Robustness of steel braced frame to resist disproportionate collapse caused by corner column removal

Abstract

Steel braces have been widely used as a major lateral stability system to resist the lateral load. However, the influences of steel braces on enhancing the load resistance in moment-resisting steel frames under column removal have not been studied adequately due to the lack of experimental data, especially under worst case scenarios, corner column removal. Thus, five two-floor steel moment-resisting subframes with or without braces were tested by applying a pushdown force. The purpose of this study is to quantify the effects of steel braces on the robustness of steel moment-resisting frames against disproportionate collapse. The test results indicated that steel braces could enhance the ultimate load bearing capacity up by 102.3%. Compared to V configuration, X configuration is more efficient in increasing the load resistance since a proportion of the vertical load may be transferred to the side column through diagonal braces straightly. The de-composition of the load bearing capacity indicated that compressive braces only affect the initial stiffness and most of the load resistance is attributed to tensile braces for both X and V configurations. De-composition of the load bearing capacity indicated that the load bearing capacity from the first floor is normally greater than that from the second floor due to greater Vierendeel action mobilized.