Analytical And Experimental Investigation On Mechanical Behavior Of Shear Connectors

The increasingly diversified construction needs have continuously updated material types,structural forms,and construction methods in composite structure technology.The research and application of shear connectors,critical components in the composite structure,have also met new challenges.Many formulas have been given through experimental and numerical studies;however,most are empirical fitting formulas,which are difficult to reflect the physical mechanism of the interaction between steel and concrete in the connectors.Therefore their applicability and expandability are limited by the test conditions.In this paper,analytical and experimental studies on headed stud connectors,steel rebar connectors,and PBL connectors are conducted,and the main results are as follows:(1)By analyzing the failure modes and load-slip curve behaviors of the test and numerical simulation results of the headed stud connectors,a deformation assumption is proposed based on the load-bearing behavior of the stud shear connectors.Moreover,a simplified analytical model that can accurately predict the load-slip curve of the stud connectors is established based on the Winkler foundation beam model,with consideration of the elastoplasticity of the steel and the cracking damage features of the concrete.Compared with the traditional empirical formulation,this model can obtain the load-slip curve directly from the material parameters and geometry of the connectors.In addition,it can consider the influence of more parameters,such as stud elongation and concrete reinforcement,on the shear resistance behavior.As a result,the analytical model is based on a definite physical mechanism and has better applicability and expandability.(2)A group of tests was designed to investigate the mechanism of reinforcementconcrete interaction for shear connector push-out tests.In order to avoid the comprehensive effects of multiple factors on the shear properties,which are often involved in the tests of existing headed stud connections,the tests focused on the effects of two key factors,the diameter of the reinforcement and the strength of the concrete,on the shear behavior of the connector.By analyzing the failure modes and test results of the specimens,the applicability of the existing empirical equations is evaluated,the applicability of the analytical load-slip curves is verified,the interaction mechanism between the connector and concrete is revealed,and the formulas for shear strength and ultimate slip of the reinforcing steel connectors are proposed.(3)The three-dimensional continuum model is proposed and validated to analyze the shear behavior of the connectors.The analytical model can further consider the interaction between the steel rebar and concrete in the shear connectors,according to which simplified formulas for the concrete’s effective height and the rebar’s effective deformation length are presented.These formulas address the shortcomings of the analytical model of the Winkler foundation beam,which is limited in application due to the lack of a concrete displacement description.This paper provides a theoretical basis for further refined analysis of the connectors’ shear behavior.(4)A group of pushout tests of PBL connectors with a large parameter range span was designed to summarize the characteristics and classification of load slip curves of PBL shear connectors.To evaluate the applicability of the existing empirical formulas for concrete dowel yield strength and propose a simplified calculation formula of the concrete dowel yield strength,which applies to large PBL connectors.The effect of rebar diameter,concrete strength,and diameter of the hole on perforated steel plates on the ultimate bearing capacity is revealed by parametric analysis,and the type and applicability of the existing empirical formulas are evaluated.The formulae for calculating the shear capacity of PBL connectors with large parameter spans are given and verified by the existing test data.