Page 318 - Forensic Structural Engineering Handbook

TEMPORARY STRUCTURES IN CONSTRUCTION 10.7

the architect or engineer: Is the temporary structure subcontractor now relieved of any fur-
ther responsibility for the adequacy of this temporary structure?
In any event, it is clear that shop drawings for temporary structures have an important
difference in the legal sense from shop drawings for the permanent structure. It is also
evident that shop drawings for temporary structures sometimes require a great deal of more
design work than is normally required for shop drawings for permanent structures.
In a forensic engineering investigation and litigation after a failure, the history of the
preparation, review, and approval of the drawings and specifications can be critically
important.
Permits. The temporary structure contractor is required to obtain permits for the work to
be done. These permits may be issued after approval of the plans for the temporary work
by the building department, when this type of approval is required. Such approvals, as an
example, might be for shoring or sheet-piling work, or for equipment that the contractor
may be required to use in performing the work. The equipment may consist of cranes or
hoists to be placed in the street or on the sidewalk. Other permits may be required for side-
walk crossings and for storage of materials in the street. In general, the cost of the permits
must be borne by the temporary structure contractor. When a permit requires a submission
of a drawing prepared by a licensed professional engineer, the drawing is the responsibility
of the temporary structure contractor. If the temporary structure contracting company does
not have a licensed professional engineer on its staff, then it is necessary for it to obtain
such a qualified individual for the preparation of the plans.
Materials and Workmanship. Temporary structures are often constructed of reusable man-
ufactured elements. Although such elements are designed and made to be reused, their repeated
transportation, assembly, loading, disassembly, storage, exposure to weather, and rough han-
dling result in their damage and deterioration. They should be inspected, their existing strength
and stability verified before use, and allowances made for their lost strengths, if any.
Contractors, especially on smaller projects, often use used materials for temporary
structures. These materials may or may not be visibly damaged, but their strengths may
well be inferior to what is required by the design. If the required member or element is not
available at the site, a contractor may substitute or make it up from other pieces, sometimes
even from scraps. If their adequacy is not verified, these materials may precipitate the failure
of the temporary structure.
Except for specially designed and controlled major temporary structures, the workman-
ship in their installation is frequently inferior to the workmanship in permanent construction.
The required tolerances are usually more relaxed, the “looks” are generally unimportant,
and the overall attitude is that “these things” are only temporary and will come down any-
way. This is all understandable as long as it does not compromise the proper performance
and safety of the temporary structure.
In the absence of strict control of the materials and standards of workmanship, these
practices of used materials and possibly inferior workmanship should be anticipated and
reflected in the design through more generous factors of safety. The forensic engineer
should not be influenced by the looks of temporary structures, but should recognize sloppy
and unsafe work when he or she sees it.
Supervision. Supervision of a temporary structure installation includes not only its initial
construction but also its adequacy during the entire period during which it is performing its
intended function. The contractor must maintain adequately trained superintendents and
supervisors who are on the site at all times when work is under way.
A qualified supervisor is one who has training and experience in the type of work which
is being done. Obviously, a supervisor who has only a general background in construction