While design codes regulate the safety of permanent works, erec- tion engineering of temporary works often requires a choice of safety factors. Such choices should be made on the basis of optim- ization of the present expected value of construction and conse- quence costs. This paper illustrates the choice of reliability level in terms of load factors for typical situations encountered in erection engineering. Reliability level depends on the exposure time to the temporary load, the costs of construction of the temporary work, and the consequences of failure. Reliability issues regarding personnel are briefly addressed. Safety decisions about the individual workers will not normally affect the design criteria because the requirement of the contractor, who must bear the risk of many workers, will be more conservative than that of the worker. In the case of exposure over a very short time period, it seems reasonable to accept a higher-than-normal risk. This may affect the design of temporary bracing and similar structures where they are needed for seismic risk, for example.
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