Accidents and Safety in Construction-10.pptx

This a chapter of Construction planning and Management

1. Accidents and Safety in Construction

2. Introduction Every day many accidents occur in factories and other construction sites. These accidents results in loss of life, property, materials and production or progress. Truly speaking the events called accidents results in something bad. For example, a person receiving an electric shock, a child falling from roof, a factory catching fire, a worker cutting his leg while operating a machine. An accident means an event that happens unexpectedly. Work situations leading to an accident may arise from faulty tools and equipment or insufficient performance of an individual, e.g., A man was killed when demolishing a corner of a filler joist floor in a multi-storey warehouse. He was breaking the concrete from the filler joist using a sledge hammer. He had completed one section and after tea break he commenced work on an adjacent part of the floor; he swung the hammer but missed his object and over balanced into the hole in the floor created by his previous effort . It may be noted that the accident could have been avoided had the man worn a safety harness, with safety line, attached to a secure part of the structure. Accidents/falls are bound to occur due to insecure foot hold at demolishing site of work Like this many lakhs of lives are lost in accidents. Hence an accident prevention programme must be initiated on every project in order to reduce the cost of construction.

3. Objects of Accident Prevention Programme To reduce human life sacrificed To reduce temporary and permanent injuries to workers To reduce loss of or damage to equipment To avoid loss of materials resulting from accidents To lesser loss of time because of accidents To have the cost of workmen's compensation to a minimum

4. Concepts of Accidents Any event that occurs all of a sudden unexpectedly, is called an Accident. Accidents are undesirable and hence, efforts should be made to avoid or reduce them. The study of accidents has shown that about 90% accidents can be avoided if proper care and precautions are taken. An accident is a mishappening and takes place without expectation. Accident may cause : Injury on the body of a man Can kill a person Loss of man hours Loss of machine hours Can cause loss of property, which may be in the form of damaged building, damaged machinery or loss of material

5. Causes Of Accidents The causes of accidents are broadly classified as under: Physical causes Physiological causes Psychological causes 1. Physical Causes : The physical causes responsible for accidents are as follows: A. Relating to Machines: The working space on the machine being less obstructs free movements of worker and material. The machine being not properly adjusted. The machine being unsuitable for the job. The machine being unguarded or improperly guarded. Electric motor on the machine not properly insulated. B. Relating to Tools: Tools being brittle, may break suddenly, e.g., blades on a saving machine Tools being worn out due to constant use Tools used being too small for the job

6. Continue C. Relating to Materials: The materials being inflammable., use of explosives and petroleum products etc The brittle material not handled with care The materials being too hot., bitumen and tar in road construction The material used being poisonous and dangerous, e.g., acids D. Relating to Uniform a. Dress being loose The sleeves of the shirt being without buttons The shoes being loose and slippery E. Relating to Environment: The floors being slippery. Poor lighting condition. Poor ventilation and unhygienic conditions. Loose electric cable and live conductors. Building use being unsafe. Use of unstable and unsafe ladder. External noises and disturbances.

7. 2. Physiological Causes The main causes of accidents on account of poor health conditions are as follows Poor eye sight, e.g., a driver while driving a vehicle may not be able to see the obstacle ahead clearly, especially when the light is dim Over Work: A tired worker loses control over his limbs and may meet with an accident. Poor health: A sound mind in a sound body is well known. A man with poor health gets tired soon and sometimes a worker does harm to his body while doing a job which is beyond his capacity Intoxication: A worker under the influence of intoxicants like wine, loses control over his limbs 3. Psychological Causes: The causes connected with the mind of a worker are listed below Worry: A person under strains of worries has least control over his mind Mental Tension: Mental tension is caused due to strained relations with superiors or co-workers and one loses control over mind. Emotional Attitude: A highly emotional man loses balance of mind quickly. Nervousness: A person who gets nervous in a particular situation, loses control over his limbs. Carelessness: A careless workers meets with an accidents more often than a conscious worker.

8. Safety Measures Safety measures for Excavation Safety measures for Drilling and blasting Safety measures for Hot bitumen works Safety measures for Scaffolding, ladders, form work Safety measures for Demolitions Safety measures for Electrical accidents 1. Safety measure for Excavation Work : Excavation work is one of the important activities in the construction of building and other projects. If proper attention is not given to safety aspect, it may become a major hazard and cause serious accidents. Basic principles for taking care of safety aspects are mentioned below Safety Precautions for working of Machines and Vehicles: Excavation machinery should be properly selected depending upon the nature of excavation and size of protect. The machinery should be kept up to date and maintenance and overhauling done regularly Person working on the machinery should be physically fit and mentally active. Faulty machines should not be allowed to be operated Any danger part of machine, e.g., belts, chain drives etc. should be provided with proper cover Proper lightning is essential for working at night.

9. B. General Guidelines: The work must be entrusted to a competent and experienced supervisor, who shall be made responsible for strict observance of safety rules. Due protection is given to excavated trenches against slides and caving during and after heavy rains and storms etc The workers should be asked to use safety appliances whenever required. Safety helmets must be used by workers where danger of falling stones etc. exists. New workers must be kept under constant supervision of experienced supervisors in tasks involving hazards. No workers should be allowed to carry on the job which he cannot do properly.

10. Drilling and Blasting 1. Safety Measures for Transportation of Explosives: a . The word “Explosive” should be written in bold letters on the sides and front face of the vehicle carrying explosives. b. The explosives should be carefully covered with heavy duty waterproof cloth in case of having open body. No inflammable substance should be carried in the vehicle carrying explosives c. The vehicle carrying explosives should be carefully inspected to ensure that it breaks are in working order and its electric wirings is insulated and there is no leakage in fuel tank and the body is free from oil, gases 2. Precautions to be Followed while Handling and Storing Explosives The packets containing explosives should be lifted carefully and not thrown from a distance. Wooden tools should be used for opening the packages. Blasting caps or primers should not be stored in the same container or room where other explosives are kept. Explosives should not be permitted nor any flame etc. should be allowed near the magazine. Warning notice should be displayed. No leaves or grass etc. be stored within 8 m of an explosive magazine.

11. Continue 3. Precautions to be followed while Handling and Storing Explosives: Smoking or fire should not be permitted where explosives are being used. After removing a part of Explosive the container must be covered properly. Explosives should not be carried in the packets of any clothing No person should attempt to remove or investigate the contents of a blasting cap. Explosives should not be handled in electrical store. Hard set explosive should not be softened by heating over a fire, or by rolling the explosive on the ground. 4. Precautions used in Drilling and loading Nature of strata should be carefully examined to avoid landslides after blasting, before planning out drilling operations. Drilling should not be done at a place where undetonated explosives suspected. Be sure that the hole is bored to full length and is free from dust etc. While loading, spare explosives should not be kept near the site The explosive should be confined to bore hole with stemming material like sand and earth clay. Wooden tamping tools are used for tamping purposes. Metal temping rods are forbidden Before loading a hole, be sure that it is cool and has no burning or hot materials in it.

12. Continue 5. Precautions followed in Electrical Shot-firing: For the Sizes of wires, fuses, circuits etc. the instructions issued by manufactures should be followed No body should be permitted to uncoil wires and open out the bare leading wires of electric blasting cap during stormy weather. Firing circuits should be fully insulated from ground or rails, pipes etc. Electric live wires should not be kept near blasting caps or other explosives except at the time and for the purpose of firing the blast Electric caps wires or leading wires should be kept short circuited until ready to fire. All holes located on a shift shall be fired on the same shift 6. Precautions observed in shot firing with safety fuse The fuse should be handled carefully, so that its cover is not damaged. The length of fuse should not be less than 1.2 m. The fuse should be tightened with a fuse lighter of proper design. Sufficient stemming should be placed over the explosives before igniting the fuse. At the time of lightning the fuse spare explosives should not be held in mind. Excessive quantities of explosives should not be taken underground

13. Continue 7. Precautions taken Before Firing and After Firing: Before firing, sufficient warning should be given to enable persons working at the site to go away from danger zone. Flag men are posted on all approaches to keep vehicles and public at least 400 metres away from the danger zone. No tools or other articles are left on the rock to be blasted. Blasting should be done according to pre-planned schedule, during fixed hours every day. Some days in a week can also be fixed. Wide publicity should be given to this programme. Daily blasting hours should be displayed on notice boards on all roads leading to the blasting site. The shot firer should not return to the blasting site until at least 5 minutes have passed since the fuses were lighted. In vase of electric shot firing, the shot holes should be examined after firing and in case of misfire, no person shall be allowed to come near blasting site for at least 5 minutes and in case of firing with safety fuse, the time for preventing entry of men to blasting site is 30 minutes

14. Precautions used for Hot Bitumen Works 1. Precautions used for Handling of Plant and Machinery: Safety precautions for working of machines and vehicles mentioned under ‘safety measures for Excavation work” apply to the machinery used for bitumen work as well. Further more, tar heating boilers should be equipped with suitable devices for recording temperature. Under no circumstances the bitumen or tar should be allowed to be overheated. By overheating tar, the binding property is destroyed and with further heating, the bitumen is likely to catch fire. 2. Precautions used for Safety of Workers: Only competent, trained and experienced workers should be deputed for bitumen works The workers who are fit physically and mentally active, should be engaged on bitumen work. The workers should be so planned that the workers are given rest at suitable interval, to avoid their getting tired. The work must be suspended during stormy weather to guard against fire hazards. When wind is blowing fast, bitumen spraying should be done carefully, keeping in view the direction of prevailing wind.

15. Continue Precautions to be Followed for Safety of Traffic: Proper sign boards indicating that bitumen work is in progress, must be displayed at both ends of the stretch of road under construction. Proper diversion should be arranged and the stretch of road under construction protected from all sides by keeping empty drums, so that road user do not enter this zone. Only half the width of road should be constructed at a time to allow the other half to be used by road users. When actual spraying of bitumen is going on, a man with red flag is posted at each end of the stretch of road, to stop/regulate the traffic.

16. Safety Measures for Ladders, Scaffolding and Formwork Ladders: A. Introduction: Ladders constitute one of the essential parts of construction equipment in any construction activity. Full attention is not being given by construction engineers to this important aspect, which results in many accidents. The accidents occur due to following reasons: Ascending or descending improperly Failure to secure ladder at top or bottom or both places. Failure of the ladder itself structurally. While carrying some load at the time of ascending or descending. The frequency of accidents could be minimised by selection of proper size and design of a ladder. B . Requirement in the Construction of Ladders: All ladders should be designed for the loads these are required to carry. Side rails of metal ladders shall be of sufficient cross section to prevent excessive deflection in use. In bamboo ladders, the rungs may be fixed to the rails with spikes of proper design and strength but in other types of wooden ladders, use of nails or spikes should not be permitted. Safety shoes shall be used to avoid danger of slipping

17. C. Instructions Regarding use of ladders: Before use, all ladders should be tested for the designed loads. The ladders should be strong as well as rigid A ladder with damaged or missing rung should not be used. Efforts should be made to promptly repair the defective ladder. The splicing of ladders should be avoided. If it is absolutely essential, the same should be done under the supervision of engineer-in-charge. Ladders leading to landing should be extended at least one metre above the landing or walkway and secured at the upper end The ladders should not be supported against window panes, sashes or other unsafe or yielding objects, not placed in fronts of doors, opening towards it. For obvious reason, metal stairs should not be used around electrical equipment. Extension ladder should not be used up to 10 m in length. Locks and guides should be properly checked to ensure proper locking and full extension of the sections. D. Periodical Inspection and Testing: Wooden ladders should be inspected at least once in a month for damages and metal ladders should be inspected at least once in three months and all parts checked for structural failure and corrosion. The ladder should be carefully inspected, if incidentally dropped or damaged in use. Continue

18. Continue 2. Scaffolding: Scaffolding is required for all types of structures constructed above ground level, e.g., brick-work, stone masonry etc. Scaffolding or staging is also required for maintenance work of many types. The particular type of scaffolding is selected, depending upon the nature of work and its situation. Various stages of construction should be erected at convenient heights. The size of different members should be properly designed for the loads these are intended to carry. The put log should be inserted sufficiently deep in the wall to avoid the risk of its sliding. No body should be allowed to stand below the scaffolding as bricks or stones may fall from top and hit the person below. Only limited load should be pot on the scaffolding which are not designed to carry huge quantities of building material or machines. The members should be thoroughly tested for their strength and inspected before these are put to use for second time and also subsequently. The wooden members should be free from dry rot or wet rot. Workers should not be allowed to light fire near the scaffolding.

19. Continue 3. Form Work: Following precautions are observed in the design, construction, use and removal of formwork The material of formwork should be as per relevant Indian Standard. The members should be properly designed and sections worked out keeping in view the loads that the form work is required to take up. The form work should be sufficiently strong under bending and sufficiently stiff to resist deflection and deformation after concrete is placed. The joints of the sheathing should be watertight so that there is no loss of cement mortar. The form work should be constructed in the manner that it is easily dimentalled , without causing any harm to the concrete or form work itself as it has to be used a number of times on future works. The form work is used again and again on works until it becomes unfit and unsafe for use. To avoid damage to concrete as well as form work, the interior surface to forms should be coated with a layer of oil, soft soap etc To allow for sags in beams, the forms are given a camber of 1 cm in 5 m length of beam. In the design of form work for columns or walls, the hydrostatic pressure of wet concrete should be taken into account. This pressure increases with increase in the quantity of water in concrete, higher rate of pouring concrete, smaller size of aggregate and lower temperature.

20. Safety Measures for Demolition of Buildings Demolition of structures is very hazardous task. The demolition work should, therefore, be effectively planned and executed at different stages, so that accidents and injuries to workers are reduced to a minimum. To ensure safety, cooperation of management, supervisor and workers, doing the work, is extremely essential. Before starting the work of demolition, the manner in which various parts of the building are supported and to what extends the step by step demolition work will affect the safety of adjoining structures, should be studied. Plan should be prepared for systematic demolition work by the site engineer and followed while doing the demolition operations. Precautions to be taken while demolishing: No part of the structure should be overloaded with demolished material. Danger span boards should be displayed near all sides of the structure under demolishing and on the approach roads leading to it at distance of 30 m. Red signals should be provided at important points at night. A watchman must be provided to stop entry for dangerous situations. Walls of adjoining buildings should be strengthened by suitable means to safeguard against any damage. Safety belts should be used while working at high levels . The demolition work should not be taken in hands at nights or during stormy weather and heavy rains.

21. Continue 2. Protection to Public: All the main roads should be kept open to public. There should be no obstruction on them at any time. Side walk should be closed or protected. In the demolition of multi-storey buildings, a strong shed is provided over side lanes, of it is within 4.5 m of the building, so that people can use the side walk without any danger. In other cases a strong railing should be provided to keep people away from the dangerous area. 3. Sequence of Demolition Operations: The demolition work is started in such a sequence that it causes minimum damage and nuisance to adjacent buildings and public. Safety requirement should also be satisfied to avoid accidents. All glazed doors, windows and ventilators should be removed before starting dismantling work. Demolition work is started from top and the work should be completed in uppermost storey before starting it in the one below it. The dismantled materials should be thrown on ground only after taking full safety precautions. It is advisable to store the debris inside the building after it is lowered down to the ground. Metallic chutes or channels are used in the removal of debris. Stairs and ladders should be kept in tact as long as possible and kept safe till demolition work of the storey above it is completed.

22. Continue 4. Demolition of Walls: The walls should be demolished in small heights, layer after layer, so that the falling debris does not make the floor collapse. The falling debris is constantly removed from the floor to avoid over loading. A weaker wall whose height is greater than 15 times its thickness, should be braced laterally. The load supporting members should be removed only after demolishing work in the storey above it is completed. The walls should be duly supported against sudden falling at the close of work. Foundation walls should be left intact to act as supports to adjoining structures and shall not be demolished till an adjoining structure has been underpinned. 5. Demolition of Floors: For demolishing floors, a slit 30 cm wide is first cut for full length of slab. Planks of 25 cm width and 5 cm thick are placed at 0.4 m spacing for workers to perform demolition work. When floors are being dismantled, no workman shall be allowed to work directly underneath. All structural members when being demolished, should be lowered from the building and not dropped. In demolishing external walls of multi-storey buildings, having heights more than 20 m it is advisable to provide platform of heavy planking, to prevent injuries to the workers and to the public. For RCC beams, a supporting rope should be put round the beam. The concrete is than removed from both ends by Pneumatic drills and the reinforcement exposed. The reinforcement should be cut in such a way that the beam could be lowered to floor level safely.

23. Electric Accidents Some of the preventive measures in case of electric accidents may be Do not guess whether electric current is flowing through a circuit. Consider that the current is flowing still it is proved not to be so. Never touch a wire till you are sure that no current is flowing. Use safety equipment, e.g., rubber gloves etc See that the electric current is not switched on when some one is working on the circuit. Do not use of aluminium ladders. Action to be Taken in case of Electrical Accidents: Switch off the mains instantaneously. If the controls are far off take something insulating like a wooden rod, rubber gloves or dry woollen cloth etc. and detect the live object from the victims body. Do not touch the person till he is free from the conducting source. Check for his breathing and send immediate message for a doctor. If breathing is not proper or missing try artificial respiration.

24. Continue Use the following method of Artificial Respiration: Put the patient flat with his face towards ground on floor Put the palms of your hands on the small of his back, with fingers spreaded on the sides of his back and thumbs almost touching Now lean gently forward with constant downward pressure. This will expel air from his lungs causing expiration. B. Use the second method of Artificial respiration: W hen it is necessary to keep patients face upward due to injury on front of the body. Let the patient lie on his back with cushion under his shoulder that the head is at a lower level with respect to chest and shoulders. Loosen the garments on chest and stomach. Now bring the arms down on each side of the chest, lean up to the chest through its arms, keep the pressure for two seconds. Repeat the movement 15 times per minutes till the respiration is restored. Further proceed according to the advice of the doctor who must be consulted before anything in the form of medicine is given.

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