Page 317 - Forensic Structural Engineering Handbook

10.6 CAUSES OF FAILURES

In the provision of a temporary structure for sheeting and shoring of an excavation, as an
example, the project design engineer for the permanent structure might merely indicate that
sheeting or shoring is required for that particular embankment. This general directive may
be required by code and/or may be incorporated on the plans or in the specifications. On the
other hand, the project design engineer may provide the design on the contract drawings.
In the first instance, the contractor in all likelihood will be required to have his or her
detailed plan checked and signed by a licensed professional engineer. The adequacy of the
sheeting and shoring will be the responsibility of the contractor together with the licensed
professional engineer. This may also require that the contractor submit the design for the
proposed sheeting and shoring to the project design engineer.
If, on the other hand, the designer of the permanent structure shows the details of the
sheeting and shoring and the contractor follows this design in the execution of the work,
then the responsibility for adequacy will rest with the original designer. Should the con-
tractor deviate from this design, and should it be shown that the deviation from the design
resulted in a failure of the sheeting and shoring to properly perform its function, then the
contractor is responsible for the damages which result from this deviation.

Specifications. The specifications for the temporary structures are usually drawn up by
the temporary structure contractor. In most cases, architects or engineers designing a per-
manent structure will not provide a design drawing or even specifications for the temporary
structure work. For example, a temporary structure contractor working on concrete form-
work will have to specify the type of plywood, framing, form ties, snap ties, braces, and
other form accessories that are required for the work. The responsibility for the adequacy
of the specified material and for its quality will be that of the temporary structure contractor.
In the case of a design which is prepared by a temporary structure contractor for the
approval of the architect or engineer, the specifications which are part of that design must
also be the responsibility of the temporary structure contractor. The specifications may
have to be reviewed by the project’s engineer or architect of record for their adequacy and
for the durability and strength of the materials. Should there then be a question about any
of these qualities, the temporary structure contractor will have to justify the appropriateness
of the specified material.

Shop Drawings. In a temporary structure, the shop drawing and its preparation are some-
what different from a shop drawing prepared by a subcontractor or supplier for a permanent
structure. The shop drawing for a temporary structure may, in fact, be a completely original
design which does not appear in any way on the contract drawings. An example of this might
be a shop drawing prepared for the dewatering system using well points. In this case, it is the
responsibility of the subcontractor of the dewatering work not only prepare the details of
where the dewatering system will be located and the type of piping and pumping equipment
that would be used, but also to incorporate in the shop drawings or its specifications the cal-
culations made by the subcontractor to ensure the adequacy of the system being installed.
Reviews and Approvals. If the temporary structure subcontractor has provided the calcula-
tions for the work to be done, the question is “Who will be responsible for those calcula-
tions?” Normally an engineer or architect checks shop drawings for “compliance only” with
the original contract drawings and specifications. In this case, however, since there are no
original contract drawings of the material or equipment being shown on the shop drawings, it
is necessary for the project’s engineer or architect to decide whether the shop drawings have
to be reviewed and approved at all. In most cases the engineer or architect will merely review
the shop drawings for interferences or for conditions which might affect the permanent works.
The following question sometimes arises when a shop drawing is submitted for
approval by a temporary structure subcontractor and is, in fact, checked and approved by