Investigation of the shear resistances of steel–concrete–steel composite structures with bidirectional webs

Steel–concrete–steel composite structures with bidirectional steel webs (SCSBWs) are used in large-scale immersed tunnels, and have been shown to have high capacity, ductility, waterproofness, and impact resistance compared to traditional structural types. Moreover, versatile construction procedures can be utilised to improve construction efficiency, because the steel plates can function as a framework during concrete casting. Recent studies have shown that there are multiple shear mechanisms in SCSBWs, and the shear resistance of these structures deserves further investigation to achieve more rational designs. Based on previous experimental and theoretical studies, numerical investigations are carried out in this study to investigate the shear resistance of an SCSBW, and an elaborate three-dimensional nonlinear finite element method (FEM) model is proposed. Based on this elaborate FEM model, a series of analyses are conducted to investigate the loading process, stress development, concrete cracking, stress state, and interfacial behaviour of SCSBWs under shear. Mutual verifications are obtained between results of the FEM model, experiments, and theory. Based on the analysis of the interfacial properties, the FEM model is simplified, and the simplified model is shown to be accurate and efficient. Further, parametric analyses are conducted, revealing that the concrete, axial web, flanges, and shear–span ratio have a significant influence on the shear resistance. Finally, a modified theoretical method is proposed to consider the influences of dowel action and small shear–span ratios, with which the accuracy of predicting the shear resistance of SCSBWs can be improved.