Formwork for Concrete Structures by R.L.Peurifoy and G.D- By EasyEngineering.net

186 Chapter Seven
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4. Improper vibration or consolidation of concrete
5. Improper or inadequate connections
6. Improper or inadequate bearing details
7. Premature stripping of formwork
8. Errors in placement of reshoring
9. Improper, or lack of, design of formwork
10. Inadequate strength of form material
11. Failure to follow codes and standards
12. Modifications of vendor-supplied equipment
13. Negligence of workers or supervisors
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In many instances the failure of formwork is a result of improper
or inadequate shoring for slabs and roofs. Because shoring systems
constitute the greatest danger of form failures, special care should be
exercised in designing and inspecting the shoring system for a concrete
structure.
Designers and constructors of formwork are responsible for compliance
with the local, state, and federal codes applicable to formwork.
The Occupational Safety and Health Act (OSHA), Subpart Q, provides
safety regulations for formwork [1]. The “Building Code Requirements
for Reinforced Concrete,” produced by ACI Committee 318 of
the American Concrete Institute, also provides requirements applicable
to formwork [2]. ACI Committee 347 publishes “Guide to Formwork
for Concrete,” which contains formwork standards [3].
Traditionally, the responsibility for formwork has been with the
construction contractor. Although codes and standards are developed
to ensure safety related to construction, it is the duty of all parties
involved in a project to achieve safety. This includes form designers,
engineer-architects, workers, supervisors, and inspectors.
Forces Acting on Vertical Shores
The forces acting on vertical shores include dead and live loads plus
impact. Dead loads include the weight of the concrete plus the weight
of any construction materials that are stored on the concrete slab
while the shores are in place. Live loads include the weights of workers
and construction equipment that move around over the decking
or the concrete as it is being placed, or soon thereafter. Although the
magnitudes of these loads may be determined or estimated with reasonable
accuracy, it appears that the effect of the impact of moving
equipment or falling concrete may have been underestimated in
some instances. This refers to concrete that is discharged from cranehandled
buckets, pumping of concrete, and motor-driven concrete
buggies.
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