Structural behavior of S-UHPC-S composite wall strips with waved tie bars: Experiment, simulation, and design

Abstract

In this paper, novel steel waved tie bar shear connectors were developed in conjunction with ultra-high-performance-concrete (UHPC) core to obtain lightweight, high-strength, and easy-construction steel-UHPC-Steel (S-UHPC-S) composite structures. To study the structural behavior of S-UHPC-S composite wall panels with waved tie bars subjected to out-of-plane loads, seven 1/2 scaled S-UHPC-S composite beams were extracted and tested under three-point bending. Test variables included longitudinal and transverse reinforcement ratios, and shear span ratio. Experimental results indicated that S-UHPC-S composite beams failed in flexure mode under the shear span ratios of 2.5 and 3.5 and in flexure-shear mode under the shear span ratio of 1.5. Increasing the longitudinal reinforcement ratio from 1.0 % to 1.5 % and 2.0 % increased the peak load capacity of the S-UHPC-S composite beams by 16.5 % and 43.6 %, respectively, but increasing the transverse reinforcement ratio had a marginal effect on the load resistance because the S-UHPC-S composite beams were dominated by flexure or flexure-shear failure mode. Full-scale models were built with the finite element (FE) software LS-DYNA. After being validated with the test results, the FE model is used to conduct extended studies. Numerical results indicate that the contribution proportion of each component to the bending moment capacity of the S-UHPC-S composite beam can be sorted in a descending order, namely, steel faceplates > UHPC > ribs > tie bars. A method was proposed to predict the failure mode of the S-UHPC-S composite beams in accordance with shear span ratios and mechanical reinforcement ratios. Finally, computation methods for flexure strength and the maximum stud spacing were developed.