Concrete-steel composite coupling beams. II: Subassembly testing and design verification

As shown in a companion paper, the embedment length of steel-concrete composite coupling beams inside wall piers should be computed by incorporating the contribution of the encasement. In lieu of detailed fiber-based analytical techniques, a simple design-oriented model was developed and verified through testing of additional specimens with more realistic loading and boundary conditions. Moreover, the influence of face-bearing plates and floor slab was examined. The developed design method results in longer embedment length, and significantly enhanced energy-dissipating characteristics, strength, stiffness, and ductility. Additional improvements are possible by using face-bearings plates. The contribution of floor slab toward stiffness of the coupling beam is lost at small deformations and may be ignored. Slab participation toward the strength of the steel-concrete composite coupling beams is different from that anticipated for conventionally reinforced concrete beams because of the amount of equivalent reinforcement provided by the flanges of the steel coupling beam.