Strength reduction factors for wind and earthquake effects

Abstract

Strength reduction factors (SRFs) are typically estimated for seismic events ignoring the influence of wind. However, considering that strong earthquakes are commonly followed by a number of moderate to strong aftershocks and that wind is constantly flowing, often with low to medium intensity but occasionally reaching high speeds, then the assumption of using only earthquake ground records to determine SRFs seems questionable. In this paper it is shown that the combined action of strong winds and earthquakes, however low its probability of occurrence, would considerably increase the ductility demand of buildings and cause a decrease in SRFs calculated by ignoring wind. The paper examines the non-linear performance of single-degree-of-freedom systems subject to various levels of winds and earthquake load and deals with the estimation of SRFs associated with those multi-hazard scenarios.