Experimental Study on the Longitudinal Shear Performance of Composite Frame Beams under Vertical Loads

Experimental research on the longitudinal shear performance of steel–concrete composite beams under vertical loads has primarily focused on simply supported beams, commonly used in bridge structures. By contrast, tests on composite frame beams with fixed connections to columns are limited, and research is yet to be fully developed. Thus, further clarification of the mechanical mechanisms of longitudinal shear in composite frame beams under vertical loads is necessary. This study experimentally and numerically investigated the longitudinal shear performance of composite frame beams under vertical loads. First, the mechanical behavior of composite frame beams under vertical loads with varying transverse reinforcements was investigated, revealing the mechanisms of longitudinal shear failure and deriving mechanical indicators for different failure modes under vertical loads. Subsequently, a shell-solid finite element model suitable for composite frame beams was developed using Abaqus. The accuracy of this model was verified using the experimental results of the composite frame beam structures investigated in this study. The results indicated that longitudinal shear failure in composite frame beams under vertical loads is ductile. Thus, in engineering design, ensuring that flexural failure precedes longitudinal shear failure is unnecessary.