Study of the strength and behaviour of single-coped beam under combined bending, shear and axial loads

Coped beams are often used as a secondary member to support a floor slab system. The coped beam ends are achieved by removing the flange(s) of the beam to facilitate the connection to the main beam. Although coped beams are mainly used to resist gravity loads in a building structure, the beams may be subjected to axial force due to the transfer of lateral loads such as wind loads from the building façade to the lateral load resisting system. Hence, the coped beams are subjected to combined loadings of bending, shear and axial force. However, existing design methods for single-coped beams do not account for the influence of axial loads and the combined load effects. This study presents an experimental and numerical investigation of the structural behaviour and local web buckling strength of single-coped beams under combined bending, shear and axial loading scenarios. Ten full-scale tests of single-coped beams subjected to combined loadings were conducted with varied test parameters including the axial force level, cope details and web slenderness ratio. In general, all the test specimens failed by local web buckling at the coped region. The test results demonstrated that the ultimate strength of the coped beam specimens subjected to gravity loads decreased with the presence of compressive axial force. For instance, a compressive axial force corresponding to 4 % of the section yield load reduced the ultimate strength of a coped beam specimen by 10.1 % when comparing to that without the compressive force. Finite element (FE) analyses were subsequently conducted to further explore the effect of axial force on the strength and behaviour of coped beams with various cope details. It was found that the existing design methods, which do not account for the combined load effects, could not produce satisfactory predictions of the web buckling strength of single-coped beams when compared to the test and FE results. To address these shortcomings, a design equation was proposed to evaluate the strength of the coped beams under combined bending, shear and axial loads. The test-to-predicted ratios based on the proposed design equation ranged from 0.94 to 1.22 with a mean value of 1.05 and a coefficient of variation of 0.07. A reliability analysis was conducted, and the results indicated that a partial factor of γ_M = 1.09 was suggested for practical application to ensure safety and reliability in structural design.