Shear strength and deformation modeling of conventionally reinforced short coupling beams

Abstract

In this paper, a mechanics based analytical truss model is proposed to predict the shear strength and deformation of conventionally reinforced coupling beams with span-to-height ratios less than 1.75 (referred to as short coupling beams). The model considers the yield of only parts of stirrups, and its load path is composed of a direct main strut connecting the compression zones at both ends of the beam and secondary struts balancing with stirrups. By satisfying the compatibility condition at the intersection node of the struts, the assignment of the applied shear load in the main and secondary struts, as well as the shear load-transverse displacement relationship of the beam, are determined. The shear strength predictions by the truss model are compared with test results of 37 conventional reinforced short coupling beams, which shows that it can accurately predict the shear strength with a coefficient of variation (COV) of 0.052, while the predictions provided by ACI 318-19 and GB 50010-2010 are relatively inaccurate (the COVs are 0.19 and 0.21, respectively). In addition, the skeleton curves of 27 short coupling beams are calculated by the truss model, and the results show that the predictions are in good agreement with the test results. In order to simplify the calculation, a simplified model is proposed based on the refined truss model. Although the accuracy of the simplified model is slightly reduced (the COV is 0.071), it is still significantly higher than those of the design codes. Based on the simplified model, a standardized design method, which indirectly considers the beam deformation capacity, is provided for practical shear design.