Use of novel perforated steel beams in lieu of RC coupling-beams in tunnel-form buildings

Diagonal reinforcement placement in reinforced concrete (RC) coupling beams of tunnel form buildings is impractical due to relatively small dimensions of such beams. Previous studies show that these elements acting as structural fuses have minor contributions to overall seismic energy dissipation. In this study, we propose a novel perforated steel coupling beam in lieu of the conventional RC coupling beam. We presented the relationships for determining the shear capacity of such beams, and then investigated their validity numerically by using ABAQUS. The nonlinear seismic responses of the proposed beam and conventional beam were compared and contrasted. The demand and capacity factors considering the influence of the parameters such as ductility, over-strength, site seismic hazard and performance levels were also evaluated. The results indicate that although steel-coupling beam reduces the global stiffness as compared to the RC coupling beam, it will not reduce the building' s overall performance under the design earthquake. In fact, use of such beams increases the ductility and the response modification factor. Their other advantages are easy to implement and repair or replace after an earthquake.