Seismic and Wind Load Considerations for Temporary Structures

Temporary structures such as scaffolds, shelters, tents, and facilities used during the reconstruction or repair of buildings and bridges, etc., are usually constructed for a limited-time use. Although the design of such structures to dead and live loads usually does not impose any particular challenge, their design for potential seismic or wind load requires more careful investigation. This is due to the fact that the service life of a temporary structure is much shorter than a “permanent structure,” and as such, the probability of load exposure to the temporary structure is substantially less. Designing a temporary structure for the same level of seismic load exposure probability than that required for a permanent structure will not be economically viable. Seemingly, it will make sense to use a reduced design load—a level proportional to the intended service life of the structure. Using a reduced load may be a reasonable assumption for a structure that is used once. However, if the decision is to reuse the structure and to keep it for a longer time than was originally intended, a question arises as to whether, with the extended usage, the safety of the structure will be compromised. This paper provides a review of available studies on seismic and wind loads for temporary structures. Further, the use of a modified risk level, estimated based on the performance record of the structure in its initial usage cycle, is suggested. This modified risk can then be employed in making a decision on whether to allow the structure to be used longer. A simple illustrative example and several conclusions are then presented in an effort to open discussions among the structural engineering community to further elaborate on the issue of design loads for temporary structures.