Summaries - Intro to Fatal Falls
The fatality of hazards can be classified into 4 different categories: Falls, Struck by objects, Electrocutions and Caught in between and Falls is ranked number one on construction sites.
Slips, Trips and Falls can happen on the same level.
Slip: happens when there is too little friction or traction between your feet (footwear) and the walking or working surface, and you loos your balance
Trip: happens when your foot (or lower leg) hits an object and your upper body continues moving, throwing you off balance
Fall: this occurs when you are too far off your center of balance; when you step down unexpectedly to a lower surface (misstep) and lose your balance e.g stepping off a curb
The result of falls on the same level is only minor injury such as sprains, strains, bruises, contusions, fractures and abrasions.
Falls can also be to a lower level such as:
from heights, into pits, into water such as wells, through roof covering, from sloping or fragile roofs, in sewers or in tunnels, from chimneys, steel structures, plant and machinery
Anatomy of a Fall: it takes 0.33 sec to become aware that you are fall, 0.66 seconds for the body to react and by the time the body generates a movement to grab, you would have fallen 10 feet and at about 64 feet, the fall is considered to be really dangerous.
The major fatalities from falls are 3: from the roof that ranks number 1, secondly from ladders and then 3rd from scaffolds.
Non fatal falls happen mostly from ladders.
A hole is a small gap or void measuring such as a pipe opening, belt hole etc
An opening is a really large gap or void in a floor or working surface, where a person along with an objects can also fall
Using Hole Covers is a specific way of overcoming hazards caused by construction holes.
When preventing hazards caused by open edges, staircases, slopping rooftops, guard rails are primarily the major safety precautions used.
A scaffold is an elevated temporary working platform which enables workers climb up and reach the working place. It is a temporary structure which consist of standards, putlogs and ledgers.
A ladder is an appliance or an equipment usually consisting of 2 side rails there are 2 side rails which are joined together at regular intervals with cross pieces also called as steps, rungs or cleeds, and primarily used for ascending or descending movement between 2 points at different levels.
Safety nets are primarily to catch workers or people when they fall down. It should be installed as close as possible under the practicable walking or working surface from where employees are expected to fall.
Final Notes/ Summarries
Safety on construction Sites
Eliminate the risk. Avoid work at heights where possible or locate plant and equipent in safe locatons where there is no risk of a fall
Guard the hazard:
with Hole Covers, Guard Rails and safety nets
3 Protect the worker
With Fall restrain systems and Fall arrest systems
Fall hazards are: Roof/floor openings, Roof slopes, Scaffolds and ladders
Before a fall- fall prevention: for holes - covers, for openings - guardrails & fall restraint system
After a fall - fall protecting: Fall arrest system, safety nets
Summaries - Fall Hazard in Concreting
Concrete is the mixture from water and cement used as a glue or a binder in construction. It may contain fine aggregate and or coarse aggregate.
Concreting operation involves primarily three steps and then an additional fourth. The first process is called shuttering of form work, the second, reinforcement and the third one is placing or pouring concrete. When the concrete has attained the desired strength, then de-shuttering is done and that is the fourth step.
Formwork is a temporary mold that acts as a support for the fresh concrete till it firms up and dries.
Requirements for formwork are:
Strength and Stability
Erection and Release
Should facilitate ease of inspection
Should permit maximum reuses thereby reducing costs
There are different forms of load which come onto the form work:
Site Precautions for Falsework for concrete structure include:
Formal Checks are recommended
Electrical Safety against electrocution for electric shutter vibrators
Fire safety of timber forms to be ensured at site
Site welding of reinforcement rods should be avoided over timber shutters
Other Site Precautions while erecting formwork include:
Erection of safety signs and barricades
All provisions of the design and drawings should be complied with any excavations nearby
The bearing soil should be sound and suitably prepared
Safety measures should be taken to prevent impact of traffic scour due to water, etc
Adequate bracings, struts and ties should be installed with the progress of erection
Inclusion of lifting points in the design and detailing of all forms which will be crane handled
Formwork Failures happen for different reasons some of which are:
Improper stripping and shore removal
Inadequate lateral bracing
Vibration due to placing equipment
Inadequate control of concrete placement
Lack of attention to Formwork details
Some guidelines for removal of Formwork and scaffolding
The Formwork should not be removed before concrete has developed sufficient strength to support itself as well as the load that are on it
The formwork should be dismantled as per the sequence and instruction of site engineer
Only workment actually engaged in removing the formwork should be allowed in the area during operation
Forms are eased off from the concrete faces so as to prevent damage to both concrete and forms
All falsework material are properly stacked and maintained in good condition.
Summaries - Fall hazards in Demolition Work
Demolition is the dismantling, destroying or wrecking of any building or structure or any part thereof. Demolition work involves many of the same hazards associated with construction work. And it possesses additional hazards
Reasons for demolition
An aged structure that has lost its static equilibrium and is likely to collapse
A structure partially collapsed due to disasters or Acts of god
Due to foundation failure on account of excessive settlements
Overloading of structure, excessive corrosion and other issues that make the structure unserviceable
To create space for new structures
A part of a new construction may have to be demolished due to design errors or changes in construction.
Before demolition starts, safe planing must be done with regards to:
The adjoining structure, a careful study shall be made of the structure which is to be pulled down and also of all its surroundings.
Structure to be demolished, a definite plan of procedure for the demolition work depending on the manner in which the loads of the various structural parts are supported to assess the possibility of an unplanned collapse of any portion of the structure
And determine the type of hazardous chemicals, gases, explosives or flammable materials inside the structure
Safe precautions before demolitions:
Danger signs shall be conspicuously posted all around the structure
The area to be barricaded or manned except during the actural passage of workmen or equipment
During nights, red lights shall be placed on the barricades
No unauthorized person shall enter the site of demolition outside working hours
PPE should be supplied to all workers and their use enforced.
Safe precautions before the demolition work
Glazed doors and windows, etc shall be removed as well as all fragile and loose fixtures. All loose plaster shall be stripped off throughout the entire building
All floor openings and shafts not used for material chutes shall be enclosed with guard rails and toe boards.
The public and workers should be protected during demolition so wherever possible the public should be prevented from the site and workers should have a proper way of entry into the structure and exit.
Actual demolition operations
The demolition shall always proceed systematically storey by storey from top to bottom
The demolition work shall be proceeded with in such a way that it causes the least damage, nuisance to the adjoining building and members of the public
and it satisfies all safety requirements to avoid any accidents.
Mechanical demolition - most widely used, uses tools for crushing concrete and shearing steel
Induced collapse - used for high-rise structures
Manual means on smaller projects - pneumatic drillers, concrete breakers
Removal of Materials - chutes
Removal of materials are chutes. Chutes, if provided at an angle of less than 45degrees from the horizontal, shall be entirely enclosed on all the four sides.
Opening for the chutes shall not exceed 1.2m in height measurd along the wall of the chute
Any opening into which workmen dump debris at the top of chute shall be guarded by a substantial guard rail.
Removal of Materials - floor opening
Total area of the hole cut in any intermediate floor, one which lies between floor that is being demolished adn the storage floor shall not exceed 25% of the floor area.
It shall be ensured that the storage floor is of adequate strength to withstand the impact of the falling material
Openings in all the floors below the floor from which materials are being removed, shall be protected by standard railing, barricades or guard rails.
No barricades or guard rails shall be removed until the storey immediately above has been demolished down to the floor line and all debris cleared from that floor
When cutting of a hole in an intermediate floor between the storage floor and the floor which is being demolished makes the intermediate floor unsafe, then such intermediate floor shall be properly shored
Signs warning of the hazard of falling materials shall be posted at each level.
Demolition of Walls
Walls are not allowed to fall as single mass upon the floors of the building and shall be removed part by part
Staging shall be provided for the men to work on, if the walls are very thin and dangerous.
No section of wall whose height is more than 15 times of thickness, shall be permitted to stand without lateral bracing
At the completion of each day's work, all walls shall be looked for stability
Foundation walls which serve as retaining walls to support earth or adjoining structure, shall not be demolished until an adjoining structure has been underpinned or braced and the earth removed by sheet piling.
Removal of Debris/ Malba
Debris is actually the serviceable component and malba is a component which has to be trashed or thrown away.
Unauthorized use of the debris or malba in any work shall not be permitted
Malba shall be removed from the demolition site to a location as required by the local civil authority.
Materials which are likely to cause dust or undue environmental pollution shall be removed from the site at the earliest and till then they shall be suitably covered.
Classifying the Debris for Disposal
Various categories of debris that may be fully or partially damaged includes earth, plaster, mortar waste, bricks, blocks, concrete, glass etc
Salvageable materials of some economic value are removed first.
Remaining debris are divided according to type
Hand tools required fro the debris removal are spades, pickaxes, hammers, chisels etc
Throwing of debris from height shall be avoided
For safety, carrying of debris on head through stairs should be avoided as much as possible
The area where debris is likely to fall should be barricaded, warning boards, danger signs displayed
If fine particles exist some water may be sprinkled to prevent dust nuisance in neighborhood.
If possible the debris shall be filled in the use gunny bags for bringing down
Glass and steel should be dumped or buried separately to prevent injury
The work of removal of debris should be carried out during day
Some general safety requirements
No demolition work should be carried out at night
No demolition work shall be carried out during storm and heavy rain
A warning device shall be installed in the area to be used to warn the workers in case of case of any danger
Goggles preferably made of celluloid lens shall be worn at the time of demolition of walls, floors, tearing plaster etc
Screens shall be placed, where necessary, to prevent flying pieces from injuring the fellow workmen
Fall protection required to prevent falling from the structure.
Summaries - Safety in Demolitions - Practical examples
Lessons from practical work
Demolition carried out improperly is risky because it can potentially cause damage to nearby structures.
When the workers are not using any PPEs, their lives are at risk.
Building with cracks and not in good condition can cause other structures connected to it to fall.
In this case, care must be given with the electric poles near the structure.
When a wrecking ball demolition is being carried out, the steel ball can weigh up to 6500 kg. So, you can
imagine its impact energy.
Because demolition is a highly destructive activity, it is very dangerous to do this with other activities going on nearby, such as the movement of vehicles around the area.
Actually, the entire area should have been isolated, barricaded, and restricted from entering.
So, you have to be very careful and guard all the blind and hazardous spots of a machine especially the equipment used for breaking and cutting concrete.
When a wall is being demolished without any standard procedure, especially if it is demolished manually, the workers should follow the proper methodology. Again, lack of planning and not using any PPEs put the lives of the workers at risk of fatality.
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