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Often the Supervisor’s evaluation
criteria are speed and dollars saved, ignoring safety and quality.
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Untrained workers can cause unsafe
conditions. An inexperienced, untrained worker who is ignorant of safe practices and
policies will not work safely. The contractor has a responsibility to examine the
worker’s level of knowledge, training, and discipline. Also, the contractor’s
training, apprentice, and enforcement programs must be beyond reproach.
When discussing worker competence, detailed attention must be focussed
on supervision. The supervisor must constantly keep safety, quality, and economy in
balance. The supervisor must never allow economic considerations to be the driving force
on the job, thereby allowing quality and safety to slip which could lead to accidents or
failure. Often the supervisor’s evaluation criteria are speed and dollars saved,
ignoring safety and quality.
Unexpected or unusual events can cause imbalances in the formwork which
could rupture the system. This is a nice way of saying "we did not expect a load from
that direction or of that magnitude." The cause of this is usually poor planning.
These accidents could range from a piece of equipment running into the formwork, to
placing material or equipment where an architect/engineer did not think people would place
such items.
Associated with an unexpected event is improper concrete placement.
Formwork is designed to accept concrete loads based on specifications. When the pour rate
and/or the pour sequence is not as specified, a potential for formwork failure exists.
Concrete placement is a critical time in the formwork’s life. It is during this
time that dynamic loads are experienced and maximum static loads are realized. If
something is wrong with the formwork, this is when it will manifest itself. Extreme care
and caution must be exercised during all pours to minimize risk and maximize safety.
The materials of the formwork are the most visible parts of the system,
however, the surface or foundation on which the forms rest is also critical. Unsafe
conditions exist when the base in unsuitable or unstable. What good is excellent formwork
if the foundation gives way?
Bracing, or the lack thereof, can lead to unsafe conditions. Most
formwork will withstand vertical loads, however, horizontal loads or slight shifts in
loads from vertical, which can occur during concrete placement, can cause an inadequately
braced system to fail. Too little or improper bracing is an unsafe condition.
Careless attention to shoring and reshoring multi-level structures is
unsafe and can lead to serious problems. If proper practices are not followed,
distribution of loads to lower floors can cause failures, thereby shifting weight to less
mature floors which increases the possibility of failure. Failure is dramatic and
progressive and increases the unsafe zone to beyond the formwork domain. Safety is
compromised when actions are not taken to address how vibration affects the formwork
system. Traffic, equipment, people, and subterranean movement all cause vibration. The
vibrations can move formwork components out of alignment. Bracing, foundations, and
attaching mechanisms can be used to minimize vibration induced movement.
Manufacturers of formwork offer a wealth of knowledge. They recommend
safe practices based on past experience and intimate knowledge of their equipment. The
manufacturer’s recommendations should be followed for maximum safety. If there is
disagreement with the manufacturer’s recommendations then they should be called to
the site for consultation. Unilateral action by the contractor may lead to unsafe
conditions.
Up to now, our discussions have focussed on construction and
maintaining formwork viability. Unsafe conditions often arise during formwork removal.
Care must be exercised to remove the formwork in accordance with standard safe practices.
The concrete should have reached a desired state of cure to the required specifications
before removal is attempted. With this in mind, care should be taken not to stress the
young concrete by removing the forms in an irregular fashion. This could cause slab
failure resulting in potential injury. |
