Formwork operations are risky, and workers are typically exposed to unsafe working conditions. The partial or total failure of concrete formwork is a major contributor to deaths, injuries, and property damages within the construction industry. This enhances the importance of Safety Formwork Operation.
Forms must be built with sufficient strength and factors of safety so they are capable of supporting all dead and live loads without collapse or danger to workers and to the concrete structure.
Contractors are generally responsible for the stability and safety of concrete formwork. Also, they are guided by several federal, state, and local codes and regulations that regulate formwork safety. Most of these documents provide general guidelines for safety but provide no guarantee against failure. Contractors typically are trying to achieve fast removal of formwork elements without compromising the safety and integrity of structures.
A floor formwork system filled with wet concrete has its weight at the top and is not inherently stable. As a result, one of the most frequent causes of failure is from effects that induce lateral forces or displacement of supporting elements; therefore, inadequate cross-bracing or horizontal bracing is one of the most frequently involved factors in formwork failure. Also, vibration is one factor that can trigger failure through inadequate bracing.
In addition formwork failures result from faulty formwork structural design, inadequate shoring and reshoring, improper construction practices during construction, unstable support or mudsills, and insufficient concrete strength to sustain the applied load after construction. The failure at one point in the formwork that can become an extensive collapse through a chain reaction.
So Formwork should be designed by an engineer or by someone who has sufficient knowledge of forces and resistance of form materials.
The safety of workers is a concern of all parties: owners, designers, and contractors. Safety is everyone’s responsibility, including workers in the field, supervisors, and top management. There are many risks in the process of erecting and dismantling formwork systems. Every precaution should be taken to ensure a safe working environment.
Safety in formwork requires that the forms be:
To ensure the safety of the structure and the protection of the workers, it is essential that formwork is designed to carry the full load and side pressures from freshly placed concrete, together with construction traffic and any necessary equipment.
The materials used to construct the forms must be of the correct size and quantity, of good quality, and sufficiently durable for the job.
#3 Avoid Deflection:
Deflection is the most important consideration for the design of formwork, the limit for deflection varies according to the class of the work. For simply supported spans, this limit is not more than span/360.