Construction Safety, Construction Quality and Demolition

URP S-09 TrainingModule S15

Construction Safety, Construction Quality and

DemolitionDate: 15 July 2021

Raquib Ahsan, PhDProfessor, Department of Civil Engineering, BUET

Relevant Chapters of BNBC 2020

Part 1 Chapter 2

Part 5 Chapter 2

Part 6 Chapters 5 and 6

Part 7

S. K. Ghosh Associates LLC International Code Council (ICC)

www.skghoshassociates.com 1

Outline of Presentation

Constructional Responsibilities and Practices

Storage, Stacking and Handling Practices

Safety during Construction

Demolition Work

Evaluation and Acceptance of Concrete

Enforcement





Planning

Construction Control

Construction Management

Protection of Public and Workers

Environmental Protection

Planning

Responsibilities: The terms of contract between the owner and the contractor, and between a consultant and the owner, shall be clearly defined and put in writing.

First aid attendant: At least one person trained in first aid for every 100 workers. Shall have a refresher course every five years and certificates renewed.

Temporary construction: Plan, layout, design and specification of all temporary constructions which are likely to interfere with right-of-way or utility services shall be submitted to the respective authorities for approval.

Preconstruction phase: Site access, protected storage, protection of personnel, maximization of activities during fair weather, special provision for activities in extreme temp, adequate lighting, care for historically important structure

Construction phase: Organizational structure, site layout, access for fire-fighting vehicle, construction strategy and sequence



Site Layout

(a) Easy access and exit, with proper parking.(b) Properly located material stores for easy handling and storage(c) Adequate stack areas for bulk construction materials.(d) Optimum location of plants and equipment (batching plants etc.).(e) Layout of temporary services (water, power, power suppression unit, hoists, cranes, elevators etc.).(f) Adequate yard lighting and lighting for night shifts.(g) Temporary buildings; site office and shelter for workforce with use of non combustible materials including emergency medical aids.(h) Roads for vehicular movement with effective drainage plan.(i) Construction safety with emergency access and evacuations and security measures.(j) Fabrication yards for reinforcement assembly, concrete casting and shattering materials; and(k) Fencing, barricades and signage.

Construction Control

Site preparation: Bush, debris etc. shall be removed, temporary

building so located to cause min fire hazard, will be made of

non-combustible materials

Permits: Storing materials on roads, using public utilities,

Digging roads, storing explosives, affecting historical structure

Tests and inspections: Authority shall inspect and test if there is

any complaint



Construction Management

Time management: The system shall include a periodic review of a project with all parameters as well as catch up plans in case of delay identified for controls and reporting from time to time.

Quality management: Quality of a project shall be planned for all activities from inception to completion.

Health, safety and environment: Various activities having impact on health, safety and environment need to be identified with their likely effect and proposed preventive corrective actions.

Cost Management: It is desired that cost of the project during constructionare monitored and controlled through a documentation system.


Adjoining property: No part of any structure, except signs, shall projectbeyond the property line.

Protective fences and railings: Railings, adjacent to footpath orexcavation, shall be at least 1m in height. Work within 1.5 m from theroad shall be enclosed with a fence not less than 2.4 m high

Canopies, overhangs and platforms: Protective canopy shall have aclear height of 2.4 m over the walkway. Shall be not less than 1.2 mwide. Braced and designed to support at least 7 kPa.

Protection of utilities: Protective frame and boarding shall be built.Precaution to be taken to prevent material blocking a sewer.




Use of road and footpath: May be used only temporarily during

construction with permission. Shall be more than 1.5 m away from a

railway track. A walkway shall be constructed. One (1) metre clear

passage shall be maintained. The permittee shall repair any damages.

Notices and signs: Outer edge shall have red lights which shall flash

continuously day and night.

Watchman and auditory signals

Safe load: Strength test to two and half times the superimposed live

load.

Environmental Protection of Public and Workers

Protection of Existing Drainage Systems and Utilities

Protection of Soil, Aquifers, and Water Channels: Safe transportationand disposal of all wastes. Shall not allow waste oils or otherpetroleum derived wastes to be used as dust suppressants. Adequatesanitary facilities for workers.

Protection of Air Quality: Measures to minimize dust-blow by regular watering.

Protection from Sound Pollution: Noisy activities shall not be carriedout from 1800 hours in the evening to 0600 hours in the morning andon non-working days and holidays in residential areas.





Manual Handling: Each workman shall be provided with suitable equipment for his personal safety as necessary.Protection against Fire: Combustible materials separated. Two types of DCPextinguishers at both open and covered locations.

Storage Requirement by Classification of MaterialsClimatically Sensitive Materials: Cement, Lime, Timber, Bamboo, Particle boardDurable Materials: Steel, Brick, Masonry block, Stones, Aggregates, WaterMaterials Vulnerable to Rough Handling: Aluminum, Fly wash, Pipes, Timber pole, Sanitary appliance, Doors, Windows, Floor tiles, sheets, cast ironInflammable and/or Fire Sensitive Materials: Plastic, Rubber, PaintsHazardous Materials: Asbestos, Acids, Explosive, Protective clothing, Personal hygiene

Loading and Unloading of Materials



Cement Storage

To be stored at the work site in a building or a shed which is dry, leak proof and moisture proof.Bags to be stacked on wooden planks maintaining a minimum clearance of 200 mm from the floor.Maximum height of the stack shall be 15 bags and the width not more than four bags or 3m.In stacks more than 8 bags high, the bags shall be arranged alternate length and crosswise.Cement shall be used in the order they are received; storage shall facilitate this requirement. Hooks shall not be used.Workers handling cement shall put on protective hand and face coverings.

Steel Storage

Reinforcement bars and structural steel sections shall be coated with cement wash before stacking.Bars of different types, sizes and lengths and structural steel sections shall be stored separately to facilitate issues.Ends of bars and sections of each type shall be painted with separate designated colors.



Brick Storage

The stacks shall be 50 bricks long and 10 bricks high and not more than 4 bricks in width.Clear distance between adjacent stacks shall be not less than 800 mm.Bricks made of clay containing lime shall be thoroughly soaked in water.The height of the stack of blocks shall not be more than 1.2 m, the length of the stack shall not be more than 3.0 m.All blocks should be water cured for 10 to 14 days and air cured for another 15 days; thus no blocks with less than 28 days curing shall be used.

Safety During Construction



Safety Management

Safety of workmen: Helmets conforming to BDS 1265 and BDS 1266; Safety goggles of accepted standard (BDS 1360). Proper protective equipment like gloves, safety boots, aprons and hand shields.Site precautions: During the erection of tall buildings, nylonnet shall be put around the building periphery 3 m to 4 mbelow the working level.Site amenities: Toilet facilities shall be provided at all construction sites. Washing facilities and Drinking water shall be provided.

Topics of Safety During Construction

Excavation and Foundation WorkPile RigConstruction of Walls

Construction of FloorsConcrete WorkFormwork and ScaffoldErection OperationsElectrification, Equipment and OperationsConstruction HazardsHigh Rise Buildings



Excavation and Foundation WorkExcavation machinery: shall be kept away from the trenches by a distance at least equal to the depth of trench to a maximum of 6 metersExcavated materials: shall be kept away from the edges of the trench.Ground water: The water shall be drawn away from the excavation.Ground conditions: Adequate precautions against quick sand, loose fills etc. shall be taken to protect the workmen.Overhang: shall be supported by props.

Blast and vibration: An analysis for the stability of slopes shall be carried

outHealth hazard: Mechanical ventilation shall be provided if there is gas/fume.Safety of materials: Materials shall be inspected by the Engineer-in-charge.Piling and deep foundations: supervised by a competent Geotech EngineerWorking in compressed air: 0.3 m3 of fresh air per minute per personAdjoining properties and service lines: Old structures to be monitored.

Pile Rig

Erection of pile rig: The frame of the rigs shall be structurally safe for all anticipated dead, live and wind loads.Operation of pile rig: Access to working platforms and top of pulley shall be provided by ladders. Working platforms shall be protected from wind and rain.Piles: Piles shall be prepared at a distance at least equal to twice the length of the longest pile, from the pile driver.Inspection and tests: Pile driving equipment shall be inspected by an engineer at regular intervals not exceeding three months.



Construction of Walls

Scaffold: The scaffold has to be checked after every 15 days in rainy season and 30 days in dry season.Ladders: Rails of ladders shall extend at least 1m above the landing. A lean-to-ladder shall have a maximum angle of 75o with the horizontal. A user shall place his feet near the ends of the rungs rather than near the middle, and face the ladder when using it. Leaning more than 300 mm from the side shall not be allowed.Opening in walls: wall opening from which there is a vertical drop of more than 1200 mm shall be guarded by barriers.Projection from walls: Formwork provided for horizontal projections shall not be removed till protection against overturning are constructed.Common hazards during walling: overhead protection against the falling materials shall be provided.

Construction of Floors

Use of sheets: Joints in corrugated galvanized iron sheets are kept secured.Platforms: Working platform required according to the type of roof shall be provided.Flat roof: The formwork shall be frequently inspected for defects. Enough walking platforms shall be provided in the reinforcement area.Openings and holes: Every temporary floor opening shall either have railing of at least 900 mm height, or shall be constantly attended.



Concrete Work

Prestressed concrete: No person shall stand in line with the tensioning elements

and jacking equipment during the tensioning operation. Also no one shall be

directly over the jacking equipment when deflection is done. Workmen shall be

prevented from working behind the jacks when the tensioning operation is in

progress by putting signs, barriers, or protective shields.

Concrete mixers: All gears, chains and rollers of mixer plants shall be guarded. All

cables, clamps, hooks, wire ropes, gears, clutches, etc. of the mixer shall be

checked and serviced once a week.

Concrete trucks and buckets: A reasonably smooth traffic surface shall be

provided for concrete trucks. Closing and locking of the exit door of the concrete

bucket shall always be checked.

Formwork and Scaffold

Scaffold and centering materials: Horizontal and inclined bracings shall be provided for posts higher than 3 m. Spans of beam bottoms shall be supported by posts at most 1 m apart if steel is used. All scaffolding exceeding 20 m or six stories in height shall be constructed of noncombustible or fire-retardant materials.Formwork for concrete: In case of removal of roof shuttering, staging has to provide below the roof.Load capacity: Weight of wet concrete: 20 kN/m3

Bamboos: Bamboos for vertical support shall not be less than 75 mm in diameter.Timber posts: Timber posts shall be used in supporting formwork up to a height of 6 m.Steel centering: Struts and diagonal braces shall be in proper position and secured.



Erection Operations

Erection and hoisting: Ropes in operation shall not be touched. The ropes shall

be chemically treated to resist dew and rotting. They shall not be tied beyond the

reach of safety belts complying to BDS 1359.

Small articles: Bolt baskets or similar containers with handles shall be provided

on floats or scaffolds where small material, such as bolts and drift pins are used.

Hoist protection: A material hoist shall not be used to transport workers;

temporary elevators shall be installed, if necessary.

Lifting gear: Lifting gears must be tested and examined by a competent person.

Cranes: The safe working load shall be clearly shown on the crane. Cranes shall

not be operated in proximity to a live overhead power line. no person under the

age of 21 years shall be allowed to operate.

Electrification, Equipment and Operations

Wiring system: No scaffolding, ladder, working platform, gangway, runway, etc. within 3 m of an un-

insulated live electric wire. The main switch board shall be located in an easily accessible and

prominent place. One CO2 extinguisher or one 5-kg dry powder extinguisher, shall be provided near

the switch board.

Guarding of cables: All cables and signal cords shall be guarded wherever pass through or cross

working spaces.

Lifts: Entry to the empty lift well shall be blocked. Notices/signs shall be displayed in the lift lobby

when the lift is not in operation.

Construction machinery: Exhaust of petrol or diesel powered machinery shall be well away from

combustible materials. All sources of ignition shall be banned near petroleum- fired equipment.

Flame cutting and welding: For all arc welding work, either a helmet or a hand-held face shield

conforming to BDS 1360 shall be used. When slag is being removed from weld by clipping, the eyes

shall be protected by goggles conforming to BDS 1360.

Riveting operation: Rivets shall be carefully handled to prevent accidental fall.



Construction Hazards

Fire hazards: Ground below the scaffolding shall be kept free from readily combustible

materials. Portable dry powder extinguisher of 3 kg capacity shall be kept near all flame

producing equipment.

Health hazards: Exhaust ventilation shall be employed in enclosed spaces. Wearing of loose

garments shall be strictly avoided. In case of a site where more than 600 workmen are

employed at any one time, or in which more than 300 workmen are employed at any one time

and is 15 km from the nearest health service facility, provision of an ambulance shall be

made.

Skin hazard: Workmen engaged in works which may splash liquid or other materials liable to

injure the skin shall have enough protective clothing to cover the body and limbs.

Noise hazard: For levels up to 110 dB, properly fitted ear plugs shall be provided. Exceeding

120 dB, noise protection helmets shall be provided.

Fire Hazard

Fire extinguishers, preferably of water type, shall be placed at strategic points.Extinguishers shall always be placed in cranes, hoists, compressors and similar places.Where electrical equipment is used, CO2 or dry powder extinguishers shall be provided.An independent water storage facility shall be provided for fire-fighting purposes.Fire walls and exit stairways required for a building shall be given priorities in construction schedule.



Demolition Work

Demolition Work

Preliminary Procedure Precautions During Demolition:

• Sequence• Walls, Floors, Special elements• Mechanical demolition

Blasting Operation and Use of Explosives:• Code of signal• Supervision and responsibility• Protection of site personnel• Safety of third parties• Use of explosives

Lowering, Removal and Disposal of Materials• Use of chutes• Removal of debris• Disposal of materials



Preliminary Procedure

Planning: Detailed survey and study.

Protection of adjoining property: Written notice to the owner of potentially affected plot.

Precautions prior to demolition: Pedestrian protection structures, danger signs, warning lights, watchmen.

Sidewalk shed: 1m high toe board above the roof of the shed.

Canopy: 600mm extended canopy at the entrance of the building.

Protection Type for Pedestrians

Type A: Total blockade of the road.Type B: Temporary diversion over the entire length of the footpath adjacent to the structure.Type C: A sidewalk shed for the entire length, in accordance with Sec 4.1.6.Type D: A fence of tightly seated 25 mm planks, minimum height 2.5 m.Type E: A railing at least 1.5 m high with mid rail and cross bracing.

Horizontal Distance frominside of the Sidewalk tothe Structure

Height to HorizontalDistance Ratio

Type of MinimumProtectionRequired

Less than 3 m 6:1 or more4:1 6:13:1 4:12:1 3:1up to 2:1

Type AType BType CType DType E

3 m 4.5 m10:1 or more6:1 10:14:1 6:13:1 4:1up to 3:1

Type AType BType CType DType E



PRECAUTIONS DURING DEMOLOTION

Wall: No large chunks; avoid piling up of debris.

Floor: No person underneath – barricaded; Hole cut for dropping debris < 25% of floor area.

Special elements: • Catch platform, • Manual roof truss demolition, • Supports for heavy floor beam, • Scaffolding for arch demolition.

Demolition of Cast-In-Situ RC

Start by removing partitions and external non-load bearing cladding.Slab removal then beams one at a timeAttach ties to the beam, expose reinforcement at the supports, cut reinforcement and lower slowly.Columns at last. Restrain at the top with wire guy ropes. Expose the base. Cut reinforcement. Slowly pull it down.Concrete wall are cut into strips and demolished similarly as columns.



Mechanical Demolition

Using mechanical devices like weight balls and power shovels.

Restricted to a height of 25 m.

Barricaded up to a minimum distance of one and a half times the height of the wall.

While in operation, no person shall be allowed to enter the building.

Miscellaneous

No demolition work shall be carried out at night, or during storm or heavy rain. If demolition has to be done at night, precautions in the form of red warning signals, sirens, working lights and watchmen shall be provided. Auditory warning devices shall be installed at the demolition site.Safety devices like industrial safety helmets, boots, gloves, goggles made of celluloid lens, safety belts etc. shall be used by the workmen.First aid box shall be made available at all demolition sites. In fire-risk area, appropriate portable firefighting appliances shall be kept at hand.



Blasting Operation

Avoid damaging underground installations.

Auditory and visual signals

Competent shotfirer. All personnel under the control of the shotfirer.

Vehicles and other mobile equipment prohibited.

In heavily built-up areas, small-scale short delay blasting techniques will be employed.

Lowering and Removal of Debris

No material shall be dropped or thrown on the ground or outside the exterior walls.

When the removal of any material causes an excessive amount of dust, it shall be wet before lowering or dropping.

Chutes shall be at the centre of the building and shall be entirely closed on all sides.

Avoid overloading of the floor with debris.

Dropping area shall be protected by rails.



Regularization of Plots

The plot shall be filled and graded.

The plot shall be maintained free from the accumulation of rubbish and water.

All previous service utility connections shall be capped.

Evaluation and Acceptance of Concrete



Frequency of Testing

Samples for strength tests shall be taken not less than

• once a day• once for each 60 m3 of concrete• once for each 250 m2 surface area for slabs or walls.

On a given project, tests shall be made from at least three randomly selected batches or from each batch.

When the total quantity of a given class of concrete is less than 20 m3, strength tests are not required.

A strength test shall be the average of the strengths of at least two 150 mm by 300 mm cylinders or at least three 100 mm by 200 mm cylinders.

Required Strength

For laboratory cured specimens:• Strength shall be considered satisfactory if

• Average of three consecutive strength tests equals or exceeds • No individual strength test falls below by more than 3.5 N/mm2.

For field cured specimens:• Procedures for protecting and curing concrete shall be

improved when is less than 85 percent of that of companion laboratory cured cylinders.



Investigation of Low Strength Test Results

If the likelihood of low strength concrete is confirmed tests of cores drilled from the area in question may be required.Concrete shall be considered structurally adequate if the average of three cores is equal to at least 85 percent of and if no single core is less than 75 percent of .If structural adequacy remains in doubt, the responsible authority may order load tests for the questionable portion of the structure

Load Test

The number and arrangement of spans or panels loaded shall be selected to maximize the deflection and stresses in the critical regions of the structural elements of which strength is in doubt.

The total test load shall not be less than

a) 1.15D+ 1.5L+ 0.4 Lrb) 1.15D+ 0.9L+ 1.5 Lrc) 1.3DTest load shall be applied in not less than four approximately equal

increments.

A set of response measurements shall be made after the total load has been applied on the structure for at least 24 hours.

A set of final response measurements shall be made 24 hours after the test load is removed.



Load Test Acceptance Criteria

The portion of the structure tested shall show no evidence of failure. Spalling and crushing

Measured deflections shall satisfy either

• ,•

The structure shall be permitted for use at a lower load rating based on the results of the load test or analysis, if approved by the Engineer.

Enforcement



Eligible Registered Professionals

Types of Work Registered Professional Minimum Experience Requirement in Years fBuilding Category

I II III IVConstructionSupervision

Architect/Engineer in their respective fieldor PEng.

NA 2 4 8

Diploma Architect/Diploma Engineer in theirrespective field

NA 2 4 20*

Building Demolition Civil Engineer NA NR 2 8

Diploma Engineer (Civil) NA 2 NE NE

Note: NA: Not Applicable, NE: Not Eligible, NR: Not Required.*Shall be countersigned by registered/licensed Architect/Engineer eligible for Building Category IV.

Inspection

All works relating to a building or structure regulated by the provisions of this Code for which permits are required shall be subject to inspection by the Building Official. Modalities and frequency of such inspections shall conform to the requirements put forward by the approving authority.



Demolition

The owner shall notify all agencies providing utility services.

Such agencies shall remove all their appurtenances and equipment.

The Building Official shall not grant any permit for demolition of a building until a release is obtained from the utility services.

The demolition work shall be done under the supervision of demolition expert.

Tests as Proof of Compliance

If, in the opinion of the Building Official, there is insufficient evidence of compliance with any of the provisions of the Code or there is evidence that any material or construction does not conform to the requirements of this Code, the Building Official may require tests to be performed as proof of compliance. The cost of any such test shall be borne by the owner.



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Construction Safety, Construction Quality and Demolition