Cyclic Behavior of Double Angle Bracing Members with End Gusset Plates.

Abstract

The performance of braced frames during earthquakes strongly depends on the behavior of bracing members and their connections. In some instances earthquakes have caused total or partial failure of double angle bracing members and their connections. This dissertation presents the results of an experimental investigation of the cyclic behavior of full-size bracing members and a study of philosophies and procedures currently employed for designing bracing members with end gusset plates. Seventeen full-size test specimens made of double angle sections connected to the end gusset plates by fillet welds or high strength bolts were tested under large amplitude cyclic loading. Members designed by current code procedures generally showed fracture during early cycles of loading. New design procedures which are proposed to improve ductility and energy dissipation capacity of the bracing members are shown to have successful results. Procedures are given for the design of end connections and stitches to survive large post-buckling deformations. While the existing building code design philosophies for bracing members connections consider only strength, it is recognized that a rational design philosophy must consider ductility of connections. Such criteria are included in proposed design procedures. Experimental full size bracing member hysteresis loops compare favorably with those calculated by means of a semi-empirical model proposed by Gugerli and Goel.