Behavior of conventional and enhanced gravity connections subjected to column loss

Gravity frames in steel buildings use simple connections designed to support gravity loads primarily in shear. Under column loss scenarios, large axial loads several times the shear demand can develop at these connections. Recent work has shown that these connections may not be capable of resisting these loads. In this paper, gravity connections studied experimentally under column loss scenarios are presented. Ten specimens of five different connection types were initially tested, including all bolted double angles, welded-bolted double angles, conventional and extended shear tab connections. Because the capacity of these connections was significantly below the required demand given by the ASCE 7 extreme event load combination (1.2D + 0.5L), two enhanced connections were developed and tested. These two connections consisted of a shear tab and a double angle connection, both reinforced with tension plates connecting the beam flanges to the column flanges. Of these two connections, the enhanced shear tab was capable of resisting the required demand.