Distribution of structural collapses and optimum reliability for infrequent environmental loads

Structures located in a particular zone of interest may be subjected to the same environmental events or the same natural phenomena that occur infrequ ently. That is, the structures are subjected to the same environmental load ing parameters such as the peak ground acceleration, the reference wind vel ocity pressure, and the total ice accumulation. Therefore, the structural c ollapses are dependent or correlated. The correlation may affect the probab ility distribution of the number of structural collapses and the optimum re liability level for upgrading the exiting structures and infrastructures. T his is investigated in this paper. It is shown that the coefficient of vari ation of the number of structural collapses is an increasing function of th e correlation coefficient. This increase can be important to the selection of optimum reliability level for retrofitting of existing structures and in frastructures when the risk aversion factor is considered. An approach by t aking the correlation among structural collapses into account in selecting the optimum upgrading level of a group of existing structures is presented and illustrated by a numerical example. (C) 2000 Elsevier Science Ltd. All rights reserved.