Optimal Knee Bracing System and Orientation for High Rise Steel Buildings under lateral loads

Earthquake Enginnering

In knee brace frame System (KBFS) the non-buckling diagonal brace provide most of the lateral stiffness, the flexural yielding of knee element provides the ductility under a severe earthquake. In this way damage is concentrated in a secondary member which can be easily repaired/replaced at minimum cost. This paper aimed at investigating and comparing various types of knee bracing systems. A regular floor plan of 16 m x 12 m is considered for 15 storey steel frame building. To study the performance of 15 storied steel frame building with different bracing systems - single diagonal knee braced (SDKBF), X knee braced (XKBF), V knee braced (VKBF), Chevron knee braced (CKBF) and X braced frame(XBF), nonlinear static pushover analysis is performed in SAP 2000(V17.2) based on ATC 40 and FEMA 356 guidelines. Parametric study for knee element angle variation (30 , 45 , and 60) is carried out. The results are compared for the seismic parameters - capacity curves, displacement, performance point, and ductility factor with different bracing systems.

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