Earthquake-resistant Design of Double-angle Bracings

Behavior of steel-braced frames during an earthquake strongly depends on the behavior of bracing members and their connections. In recent years, considerable research has been done on behavior of bracing members under cyclic loading. However, studies on the behavior of their connections are almost nonexistent. A number of observers who have studied structures damaged by earthquakes have reported total or partial failures in the connections of bracing members. These observed failures clearly indicate a need for evaluation of current philosophies and procedures employed in design practice. Simplified design procedures are used in practice even though it is known connections have complex stress distributions. Most of these design procedures are based on the studies of monotonically loaded connections and were intended to be used in design of connections subjected to nonreversible loads. Thus, the cyclic forces and deformations induced in the bracing members and their connections during a strong ground motion earthquake are not considered in such procedures.