Concrete-steel composite coupling beams. I: Component testing

A viable alternative to reinforced concrete coupling beams with heavily reinforced diagonal struts is steel or steel-concrete composite beams. A limited number of previous studies have examined various issues related to design of steel coupling beams. In this and a companion paper, cyclic response of steel-concrete composite coupling beams is addressed. The research results show that nominally reinforced encasement around steel coupling beams contributes to the strength and stiffness, and web stiffener plates can essentially be eliminated as the encasement provides adequate lateral stability for the shear-yielding web coupling beams. Although current design practice is conservative in terms of design and detailing of the beam, the overall behavior of composite coupling beams is not necessarily conservative. The design needs to consider the additional stiffness and strength in order to ensure proper calculation of design forces in the walls and coupling beams, and to dissipate the input energy through formation of plastic hinges in the beam and not in the connection region. Revision of current design guidelines is recommended.