Study On Mechanical Properties Of Steel-Concrete Composite Cast-in-Place Belt

As an important link in the construction of prefabricated bridge panels,cast-in-place belt is the most prone to diseases due to the complex force of the new and old concrete combined with the facial position.The construction quality of cast-in-place belt directly affects the quality and speed of bridge panel construction.In this paper,according to the stress characteristics of the cast-in-place belt of the T-beam bridge panel,a type of cast-in-place belt of steel-concrete composite structure is designed.In the steel-concrete composite structure,the experimental research and finite element analysis of the bending performance of the T-beam bridge panel under the action of positive bending moment are carried out,and the design parameters are optimized.The theoretical bearing capacity calculation formula of the cast-in-place belt of the steel-concrete composite structure is studied.The fatigue performance of steel-mixed cast-in-place strip is studied.The main work and conclusions are as follows:(1)Through the bending test of the bridge panels under load,the differences of the structural bending capacity,deformation,failure mode and joint mechanical performance of the cast-in-place strip of the traditional T-beam bridge panels and the steel-concrete composite T-beam bridge panels under load are compared.The results show that the cracking load of the traditional cast-in-place zone is 25 KN and the failure load is 148 KN.The cracking load and failure load of cast-in-place steel concrete composite structure are 58 KN and 178 KN.Compared with the traditional cast-in-place strip,the bearing capacity of the cast-in-place strip of the steel-concrete composite structure bridge panel increased by 20% and the cracking load increased by 132%.The initial cracking load of the traditional cast-in-place strip is about 17% of the failure load,and the initial cracking load of the cast-in-place strip of the steel-concrete composite structure is about 30% of the failure load.The mechanical performance of the cast-in-place strip of the steel-concrete composite structure is better than that of the traditional cast-in-place strip of the bridge panel.(2)By using the cohesive force model to simulate the cast-in-place zone,and using the methods of normal hard contact and tangential friction to simulate the interface between steel and concrete,the finite element model of cast-in-place zone of traditional cast-in-place zone and steel-concrete composite structure was established,and the whole process of the simulation test loading until the failure of the specimen was simulated.The finite element simulation results are compared with the test data.The results show that the load displacement curves obtained from the finite element simulation results are in good agreement with the test results,which indicates that the finite element model can effectively simulate the whole test process and prove its applicability.(3)Through the finite element software for parameter analysis,explore the impact of cast-in-place strip of steel-concrete composite structure on its cracking load and ultimate bearing capacity when the diameter of shear connectors,the spacing of shear connectors,the thickness of steel plate and the strength of steel plate material change,and optimize the structural design combination.The results show that when the stud diameter is 15 mm,the steel plate thickness is 8mm and the steel strength is Q390,the mechanical properties of the structure can be reached to the best state while the material is utilized to the maximum.After the optimized design of composite beams,the cracking load and ultimate bearing capacity of composite beams increased by 25% and12.4% respectively.(4)The theoretical calculation formula of the bearing capacity of the traditional cast-in-place belt in the form of ring lap reinforcement and the theoretical calculation formula of the ultimate bearing capacity of the cast-in-place belt in the form of steel and concrete composite structure in the case of full shear connection and partial shear connection are studied.The theoretical calculation results are compared with the experimental data and the finite element calculation results.It is found that the theoretical calculation results are slightly smaller than the experimental and finite element data.But the overall error is less than 10%,which proves that it has good applicability.(5)The fatigue performance of cast-in-place belt of traditional cast-in-place belt and steel-concrete composite structure is studied.The fatigue life of cast-in-place belt of traditional cast-in-place belt and steel-concrete composite structure under the same load amplitude is simulated by Fe-safe software.The results show that,compared with the traditional cast-in-place belt,the joint area of the cast-in-place belt of the steel-concrete composite is less prone to fatigue failure.The fatigue life of the steel bars in the traditional cast-in-place belt is about 740,000 times,and the fatigue life of the steel bars in the cast-in-place belt of the steel-concrete composite structure is more than 1 million times.The fatigue performance of the cast-in-place belt of the steel-concrete composite structure is better than that of the traditional cast-in-place belt.