakland (CA), USA, 1998. effects of flexible and weak ground storeys by (a) 1971 San Fernando Earthquake ensuring that too many walls are not discontinued in the ground storey, i.e., the drop in stiffness and strength in the ground storey level is not abrupt due to the absence of infill walls. The existing open ground storey buildings need to be strengthened suitably so as to prevent them from collapsing during strong earthquake shaking. The owners should seek the services of qualified structural engineers who are able to suggest appropriate solutions to increase seismic safety of these buildings.

(b) 2001 Bhuj Earthquake

Figure 3: Consequences of open ground storeys in RC frame buildings – severe damage to ground storey columns and building collapses.

Direct flow of forces through walls The Problem Open ground storey buildings are inherently poor systems with sudden drop in stiffness and strength in Figure 5: Avoiding open ground storey problem – the ground storey. In the current practice, stiff masonry continuity of walls in ground storey is preferred. walls (Figure 4a) are neglected and only bare frames are considered in design calculations (Figure 4b). Thus, the inverted pendulum effect is not captured in design. Related - Earthquake Tip Tip 6: How Architectural Features Affect Buildings During Infill walls not Earthquakes? considered in Tip17: What are the Earthquake Effects on Reinforced Concrete upper storeys Buildings?

Resource Material IS 1893(Part 1) (2002), Indian Standard Code of Practice for Criteria for Design of Earthquake Resistant Structures, Bureau of Indian Standards, New Delhi. (a) Actual building (b) Building being assumed Next Upcoming Tip in current design practice Why are short columns more damaged during earthquakes?

Figure 4: Open ground storey building – Authored by:

assumptions made in current design practice C.V.R.Murty are not consistent with the actual structure. Indian Institute of Technology Kanpur Kanpur, India Improved design strategies Sponsored by: After the collapses of RC buildings in 2001 Bhuj Building Materials and Technology Promotion earthquake, the Indian Seismic Code IS:1893 (Part 1) - Council, New Delhi, India 2002 has included special design provisions related to soft storey buildings. Firstly, it specifies when a This release is a property of IIT Kanpur and BMTPC New building should be considered as a soft and a weak Delhi. It may be reproduced without changing its contents and with due acknowledgement. Suggestions/comments storey building. Secondly, it specifies higher design may be sent to: [email protected]. Visit www.nicee.org or forces for the soft storey as compared to the rest of the www.bmtpc.org, to see previous IITK-BMTPC Earthquake Tips. December 2003

Appendix N Seismic Safety for Adobe Homes

REPORT June 2015 Nepal Post-Earthquake Building Safety Evaluations Central Asia Earthquake Safety Initiative SEISMIC SAFETY FOR ADOBE HOMES: what everyone should know

Seismic Damage to Adobe Homes Central Asia is known for periodic large earthquakes. Strong earthquakes can cause damage or destruction to adobe buildings, causing death, disability, serious injuries, and economic losses. Strong earthquakes in seismic regions are inevitable! Build your house safely to avoid future disaster! Damage to an adobe building in the January 2000 Kamashi Earthquake, Uzbekistan, (Khakimov Sh.A., Nurtaev B.S.) Adobe Homes Can be Built to Resist Earthquakes In order to resist earthquake damage any type of construction must be well-designed, use proper materials and be well-constructed. Every additional measure taken to increase seismic- resistance, will improve safety for building users. When you are going to construct adobe buildings, do as many of these steps as possible! EVERY LITTLE BIT HELPS! Adobe material is brittle and weak and more vulnerable to earthquake damage than well-built buildings reinforced with wood columns and diagonal bracing (synch), or masonry buildings with reinforced concrete columns or reinforced-concrete frame-buildings with infill walls. Because adobe is brittle and weak, adobe construction is not legal in many high seismic zones or in urban areas.

The techniques shown in this booklet are intended to 1) reduce damage to adobe homes in small and medium earthquakes, and 2) help reduce collapse ! of adobe homes in earthquakes. They MAY NOT PREVENT COLLAPSE in strong earthquake. This advice is intended for seismic regions less than or equal to MSK 8.

Light Roof with Long Eav es Well Connected Horizontal Foundation, Seismic Beams Walls and Roof and Lintels

Limited openings Good Quality away from corners Flat, Firm, Dry Site Construction

Regular, Low, Symmetrical Layout LAYING A GOOD FOUNDATION

Good Site Selection > 1 m > 3 m

Adobe buildings SHOULD be built on leveled ground, at least 1 meter away from the edge of slopes, more if slope is steep and at least 3 meters from retaining walls or steep banks.

Adobe buildings SHOULD NOT Adobe buildings SHOULD NOT Adobe buildings SHOULD NOT be built against a slope where be built near clif f s where they be built near steep slopes where soil pressure may cause building might slide of f due to land slides. f alling rocks and debris may collapse. damage the house.

Good Foundation Every seismic-resistant adobe building needs a solid foundation that is well connected to the walls. Reinforced monolithic concrete foundations are best. If fired brick or rubble stone foundations are used, add a reinforced concrete beam on the top of the foundation. The foundation should extend 40cm below the ground for stability and ideally 50cm above the ground to protect walls from rain water damage and ensure that adobe bricks remain above the snow blanket in the winter. The building must be connected to the foundation so that it does not slip off. First embed large rocks in the foundation so that they project up to the height of one adobe brick. Then construct the adobe wall to fit bricks snuggly against the embedded rocks using full or half size bricks. A damp-proof course will prevent rising moisture from damaging the walls over time. Bitumen and ruberoid glues are commonly used, but these can be slippery. A thin layer of cement-sand (1:2) provides a good non-slippery damp-proof course. A damp-proof course Fit bricks snugly around rocks

Embed large rocks

30 cm, ideally 50 cm

40 cm Solid foundation Ground DESIGN AND MATERIALS

Anti-Seismic Layout To resist earthquakes, adobe buildings should have a simple one-story square design and be no longer than 20 meters. Walls must be short and thick (the thicker the better) to be earthquake resistant and well-supported by interior cross-walls or exterior buttresses. There should be at least one longitudinal interior wall. Window and door openings on each side of the building should take up no more than one-third of the length of the wall. Each opening should be no more than 1.2m wide, and at least 1.2m away from building corners. Ideally the number and size of openings should be the same on opposite sides of the building. MAXIMUM length Simple ≤ 5 m between cross wall 5 m square one story design with MAXIMUM length of 20 m MAXIMUM wall ≤ 3 m height 3 m ≥ 1.2 m ≤ 1.2 m MINIMUM ≥ 1.2 m distance from ≤ 1.2 m Minimum Maximum Maximum corner 1.2 m ≥ 1.2 m Wall Wall Length MAXIMUM opening thickness Height between width 1.2 m Cross Walls 50 cm 3.0 m 5 m Good Quality Adobe Material Good quality soil must be used to make all adobe bricks and mortar, or rammed earth walls. Straw, especially from rye, can improve the strength of adobe. Straw can reduce cracking, especially when the adobe has high clay content. Test your materials! • Adobe bricks and mortar should not have large visible cracks after drying for 48 hours. To test the mortar, place it between two bricks. After 48 hours, pull the bricks apart and examine the mortar. If there are large visible cracks in the bricks or mortar, increase the amount of course sand in the mix and repeat the test. • Fully dried bricks (1-4 weeks depending on weather) should be able to be dropped on their edge from 2m height onto the ground. There should be no large cracks or breaks, except for some moderate damage on the corner that hit the ground. After drying 24 hrs, squeeze

• Roll adobe mixture in y our hand or on a table • A 2cm ball of adobe should NOT be able to be (approximately 2.5cm diameter). Push one end ov er the table slowly . Measure the length of broken in y our hand af ter dry ing f or 24 hours. the piece when it f alls. If it is <4cm then add If it can be broken, there is not enough clay . clay . If it is >15cm then add sand. Look f or another source of soil. SEISMIC BELTS FOR STRONG WALLS

Seismic Belts Placement “Seismic belts” are the most important elements in adobe construction for preventing earthquake collapse. Minimally one continuous wooden seismic belt should be placed at the top of all interior and exterior walls. The concrete foundation acts as a second belt. Ideally additional belts can be placed at the sill and lintel levels.

ceiling level lintel level sill level plinth level

Seismic Belts Construction and Connections Seismic belts can be made out of solid wood planks or poplar saplings, joined together with crossbars. The belts should be 20-50cm wide, and approximately 5cm high. Belts . should be braced at wall corners. Sapling belts should be flattened so they rest securely on the wall and 2cmx 5cm cross bars should be placed every 50 cm to create a lattice across the frame. This should later be filled in with adobe mortar. flattened sapling logs planks corner braces 2cmx 5cm cross bars

≤ 50 cm

The roof level seismic belt must be connected to the walls to be effective. This can be done by 1) using diagonal bracing between roof-level seismic belt and the lintel or 2) inserting galvanized steel anchor bolts or wooden dowels (40-50 cm) through the seismic belt into the wall.

diagonal bracing adobe mortar infill connects roof belts to lintel belt or beam When there is no seismic belt at ≥ 50 cm the lintel level, lintels should extend a minimum of 50 cm past the edges of the windows and door. STRONG CONNECTIONS

Connecting Adobe Walls to Each Other In the past people used reeds laid along brick courses to strengthen adobe walls. During earthquakes, these reeds helped keep corners and wall intersections from tearing apart. When reeds are not available corner strengtheners can be made from high-quality wov en poly propylene or poly ethylene plastic. 15 cm holes in center of corner strengtheners made f rom high quality corner strengthener wov en poly propy lene or poly ethy lene plastic ≥ 1 m

≥ 1 m ≥ 1 m

Add strengtheners in all corners between courses of adobe bricks and rammed earth at approximately every half-meter of vertical height. If seismic belts are not used at the window sill and lintel levels, then be sure to include strengtheners at those levels as well Strengtheners can be made out of high quality wov en poly propylene or poly ethylene plastic (potato/rice) bags cut to size. Holes of about 15 cm should be made in the center of the strengtheners to allow mortar to contact adobe courses above and below. The corner strengtheners should extend at least 1 m from the interior face of perpendicular walls.

Ceiling and Roof Construction and Connections Adobe homes with heavy soil roofs are more easily damaged in earthquakes and more likely to kill occupants. Roofs should ideally be made of light weight material like galvanized iron or asbestos tiles. Insulation should be of lightweight material like reeds, straw or synthetics. A thin layer of soil can be added to help hold the insulation in place. 25-30 mm secondary ceilings should be nailed to ceiling beams. These beams should be connected to the seismic belt to help hold walls together during an earthquake. Hipped roofs (a roof that slopes on all four sides) are preferable to pitched (a roof that slopes on only two sides) and flat roofs. If a pitched or flat roof is used it should be braced using diagonal wires or wooden braces to connect roof rafters as shown below. Roof rafters should be bolted to the roof level seismic belt. Eav es should extend at least 50cm past the wall, to protect walls from moisture. light weight straw diagonal wires or wooden joists used to or sy nthetic strengthen hipped and f lat roof s insulation

ceiling beams nailed to seismic belt

25-30 mm thick secondary ceiling nailed to ceiling roof rafters nailed or beams bolted to seismic belt MAINTENANCE AND RETROFITTING

KEEP HOUSE WELL MAINTAINED

Adobe homes can be seriously damaged by moisture from rain and standing or rising water. However, a well-built and maintained adobe home that has not been seriously damaged may last for decades. Look out for things that can cause your home to deteriorate and become more vulnerable to earthquakes. Regularly replace any Inspect ev ery 6 exposed and rotting months, and replace sections of beams, damaged or leaking lintels and roof rafters. sections of roof. Construct large roof ov erhangs to protect adobe walls from moisture.

≥ 50 cm

Regularly replace white wash to protect walls from water.

Ensure that wood piles, bushes and other items are Collected rain water not placed against walls with gutters and where they can trap release away from moisture and damage walls. building.

RETROFIT WEAK OR DAMAGED ADOBE

Adobe buildings that have not been built with seismic-resistant measures may be strengthened by a variety of techniques. Although this may not save the house, it may prevent collapse and save lives. These techniques are being researched and you should check with your state construction authority, engineers at local institutes of seismic resistant construction, and adobe construction experts for the most reliable and up-to-date information about methods.

Some of these include: • adding seismic belts • adding buttresses • tying roof to walls • adding vertical reinforcement in the walls or on wall exterior using galvanized wire mesh, cane or wood poles • adding vertical and horizontal bands of galvanized wire mesh overlaid with shotcrete at corners, tops of walls and around wall openings • wrapping with polypropylene bands © 2005, GeoHazards International

Appendix O Boundary Wall Construction Guide

REPORT June 2015 Nepal Post-Earthquake Building Safety Evaluations

APPENDIX P American Society of Civil Engineers Code of Ethics

REPORT June 2015 Nepal Post-Earthquake Building Safety Evaluations

Code of Ethics1

Fundamental Principles2 Engineers uphold and advance the integrity, honor and dignity of the engineering profession by:

1. using their knowledge and skill for the enhancement of human welfare and the environment; 2. being honest and impartial and serving with fidelity the public, their employers and clients; 3. striving to increase the competence and prestige of the engineering profession; and 4. supporting the professional and technical societies of their disciplines.

Fundamental Canons 1. Engineers shall hold paramount the safety, health and welfare of the public and shall strive to comply with the principles of sustainable development3 in the performance of their professional duties. 2. Engineers shall perform services only in areas of their competence. 3. Engineers shall issue public statements only in an objective and truthful manner. 4. Engineers shall act in professional matters for each employer or client as faithful agents or trustees, and shall avoid conflicts of interest. 5. Engineers shall build their professional reputation on the merit of their services and shall not compete unfairly with others. 6. Engineers shall act in such a manner as to uphold and enhance the honor, integrity, and dignity of the engineering profession and shall act with zero-tolerance for bribery, fraud, and corruption. 7. Engineers shall continue their professional development throughout their careers, and shall provide opportunities for the professional development of those engineers under their supervision.

Guidelines to Practice Under the Fundamental Canons of Ethics

Canon 1. Engineers shall hold paramount the safety, health and welfare of the public and shall strive to comply with the principles of sustainable development in the performance of their professional duties.

a. Engineers shall recognize that the lives, safety, health and welfare of the general public are dependent upon engineering judgments, decisions and practices incorporated into structures, machines, products, processes and devices. b. Engineers shall approve or seal only those design documents, reviewed or prepared by them, which are determined to be safe for public health and welfare in conformity with accepted engineering standards. c. Engineers whose professional judgment is overruled under circumstances where the safety, health and welfare of the public are endangered, or the principles of sustainable development ignored, shall inform their clients or employers of the possible consequences. d. Engineers who have knowledge or reason to believe that another person or firm may be in violation of any of the provisions of Canon 1 shall present such information to the proper authority in writing and shall cooperate with the proper authority in furnishing such further information or assistance as may be required. e. Engineers should seek opportunities to be of constructive service in civic affairs and work for the advancement of the safety, health and well-being of their communities, and the protection of the environment through the practice of sustainable development. f. Engineers should be committed to improving the environment by adherence to the principles of sustainable development so as to enhance the quality of life of the general public.

Canon 2. Engineers shall perform services only in areas of their competence.

a. Engineers shall undertake to perform engineering assignments only when qualified by education or experience in the technical field of engineering involved. b. Engineers may accept an assignment requiring education or experience outside of their own fields of competence, provided their services are restricted to those phases of the project in which they are qualified. All other phases of such project shall be performed by qualified associates, consultants, or employees. c. Engineers shall not affix their signatures or seals to any engineering plan or document dealing with subject matter in which they lack competence by virtue of education or experience or to any such plan or document not reviewed or prepared under their supervisory control.

Canon 3. Engineers shall issue public statements only in an objective and truthful manner.

a. Engineers should endeavor to extend the public knowledge of engineering and sustainable development, and shall not participate in the dissemination of untrue, unfair or exaggerated statements regarding engineering. b. Engineers shall be objective and truthful in professional reports, statements, or testimony. They shall include all relevant and pertinent information in such reports, statements, or testimony. c. Engineers, when serving as expert witnesses, shall express an engineering opinion only when it is founded upon adequate knowledge of the facts, upon a background of technical competence, and upon honest conviction. d. Engineers shall issue no statements, criticisms, or arguments on engineering matters which are inspired or paid for by interested parties, unless they indicate on whose behalf the statements are made. e. Engineers shall be dignified and modest in explaining their work and merit, and will avoid any act tending to promote their own interests at the expense of the integrity, honor and dignity of the profession.

Canon 4. Engineers shall act in professional matters for each employer or client as faithful agents or trustees, and shall avoid conflicts of interest.

a. Engineers shall avoid all known or potential conflicts of interest with their employers or clients and shall promptly inform their employers or clients of any business association, interests, or circumstances which could influence their judgment or the quality of their services. b. Engineers shall not accept compensation from more than one party for services on the same project, or for services pertaining to the same project, unless the circumstances are fully disclosed to and agreed to, by all interested parties. c. Engineers shall not solicit or accept gratuities, directly or indirectly, from contractors, their agents, or other parties dealing with their clients or employers in connection with work for which they are responsible. d. Engineers in public service as members, advisors, or employees of a governmental body or department shall not participate in considerations or actions with respect to services solicited or provided by them or their organization in private or public engineering practice. e. Engineers shall advise their employers or clients when, as a result of their studies, they believe a project will not be successful. f. Engineers shall not use confidential information coming to them in the course of their assignments as a means of making personal profit if such action is adverse to the interests of their clients, employers or the public. g. Engineers shall not accept professional employment outside of their regular work or interest without the knowledge of their employers.

Canon 5. Engineers shall build their professional reputation on the merit of their services and shall not compete unfairly with others.

a. Engineers shall not give, solicit or receive either directly or indirectly, any political contribution, gratuity, or unlawful consideration in order to secure work, exclusive of securing salaried positions through employment agencies. b. Engineers should negotiate contracts for professional services fairly and on the basis of demonstrated competence and qualifications for the type of professional service required. c. Engineers may request, propose or accept professional commissions on a contingent basis only under circumstances in which their professional judgments would not be compromised. d. Engineers shall not falsify or permit misrepresentation of their academic or professional qualifications or experience. e. Engineers shall give proper credit for engineering work to those to whom credit is due, and shall recognize the proprietary interests of others. Whenever possible, they shall name the person or persons who may be responsible for designs, inventions, writings or other accomplishments. f. Engineers may advertise professional services in a way that does not contain misleading language or is in any other manner derogatory to the dignity of the profession. Examples of permissible advertising are as follows:

 Professional cards in recognized, dignified publications, and listings in rosters or directories published by responsible organizations, provided that the cards or listings are consistent in size and content and are in a section of the publication regularly devoted to such professional cards.  Brochures which factually describe experience, facilities, personnel and capacity to render service, providing they are not misleading with respect to the engineer's participation in projects described.  Display advertising in recognized dignified business and professional publications, providing it is factual and is not misleading with respect to the engineer's extent of participation in projects described.  A statement of the engineers' names or the name of the firm and statement of the type of service posted on projects for which they render services.  Preparation or authorization of descriptive articles for the lay or technical press, which are factual and dignified. Such articles shall not imply anything more than direct participation in the project described.  Permission by engineers for their names to be used in commercial advertisements, such as may be published by contractors, material suppliers, etc., only by means of a modest, dignified notation acknowledging the engineers' participation in the project described. Such permission shall not include public endorsement of proprietary products.

g. Engineers shall not maliciously or falsely, directly or indirectly, injure the professional reputation, prospects, practice or employment of another engineer or indiscriminately criticize another's work. h. Engineers shall not use equipment, supplies, laboratory or office facilities of their employers to carry on outside private practice without the consent of their employers.

Canon 6. Engineers shall act in such a manner as to uphold and enhance the honor, integrity, and dignity of the engineering profession and shall act with zero-tolerance for bribery, fraud, and corruption.

a. Engineers shall not knowingly engage in business or professional practices of a fraudulent, dishonest or unethical nature. b. Engineers shall be scrupulously honest in their control and spending of monies, and promote effective use of resources through open, honest and impartial service with fidelity to the public, employers, associates and clients. c. Engineers shall act with zero-tolerance for bribery, fraud, and corruption in all engineering or construction activities in which they are engaged. d. Engineers should be especially vigilant to maintain appropriate ethical behavior where payments of gratuities or bribes are institutionalized practices. e. Engineers should strive for transparency in the procurement and execution of projects. Transparency includes disclosure of names, addresses, purposes, and fees or commissions paid for all agents facilitating projects. f. Engineers should encourage the use of certifications specifying zero-tolerance for bribery, fraud, and corruption in all contracts.

Canon 7. Engineers shall continue their professional development throughout their careers, and shall provide opportunities for the professional development of those engineers under their supervision.

a. Engineers should keep current in their specialty fields by engaging in professional practice, participating in continuing education courses, reading in the technical literature, and attending professional meetings and seminars. b. Engineers should encourage their engineering employees to become registered at the earliest possible date. c. Engineers should encourage engineering employees to attend and present papers at professional and technical society meetings. d. Engineers shall uphold the principle of mutually satisfying relationships between employers and employees with respect to terms of employment including professional grade descriptions, salary ranges, and fringe benefits.

1The Society’s Code of Ethics was adopted on September 2, 1914 and was most recently amended on July 23, 2006. Pursuant to the Society’s Bylaws, it is the duty of every Society member to report promptly to the Committee on Professional Conduct any observed violation of the Code of Ethics. 2 In April 1975, the ASCE Board of Direction adopted the fundamental principles of the Code of Ethics of Engineers as accepted by the Accreditation Board for Engineering and Technology, Inc. (ABET). 3In October 2009, the ASCE Board of Direction adopted the following definition of Sustainable Development: “Sustainable Development is the process of applying natural, human, and economic resources to enhance the safety, welfare, and quality of life for all of the society while maintaining the availability of the remaining natural resources.”

APPENDIX Q References

REPORT June 2015 Nepal Post-Earthquake Building Safety Evaluations

References

ACI 318, 2010, “Building Code Requirements for Structural Concrete and Commentary,” American Concrete Institute, USA

ATC 20-1, 2005, Field Manual: Post Earthquake Safety Evaluation of Buildings, ATC 20-1, prepared by the Applied Technology Council, Redwood City, California.

FEMA E-74, 2012, Reducing the Risks of Nonstructural Earthquake Damage: A Practical Guide, prepared by the Applied Technology Council (ATC), under contract from the Federal Emergency Management Agency (FEMA), Washington, D.C.

FEMA 154, 2002, Rapid Visual Screening of Buildings for Potential Seismic Hazards: A Handbook, Second Edition, prepared by the Applied Technology Council, Washington, D.C.

FEMA 155, 2002, Rapid Visual Screening of Buildings for Potential Seismic Hazards: Supporting Documentation, Second Edition, prepared by the Applied Technology Council, Washington, D.C.

FEMA 306, 1998, Evaluation of Earthquake Damaged Concrete and Masonry Wall Buildings – Basic Procedures Manual, Federal Emergency Management Agency, Washington, D.C.

FEMA 307, 1998, Evaluation of Earthquake Damaged Concrete and Masonry Wall Buildings – Technical Resources, Federal Emergency Management Agency, Washington, D.C.

FEMA 308, 1998, The Repair of Earthquake Damaged Concrete and Masonry Wall Buildings, Federal Emergency Management Agency, Washington, D.C., U.S.A.

IS 456, 1978, Indian Standard, Code of Practice for Plain and Reinforced Concrete, Bureau of Indian Standards, New Delhi, 110002, India.

IS 1893, 1984, Indian Standard, Criteria for Earthquake Design of Structures, Bureau of Indian Standards, New Delhi, 110002, India.

IS 1893, 2002, Indian Standard Code of Practice for Criteria for Design of Earthquake Resistant Structures, Bureau of Indian Standards, New Delhi.

IS 4326, 1993, Indian Standard, Code of Practice for Earthquake Resistant Design and Construction of Buildings (3rd Revision), Bureau of Indian Standards, New Delhi, 110002, India.

IS 13827, 1993, Indian Standard, Guidelines for Improving Earthquake Resistance of Earthen Buildings, Bureau of Indian Standards, New Delhi, 110002, India.

REPORT June 2015 Nepal Post-Earthquake Building Safety Evaluations

IS 13828, 1993, Indian Standard, Guidelines for Improving Earthquake Resistance of Low Strength Masonry Buildings, Bureau of Indian Standards, New Delhi, 110002, India.

IS 13935, 1993, Indian Standard, Repair and Seismic Strengthening of Buildings – Guidelines, Bureau of Indian Standards, New Delhi, 110002, India.

NSET, 2009, Seismic Vulnerability of Evaluation Guidelines for Private and Public Buildings, National Society for Earthquake Technology, Kathmandu, Nepal.

UNIDO, 1983, Repair and Strengthening of Reinforced Concrete, stone and Brick-Masonry Buildings, UNDP/UNIDO Project RER/79/015, Vienna.

REPORT June 2015 Nepal Post-Earthquake Building Safety Evaluations 728 – 134th St SW Suite 200 Everett, WA 98204 Tel 425-741-3800 Fax 425-741-3900 www.reidmiddleton.com