Outrigger Beam–Wall Connections. II: Subassembly Testing and Further Modeling Enhancements

Adequate strength of headed studs under cyclic loads is a prerequisite for satisfactory performance of outrigger beam–core wall connections that commonly use multiple headed studs. Previous studies have typically not investigated the effects of reinforcement around studs, and have not accounted for the effects of cracking, damage, and yielding of reinforcement on the strength of studs. To remedy these deficiencies, two 1/4-scale subassemblies that contain a cantilever wall and two outrigger beams with and without floor diaphragms were subjected to cyclic loading. The wall reinforcement around the connection was selected according to the anticipated level of cracking and plastic hinge formation. The design methodology followed in this research resulted in connections that could develop and exceed the design forces despite extensive cracking and yielding of wall reinforcement around the headed studs. The presence of heavily confined wall boundary elements around headed studs increases the capacity. Simple methods to account for the influence of cracks and strengthening effects of boundary elements were developed. The resulting analytical model was able to accurately establish the expected mode of failure and capacity of outrigger beam–wall connections. For the outrigger beam–wall connection detail selected, the outrigger beam was found to transfer the majority of diaphragm forces directly to the core wall with negligible participation by the floor. Therefore, floor slab–wall connections can be based on simple details that resist only gravity loads unless the connections are specifically designed to transfer the diaphragm forces to the wall.