Numerical and theoretical studies on shear behavior of steel-UHPC composite beams with waffle slab

Abstract

UHPC waffle slab was proposed to utilize the excellent material properties of UHPC and improve the rigidity of bridge deck. The flexural behavior of steel-UHPC composite beams with waffle slabs (SUCBWS) has been studied recently while the shear behavior of SUCBWS is still limited. This paper aims to supply the gap in the research system of mechanical properties of the novel bridge deck system. Based on the experimental study of four SUCBWS, a three-dimensional finite element model (FEM) was developed to investigate the shear behavior of SUCBWS. Extensive validations of the numerical analyses against the reported tests proved that FEM is reasonable. Meanwhile, the shear working mechanism of SUCBWS was analyzed. A subsequent parametric study was conducted to investigate the effects of shear span ratio, yield strength of steel, degree of shear connection, the ratio of rib height to top flat plate thickness and adding haunch at the rib-to-plate interface on the shear behavior of SUCBWS. Results show that shear span ratio and degree of shear connection present an obvious influence on ultimate bearing capacity, stiffness, ultimate deflection and failure mode of the composite beam. The shear span-to-depth ratio increased 1.34 to 3.14 resulted in a decrease in stiffness and shear strength while an increase in ultimate deflection. The increase of the degree of shear connection (from 0.5 to 1) improved the stiffness and ultimate bearing capacity but reduced the ultimate deflection. Adding the haunch at the rib-to-plate interface can significantly improve the integrity and decrease the risk of longitudinal splitting failure of the UHPC waffle slab. The high-strength steel can match well with the UHPC waffle deck so as to improve the ultimate bearing capacity of SUCBWS. The increase of the ratio of rib height to top flat plate thickness showed a limited influence on shear behavior of composite beams and the value of 3 is recommended for the design of SUCBWS. Meanwhile, the shear composite action coefficient, shear contribution coefficient of top flat plate and ribs were proposed to develop the theoretical models for predicting the shear capacity of SUCBWS and providing a reference for the design of SUCBWS. Besides, the effect of the haunch size at the rib-to-plate interface on the mechanical performance of SUCBWS should be further quantitatively analyzed.