Analytical evaluation of diagonally reinforced concrete coupling beams under lateral loads

Through an analytical study, this paper evaluates various geometrical, reinforcement, material, and boundary conditions that affect the behavior of diagonally reinforced concrete coupling beams under reversed-cyclic lateral loading. To isolate the primary load-resisting components inside the beams, a two-dimensional nonlinear strut-and-tie model is developed based on comparisons with the measured behavior of coupling beams from previous research. With the exception of one specimen, the previous experiments were conducted on beams free to displace axially, ignoring the axial restraining forces that develop in a multi-story coupled wall structure. The paper shows that this boundary condition can result in an unconservative evaluation for the design of the beams, in particular with respect to the diagonal struts in compression. The development of the longitudinal beam reinforcement (to achieve the yield strength) across the beam-to-wall joints can also induce more critical conditions for the compression struts.