Strength reduction factors for wind and earthquake effects

Strength reduction factors are typically estimated for seismic events ignoring the influence of wind. However, if we consider 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 earthquake ground records only to determine strength reduction factors seems questionable. In this paper is shown that the combined action of strong winds and earthquakes, however its low probability of occurrence, would considerably increase the ductility demand of buildings and cause a decrease of strength reduction factors 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 strength reduction factors associated to those multi-hazard scenarios.