Effect of flanged walls on the seismic performance of tall buildings

SUMMARY Flanged walls are a common feature in concrete and masonry construction that require special consideration because of the distinct nature of their response to earthquake forces. Flanged walls typically have different strength, stiffness and ductility capacities in the two opposite directions when loading is parallel to the web. Their effect on seismic response is particularly critical in tall buildings because the height of the walls usually ensures that the flanges are fully effective under lateral loads. An existing building is used to investigate the effect of flanged walls on building response. A performance-based approach with three levels of ground motion is used, and nonlinear time history analyses are utilized to determine the structural and non-structural damage for each level of ground shaking. Structural damage is determined with limit state methodology while non-structural damage is evaluated by correlating inter-story drifts and floor accelerations to damage in the non-structural building components. The analyses show that buildings with flanged walls will incur less structural damage from moderate earthquakes than corresponding buildings without flanged walls. On the other hand, major earthquakes that impose large ductility demands may cause significantly more structural damage in flanged walls. Nonstructural damage in flanged-wall buildings is about 20‐40% greater than that in buildings without flanged walls. The increase in non-structural damage is also greater when there are large ductility demands. # 1997 John Wiley & Sons, Ltd.