Cyclic experimental behavior of angles and applications for connection design and modeling

Recent work on the seismic behavior of low-ductility steel braced frames has suggested that adding top and seat angles to gravity framing connections can increase a building’s reserve capacity and hence its collapse performance. To this end a comprehensive suite of 133 tests has been developed and is currently in progress to establish a baseline of ultimate capacities under monotonic and cyclic loading. Angles range in size from L4x4x5/16 to L8x6x3/4, and will be fastened using 3/4” A325, 1” A325, and 1” A490 bolts. The distance from the heel of the angle to the bolt centerline in the vertical leg, referred to as the gage, has previously been shown to be an important parameter, particularly in relation to the thickness of the angle. Low gage-to-thickness ratios indicate stocky configurations, while high ratios indicate slender, flexure-controlled configurations. The ratios within this study range from 1.25 to 8.00. Based on the test results, this study aims to develop simple analytical models that can reasonably predict ultimate moment capacities and rotations of beamto-column connections reinforced with top and seat angles.