Study On Shear Resistance Of Wet Joint Of UHPC Beam With Steel Plate

Prefabricated bridges are widely used because of their convenient construction and simple structure.Small and medium-sized prefabricated concrete bridges have become the mainstream in our country’s highway bridges.But at the same time,due to the insufficient performance of ordinary concrete,most prefabricated precast bridges have various problems such as concrete cracking and joint aging.Among them,the joint problem is the most serious,which is related to the low strength,poor durability,and easy cracking of ordinary concrete.Therefore,lighter,high-strength,and durable materials are the key to breaking through this problem.UHPC(Ultra High Performance Concrete)is a new type of cement-based material with ultra-high strength,high toughness and durability.If UHPC can be used as a joint material for fabricated bridges,it can not only solve the durability problem of ordinary concrete joints,but also further optimize the local structure of the structure,so that the fabricated bridge will develop towards the goal of lighter weight,larger span,and economic and environmental protection.Therefore,the research on the joint structure of UHPC is of great significance.In this paper,a diamond-shaped UHPC seam structure with steel plates is designed.The steel plate at the lower edge of the tension zone is used to solve the problem of UHPC fiber discontinuity at the joints.Three seam beams with steel plates with longitudinal ribs and one steel plate without longitudinal waists are adopted.The shear test of a total of 7 test beams,such as a reinforced seam beam and 3 complete beams with steel plates,is used to study the shear resistance of the joint structure.And apply Abaqus finite element software modeling for comparison verification and parameter analysis.Finally,a calculation formula for shear capacity is established based on the test results and the theory of shear analysis.The main work content and research conclusions are as follows:(1)The shear test of 3 seam beams with steel plate with longitudinal waist reinforcement,1 seam beam with steel plate without longitudinal waist reinforcement,and 3 complete beams with steel plate was carried out.The test results show that as the shear-span ratio increases,the UHPC beam’s shear bearing capacity decreases,and the ductility is the best when the shear-span ratio is 2.4;the failure mode of the joint beam is joint dislocation shear failure,and the main crack is along the joint It develops near the mid-span side,the middle and lower part of the joint is dislocated,and dense oblique cracks appear on the side near the fulcrum;when the shear span ratio is 3.2,the failure mode of the complete beam is bending-shear failure,when it is 1.4,it is shear compression failure,and the main crack is bending Oblique cracks in the middle of the shear section;the bearing capacity of the joint beam under the same shear span ratio is lower than that of the complete beam;the waist reinforcement improves the shear bearing capacity of the UHPC joint beam.(2)Using ABAQUS software for finite element analysis,simulating the shear loading process of the test beam,the load-displacement curve,ultimate bearing capacity and concrete plastic strain cloud diagram are obtained.The simulation results are compared with the test results to verify the correctness of the finite element simulation.The results show that the finite element Analysis can effectively predict the loading results of test beams.The parameter analysis between different steel plate thickness and stud spacing is carried out.The results show that the steel plate thickness and stud spacing have a significant impact on the shear resistance of UHPC beams.Appropriate increase in steel plate thickness and reduction of stud spacing can effectively improve its shear resistance.Bearing capacity.(3)The UHPC shear capacity calculation formula in the French code(SETRAAFGC 2016),the "Technical Specification for Fiber-reinforced Concrete Structures"(CECS38: 2004)and the Japanese UHPC Guide(JSCE 2006)were used to check the test beams.The results It shows that the calculated value of the joint beam is greater than the test value,and the complete beam is less than the test value,and the dispersion degree of the complete beam is the smallest when the French standard calculates the complete beam.Drawing on the sub-item calculation method of French code and considering the effect of longitudinal reinforcement pin and stud tensile effect,the shear bearing capacity model and design calculation formula of UHPC wet joint beam with steel plate are proposed.(4)The first fully permeable UHPC rigid frame arch bridge in my country(K7+164vehicle overpass),which applied the UHPC diamond-shaped wet joint structure with steel plate,was checked.The results show that the joint structure can meet the requirements of the bridge Shear resistance requirements.