Concrete-steel composite coupling beams. I: Component testing

A viable alternative to reinforced concrete coupling beams with heavily rei nforced diagonal struts is steel or steel-concrete composite beams. A limit ed number of previous studies have examined various issues related to desig n of steel coupling beams. In this and a companion paper, cyclic response o f steel-concrete composite coupling beams is addressed. The research result s show that nominally reinforced encasement around steel coupling beams con tributes to the strength and stiffness, and web stiffener plates can essent ially be eliminated as the encasement provides adequate lateral stability f or the shear-yielding web coupling beams. Although current design practice is conservative in terms of design and detailing of the beam, the overall b ehavior of composite coupling beams is not necessarily conservative. The de sign needs to consider the additional stiffness and strength in order to en sure proper calculation of design forces in the walls and coupling beams, a nd to dissipate the input energy through formation of plastic hinges in the beam and not in the connection region. Revision of current design guidelin es is recommended.