Study On Shear Properties Of Stud And PBL Composite Shear Con-nector On Steel-UHPC Interface

The hybrid beam(column)structure has the advantages of light w eight and economy,and has a wide range of uses in b ridge engineering.The key part of the hybrid beam(column)structure is the steel-concrete section,and the steel-concrete section generally adopts shearing Force connectors to transmit internal forces.Ordinary concrete is usually poured in the ordinary steel-concrete joint section.The strength of ordinary concrete is low.The high stress transmitted from the steel structure need s to be diffused through a series of complex structures in the joint sectio n to ensure the safety of the concrete,but in fact The combined section is not only long in length,but also has a very complex internal structure.Therefore,it is difficult to av oid concrete voids and concrete cracks in the joint section,which may lead to bad influences on the safety and mechanical performance of engineering.The use of ultra-high performance concrete(UHPC)with excellent mechanical properties and excellent dura bility can greatly shorten the length of the joint section,simplify the in ternal structure of the joint section,ensure the quality of pouring,and effectively improve the mechanical performance and durability of the joint section.In order to deeply study the shear performance of steel-ultra-high performance concrete(UHPC)interface studs and PBL hybrid shear connectors,this pa per proposes a practical calculation method to guide engineering design applications,and mainly completes the following work:(1)Based on the actual engineering background,a total of 12 model specimen s of 6 types were designed and the roll-out test was completed.The mechanical properties of stud shear connectors,PBL shear connectors,and stud-PBL hybrid shear connectors at the steel-UHPC interface are studied,and the load-slip curves and limits of various shear connectors are analyzed.as well as their bearing capacity and destruction form.By using the strain gauges pasted at the root of the welding stud and the edge of the aperture of the perforated plate respectively,we can get their load-strain curves.The test analysis and results show that the load-slip curves of the three types of shear connectors have similar curve characteristics;in terms of failure mode,UHPC does not have large area failure,but only has local failure in the weak connection area.(2)Using the Explicit module in the ABAQUS finite element analysis software,the simulation and parameter analysis of the stud-PBL hybrid shear connection in UHPC and the PBL shear connection without penetration reinforcement in UHPC were carried out;In,based on the test data,the plastic damage model was used to define the UHPC material,the ductile metal damage model was used to define the stud material,and the loading process was simulated by quasi-static analysis.The final simulation results are in good agreement with the push-out test results.The whole process of damage and failure of the stud-UHPC hybrid shear connector was analyzed by using the simulation results of the finite element model,and the stress mechanism of the stud-PBL shear connector in UHPC was further clarified.At the same time,the parameter analysis results show that,when 13mm< stud diameter <22mm,120mm<stud height<200mm,40mm< PBL diameter <60mm,120MPa< UHPC strength<160Mpa,the PBL diameter has a significant effect on the shear capacity of the hybrid shear connector,while the stud diameter,stud height,UHPC strength and othe r parameters have little effect.(3)Based on the experimental data and the results of the finite element calculation,considerding theoretical analysis,the theoretical calculation methods of the shear performance of various types of shear connectors in o rdinary concrete and UHPC were collected and sorted out by various scholars.The steel-UHPC interface bolt connection,the load-relative slip full curve formula and the ultimate bearing capacity calculation expression of the PBL connection,and on the basi s of the principle of distributing the load according to the stiffness,the steel-UHPC interface bolt is proposed.Load-slip full-curve formulation for a nail-PBL hybrid shear connection.Finally,the practical formula of steel-UHPC interface stud and PBL hybrid shear connection proposed in this paper is used to check the actual bridge pier column.and normal usage requirements.