Technical Guidelines on Building Demolition Work in Sri Lanka

Draft Technical Guidelines on Building Demolition Work in Sri Lanka

National Building Research Organisation

OCTOBER 2019 // Published by:

National Building Research Organisation (NBRO), 99/1, Jawatta Road, Colombo 05.

Publication No. : NBRO/PMD/01

Funded by: Government Research Grant - 2018

1st Edition – December 2019

No part of this Publication shall be reproduced or transmitted in any form or by any means without permission of the National Building Research organisation (NBRO).

Disclaimer With regard to the information available in this Document neither the National Building Research Organisation nor any of its employees and/or agents make any warranty, express or implied or assumes any legal liability or responsibility for accuracy or completeness of any information. The National Building Research Oranisation shall not be liable to you or any third party for any, direct, incidental, consequential or exemplary damages or loss of profit resulting from any use of such information.

FOREWORD

In the recent past, a series of tragic incidents with fatalities associated with building demolition work have been reported specially in urban areas of Sri Lanka.

A situational analysis of the present practice of building demolition work conducted by the National Building Research Organisation (NBRO) revealed that there was no guidelines on building demolition work in the Sri Lankan context and as a result, such works were carried out mostly without professional involvement. It further revealed that no institution in Sri Lanka, had been formally made responsible for regulation of building demolition work in order to ensure safety of life and property.

Hence, preparation of a set of technical guidelines on planning & execution of safe building demolition work in Sri Lanka was identified by NBRO as an urgent national need and same was also highlighted at the Annual Industry Consultation Meeting – 2018 organized by NBRO.

I wish to gratefully acknowledge tremendous effort made by the following Steering Committee appointed by NBRO in achieving this nationally important task:

 Dr.(Eng.) Sudhira De Silva - Senior Lecturer, University of Ruhuna  Eng. Clarence Perera - Consultant, NBRO  Archt. G.A.P. Ganepola - Consultant Architect, Project Management Division, NBRO

 Eng.(Mrs.) J.K. Jayawardena - Director Project Management Division, NBRO  Eng.(Ms.) K.M.D.N.K. Kahahengoda Senior Engineer, - Project Management Division, NBRO

 Eng. L.N. Pallegama - Structural Consultant, Project Management Division, NBRO  Eng. Dhammika Silva - Structural Consultant, Project Management Division, NBRO  Eng.(Mrs.) Sunethra Muthurathne Director, Building Material Research & Training - Division, NBRO

 Eng.(Ms.) Ishani Kulasekara - Assistant Director, Technology and Research, Construction Industry Development Authority

 Mr. H.S.D. Premasiri - Senior Scientist, NBRO  Eng.(Mrs.) N.G.R.K. Gunathunga - Civil Engineer, NBRO

 Eng.(Ms.) T.N. Gamage - Civil Engineer, NBRO

 Eng.(Ms.) T. Pathirana - Civil Engineer, NBRO

My special thanks are due to Eng. (Mrs.) J.K. Jayawardena, Director Project Management Division who first, conceptualized this initiative and also headed the Steering Committee.

I greatly appreciate the valuable constructive suggestions & guidance offered by Archt. G.A.P. Ganepola, Consultant Architect, NBRO and Dr. (Eng.) Sudhira De Silva, Senior Lecturer, University of Ruhuna, Eng. Clarence Perera, Consultant, NBRO throughout the planning, development and finalization of this Publication.

I wish to acknowledge with grateful thanks the support extended in numerous ways by the NBRO staff towards successful completion of this Task.

I am also very grateful to the contractors in the field of building demolition who supported the NBRO Research Team in numerous ways.

I hope that this Publication will be a useful guide at national level for relevant professionals in the construction Industry in planning & direction, monitoring & supervision in ensuring safety of life and property.

iii

PREFACE

This Publication elaborates in the form of Technical Guidelines, safe practices on demolition of low-rise buildings of masonry & reinforced concrete framed structures with in-filled walls that are recommended to be adopted in urban/ congested locations of Sri Lanka.

Focus attention has been drawn to selected building demolition processes of different scales recently carried out in Colombo while reviewing relevant on-going practices in Sri Lanka as well as globally adopted codes and practices on building demolition.

These Technical Guidelines have been formulated mainly on the following in line with the appropriate practices adopted globally:

 Different demolition approaches;  Planning and managing demolition work;  Preparation of demolition plan and stability report on the building;  Debris and waste handling;  Health and safety measures, and;  Different methods of demolition.

However, this Publication is not intended to be an exhaustive explanation on various building demolition projects and therefore, it is strongly recommended that individual professional judgment be exercised over and above these Technical Guidelines wherever required during planning, design and execution of respective building demolition work.

GLOSSARY

In this document, unless the context otherwise requires, the following interpretation of terms and definitions holds good and correct solely for the purpose of this guideline

 Authorized Body Corporate body appointed by the state for approval of building demolition work in Sri Lanka to be formed/ appointed  Demolition means dismantling, razing, destroying or wrecking any building or structure or any part thereof by pre-planned and controlled methods  Registered Civil Engineer who is a chartered Engineer and who fall Structural into the category of qualified persons eligible to design Engineer and supervise the construction of buildings and other engineering structures, and to certify Structural Engineering aspects, and who is listed in the Directory of Structural Engineers of The Institution of Engineers, Sri Lanka  Contractor any person or entity executing demolition works under a (Demolition) construction contract  Constructor any person who undertakes, whether exclusively or in conjunction with any other business to carry out any construction work on his own account or for or on behalf of another person  Building Survey an inspection on the building and its surroundings aiming at spotting any potential problems that may arise during demolition and developing a method statement for demolition  Catch Platform is a temporary structure erected on top of the covered walkway or underneath the structures that are being demolished including, but not limited to, balconies and cantilevered structures for the purpose of catching and retaining debris and to protect the area beneath such structures being demolished

 Catchfan is a temporary structure erected around and attached to or abutting the exterior wall of the building being demolished for the purpose of catching and retaining debris that fall outside the building  Covered means a temporary structure with protective roof erected Walkway along the site boundary and on or adjacent to the existing footpath to protect pedestrians from the falling debris during demolition  Hoarding means a temporary fence enclosure erected along the site boundary to separate the demolition site from the adjacent properties  Shoring System of auxiliary supports which provides a load path to maintain stability during temporary states of the structure

ABBRIVIATIONS

 CEA – Central Environmental Authority  CMC – Colombo Municipal Council  C & D – Construction and Demolition  NBRO – National Building Research Organisation  NEA – National Environmental Act  PPE – Personal Protective Equipment  PCB - polychlorinated biphenyls  RSE – Registered Structural Engineer

CONTENTS Page No.

Foreword ...... ii

Preface ...... iv

Glossary ...... v

Abbriviations ...... vi

Table of Figures...... ix

List of Tables ...... xi

1. INTRODUCTION ...... 1

1.1 Scope ...... 1

1.2 Normative References ...... 2

1.3 Flow chart for Building Demolition Procedure ...... 2

2. Demolition Approaches...... 3

2.1 Demolition options...... 3

2.2 Selection of the approach ...... 3

2.3 Choosing the methodology ...... 4

2.4 Demolition Techniques ...... 4

2.5 Partial Demolition activities in structural refurbishment ...... 5

3. Planning and Managing ...... 6

3.1 Planning considerations ...... 6

4. Demolition Plan and Stability Report ...... 11

4.1 Pre-Demolition Survey ...... 11

4.2 Demolition Plan and Stability Report ...... 14

5. Structural Stability of The Building ...... 18

5.1 Identifying structural hazards ...... 18

5.2 Avoidance of unplanned structural collapses ...... 26

6. Debris and Waste Handling ...... 32

vii

6.1 Debris loading and unloading ...... 32

6.2 Waste Management ...... 34

6.3 Debris disposal ...... 35

6.4 Regulation on waste management in Sri Lanka ...... 37

7. Health and Safety ...... 39

7.1 Insurance cover ...... 39

7.2 Precautionary Measures ...... 39

7.3 Protection of Properties...... 45

7.4 Special Safety Considerations ...... 47

7.5 Health Hazards ...... 55

7.6 Environmental Precautions ...... 57

8. Methods of Demolition ...... 60

8.1 General ...... 60

8.2 Top Down-Manual Method ...... 61

8.3 Top Down-By Machines ...... 75

8.4 Demolition of Basement and retaining walls ...... 88

References ...... 89

ANNEX 01 ...... 1

Legislation and statutory regulations ...... 2

ANNEX 02 ...... 1

Useful contacts for demolition work ...... 2

ANNEX 03 ...... 3

Sample Demolition Plan And Stability Report For Top Down mechanical method ...... 4

ANNEX 04 ...... 11

viii

TABLE OF FIGURES

Page No.

Figure 2.1 - Demolition Options ...... 3 Figure 3.1- Demolition planning considerations ...... 6 Figure 5.1 – Flowchart for ascertaining structural stability of the building for demolition .... 19 Figure 5.2 - Space frame roof structure at Pallekele stadium, Sri Lanka ...... 20 Figure 5.3 – High bay warehouse ...... 21 Figure 5.4 - Arches at Galle fort, Dutch Hospital ...... 21 Figure 5.5 - Domes houses at Pothuvil ...... 22 Figure 5.6 - Multy-bay portal frames (JZ Flowers International, England) ...... 22 Figure 5.7 Lift – Slab structures (a) Construction of L'Ambiance Plaza, image via NIST (b) The Huron Towers in Ann Arbor, Michigan, utilized the lift slab technique ...... 23 Figure 5.8 - Retained facade (Nippon Hotel, Colombo 02) ...... 23 Figure 5.9 - Ca Doro Building, Scotland, façade retention to support external walls during the demolition of the internal walls and floors ...... 24 Figure 5.10 - Cable stayed Roof (McCormick Place, exhibition hall, Chicago, Illinois, USA, 1986) ...... 25 Figure 5.11 - Collapsed building during demolition (a) 9.14 m height walls without lateral supports (b) Collapsed building to the adjacent site causing fatalities ...... 27 Figure 5.12 – Essential elements of top down demolition process ...... 28 Figure 5.14 - Plan of typical progressive demolition sequence, column to column maintaining “square” to provide lateral support ...... 29 Figure 5.15 - Typical structure demolition sequence working "top down" outwards towards shear walls (strong points), i.e. lift shafts and stairwells ...... 30 Figure 6.1 - Opening created to form a chute in a demolition site ...... 33 Figure 6.2 - External Debris chute ...... 33 Figure 6.3- Hierarchy for demolition waste management ...... 34 Figure 7.1 - Hoarding and Covered Walkway criteria ...... 42 Figure 7.2 - Cantilever towers ...... 44 Figure 7.3 - Raking shores ...... 45 Figure 7.4 - Safety Warning Boards ...... 50 Figure 7.5 - Personnel Protective Equipment ...... 51

Figure 7.6 - Personal Protective Equipment ...... 52 Figure 7.7 - Site personal health governing factors ...... 56 Figure 7.8 - Pressurized water spraying during demolition ...... 58 Figure 8.1 - Flow chart for demolition sequence ...... 62 Figure 8.2 - Demolition of Cantilevered Reinforced Concrete Slab (Manual Method) ...... 63 Figure 8.3 - Demolition of Cantilevered Reinforced Concrete Slab and Beam (Manual Method) ...... 64 Figure 8.4 - Demolition of external Beam (Manual Method) – dismantle the entire beam section ...... 66 Figure 8.5 Adjustable steel jacket ...... 67 Figure 8.6 - Details for Securing External Beams before Dismantling (Manual Method) ...... 67 Figure 8.7 – Pre-weakening of column – cut reinforcement in exterior side ...... 68 Figure 8.8 - Pre-weakening and dismantling of column (Manual Method) ...... 68 Figure 8.9 - Felling of a reinforced concrete wall with beam (Manual Method) ...... 70 Figure 8.10 - Felling of reinforced concrete wall separately from the cross beam (manual method) ...... 71 Figure 8.11 - Demolition of two way slab (Manual method) ...... 72 Figure 8.12 - Demolition of secondary beam (Manual Method) ...... 74 Figure 8.13 - Details for securing secondary beams before dismantling (Manual Method) ... 75 Figure 8.14 - Typical sequence of top down method with mechanical equipment ...... 80 Figure 8.15 - Demolition of cantilevered slab by mobile machine (conventional method) .... 81 Figure 8.16 - Demolition of reinforced concrete frame by excavator with breaker ...... 85 Figure 8.17 - Demolition of reinforced concrete wall by excavator ...... 87

LIST OF TABLES

Page No.

Table 1 - Classification of waste generated in demolition sites...... 35 Table 2 - Summary of precautionary measures for hoarding, covered walkway and catch platform ...... 40 Table 3 - Categorization of structures according to the type of building (from ISO-4966: 1990E) ...... 46 Table 4 - Interim Standards for vibration of the Operation of Machinery, Construction Activities and Vehicle Movements Traffic ...... 46

Section 01

1. INTRODUCTION

Unavailability of statutory technical guidelines, codes, safety standards or regulations and lack of involvement of relevant professionals in planning & direction, monitoring & supervision in ensuring safety of life and property, appeared to have been the main reasons for series of tragic incidents recently associated with building demolition work in Sri Lanka.

This draft guideline was prepared to provide guidance on safe and good practices for demolition works. Current practice of building demolition projects is mostly done using the experience of the contractor. Introducing this guideline would make them aware of the technical approach to the demolition activities.

1.1 Scope

This Publication outlines the good practices to be adopted in building demolition projects that are especially suitable for demolition of buildings located in highly congested urban areas.

The scope of this guideline is limited to the following:

a) Demolition of buildings up to 5 storeys (G+4) inclusive of any basement, roof top apartment any building the height of which does not exceeds fifteen meters (15 m) above the adjoining street. b) Demolition of buildings or RCC structures consist of (Reinforced Concrete) column, beam, slab with brick infill walls and masonry structures c) Full and partial demolition of buildings; d) Demolition of buildings using Top down method by manual method and mechanical method

Above mentioned scope had been established in the preparation of this guideline, and this document covers only the subject matter falling within that scope. Any other demolition method or activity may also be used subject to careful consideration and recommendations made by a Registered Structural Engineer.

Section 01

1.1.1. Owner’s/ client’s Responsibilities When an owner or a client hands over a building for demolition to a demolition contractor;

a) The building shall be free of all hazardous materials b) Disconnection of existing utility services

1.2 Normative References

The following documents were used in the preparation of preparing this document;

a) BS 6187: 2011 Code of Practice for full and Partial Demolition b) Code of Practice for Demolition of Buildings by Hong Kong Building Department in Year 2004 c) Draft document on “National Guidelines - Construction and Demolition Waste Management” October 2018 published by Construction Industry Development Authority (CIDA)

1.3 Flow chart for Building Demolition Procedure

Given in Annex 04

Section 02

2. DEMOLITION APPROACHES

2.1 Demolition options

The following are some different options associated with building demolition

Complete Demolition Reuse

Partial Demolition

Rebuilding Demolition Options

Whilst in Use Structural Refurbishment Whilst not in Use

Figure 2.1 - Demolition Options

2.2 Selection of the approach

Following factors shall be taken into account when deciding the demolition process:

a) Health and safety; b) Structural Characteristics; c) Site Conditions/Locations; d) Demolition Cost; e) Time/Duration; f) Past Experience of the contractor in similar projects; g) Waste Disposal Method; h) Permitted level of nuisance; i) Removal or relocation of utility and service lines; j) Sustainability; k) Client issues.

Section 02

2.3 Choosing the methodology

In demolition activities the final anticipated outcome is the removal of the building by executing a safe procedure to remove the building.

Three suitable methodologies for building demolition have been listed below.

a) Manual Method;

b) Mechanical Method (Application of machinery).

c) A combination of Manual and Mechanical Method.

When selecting a suitable methodology for demolition factors mentioned in Section 2.2 shall be considered. Also it is encouraged to use sustainable demolition approaches such as reduce, reuse and recycle of demolition waste.

2.4 Demolition Techniques

 Manual Demolition  Remotely controlled machines and robotic devices  High-reach machines (Hydraulic crushers with long boom arm, Wrecking ball)  Cutting by drilling and sawing  Use of chemical agents  Using explosives  High-pressure water jetting

There are number of demolition techniques available apart from the techniques listed above. In this guidelines it is focused on Manual demolition methods and mechanical demolition method only (Using excavator with breaker and excavator with hydraulic crusher). Other methods of demolition can be used as per the instructions and guidance by the Registered Structural Engineer.

Section 02

2.5 Partial Demolition activities in structural refurbishment

Partial demolition of a building is a special case compared with complete demolition. During structural refurbishment and retrofitting works, partial demolition is required. Such demolition activities can alter the functioning of load- bearing parts of the structure. Hence, it is necessary to assess the following issues.

a) The load-bearing requirements of building elements to effectively support remaining structures; b) Necessity for temporary support during demolition and reconstruction; c) The potential for unplanned collapse of structure (e.g. often due to lack of understanding of traditional building construction); d) Fire safety (e.g. protection against fire, fire loading and fire escape methods). (Refer Chapter 7); e) All services, including electricity, water, sewerage, communication low voltage wiring, and gas (e.g. isolation and disconnection of services); f) Health issues (e.g. noise and vibration, asbestos, lead in paints, silica originated by construction dust, polychlorinated biphenyls (PCBs) in the removal of transformers, zoonoses carriers present at abandoned areas, welfare facility requirement]. g) Client issues (e.g. raising awareness, client’s requirements and experience).

Competent person should investigate and assess requirements of the following parties;

i. Client; ii. Occupier of the building; iii. Contractor; iv. Any third parties.

Section 03

3. PLANNING AND MANAGING

3.1 Planning considerations

3.1.1. General Following factors as described in Section 3.1.2 to 3.1.8 shall be addressed;

Before starting demolition work, the following factors should be studied and these listed factors have been further described throughout the document.

a) Knowledge of the site b) Legal requirements and consents c) Program and time framework d) Public Protection e) Structural stability f) Environmental management g) Safety and health of people

Public protection Program and Structural time stability of the framework building

legal Environmental requirement Management and consents

Planning Safety and Knowledge of Demolition health of the site Projects people

Figure 3.1- Demolition planning considerations

Section 03

3.1.2. Knowledge of the site

After conducting a Building Survey (as detailed in section 4.1.1), it will be necessary to conduct a detailed survey of the demolition site, considering the factors given below. Where applicable, it will be necessary to conduct a detailed survey of the disposal site to which the debris are transferred to and a study on the transfer route.

a) The extent of decommissioning. b) Details of the electrical isolation and disconnection of other services c) Details of temporary supplies connected to demolition site d) Knowledge and history of the structure such as construction materials, structural integrity of the building and location. e) Isolation and protection measures for adjacent structures. f) Hazardous materials. It will be necessary to know whether this site or the building to be demolished was used to store or process any toxic chemicals, resulting pollution of the ground (i.e. whether the site is a brownfield) or leaving behind hazardous materials at the site. g) Previous uses of the site.

3.1.3. Permissions, consents and license required in demolition work

Note: Legislation and statutory regulations in Sri Lanka related to building demolition is attached in Annex 1. Also useful contacts of Authorities/ institutions related to demolition work is given in Annex 2.

In the planning stage of demolition process relevant permissions/license or consents shall be obtained in order to continue smooth flow of work as well as to ensure the safety of the property and public. Following areas shall be considered;

a) Control minimization of noise, vibration and dust due to the demolition activity;

Section 03

b) Disturbance to the adjoining property; c) Waste disposal; d) Utility management; e) Using highway or private road; f) Total or partial closure and traffic control; g) Use of heavy vehicles, machinery and parking; h) Erection of temporary supports over pavements, roads, sidewalls; i) Architecturally, environmentally, aesthetically and archeologically valuable areas and buildings.

3.1.4. Program and Time framework Demolition activities shall be planned before executing demolition work and time framework with activity breakdown program shall be submitted along with the demolition plan. Following factors shall be considered in preparing the demolition plan.

a) The proposed demolition sequence with time framework (Method statement items shall be tally with the activities itemed here); b) Required plant and machinery and usage; c) Waste management, storage plan; d) Safety arrangements; e) Traffic arrangement ; f) Weather prediction during the project.

Note 1: Project start and end dates shall be clearly mentioned in the work program.

Note 2: Detailed description on demolition plan is given in Section 4.2

Section 03

3.1.5. Public Protection Necessary actions shall be taken to ensure the safety of the general public. Attention need to be given to following;

a) Site entry control and site security; b) Presence of hazardous materials at site; c) Safety of the public during the demolition work; d) Danger to neighboring properties due to demolition work.

3.1.6. Structural stability Demolition process shall ensure the structural stability of the building and neighboring buildings during the demolition process as well as

a) Maintenance of residual structural stability, avoiding unplanned and premature collapses; b) Demolition sequence, pre-weakening and residual strength of the structure designed by a Competent Engineer under the guidance of Registered Structural Engineer; c) Precautionary measures taken such as temporary supports, scaffolding etc. also taking into consideration adjacent structures, designed by a competent engineer under the guidance of Registered Structural Engineer; d) Previous collapse history of same type of buildings.

Note: Detailed description on structural stability is given in Section 5

3.1.7. Environmental management Reduction measures for the following shall be included in preparing the demolition process:

a) Noise control; b) Dust emission control; c) Waste management; d) Reuse and recycle methods of demolition waste; e) Hazardous waste management;

Section 03

f) Air quality; g) Ground vibration; h) Conservation of environmental sensitive areas, ecological, historical valuable areas.

Note: Detailed description on environmental concerns with permissible levels given in Section 7.6

3.1.8. Safety and Health of People Following areas shall be considered generally:

a) Insurance cover; b) Precautionary measures taken to protect the public and site personnel; c) Protection to adjacent properties; d) Safety precautions taken for site personnel; e) Health hazards; f) Environmental Precautions.

Note: Detailed description on environmental concerns with permissible levels given in Section 7.6

Section 04

4. DEMOLITION PLAN AND STABILITY REPORT

4.1 Pre-Demolition Survey

Prior to commencing the building demolition, it will be necessary to carry out a building survey to assess the prevailing situation of the surroundings (as detailed in Section 4.1.1); and a condition assessment of the building to be demolished (as detailed in Section 4.1.2). Based on the information a demolition plan and a stability report shall be prepared. All pre-demolition photographic and video evidences together with relevant reports should be archived for future reference.

4.1.1. Building Survey Building survey means an inspection carried out on the site and its surroundings including all buildings and structures aiming at spotting any potential problems during all stages of demolition and this survey shall be approved by a chartered Town Planner/ Urban designer/ Civil Engineer. Following items shall be included in the survey:

(a) Layout plan showing adjoining properties and their present uses (provide in the reference - service station storing fuel, warehouses, industries, public buildings such as schools, hospitals and places of worship and buildings used as homes for the disabled, children and the elderly); (b) Neighboring building types (e.g. Schools, hospitals, residential, commercial etc.) and dimensions and distance to the demolition site; (c) Neighborhood sensitivity to noise, vibration, dust and traffic impact; (d) Common staircases and party walls shared with adjoining buildings; (e) Pedestrian pavements, walk paths, hoarding and the requirement for covered walkways; (f) Roads, streets and railway lines; (g) Record of existing traffic condition;

Section 04

(h) Presence of wastewater, hazardous materials, matters arising from toxic chemicals, flammable or explosive and radioactive materials, etc. and possible presence of materials which can contribute to air pollution and soil contamination of surrounding area; (i) Utilities arrangement record in the surrounding area including the presence of any overhead power or communication lines; (j) Problems on sloping sites and impacts on adjoining sites caused by proposed demolition; (k) Drainage conditions/ paths in the area, water receiving bodies, erosion and the possibility of blocking due to proposed demolition; (l) Crack survey of surrounding buildings and if necessary, inspection of existing drawings and structural conditions of adjoining structures and shoring which may be affected by the proposed demolition work by the Registered Structural Engineer.

4.1.2. Condition assessment of building to be demolished Condition assessment of a building is an evaluation of the present condition and assessment of structural integrity to ascertain its fitness for designated use and if there are any deviations, may contain recommendations for retrofitting. The following factors should be considered in a condition assessment of a building to be demolished and such assessment shall be carried out under the supervision of a Registered Structural Engineer. (Section 5.1.2. Includes identification of structural elements and forces in stability assessment).

Evaluation of the present condition

a) Existing architectural layout plan and other drawings (Structural, Services) of the building (Important in case of unplanned collapse of the structure to justify original condition of the structure); b) Type and quality of Construction materials; c) Existing uses and previous uses of the building;

Section 04

d) Type of use such as residential, commercial, hospital, school etc. and level of service loads applied; e) Record of utility supplies with location details; f) Presence of wastewater, septic tanks and treatment plants; g) Presence or the contamination by previously stored hazardous materials such as radioactive materials, explosives, toxic chemicals, fuels or other flammable materials; h) Presence of materials that can cause soil contamination or air pollution such as asbestos; i) Presence of cracks, roof leaks, storm water stagnation, subsidence etc. as in the case of a standard building condition assessment (The complete building condition assessment procedure has been given in Guidelines on structural appraisal of existing buildings with reinforced concrete and masonry structures in Sri Lanka). Assessment of structural integrity will be done paying attention to the following: i. Structural framing plans and structural reinforcement details; ii. presence of extraordinary loading on the structure that may cause abnormal structural behavior during demolition, (e.g. Towers); iii. External loads (e.g. external clamping to building such as exhaust ducts); iv. Any dilapidation and degree of deterioration on any structural elements; v. The nature of walls, whether it is block wall, reinforced concrete walls, load bearing walls or partition walls; vi. Cantilevered structures such as canopies, balconies, arches or other forms of architectural features.

Note: If structural details are unavailable then cover meter tests, inspections using BPR (Building Penetrating Radar) and bar sizes of the main elements with approximate strength of the concrete shall be obtained by conducting tests. Also examination of rebar condition by exposing some key structural elements should be done as a part of condition assessment of the building.

Section 04

4.2 Demolition Plan and Stability Report

4.2.1. Demolition Plan a) Demolition Plan is a document prepared by the Registered Structural Engineer appointed by the building owner and /or Demolition Contractor for the purpose of submitting to the Authorized Body for obtaining prior approval before commencing building demolition. This document should be prepared with due reference made to Building Survey and Condition assessment of building to be demolished. Demolition Plan will guide to protect the site personnel, protecting the public and surrounding areas ensuring stability of the building to be demolished during all stages of demolition thereby preventing unintentional collapses. A properly prepared demolition plan should contain the following: b) A plan of the site and surroundings showing:  The location of the building to be demolished with detailed topography of site;

 Type of adjacent buildings (residential, hospitals, schools, commercial etc.);  The distances from the building to be demolished to its adjacent buildings, streets, structures and significant street furniture;  Locations of site cameras (CCTV) as decided by the qualified person;  Service lines pass through the site. (Electrical, water, communication, sewage);

c) A layout plan of all floors of the building to be demolished, showing;  The condition assessment of the building;  Occupancy usage of the floors in case of a partial demolition;  Principal materials of construction;  All affected buildings/structures/streets/land and services including utilities;

Section 04

d) A plan showing the structural arrangement and construction of all unconventional structural elements and Structural Calculations assessing the existing stability of the building to be demolished; e) A plan showing the sequence of demolition activities indicating demolition of particular structural members together with the timeframe; f) Method statement (Describe stability of the building to be demolished during all stages of demolition) showing in detail how each activity is carried out indicating the method of demolition to be adopted including the restrictions on the use of any particular type of equipment (Section

4.2.1.1 includes detail description); g) a plan showing the route of movement of powered mechanical plants and equipment including the method of lifting mechanical plant; h) any structural alterations required to suit the demolition such as strengthening of deteriorated key structural members; i) A plan showing all precautionary measures for the protection of the public including hoardings, covered walkways, catch platforms, catch fans, scaffolding, protective screens, safety nets and safety boards; j) A plan showing the proposed structural calculations for all temporary supports and bracings in the case when powered mechanical plants or equipment are used; k) A plan showing the proposed structural support system, shoring and precautionary measures for all affected adjacent buildings, slopes, retaining structures and services at each stage of the demolition works; l) A plan on the proposed methods for debris handling including, permissible accumulation of building debris at upper floor levels and at ground floor and disposal [refer document on “National Guidelines - Construction and Demolition Waste Management” October 2018 published by Construction Industry Development Authority (CIDA)] m) If hazardous materials are present, a plan showing the handling of such materials (Section 7.6.4);

Section 04

n) A plan showing method of disconnecting the utilities and supplying of necessary temporary utilities during the demolition procedure;(Section 4.2.1.2); o) A report on the stability of neighboring buildings, adjoining properties which may be affected by the demolition work as decided by the Registered Structural Engineer.

4.2.1.1. Method Statement

Method statement shall be prepared at the planning stage of a demolition project when the demolition plan is preparing. Method statement shall be prepared explicitly but succinctly including the demolition sequence, plant and types of equipment to be used and precautions to be taken etc. Method statements shall be live documents and modified as required to the site condition with the approval from Registered Structural Engineer and updated approved method statement procedure shall be informed to the site supervisor.

Format

 A logical order shall be followed  Should be easy to understand  Critical task shall be specified in detail  Date and revision number shall be included  Include site plan, annotate diagrams and detailed program for the work

4.2.2. Stability Report

This shall be prepared by the Registered Structural Engineer and shall include the following:

a) A report on the stability of the building to be demolished during all stages of demolition including residual strength of the building; b) In the case when powered mechanical plants or equipment are used, structural calculations for all temporary supports and bracings;

Section 04

c) A report on the stability of neighboring buildings, adjoining properties which may be affected by the demolition work as decided by the Registered Structural Engineer.

A check list for preparing a Demolition plan and stability report is depicted in Annex 01

Section 05

5. STRUCTURAL STABILITY OF THE BUILDING

In demolition projects maintaining structural stability is a prime concern. Whether it is a full or partial demolition, throughout the demolition process (before, during and decommissioning) complete understanding of the structural stability of the structure itself and interrelationship with adjacent structures and surrounding environment shall be obtained. This chapter gives further understanding to the reader giving important factors to be concerned to maintain structural stability throughout the project.

5.1 Identifying structural hazards

5.1.1. Types of work involving structural instability during demolition Instabilities in an existing structure are caused by the following demolition activities during demolition of a building and therefore, degree of such instabilities should be assessed beforehand. Such assessment should cover the said activities and any other activity that might cause instability. Further, in the case of a partial demolition of a building, its stability should be assessed after the partial demolition and any modification carried out.

i. Chimney breast/stack removal; ii. Loft conversion or removal iii. Facade retention or removal. iv. Cutting floors including cantilevered canopies create mezzanine/two storey height areas in the building interior. v. Removal of roof cover and roof truss; vi. Removal of walls; vii. Removal of floors, column or beams; viii. Forming new openings; ix. Accumulation of debris on floor slabs; x. Removal of stair cases, ramps and lift wells xi. Excavation/removal of foundations, etc., xii. Alterations done in traditional building structures. xiii. Structural refurbishment, rebuilt and retrofitting works.

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Acquire knowledge on site condition in detail

Identify structural hazards

Selecting appropriate demolition technique

Is method chosen suitable for the structure No being demolished

Yes

Select type of demolition to be used

Is health and safety compromised by Yes choice made?

Is unplanned collapse possible? Yes Will temporary No support prevent

No this?

No Can a safe working area and exclusion Yes zone be established?

Yes

Proceed with demolition

Figure 5.1 – Flowchart for ascertaining structural stability of the building for demolition

(Source: BS 6187:2011 code of practice for full and partial demolition)

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5.1.2. Identification of structural elements and forces in stability assessment a) Stability-sensitive structures and elements

Expert engineering advice might be required to identify and assess the demolition method of stability- sensitive structures and elements. Figure 5.2 – 5.8 are some examples for stability sensitive structures.

i. Space frame roof structures

Figure 5.2 - Space frame roof structure at Pallekele stadium, Sri Lanka

(https://www.inspirock.com/sri-lanka/kandy/pallekele-international-cricket- stadium-a1139395553)

ii. High bay warehouses

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Figure 5.3 – High bay warehouse http://www.nkb.nu/wp-content/uploads/2017/08/kia-led.jpg

iii. Structures with unbalanced thrusts such as single and multiple arches, domes, kilns and single and multi-bay portal frames.

Figure 5.4 - Arches at Galle fort, Dutch Hospital

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Figure 5.5 - Domes houses at Pothuvil

http://static.monolithic.com/gallery/nonprofit/solidhouse/pic13.html

Figure 5.6 - Multy-bay portal frames (JZ Flowers International, England)

https://pbs.twimg.com/media/DgOnFo2W4AE3ph2.jpg

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iv. Lift-slab structures - lift-slab construction is a precast method of construction of slab on the ground and then lifting it to the structure

(a) (b)

Figure 5.7 Lift – Slab structures (a) Construction of L'Ambiance Plaza, image via NIST (b) The Huron Towers in Ann Arbor, Michigan, utilized the lift slab technique

https://skyrisecities.com/news/2017/04/tragedy-sparked-decline-lift- slab-construction

v. Retained facades.

Figure 5.8 - Retained facade (Nippon Hotel, Colombo 02)

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https://www.google.com/maps/@6.9234131,79.8523035,3a,75y,357.68h,94.0 7t/data=!3m6!1e1!3m4!1s0kwmSNYOlRRuH9xdvSLthQ!2e0!7i13312!8i665 6

Figure 5.9 - Ca Doro Building, Scotland, façade retention to support external walls during the demolition of the internal walls and floors

https://www.rmdkwikform.com/wp-content/uploads/2018/02/Refurbishment- Portfolio-UK.pdf

vi. Crosswalls and walls formerly restrained by roofs or floors. vii. Structures retained by features such as ground anchors. viii. Structures that provide stability to adjacent structures, e.g. basements and arches. ix. Structures which need stability from adjacent structures, e.g. arches. x. Structures in which the floors are suspended by hangers, e.g. hanging bolts, from overhead cross beams supported by a structural central core.

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xi. Cable stayed roofs.

Figure 5.10 - Cable stayed Roof (McCormick Place, exhibition hall, Chicago, Illinois, USA, 1986)

Source:https://www.som.com/FILE/16098/mccormickplacephase2_1 575x900_sadin_photo_group_ltd__1989_ben_altman_01jpg.jpg

b) Structural forces causing instability during demolition

During demolition of a building there can be different structural forces resulting due to various reasons such as unbalanced thrusts, lateral forces such as wind loading due to sway movement, etc. and these forces can cause structural instability. The Structural Engineer should refer to applicable standards and codes of practice in the assessment of such instability of the structure.

Potential causes of structural instability usually are:

i. interruption of a load path (the way load is transmitted to the ground) due to removal of structural elements and inability of the rest of the structure to support; ii. unbalanced thrusts caused by lateral components of forces, e.g. from sway loads and wind loads;

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iii. forces on basement walls from adjacent properties and thoroughfares (i.e. roads or paths forming routes between two places); iv. backfill loads affecting the stability of adjacent basements and other walls; v. Stress release of post-tensioned concrete beams; vi. propping effect on vertical cantilever walls (External props counter balance the lateral force in addition to the retaining wall) vii. Eccentric loadings such as presence of unaligned load bearing walls;

5.2 Avoidance of unplanned structural collapses

Demolition plan shall be prepared taking into consideration all structural aspects before and during demolition and giving methods and sequences of work properly, so that sudden and unintentional collapses can be prevented.

During demolition structure can collapse prematurely as shown in Figure 5.10 or unintentionally and such failures occurred due to inadequate residual structural stability;

This warehouse collapsed during demolition due to the inadequate lateral supports provided to the 9.14 m (30 feet) height wall;

Approx. 9.14 m (30’) height walls Without lateral supports

(a) (b)

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Figure 5.11 - Collapsed building during demolition (a) 9.14 m height walls without lateral supports (b) Collapsed building to the adjacent site causing fatalities

CAUTION 1: Floors should not be overloaded with machinery and/or debris

CAUTION 2: Some floor slabs are strong in one direction but weak in another direction. Therefore, this sensitivity to the orientation should be carefully studied before imposing loadings such as machines or with debris.

5.2.1. Adequacy of residual structural stability during demolition Maintaining adequate residual structural stability throughout the demolition process is very important. Before commencing demolition, the load paths of the structure shall be understood and residual strength shall be calculated predicting the ability to bear the loads by the remaining elements at each stage of demolition.

There could be unforeseen situations arising as the demolition proceeds. These should be brought into the notice of Authorized Person immediately and suitable changes in the demolition plan shall be done to redress such situations by the guidance of Authorized Person.

Temporary supports shall be provided when the residual structural strength is insufficient to bear or to redistribute the loads. Also, restrictions for imposed loading and loading areas shall be implemented during demolition work. In advance, calculations shall be given confirming the residual strength of the structure after removal of particular sections. Primary attention shall

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be given to these facts in the planning stage of the demolition in order to prevent sudden collapses during demolition.

3 - Outer wall of the structure being demolished 4 - Example of progressive demolition 5 - Temporary designed exclusion zone boundary during erection and dismantling of the security barrier 6 – Materials to be removed only when no refurbishment or demolition work is in progress 7 – Example of secure continuous barrier on stable supports 8 – Designed floor propping if required

Figure 5.12 – Essential elements of top down demolition process

Demolition work shall be carried out in a progressive manner. Exclusion zone should be designed to suite the demolition or modification work. It is important to have a proper barrier surrounding the proposed exclusion zone at all times and the floors beneath the working area should also be included with in the exclusion zone. Well-designed floor propping should be provided where necessary. If the exclusion zone is considered as insufficient then demolition

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should be carried out carefully with in a contained area so that the surrounding areas are safe. Debris removal should be done only when demolition or modification work is not in progress.

Whenever there is sufficient buffer zone, sufficient working space and accurate predicted debris area are all available then demolition of low-rise building can be carried out at the ground level easily using machine mount on ground.

1 – Structure being demolished 2 – Buffer area 3 – Exclusion zone boundary 4 – Limit of predicted debris area 5 – Limit of designed drop area 6 – Safe working space 7 – Demolition machine

Figure 5.13 - Plan of typical progressive demolition sequence, column to column maintaining “square” to provide lateral support

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Whenever possible demolition should be carried out in a symmetrical manner, so that the residual stresses in the building are evenly distributed for some extent.

1 – Exclusion zone 2 - Lift shaft 3 - Stairwell Figure 5.14 - Typical structure demolition sequence working "top down" outwards towards shear walls (strong points), i.e. lift shafts and stairwells

Sometimes low-rise buildings can be symmetrical with strong points on both sides such as lift shafts and stairwells. Then demolition may be started from the top floor and then proceeded to the floors below as shown by Figure 5.14. Demolition can be proceeded from top floor up to the first floor in a way such that lesser floor area is demolished at each step so that the debris from upper floors can be brought down to the ground reducing debris fall height.

5.2.2. For pre-weakening of structures When deliberate felling of building element is involved such as demolition of a column, pre-weakening is used. Columns can be removed by weakening at the bottom and pulling down using ropes. Pre-weakening method of demolition for columns are given in Section 8.2.5. Also, it is important to ensure that extent of the pre-weakening is as recommended and elements to be broken at site are matched with the demolition sequence given by the Engineer to avoid over breaking. When the reinforcement is cut using gas cutters in pre-weakening,

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shims1 shall be placed between the voids to control the premature collapse. These demolition methods shall be approved only by Registered Structural Engineer.

5.2.3. Temporary structural support for stability Temporary supports are provided to avoid premature collapses due to loadings such as eccentric loads, lateral loads, imposed loads etc. Also, in order to obtain required residual strength during demolition, temporary supports are used. These shall be designed by a competent person with a sound knowledge in Structural Design (Registered Structural Engineer) who should be responsible for the stability of the building throughout the demolition process. This section was included in this chapter to emphasize the importance of temporary structures in building demolition; detailed section on Temporary Structures are given in Section 7.2.3.

5.2.4. Decommissioning of demolition Due to various reasons such as unfavorable weather conditions, contractor’s issues, demolition projects may need to be halted temporarily. Prior to decommissioning a demolition project, precautionary measures shall be applied to prevent unplanned collapses in the remaining elements. Residual strength of the remaining structure shall be assessed considering all possible external effects such as wind effect, weather condition, change of material properties due to exposure, vibration effect etc. Also, it is important to identify and mitigate the risks at site such as unauthorized entry of public (Refer Section 7.4.3). Therefore, attention shall be paid to the recommendation given by Authorized Person. Approval shall be obtained submitting safety measures taken to decommission

31 1Shims - thin strip of material used to align parts, make them fit

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6. DEBRIS AND WASTE HANDLING

Debris generated in demolition sites are falling in the Construction and Demolition Waste Category (C & D). In Sri Lanka generally around 40% of total waste generated are C & D Waste (Central Environmental Authority, Guidelines on Sustainable Management of Waster Matter Generated in the Construction and Demolition of Buildings, 2017).

In the Demolition sites, the demolition contractor is responsible to ensure that the waste generated in the demolition site are handled and disposed properly complying with the existing regulations. Following described are further details to refer and it is always encouraged to reuse and recycle the debris generated to minimize the impact to environment.

6.1 Debris loading and unloading

Demolition plan shall include waste management plan including method of debris loading and unloading and precautionary measures taken to reduce risk involved in those activities. A safe route and time plan shall be implemented with minimum disturbance to the surrounding area.

When debris are allowed to fall freely to ground, exclusion zone or chute shall be placed and appropriate measures to taken off the bouncing effect and dust created. Effective communication should be established to ensure that the exclusion zones are clear from personals. The safety officer shall be present at site to ensure the safety.

6.1.1. Chute Chutes are used to move debris from higher floor levels to down floor levels. In demolition sites generally lift shafts are used as a chute. Debris shall be removed periodically. If openings are created on floor following shall be ensured;

i. Total openings shall not be greater than 25% of the total 1aggregate floor area; ii. Each opening shall not be larger than 900 × 900 mm unless it shall be justified by engineering calculation remaining structure is safe to withstand the impact force during demolition;

1Aggregate floor area - the aggregate area of every floor in a building or extension, calculated by reference to the finished internal faces of the walls enclosing the area, or if at any point there is no such wall, by reference to the outermost edge of the floor 32

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iii. When forming openings, structural elements such as beams shall not damage/cut any; iv. Opening shall be protected by edge barriers.

Figure 6.1 - Opening created to form a chute in a demolition site

Figure 6.2 - External Debris chute

https://www.hss.com/hire/p/rubbish-chute-section

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If chutes are created externally, adequate clear space and dust barrier shall be present. Old metal barrels shall not be used to create refuse chutes. External refuse chute shall be with adequate strength to withstand the impact when debris are falling through the chute.

6.2 Waste Management

Detailed waste management plan shall be submitted by the Demolition contractor along with the demolition plan. Authorized Person should ensure that a debris disposal and management system is prepared and implemented by the Registered Specialist Contractor (Demolition). When the demolition techniques are selected, waste management shall be considered in the Figure 6.3 order giving priority from top to bottom.

- Lowering the Reduce amount of waste produced - Using Materials Reuse repeatedly

- Using materials to make new Recycle products

- Recovering energy from waste Recovery

Landfill - Safe disposal of waste to land

Figure 6.3- Hierarchy for demolition waste management

 Reduce – To reduce the demolition waste, the need to demolish buildings has to be reduced by restoration of existing buildings with proper maintenance.  Reuse – Demolition technique shall be selected to salvage usable materials. Manual methods of demolition are the most suitable approach to get reusable materials. Generally doors, windows, roofing sheets etc. can be reused if they are in good condition prior to demolition.

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 Recycle – To produce a usable product. Metals such as steel, copper and brass are recycled. Currently, there is a good recycle market for C & D waste. Most popular usage is for road sub layer fillings and land fillings.  Recovery – Recovering energy from waste, such as incineration with energy recovery.  Landfill – Disposal of waste by without energy recovery

Waste Management plan shall include the following details:

a) Method of handling demolished debris. This shall include the routing movement of debris from each floor; b) Loading and unloading process and transportation of debris; c) Time and number of periodic disposal routines; d) Record of debris transporting vehicle information and landfill sites; and e) The site supervisory personnel responsible for the debris management system.

The plan should be updated regularly including waste generated and recovery/disposal routes.

6.3 Debris disposal

Waste generated in a demolition site has classified in to three categories according to their composition and potential to harm the environment as shown in Table 1.

Table 1 - Classification of waste generated in demolition sites

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Hazardous Major Minor Nonhazardous demolition demolition Nonhazardous waste waste demolition waste PVC Soil,sand,gravel, Conduits(iron,plastic),Pipes(GI,Iron asphaltic substances ,plastic)

Electrical waste Concrete, bricks, Electrical fixtures mortar, plaster, (Copper/aluminum wiring, wooden cement blocks, baton, plastic switches, wire Roofing tiles insulation)

Asbestos Steel (RCC, Panels (Wooden, laminated) material, Door/window treated timber frames, roofing supports, ironmongery, etc.)

Gypsum Rubble, Stone glazed tiles, glazed panels boards, other (marble, granite, sand roofing sheets stone)

Timber wood Sachets of tobacco and other plastics, Thermopolis, etc. Glass

In general, domestic wastes such as furniture, household appliances, etc., metal components such as window frames, pipes, etc., timber components such as doors, wooden floors, etc., other wastes such as tiles, asphaltic materials, ceramic products should be removed first. Most of these materials may be recycled. The building demolition shall begin after all the above non-structural materials have been deprived and removed.

6.3.1. Hazardous Waste When asbestos material generated in demolition sites are planning to dispose, the contractor should submit method statement for offsite removal of asbestos. Under a 1.25m thick soil layer where no excavation will be done asbestos should have buried and it is recommended by Central Environment Authority, Sri Lanka. Other hazardous chemicals such as radioactive

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luminous paint, lead paint, isocyanides, PCBs, mercury, acids, alkaline solutions, fumigation agents, water treatments, wood treatments or dusts, should be eliminate under guidance of appropriate specialist.

Firstly, ascertain the extent of hazardous risk which associate with the chemicals and implement the preventative and protective measures required for treatment and safe disposal.

For electronic waste, burning and disposal shall be avoided and storing should have done carefully at all times. Specifically, before sent to the recycling, compound/fluorescent electric bulbs should handle carefully.

6.4 Regulation on waste management in Sri Lanka

Direct regulations for demolition waste management in Sri Lanka are not available. But following regulations are relevant to management of demolition waste in Sri Lanka.

i. The amended National Environment Act (NEA) no.53 of 2000

ii. Under the legal provision of Environment protection of NEA

iii. Order published under the Gazette Notification No.1533/16 dated on 25.01.2008

iv. Order published under the Gazette Notification No.1534/18 dated on 01.02.2008(National Environment protection and Quality regulations)

v. Order published under the Gazette Notification No.1627/19 dated on 10.11.2009(Municipal Solid waste)

vi. Regulation published under the Gazette Notification No.850/4 dated on 20.12.1994(Appeal procedure)

vii. Regulation gazette notification No.924/13-1996/05/23; Introduction of Hazardous Waste management System

Solid waste management rule of Western Province No.01 of 2008 were introduced via extraordinary Gazatte No.1560/6 on 30th July 2008 status as any solid waste generated from construction or any rubble or debris from demolition shall not be

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mixed with any other waste and shall be handed over to the respective Local Authority or Authorized Body.

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7. HEALTH AND SAFETY

7.1 Insurance cover

Contractor shall obtain an insurance cover at least one from the following categories. (This is a mandatory requirement for the contractor)

a) Workmen’s compensation insurance b) Third party insurance c) Contractor’s all risk insurance

7.2 Precautionary Measures

Demolition of a building is associated with risk based activities which can affect the site personnel, general public, pedestrian, adjacent properties and traffic. Site safety features shall be designed and prevent vulnerability of accidents, difficulties attached in demolition activities and ensure the safety of the people. Proper safety features shall be designed considering all possible loads and load combinations at each stage of demolition and vibration impact by the Registered Structural Engineer in order to make sure that the demolition can be carried out safely and the site personnel is protected. The Contractor (Demolition) shall carry out the demolition works including precautionary measures in accordance with the approved plans and other related documents, and provide continuous supervision to the works.

7.2.1. Hoarding and Covered Walkway Generally hoarding isolates the demolition site from the public and provides the protection to the public during the demolition of the building. Also it prevents the unauthorized access and trespassing. To provide additional protection to the public and traffic from debris falling, covered walkway in conjunction with catch platform can be installed. Registered Structural Engineer shall design them to suit individual site circumstances. Suggested designs for hoarding, covered walkway and catch platform are listed in the following;

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a) Hoarding, Covered walkway and catch platform requirements Requirement for covered walkway depend on the height of the building to be demolished. The requirement for hoarding and catch platform are as described in Table 2 and as illustrated in Figure 7.1 (a), (b) and (c):

Table 2 - Summary of precautionary measures for hoarding, covered walkway and catch platform

Precautionary Prerequisite measure Hording a clear space between the building line and the lot boundary equal to or more than the building height (clear space) Covered with clear space less than the building height walkway Covered With clear space less than half the building height. walkway with No catch platform is required for building less catch platform than 4 m high hoarding and/or along the full length of the site boundary adjacent covered to public access walkway b) Proper use of covered walkway Roof of the covered walkway shall not be accumulated by debris and it shall not be used for other purposes such as storage of building materials and equipment.

Minimum vertical clearance – 2.3 m

Minimum clear width – 1.1 m

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Building

Hoarding

(a) Case 1 : Only hoarding is required, if clear distance ≥ H

H Covered walkway

H ≥ Clear distance ≥ H/2

Site boundary and hoarding

(b) Case 2 : Hoarding and covered walkway required if

H > clear distance ≥ H/2

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H > 4m Catch platform

Covered walkway

Clear distance ≤ H/2

Site boundary and hoarding

(c) Case 3: Hoarding covered walkway and catch platform are required if clear distance < H/2. Catch platform not required for buildings less than 4m high.

Figure 7.1 - Hoarding and Covered Walkway criteria

7.2.2. Scaffolding and Screen Covers a) Scaffolding Metal scaffolds shall be used for demolition projects. Demolition work shall be carried out by trained workmen under the immediate supervision of competent person. Competent Person shall check scaffold before using the scaffolding for the first time, during demolition with regular intervals, after addition, after dismantling or any other addition, after adverse weather conditions and any time where can be deviation in the structural stability.

Supports with adequate strength for the scaffolds should be provided to hold the vertical and lateral loads imposed on the scaffolds, catchfans and work platforms, etc. Registered Structural Engineer shall design the steel brackets and anchors fixed to the existing building or other kinds of supporting system. Debris shall be removed periodically and shall not exceed the limit given by the Registered Structural Engineer. Special attention to following factors shall be paid:

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i. Unplanned removal of scaffold ties; ii. Minimize debris falling from heights on to the scaffolding; iii. Scaffolds shall be close boarded against the building façade;

b) Screen Covers Over the scaffolds, two layers of protective screen shall be fixed to completely enclose the building structure for retaining dust and small debris.

[BS 8144: 2007 “Code of Practice for Safety Nets on Construction Sites and Other Works” may be referred to.]

c) Catch fan Catch fans are installed to catch small pieces of building debris which can pass through the protective screen and the net. A small piece could be harmful when falling from heights with carried kinetic energy.

7.2.3. Temporary Supports Temporary supports shall not be removed until its resisting loads are completely removed. Site Supervisor shall be appointed by the contractor for routine inspection and maintenance of temporary supports until it is removed.

Following conditions shall be addressed when designing temporary supports.

i. Inadequate structural stability of the building to be demolished; ii. Movement of the structure due to external load and vibration of the mechanical plant; iii. Load due to debris accumulation; iv. Structural stability of the partially demolished buildings and decommission; Temporary supports such as shoring/ propping can be provided for horizontal and vertical loads. Vertical supports can be single props, towers, spanning beams and trusses, needling beams, back propping and underpinning. For horizontal loads shoring/ propping such as braced towers, façade retention systems, raking props (transfer horizontal load to the

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ground), flying shores (horizontal props which transfer load to a stiff point at same level in areas such as lift core or return wall).

7.2.3.1. Temporary supports for Cantilevered Structures During the demolition of cantilevered structures, temporary supports shall be required and anchorage or holding down load of the cantilevered structure must not be removed until the temporary support is provided.

7.2.4. Catch Platform In accordance with the requirement, catch platform shall be provided on top of the covered walkway. Special structural elements such as pre-stressed concrete elements, architectural features shall be protected by catch fans for falling debris. These shall be designed and installed prior commencing the demolition.

7.2.5. Facade retention Façade retention system can be either independent or mutual and designed by a Registered Structural Engineer with structural knowledge.

a) In an independent system, raking shores or cantilever towers are used to fully support the facade.

Figure 7.2 - Cantilever towers

(https://www.lakeside-hire.co.uk/towers-cantilever-scaffold-towers/ )

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Figure 7.3 - Raking shores

(http://www.apexscaffolddesign.com/ind_portfolio.php?id=24#)

b) In a mutual system the different retained elements are linked together with horizontal shores so that they act compositely together.

7.3 Protection of Properties

When the demolition affects adjacent properties such as buildings, utilities, slopes, retaining walls or land precautionary measures shall be taken by means of above Section 7.2 mentioned methods or any other. Shared party walls, stair cases, maintaining access for adjacent properties need to pay special attention.

1.2.1. Vibration Depending on the demolition method vibration will effect on neighboring buildings in various extent. Also the traffic vibration caused by heavy duty vehicles might effect in a significant level. Demolition contractors are advised to carry out vibration monitoring and if needed pre-crack survey as recommended by the Registered Structural Engineer.

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As a general guideline, the peak particle velocities (PPV) at any adjoining structure shall not exceed the stipulated levels of the interim vibration standard level given by the CEA.

Table 3 - Categorization of structures according to the type of building (from ISO-4966: 1990E)

Category of the structure of the Description building Resistance to Multi storey buildings of reinforced concrete the vibration or structural steel, with in filling panels of decreasing Type 1 block work, brick work or precast units not designed to resist earthquakes Two-storey domestic houses & buildings constructed of reinforced block work, Type 2 precast units, and with reinforced floor & roof construction, or wholly of reinforced concepts or similar, not designed to resist earthquakes. Single and two-storey houses & buildings made of lighter construction, using Type 3 lightweight materials such as bricks, cement blocks etc, not designed to resist earthquakes Structures that, because of their sensitivity to vibration, do not correspond to those listed Type 4 above 1,2 & 3, & declared as archeologically preserved structures by the Department of Archaeology (Source: proposed air-blast over pressure and ground vibration standards for Sri Lanka by CEA)

Table 4 - Interim Standards for vibration of the Operation of Machinery, Construction Activities and Vehicle Movements Traffic

Category of the Type of Frequency of Vibration in structure as Vibration Vibration PPV given in Table (Hz) (mm/Sec.) 1.1 0 –10 5.0 Continuous 10-50 7.5 Type 1 Over 50 15.0 0 –10 10.0 Intermittent 10 –50 15.0 Over 50 30.0 0 -10 2.0 10-50 4.0

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Continuous Over 50 8.0 Type 2 0 –10 4.0 Intermittent 10 –50 8.0 Over 50 16.0 0 -10 1.0 Continuous 10 - 50 2.0 Type 3 Over 50 4.0 0 - 10 2.0 Intermittent 10 – 50 4.0 Over 50 8.0 0 - 10 0.25 Continuous 10 – 50 0.5 Type 4 Over 50 1.0 0 – 10 0.5 Intermittent 10 - 50 1.0 Over 50 2.0 Notes

1. Please see separate measurement methods 2. The values given above are in such a way that minor damage is unlikely as the nearby house/building (proposed air-blast over pressure and ground vibration standards for Sri Lanka by CEA)

Reduction measures: use equipment which are high tech with low vibration mechanics, debris falling height reduce or use vibration absorbing materials such as rubber at the point of falling, if possible temporary ground separation between the source and receiver.

7.2.2 Shoring Shoring shall be required in demolition work such as removing foundation, demolition of buildings with basements etc.

7.4 Special Safety Considerations

7.4.1. Training and communication Site personnel shall be informed by the safety officer at the beginning of the project regarding the safety precautions and risk involved during the demolition activities including the following items:

i. Information related to the project such as proposed methods and procedures

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ii. Risk involved or potential danger in working at heights, confined spaces, Lifting Appliances and Lifting Gears, Hot Works etc. iii. Health Hazards in demolition works iv. Safety measures such as use of Personal Protective Equipment and site access

7.4.2. Site Inspection and maintenance Site inspection shall be performed periodically (Daily) by a competent person appointed by the demolition contractor and any movement, damage or distortion to the temporary structures shall be identified and repaired immediately.

Contractor or his representative shall monitor the demolition work full time throughout the day and ensure the safety of the partially demolished structure at the end of the day before leaving the site.

If discrepancies with the method statement are discovered during the inspection, he/she shall inform the Registered Structural Engineer regarding the discrepancies and suspend the demolition work until written instructions are received.

7.4.3. Site security Demolition site shall be completely covered by screen cover and separated from the public by means of fence, barriers and hoarding etc. Fencing of not less than 2 m shall be installed and high standard site security shall be established to prevent unauthorized access because public is likely to be curious about the demolition work and ignorant of the potential risk. Access gates should be secured outside working hours also. Apart from the above, following factors also shall be considered:

a) Excavated areas shall be secured by safety barricade tapes; b) Immobilize vehicles and plants shall be secured; c) Isolate electricity and gas supplies, or enclose them in locked compounds;

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d) Outside working hours, remove ladders which provide access from the ground to the first landing place and store them in a secure area; e) Secure potential access points to buildings, including windows;

Note: Barricade tape is brightly colored tape that is used to warn or catch the attention of passers-by of an area or situation containing a possible hazard. It acts as a minor impediment to prevent accidental entrance to that area or situation and as a result enhances general safety.

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Figure 7.4 - Safety Warning Boards

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7.4.4. Site Access Site entrances shall be kept to the minimum and site access path shall be with free from potential hazards. Warning signs should be used to communicate the presence of hazards to site personnel and third parties.

7.4.5. Personal protective equipment on site Safety helmet should be worn by every site personnel along with suitable basic protective equipment such as footwear, gloves, eye protection, hearing protection, ori-nasal masks or any other respiratory protection equipment, high visibility clothing and fall arrest systems where necessary. Before using PPE adequate training shall be given and such equipment shall be maintained and stored to meet the required level of performance.

Site Safety

Figure 7.5 - Personnel Protective Equipment

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Safety Helmet Safety Glasses Safety Gloves

Ear Plugs Safety Boots High visibility cloths

Figure 7.6 - Personal Protective Equipment

7.4.6. Emergency Procedures Minimum of one emergency exit shall be maintained during demolition process. A clear path shall be maintained free of obstruction and properly marked with yellow arrows and exit signs. Emergency arrangements shall be provided as appropriate general items are given below:

a) Effective communication b) Training on emergency procedures c) Equipment for rescue and resuscitation d) Measures for raising the alarm and rescue e) Fire safety measures f) First aid

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g) Public emergency services

7.4.7. Hazards from services and combustible materials Underground and overhead services such as electric, water, sewage, telephone and other communication and services supply shall be disconnected or abandoned before commencing the demolition work. Relevant authority such as Ceylon Electricity Board, Water Board etc. shall be informed when service line interrupted activity is included in the demolition process. Arrangement shall be made to ensure that all the service lines which can affect are properly disconnected and confirmed by respective officer.

Following are some works which can damage the service lines:

a) When moving heavy plants over underground service lines; b) Ground transmitted vibration due to the plant operation; c) Work which might give rise to ground movement.

When the demolition involves combustible materials, precautions should be taken to prevent fire or explosion. There could be a fire hazard when the gas cutter is used. There could be health hazard due to toxic combustion products, therefore methods of demolition likely to cause ignition should be avoided. Contractor shall maintain firefighting appliances in good condition and free from defects.

7.4.8. Disconnection of Utilities a) Owner shall be responsible of disconnecting the utilities prior handing over the building to the contractor to demolish; b) Prior to actual demolition contractor (demolition) shall keep records of the available utilities and identify the effects of demolition on utilities; c) All utilities shall be terminated prior starting the demolition activities and rearranged where necessary; d) Provide fences demarcating boundaries to operate machines safely without touching service lines such as overhead electric lines;

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e) Temporary utility supply shall be given which will be needed for the execution of the demolition work. 7.4.9. Maintenance of Certain Utilities During demolition, the following shall be required to provide a safe and healthy working environment: a) Temporary water supply shall be required to provide water spraying during demolition as dust pollution abatement measures; b) Temporary telecommunication link between the demolition site and outside shall be maintained for both security and communication reasons; c) Temporary electricity supply for lighting and other construction use; d) Necessary approval shall be taken for temporary utility supplies; e) In the case when temporary utilities are available, all such temporary utilities, including electrical fittings shall be weather- proofed; f) Safety warning lights indicating connection lines and “Emergency Stop” of connection lines;

7.4.10. Falling and projected materials Operation areas shall be identified where deliberate dropping, or potential for dropping of materials could occur. People should be kept away from such areas and necessary precautionary measures shall be taken. Adequate temporary supports shall be installed where necessary before commencing the demolition work.

7.4.11. Flooding When demolition take place in areas like deep basements, underground tunnels, cooling water culverts, plant rooms and excavations, the contractor shall pay special attention to assess the risk of flooding. When the work program is preparing adequate time allocation and necessary precautions shall be given with predicted weather condition.

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Also adequate pumping arrangement shall be given to control water seepage.

7.4.12. Protection of Traffic Road closures shall be avoided as much as possible when demolition work carry out especially when mobile cranes, heavy trucks are involved. Temporary closure of a traffic lane may be considered only when there are no any other alternatives and at such events road closure may be considered for night work.

Traffic controller outside the site shall be appointed and active alarms, active warning alarms shall be installed. Sufficient illumination level should be maintained outside the site, especially near walkways.

7.4.13. Incomplete Demolition Projects When a demolition project is shut down for a prolonged period before its completion, the remaining structure, if any, shall be stabilized by temporary support and/or bracing systems.

i. Deny unauthorized access to the site; ii. Warning signs and safety alarms.

7.5 Health Hazards

Health hazard associated in demolition activities can be categorized in to following in general:

a) Inhaled or ingested gases, vapors, fumes, dusts which can be acutely or chronically toxic, allergenic, carcinogenic b) React with or be absorbed through skin can be toxic resulting dermatitis or cancer c) Irritation can occur due to the large quantity of dusts d) Hearing problems due to being at high noise operation areas for a prolonged period and not using hearing aids

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Exposure to dust

Occupational Exposure to diseases chemicals

Fire damage First aid and facilities ventilation

Noise Sanitation exposure

Figure 7.7 - Site personal health governing factors

7.5.1. Welfare and first aid a) Welfare facilities for the site personnel

Welfare facilities for the site personal shall be provided and maintained sufficiently including sanitary facilities (including clean water and washing facilities). Accommodation shall be provided in the immediate vicinity to the site with convenient access for the work place.

b) First aid

A first aid box shall be present at site with enough equipment to cope with the number of workers on site. A responsible person shall be appointed at the beginning of the work to take charge of first aid arrangements.

7.5.2. Lone-working Lone workers are those who work by themselves without close or direct supervision. The contactor has a duty to assess the risks to lone workers and

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take steps to avoid or control risks where necessary. But it is recommended at least two workers to work together where possible.

7.5.3. Working in confined spaces and hazardous atmospheres When demolition in confined spaces such as shafts, culverts, manholes shall be planned only if there are no other practical method of demolition without entry is available. Any confined space could be vulnerable for converting to hazardous atmosphere.

Before demolition commencing demolition and decommissioning, hazardous spaces shall be properly marked by warning notices. Hazardous atmospheres can be created by demolition activities such as use of flame cutting equipment, leakages from gas cylinders, release of entrapped air. Prior to entering such spaces steps shall be taken to ensure the safety of the work personal.

7.6 Environmental Precautions

7.6.1. Air Pollution Main air pollutant generated in demolition activities are dust particles (described in Section 7.6.2 (a)). Other than the dust there can be diesel fumes generated by mechanical plants or equipment. Burning of waste shall prohibited on site.

7.6.2. Dust and Noise a) Dust

Concrete breaking, handling of debris and hauling process are main sources of dust from building demolition.

Dust level should be maintained below 0.450 mg per m3 of air at a distance of 10m down wind direction as 3 hour average.

(Interim source emission regulation, CEA)

Mitigation measures: Temporary screen cover shall be provided to minimize dust, pressurized water spraying during demolition.

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Figure 7.8 - Pressurized water spraying during demolition b) Noise

When the site personnel are exposed to noise at the construction sites proper safety equipment should be made available. The employer should provide safety gear to personnel if the noise exposures or exceed an eight hour time weighted average sound level of 85 dBA.

For the increase of each 5dB the exposure period should decrease by two fault. (Multiply by 0.5)

When the site personnel are exposed to sound levels exceeding those levels administrative or engineering controls must be used. Concrete cutting is a huge noise hazard on site and it is often around 110- 115dBA.

(Federal highway association of USA (FHWA - refer for more details)

Demolition sites are also considered as a construction site in according to the national noise regulations in Sri Lanka. Therefore the noise level

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at the boundary of the demolishing site should be maintained below 75dB during day time (6.00 to 21.00) and below 50dB during night time (21.00 to 6.00)

(National Environmental (Noise Control) Regulations No.1 1996)

Noise reduction – use of low noise technological equipment for demolition work, use of temporary barriers, arrange activity schedules with high noise activities to operate in minimum duration, reduce fall height of debris

7.6.3. Water In demolition site main cause for water pollution is water contaminated with demolished material which generally increase turbidity and dissolved matter. Therefore use of simple filtering system or sedimentation tank will be satisfied to treat waste water. However contamination with other chemical materials may need satisfactory treatment.

The discharge of wastewater from demolition sites requires to maintain the relevant standard stipulated by the CEA and sometime require a license that applicable for the discharge.

Contractor (Demolition) shall maintain proper control of temporary water supply and an effective temporary drainage system.

(National environmental protection and quality regulation 01 – 2008)

7.6.4. Hazardous Materials Handling of hazardous materials are discussed in Section 6.3.1.

The management of waste must fully comply with the Waste Disposal Ordinance of CMC

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8. METHODS OF DEMOLITION

There are many techniques used in the world for demolition of buildings. Compact machines, high-reach machines, tower and other high-reach cranes, remotely controlled machines and robotic devices, demolition using chemical agents, by explosives, high pressure water jetting and metal powder cutting etc.

This guideline describes only the demolition of common structural elements by manual and mechanical (machine) methods. Other techniques mentioned above shall not be discussed in this document.

8.1 General

The choice of the demolition method depends on the following factors as given in clause 2.2

a) Health and safety

b) Structural Characteristics

c) Site Conditions/Locations

d) Demolition Cost

e) Time/Duration

f) Past experience of the contractor in similar projects

g) Waste Disposal Method

h) Permitted level of nuisance

This guideline describes only the demolition of common structural elements (slab, beam and columns) by manual and mechanical (machine) methods. Other techniques mentioned above shall not be discussed in this document. Each building has its specific features to consider. Therefore, the demolition procedure for each site has to be proposed by a competent engineer under guidance of Registered Structural Engineer considering the factors given in Section 8.1.

For sites situated in busy urban areas, most applicable method is top down method. If there is sufficient clear space, other mechanical methods which are applied from the outside of the building may be used. Hand held tools or the cut and lift process

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may be used as a safe solution for structural projections such as balconies, canopies and verandahs extending beyond the building lines.

8.2 Top Down-Manual Method

Structural elements shall be broken down leaving the reinforcement, until the concrete connecting to reinforcement is sufficiently broken away. In congested areas cantilevered canopies, balconies and exterior walls are critical elements due to the risks to the public.

If rope or tie wires are used to pull down the structural elements, the pulling wire must be at least 4 times stronger than the anticipated pulling force. In addition, workers shall be shielded from the rope or tie wires. The rope or tie wire shall be checked at least twice per day.

(Buildings Department, 2004)

8.2.1. Demolition Sequence The demolition sequence given here is a general sequence which could deviate according to site conditions, restrains, the building layout, the structural layout and its construction;

a) Doors, windows and non- structural features shall be removed and reused as much as possible; b) Prior to demolition of main structure, all cantilevered structures, canopies, verandahs and features attached to the external walls shall first be demolished; c) All lift machine rooms and water tanks at the top shall be demolished to the main roof level in “top down” sequence and roof structure shall be dismantled or removed, and the material be re-used where applicable; d) Demolition of the floor slabs shall begin at mid span and work towards the supporting beams; e) Floor beams shall be demolished according to the order given below:

i. cantilevered beams;

ii. secondary beams;

iii. main beams.

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f) Beams shall be propped prior to loss of support or restraint; g) Non-load bearing walls such as partition walls shall be removed; h) Load bearing walls and columns shall be removed after removing the beams on top;

All cantilevered structures, canopies, verandahs and features attached to the external walls

Roof structure

Non-load bearing walls shall be removed prior to demolition of load bearing walls;

Demolition of the floor slabs

Floor beams

Columns and load bearing walls shall be demolished after removal of beams on top

Figure 8.1 - Flow chart for demolition sequence

8.2.2. Cantilevered Structures and Balconies Temporary supporting structure, catch platform and/or temporary platform shall be placed underneath a cantilevered structure or balcony prior to the demolition and precautionary measures shall be taken to ensure the safety of the public. The general sequence of dismantling cantilevered slabs and beams are given in the following procedure;

a) Exterior brick in-fill walls shall be demolished leaving the reinforced frame behind as described in Section 8.2.5. a) b) Any dead load or structure supported by the cantilever slab shall be removed; c) Starting from the exterior edge of the cantilevered slab, the concrete shall be broken down working inwards towards the supporting beams;

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d) After the demolition of the connecting slab, the cantilevered beam shall be demolished but not advance further than the slab (so that the support for the slab shall be maintained). Figure 8.2 and Figure 8.3 illustrates the demolition of cantilevered beam

with the slab;

Figure 8.2 - Demolition of Cantilevered Reinforced Concrete Slab (Manual Method)

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Figure 8.3 - Demolition of Cantilevered Reinforced Concrete Slab and Beam (Manual Method)

8.2.3. Arches Arches can be fixed type or hinged type. Forces in the arches are carried to ground as thrusts. In order to ensure the stability of the arches during demolition, forces shall be balanced. Following can be applied where applicable:

a) shoring to transmit horizontal thrusts to the ground; b) building in temporary tie bars; c) reducing vertical imposed loads; d) demolition of the arch in whole strips; and e) Some combination of a) to d).

8.2.4. Roof Trusses Roof truss shall be removed progressively, ensuring stability of the remaining structure. Temporary bracings or supports shall be added where necessary. Generally the bottom ties of the truss shall not be cut. Large trusses might need additional supports and removed section wise. Removal process of larger roof trusses such as industrial buildings shall be decided by a Registered Structural Engineer.

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8.2.5. Exterior walls, Beams and Columns a) Brick in-fill Wall i. Using working platforms outside of the building, in-fill bricks shall be removed pushing inward, before removing the reinforced concrete framing to avoid any potential hazard of bricks falling out of the building; ii. Brick layers of not larger than 300mm shall be removed starting from the top and move downwards; iii. Reinforced frame shall be removed by separating the individual columns/ beams or taking down the frame of a bay between two columns as described in 8.2.5 b) and c) b) Exterior Beam i. Exterior beam could be demolished by two methods:  Gradually breaking away the concrete of the beam or;

Dismantling the entire beam section as shown in (b) Step 02: Lowering of beam

 Figure 8.4 (a) and (b). ii. Wire and winch or other systems shall be used to secure the cross beam to other structural members; iii. Expose the reinforcement by breaking away the concrete at both ends near its columns; iv. Reinforcement shall be cut at one end to allow the beam to partially drop. The wire shall safely winch the beam down to the building floor in a controlled manner; and

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v. The dismantling would be completed by cutting the reinforcement at the remaining end, in a controlled manner the beam will then be lowered completely.

(a) Step 01: Pre-weaken the beam edge

(b) Step 02: Lowering of beam

Figure 8.4 - Demolition of external Beam (Manual Method) – dismantle the entire beam section

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Figure 8.5 Adjustable steel jacket

Figure 8.6 - Details for Securing External Beams before Dismantling (Manual Method) c) Exterior Column i. Using a wire and winch, top of the column shall be secured by tying it to a nearby structural member; ii. Bottom of the column shall be pre-weaken by breaking away the concrete cover and cutting the reinforcement at the exterior side of the column as shown in Figure 8.7;

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Interior side Exterior side

Figure 8.7 – Pre-weakening of column – cut reinforcement in exterior side

(iii) After pre-weakening, the column shall be pulled down by the wire and winch towards the interior in a controlled manner (Figure 8.8).

Figure 8.8 - Pre-weakening and dismantling of column (Manual Method)

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d) Exterior Reinforced Concrete Frame

The exterior reinforced concrete frame may be demolished in sections. Demolition procedure as described below:

i. A bay of not wider than 3 m between two adjacent columns shall be an optimum section for manual demolition; ii. Before disconnecting the framing from the remaining structure, the frame section shall be secured to other structural members by means of wire and winch; iii. Bottom of the two columns shall be pre-weakened and removed as described in Section 8.2.5 c); iv. The reinforcing bars connecting the beams shall be cut off after pre-weakening. The framing shall be pulled down by exerting force through winch and pulley system. e) Reinforced Concrete Wall

I. Load Bearing Wall

Reinforced concrete walls shall be demolished by cutting down into manageable sections of not wider than 2 m. Demolition procedure of concrete wall sections are as following procedure (Figure 8.9 (a) and (b)):

i. Using wire and winch system, wall section shall be secured before starting demolition; ii. Using hand held tools the concrete along the cut lines of the interior face of the wall section shall be broken away after pre-weakening the bottom of the wall section. iii. Pre-weakening shall be as described in Section 8.2.5 c)

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iv. The operation must be careful to minimize debris from falling out from the building; and v. After removing the concrete along the cut line, the reinforcing bars along the vertical cut line shall be separated. Then the cut section shall be pulled towards the building using the wire and winch system.

(a) Prior to pulling of the concrete wall

(b) Pulling of concrete wall after cutting reinforcement

Figure 8.9 - Felling of a reinforced concrete wall with beam (Manual Method)

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(a) Prior to pulling of the concrete wall

(b) Pulling of concrete wall on rubber pad

Figure 8.10 - Felling of reinforced concrete wall separately from the cross beam (manual method)

II. Non-Load Bearing Wall Demolition of non-load bearing walls are similar to that of load bearing walls except from the beams are removed at latter stage as illustrated in Figure 8.10.

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8.2.6. Floor Slabs Typical demolition procedure for reinforced concrete slabs are shall be done as per Section 8.2.6. Concrete shall be broken away leaving the reinforcement until the concrete is completely removed.

Figure 8.11 - Demolition of two way slab (Manual method)

a) Two Way Slab Two way slab shall be demolished starting from the middle of the slab and advance towards the four sides as shown in Figure 8.11.

b) One Way Slab One-way slab is a slab which is supported by beams on the two opposite sides to carry the load along one direction. When one-way slab is demolished following procedure shall be followed:

i. Start breaking of concrete at the unsupported end; ii. Break the concrete as strips perpendicular to the supported ends; iii. Start breaking the concrete at the middle and proceed towards supported ends.

c) Flat Slab A flat slab is a two-way reinforced concrete slab that usually does not have beams or girders, and the loads are transferred directly to the

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supporting concrete columns. When flat slab is demolished following procedure shall be followed:

i. Start breaking of concrete at the center of the bay; ii. From the center proceed towards the supporting columns; iii. Premature weakening of columns or supporting walls shall be avoided; iv. When the demolition advance in column strips, adequate supports shall be provided. (In the flat slab, the columns strips are the section that are center aligned with column and has the width equal to 1/4th of the shorter span on each side)

8.2.7. Interior/Secondary Beams Interior/secondary beams are horizontal beams connecting primary beams. These beams normally support floor slabs on both sides. In demolition all dead loads imposed on the beam and slabs supported by the beam should be removed first after which these beams can be removed. The dismantling of interior or secondary beams is illustrated in Figure 8.12 (a) and (b). Details for securing secondary beams before dismantling given in Figure 8.13. Alternative securing method can be used as given in Figure 8.5

8.2.8. Interior Columns Demolition of interior column is similar to the method described in Section 8.2.3 c).

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(a) Pre-weakening of interior secondary beam edge

(b) Lowering of interior secondary beam

Figure 8.12 - Demolition of secondary beam (Manual Method)

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Figure 8.13 - Details for securing secondary beams before dismantling (Manual Method)

8.3 Top Down-By Machines

When demolition is done using machines, first the mechanical plant is lifted and placed on the slab using mobile crane or any other suitable method. Rest of the sequence of top down by machine is similar to the top down manual method only the demolition is done using mechanical plant. If rope or tie wires are used, wire strength shall be at least 4 times the anticipated load and workers shall be protected or stay away from the pulling area.

a) Supports for Machines

Structural Engineer shall assess the imposed load and the vibration induced by the mechanical plant and adequate supports shall be provided. The movement of the mechanical plant shall be prohibited in areas such as building edges (minimum distance of 2m), floor openings (minimum distance of 1m) and cantilever structures. Boundary of the mechanical plant moving shall be marked by appropriate methods.

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b) Lifting of Machinery

Using a mobile crane or by other means, mechanical plant shall be placed after dismantling of the roof. The operating area shall be blocked off during the lifting operation and for special attention on high tension power supply shall be given in operating. Registered Structural Engineer shall design the propping arrangement and propping shall be installed prior to the lifting operation. c) Temporary Ramp Construction

Mechanical plant shall be moved down to the next floor by means of a ramp made of steel or any other material which can be safely bear the load of the mechanical plant and ramp shall be dismantled after moving the mechanical plant.

Ramp made of debris is not a safe practice to be adopted without professional involvement.

8.3.1. Demolition Sequence General demolition sequence when using mechanical plant is as given below. This can deviate depending on the general conditions given in Section 8.1.

a) Place the mechanical plant on to the top most floor as described above after dismantling the roof; b) All cantilevered slabs, canopies, beams shall be demolished prior to demolition of internal floors; c) Structural elements shall be demolished in the order of slab, secondary beams, main beams respectively;

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d) Mechanical plant shall be lowered to the next floor by means of ramp or any other method; e) Mechanical plant should work while placed on structural elements on a floor f) After completing demolition on a particular floor, the mechanical plant should descend the floor immediately below from where the plant will demolish the remaining elements in the floor above; g) When breaking a wall panel, including beams and columns they shall be demolished by gradually breaking down the concrete or by pulling them down in a controlled manner as shown in Figure 8.16 and Error! Reference source not found.Figure 8.17; Illustration from Figure 8.14 (a) – (f) shows typical mechanical demolition procedures;

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(a) Demolition of slabs and beams

(b) Continue demolition of slabs and beams

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(d) Demolition of interior column may needed to create access and working room for exterior wall demolition. Demolish column by first pre-weakening the bottom, then dismantled by machine in fully controlled motion.

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(e) Cutting the exterior wall in section and pre-weakening of columns. Cutting should be careful to minimize debris falling outside

(f) Machine should be used to brace the wall section while cutting the reinforcing bars connecting the wall section. The wall section shall be pulled down in controlled motion

Figure 8.14 - Typical sequence of top down method with mechanical equipment

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8.3.2. Cantilevered Canopies and Balconies Cantilevered canopies and balconies can be removed by sections. Sections shall be cut considering its weight which can be lifted by derrick arm. Concrete can be cut using concrete cutting machines or any other method.

(a) Case 1 – Machine mounted on suspended floor

(b) Case 2 – Machine mounted on ground

Figure 8.15 - Demolition of cantilevered slab by mobile machine (conventional method)

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8.3.3. Exterior Walls, Beams and Columns Demolition of exterior walls shall be done by sections. Short span slab portion of about 300 mm shall be left at the peripheral beam to keep the loading resultant further into the building. Width of the wall section shall be determined by the Registered Structural Engineer and the mechanical plant shall require adequate capacity to safely handle the wall section.

a) Brick in-fill wall Working platform may be used from the exterior side of the building removing bricks manually starting from the top layer pushing in to the building. After removing the infill bricks, concrete frame can be removed as method described in Section 8.3.5 c) b) Exterior Column i. Column shall be braced using excavator arm with wire or hydraulic crusher attachment; ii. Pre-weakening of the column bottom shall be performed as described in Section 8.2.5 c); iii. Using an excavator arm column shall be pulled in to the building in a controlled manner. c) Exterior Reinforced Concrete Frame Removal of exterior concrete frame shall be done as described in the following steps: i. Concrete shall be broken first along the proposed line. The excavator arm shall secure the concrete frame and also reinforcement can be left to stabilize the structure ii. As described in Section 8.2.5 c) pre-weakening may be performed at the bottom of the columns. While cutting the reinforcement at the concrete removed areas, excavator arm shall continue to stabilize the structure iii. Concrete frame shall pull on to the floor using the excavator arm as shown in Figure 8.16 (a) and (b).

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d) Reinforced Concrete Wall

Demolition process of reinforced concrete wall section is similar to that of a reinforced concrete frame described in above Section 8.3.5. c). Demolition of a reinforced concrete wall section is illustrated in Figure 8.17and is described by the following:

i. Concrete wall shall be demolished in sections and the width of such wall section shall be determined by the Registered Structural Engineer; ii. Concrete wall section shall be vertically separated from the remaining wall by breaking away the concrete while keeping the reinforcing bars intact to provide necessary support to the wall section; iii. If the wall section to be demolished contains columns, pre- weakening shall be performed at the level where the wall is to be separated as shown by Figure 8.7. Pre-weakening of column is referred to in 8.2.5 c); iv. Level up to both vertical separations is done and pre-weakening of columns is done shall be decided by the Registered Structural Engineer; v. The wall section should be held securely using the machine arm during the cutting of the reinforcements along both sides of the wall section; and vi. After the reinforcing bars are cut, the machine arm shall steadily guide and pull down the wall section into the building. 8.3.4 Floor Slabs Floor slabs concrete shall be removed by machine with breaker, hydraulic crusher or other appropriate method. Reinforcement shall be cut afterwards. Method of demolition of slab is similar to the method described in Section 8.2.6

8.3.5 Interior Beams Interior Beam may be demolished by breaking the concrete away gradually and cutting the reinforcement afterwards.

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8.3.6 Interior Columns The same procedures as described for the exterior column in Section 8.3.5 b) should be used to demolish reinforced concrete interior column.

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(a)

(b)

Figure 8.16 - Demolition of reinforced concrete frame by excavator with breaker

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(a)

(b)

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(c)

(d)

Figure 8.17 - Demolition of reinforced concrete wall by excavator

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8.4 Demolition of Basement and retaining walls

Structure with basement or retaining wall shall be demolished under the guidance and recommendation of a Registered Structural Engineer. Additional information

Regarding previous structural assessment should be referred. Special attention shall be given to factors such as given below:

i. Whether the intermediate walls or floors are supported by the retaining structures; ii. Whether the retaining wall is supporting a road or highway; iii. Whether water is allowed or not to drain in depending on the water table of the area and also dewatering requirements; iv. Prevent penetrating water in to neighboring buildings and provisions for water proofing where necessary; v. Adequate buttressing wall/ shoring or ramping shall be provided to support the retaining wall if the basement, cellars, vaults or voids need to be left open. vi. When the basement, cellars, vaults or other voids need to be backfilled effect to the adjoining party shall be assessed; (whether induced ground pressure due to the fill can be withstand by the adjoining property adequate supporting shall be given with provisions for water proofing)

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REFERENCES

1. Arham Abdullah and Chimay J. Anumba (Loughborough University, United Kingdom). (2015). Decision Tools For Demolition Technique Selection.

2. BSI. (2011). BS 6187 Code of Pracxtice for Full and Partial Demolition of Buildings. British Standard Institute.

3. Buildings Department, H. K. (2004). Code of Practice for Demolition of Buildings. Hong Kong.

4. Central Environmental Authority. (2008). Proposed air-blast Over Pressure and Ground Vibration Standards for Sri Lanka. Pollusion Control Division.

5. Central Environmental Authority. (2017). Guidelines on Sustainable Management of Waster Matter Generated in the Construction and Demolition of Buildings. Waste Management Unit.

6. Rameezdeen Rameezdeen,Chaminda Pathirage,Saman Weerasooriya. (2003). Study of Construction accidents in Sri Lanka. Built-Envirnment-Sri Lanka-Vol.04, (p. Vol.04).

7. Sri Lanka Institute of Architects. (2016). Construction Site Safety Manual for Consultants. Colombo 07: Professional Affairs Board, Sri Lanka Institute of Architects.

Annex 01

ANNEX 01

Legislation and statutory regulations

Annex 01

LEGISLATION AND STATUTORY REGULATIONS

Authority Regulation/ Act / Ordinance National Environmental (Protection and Quality) Regulations, No. 1 of 2008. The National Environmental (Ambient Air Quality) Central Environmental Authority Regulations, 1994, published in Gazette Extraordinary, No. (CEA) 850/4 of December, 1994 National Environmental (Noise Control) Regulations No.1 1996 Proposed air-blast over pressure and ground vibration standards for Sri Lanka Construction Industries and Development Authority ( CIDA) Urban Development Authority “Each DGP should identify the architecturally, environmentally, (UDA) aesthetically and archeologically valuable areas and buildings and it should be listed so that no demolitions, changes, alterations or additions should be done without the prior approval of the Authority (UDA).” – Development Guide Plan (DGP), City of Colombo Development Plan (compiled edition), March 2018

Annex 02

ANNEX 02

Useful contacts for demolition work

Annex 02

USEFUL CONTACTS FOR DEMOLITION WORK

Type of organisation Organisation Professional Bodies Institute of Engineers Sri Lanka

Industry Associations Training Bodies Advance Construction Training Academy

Government Department Agencies and  Central Environmental Authority Organisations  Urban Development Authority  National Building Research Organisation  Construction Industry Development Authority  Colombo Municipal Council

Utilities/ Services regulators  Ceylon Electricity Board  National Water Supply and Drainage Board Other industry resources

Annex 03

ANNEX 03

Sample Building Demolition Plan

Annex 03

SAMPLE DEMOLITION PLAN AND STABILITY REPORT FOR TOP DOWN MECHANICAL METHOD

1. DEMOLITION PLAN

1.1. The demolition plan shall consist of the following :

a. Site Plan and Adjoining Site Conditions. b. As built drawings (Sections and elevations of the building) and information on existing building structure. c. Demolition procedure and sequence d. Precautionary Measures e. Temporary Support System

1.2. Stability Report

1.2.1. The stability report of this project shall consist of the following: a. A Stability report to justify the safety of the existing building during all phases of demolition.

b. A structural check with calculation on the support of cantilevered slab and beams.

c. A structural check with calculation on the support to typical floors catering for the loading due to powered mechanical plants.

d. A structural check with calculation on the temporary ramp design to allow the descending of the machines.

e. A stability report with calculation to justify the safety of lifting of the machine to the roof.

f. A structural check with calculation on its hoarding, covered walkway, and catch platform.

Annex 03

Sample Demolition Plan (Please note that this is only for guidance and included in short form for the ease of understanding) Duly completed and certified demolition plan shall be submitted to the Authorized Body by the Demolition Contractor Documents to be Demolition Plan submitted Site Plan and Adjoining Site Conditions Typical Floor Plan and Existing Building Information Elevation Demolition procedure and sequence Precautionary Measures Typical Support

Stability Report A Stability report to justify the safety of the existing building during all phases of demolition. A structural check with calculation on the support of cantilevered slab and beams if available A structural check with calculation on the support to typical floors catering for the loading due to powered mechanical plants A structural check with calculation on the temporary ramp design to allow the descending of the machines A stability report with calculation to justify the safety of lifting of the machine to the roof A structural check with calculation on its hoarding, covered walkway, and catch platform

Annex 03

Authorized person shall submit the following information

Item Tick if Information requested Provided No. required (Yes/No)  Site safety supervision plan  The name of technical competent person and their particulars  Details of operators of powered mechanical plant or equipment proposed to be used  Details of the debris disposal and management system  Details of the site engineer

General 1. Details of the building owner

Information - Name

- Address

- Contact details 2. Description of site area

- Address

Annex 03

- Total area of land (m2)

- Local authority (Land belongs to)

3. Boundary Conditions

- North

- East

- South

- West

- Topography

4. Traffic Condition

5. Adjacent Utilities

- Above ground

- Under ground

- Utility plans available Yes No Ex. Electricity, Water, Telephone, Sewer, Gas 6. Adjacent buildings

- Structural conditions Ex. No significant deterioration or damage to the structural element or significant foundation settlement were observed. These adjacent buildings appear to be properly maintained and would not be adversely affected by the demolition of the building

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- Party wall and common features

- Presence of independent walls Yes No Physical separation between the premises and the adjacent buildings Yes No

- Details if available

Building Details 7. General information and dimensions

- Age :

- Use :

- Building foot print

- Overall height

- Floor to floor height As built drawings ( Available/ Not available) 8. Structural System

- Structure Ex. The building is reinforced concrete construction with conventional slab, beam, column and rigid frame design. It is supported on pile foundation

- Present State

Ex. The inspection reviewed that the building is well maintained and kept in good conditions. Other than minor cracks appearing on the finishing, no serious deterioration or damage to the structural element was observed

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9. Special structural features Ex. The building has cantilevered balconies projecting over the existing foot path on xx street. There is no other special structural element in the building

10. Presence of Hazardous materials (Yes/No) If yes attach plan of removal off the site prior to commencement of demolition work Method 11. Information which need to be included in the method statement

Statement of - Method of demolition (with drawings if possible) Demolition - Excavator details and it’s movement restrictions Work - Demolition of exterior / common walls Exterior wall (Descriptive plans shall be - Lifting method of excavator submitted - Demolition sequence covering the items) Precautionary 12. Utilities disconnection Measures 13. Covered walkway and catch platform (Descriptive 14. Scaffolds, working platforms, screens and catchfan plans shall be 15. Temporary supports submitted Arrangement plan attached Yes No covering the 16. Debris handling items) plan attached Yes No 17. Special site safety

- Emergency exit

- Fire prevention 18. Training 19. Dust and noise 20. Maintenance and inspection 21. Emergency plan

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22. Post demolition

...... Demolition Contractor Consultant Demolition Owner/ Applicant Engineer

Name Name Name Address Address Address

Signature Signature (Professional Signature Stamp) Date Date Date

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ANNEX 04

Flow Chart for Building Demolition Procedure

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