of Standards Rational Bureau Admin. Bldg. ybrary. E-01 l^r.^ APR 2 3 1971 BUILDING SCIENCE SERIES 34 Strength of Masonry Walls Under Compressive and Transverse Loads The Building Science Series The Building Science Series disseminates technical information developed at the National Bureau of Standards on building materials, components, systems and whole structures. The Series presents research results, test methods and per- formance criteria related to the structural and environmental functions and the durability and safety characteristics of building elements and systems. These publications, similar in style and content to the NBS Building Materials and Structures Reports (1938-59), are directed toward the manufacturing, design, construction and research segments of the building industry, standards orga- nizations and officials responsible for building codes. 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(013.29/2:23) 25 cents • Natural Weathering of Mineral Stabilized Asphalt Coatings on Organic Felt. (C 13.29/2:24) 30 cents • Structural Performance Test of a Building System. iC 13.29/2:25) S1.25 • Exploratory Studies of Early Strength Development in Portland Cement Pastes and Mortars. (013.29/2:28) 25 cents • 1964 Exposure Test of Porcelain Enamels on Aluminum — Three Year Inspection. (013.29/2.29) 25 cents • Flexural Behavior of Prestressed Concrete Composite Tee— Beams (013.29/2:31) 25 cents • Compressive Strength of Slender Concrete Masonry \^ aUs (013.29/2:33) 40 cents Send orders (use Superintendent of Documents Catalog Nos.) with remittance to: Superintendent of Documents. L".S. Government Printing Office, Washington, D.C. 20402. Remittance from foreign countries should include an additionsd one-fourth of the purchase price for postage. [See mailing list announcement on last page.] UNITED STATES DEPARTMENT OF COMMERCE • Maurice H. Stans, Secretary NATIONAL BUREAU OF STANDARDS • Lewis M. Branscomb, Director Strength of Masonry Walls Under Compressive and Transverse Loads F. Y. Yokel, R. G. Mathey, and R. D. Dikkers Building Research Division Institute for Applied Technology National Bureau of Standards Washington, D.C. 20234 Building Science Series 34.' Nat. Bur. Stand. (U.S.), Bldg. Sci. Ser. 34, 74 pages (Mar. 1971) CODEN: BSSNB Issued March 1971 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 (Order by SD Catalog No. C 13.29/2:34). Price 70 cents MAY 7 km The contents of this report are not to be used for advertising or promotional purposes. Citation of proprietary products does not constitute an official endorsement or approval by the National Bureau of Standards for the use of such commercial products. Library of Congress Catalog Card Number: 77-608986 Contents Page List of symbols V SI conversion units VI Abstract 1 1. Introduction and objective 1 2. Scope 1 3. Materials 2 3.1. Brick 2 3.2. Concrete masonry units 2 3.3. Mortar 3 4. Test specimens 3 4.1. Description of walls 3 4.2. Fabrication of walls 6 4.3. Description and fabrication of prisms 6 5. Testing procedures 7 5.1. WaU tests 7 5.2. Instrumentation for wall tests 8 5.3. Prism tests 9 5.4. Instrumentation for prism tests 9 6. Test results 9 6.1. Wall test results 9 6.2. Description of wall failures 13 6.3. Prism test results 21 7. Theoretical discussion 23 7.1. Introduction 23 7.2. Interaction between vertical loads and moments 23 7.2.1. General discussion "23 7.2.2. Cross-sectional moment capacity. 25 7.2.2.1. Solid prismatic sections 25 7.2.2.2. Symmetrical hollow sections 29 7.2.2.3. Asymmetric sections 30 7.3. Slenderness effects 32 8. Analysis of test results 35 8.1. Introduction 35 8.2. Stress-strain relationships 35 8.3. Cross-sectional capacity 35 8.4. Wall strength 38 8.4.1. General discussion of the test conditions 38 8.4.2. Concrete block walls 39 8.4.2.1. 8-in hollow concrete block walls 39 8.4.2.2. 8-in solid concrete block walls 43 8.4.2.3. Conclusions 44 8.4.3. Brick walls 44 8.4.3.1. Comparison of brick wall systems 44 8.4.3.2. Correlation of test results with theory 48 8.4.3.3. Conclusions 51 8.4.4. Cavity and composite walls 51 8.4.4.1. Comparative strength of walls 51 III Page 8.4.4.2. 4-2-4-in cavity walls of hollow concrete block 52 8.4.4.3. 4-2-4-in cavity walls of brick and hollow concrete block 54 8.4.4.4. 8-in composite brick and hollow concrete block walls 58 8.4.4.5. Conclusions 60 9. Recommendations and discussion of present design practice 61 9.1. Determination of transverse strength of masonry walls 61 9.2. Discussion of present design practice 62 9.2.1. ANSI building code requirements 62 9.2.2. SCPI standard for engineered brick masonry 63 9.2.3. NCMA and ACT recommendations 65 9.3. Recommended research 66 10. Summary 67 10.1. Conclusions from test results 67 10.2. Comparison of test results with existing design practice 67 11. Acknowledgment 68 12. References 68 IV List of Symbols A Area of net section M'o Maximum moment in the direction of the a Flexural compressive strength coefficient transverse loads caused by these loads af'm Flexural compressive strength of masonry under given conditions of end fixity b Width of wall Ml Maximum moment considering tensile strength Cm Moment correction coefficient (section 7.3) with zero vertical load (section 7.2.2.1) c Distance from centroid to outer fiber m Stiffness ratio in composite section (section E Modulus of elasticity 7.2.2.3) Ei Initial tangent modulus of elasticity P Applied vertical compressive load; also de- e Eccentricity relative to centroid of uncracked notes resultant force on wall section section P' Resultant compressive force acting on wall ca- Distance from centroid to edge of kern section Fa Allowable axial compressive stress Pall Allowable axial load fa Computed axial compressive stress Pc Vertical load capacity when load is applied at Fm Allowable flexural compressive stress the minimum eccentricity at which section /,„ Computed flexural compressive stress cracking occurs (section 7.2.2.1) f'm Compressive strength of masonry determined Per Critical load for stability induced compression from axial prism tests failure computed on the basis of a modified /'( Tensile strength of masonry determined from EI, accounting for section cracking and re- modulus of rupture tests duced stiffness at maximum stress (section g Moment coefficient in the approximate evalua- 7.3) tion for Me (section 7.2.2.2) Pcro Critical load, computed on the basis of the Ti Unsupported height of wall initial tangent modulus of elasticity and an / Moment of inertia of section uncracked section (section 7.3) /„ Moment of inertia of section based on un- Pk Vertical load capacity when load is applied at cracked net section the edge of the kern of a wall section (sec- k Reduction coefficient to account for end fixity tion 7.2.2.1) kh Unsupported height of wall reduced for end P0 Short wall axial load capacity determined on fixity the basis of prism strength (section 7.2.2.1) M Moment s Ratio of tensile strength to axial compressive Mc Cracking moment (section 7.2.2.1) strength of masonry (f'tlf'm) M'c Maximum cracking moment (section 7.2.2.1) T' Resultant Me Maximum moment capacity, computed using tensile force acting on cross section linear stress gradients (section 7.2.2.1) t Thickness of wall Mend Maximum transverse end moment resulting u Uncracked thickness in cracked section (fig- from fixity at wall supports ure 7.2) Met Total maximum moment capacity of cavity V Horizontal reaction wall (section 8.4.4.3) w Distributed transverse load Mk Moment developed by Pk, applied at the edge A Maximum transverse deflection of the kern Mo Maximum moment caused by transverse load 8 Transverse deflection under pin ended conditions A/ Difference in force (figure 7.4) V SI Conversion Units In view of present accepted practice in this country in this technological area, common U.S.