Nonlinear Wind and Earthquake Loads on Tall Steel-Braced Frame Buildings

Although time-domain response analyses have been commonly used in the design of tall buildings, the code-based wind design continues to rely on prescriptive static methods. Moreover, buildings subjected to both earthquakes and wind, where both are critical, could be prone to ineffective seismic response (increasing bottom-floor member sections due to wind demand reduces the system's ductility) and noneconomic lateral force-resisting system (design for elastic response under wind loads). The incompatibility in the current building code when addressing the seismic and wind design such as: the consideration of different return periods for wind and earthquake; design for ductility under earthquake versus the elastic response under wind; and the governing lateral load for tall steel buildings of rectangular floor plans located in moderate-to-high seismic zones, are discussed herein. First, a design methodology for developing along-wind history series, generated from wind-tunnel pressure records available from the Tokyo Polytechnic University aerodynamic database, is provided. Then, incremental dynamic analyses under winds and earthquake loads are carried out independently in a case study, and insights into the collapse mechanisms are presented. The findings show that the annual failure probability under wind is greater than that under earthquakes.