Design Recommendations for Steel Reinforced Coupling Beams
Design and modeling recommendations for steel reinforced concrete (SRC) coupling beams are provided for both code-based (prescriptive) design and alternative (non-prescriptive) design accomplished using linear response spectrum or nonlinear response history analyses. SRC coupling beams provide an alternative to reinforced concrete coupling beams, diagonallyreinforced for shorter spans and longitudinally-reinforced for longer spans, and offer potential advantages of reduced section depth, reduced congestion at the wall boundary region leading to cost savings, improved degree of coupling for a given beam depth, and improved deformation capacity. The recommendations incorporate information from the 2010 AISC Seismic Provisions, which are primarily based on beam tests of shear-yielding members, as well as new information obtained from four large-scale tests of flexure-yielding SRC coupling beams without face bearing plates and auxiliary transfer bars, which are required by the 2010 AISC Seismic Provisions. For prescriptive design, recommendations are provided to determine the required embedment length of the structural steel member into the reinforced concrete wall, effective coupling beam stiffness, nominal (lower bound) and expected (upper bound) flexure and shear strengths, and beam and wall detailing. For alternative (non-prescriptive) design, additional parameters are provided to define the deformation capacity (to complete the backbone relations) and to address cyclic degradation.