Experimental Study On Lightweight UHPC Rigid Frame Arch Bridge And Its Wet Joints

This paper applies the UHPC(ultra-high performance concrete)material to rigid frame arch bridges after doing researches on various types of bridge structures and propose and optimize a lightweight UHPC rigid frame arch bridge structure,which fully utilizes the excellent properties of the material and the structural advantages of rigid frame arch bridges,reduces the dead load significantly and the difficulty of construction,improves the durability,reduces the maintenance and makes the structure more beautiful.The lightweight UHPC rigid frame arch bridge is a precast bridge.The UHPC wet joint is the key structure to the bridge.In order to study the influence of different types of UHPC wet joint structure on the flexural behavior of structures,I proposed four wet joint structures with vertical joint,rhombus joint,vertical joint with upper and lower strips and rhombus joint with upper and lower strips,respectively.We carried out UHPC wet joint optimization tests.The results show that the flexural behavior of perfect beam is better than that of the beam with joint.Due to discontinuous steel fiber at the joint,the tensile strength is extremely small.Among the four joint structures,the rhombus joint with upper and lower strips has the best flexural capacity.According to test results,equations for the flexural capacity of UHPC beam with various joint structures are suggested,and the calculated value is in good agreement with the experimental results.In this paper,a rhombus joint structure with upper and lower strips is designed.In order to study the mechanical performance of the structure and find out the construction measures that can improve its operational performance and safety.An 1:2 scale model test is conducted,the test results demonstrate that the joint reduces the mechanical properties of the structure,but the joint structure still meets the operation and safety requirements of the engineering projects;in practical projects,the joint structure should add constructional reinforcements to increase the flexural performance;the reserved steel reinforcements at joints must be welded with the lapped reinforcements to ensure the operational performance and safety of the structure;the material at the joint should use the material without expansion agent or the material meeting the mechanical requirements with expansion agent.The nonlinear analysis of the test models was studied by finite element model using ABAQUS.The results reveal that the theoretical values agree well with the test results,and the accuracy and applicability of the material parameters in the ABAQUS d amage plastic model is verified;the Coulomb friction model is used for simulating the friction between joint interfaces,and the simulated results fit well with the experimental values.This paper relies on the trial design of Gao-en highway K7+164 flyover.The span of the bridge is 58 m.The overall length is 66 m.The width is 5.5m.The span of arch is 58 m,the rise of arch is 6.5m,so the rise-span ratio is 1/8.9(f/L=6.5/58).It consists of 3 pieces of UHPC arch ribs,on which NSC(normal strength concrete)deck of C50 is casted.The bridge deck is connected to the arch rib and the y share the load together.The bridge parts should be precast in the factory and assembled through wet joints castin-place.After that the bridge deck should be cast on them,and then the second stage construction should be conducted.Based on China code for bridge,French recommendations and other foreign codes,the finite element analysis is carried out using MIDAS and calibrated by the model tests results.The results indicate that the design is safe and reasonable,and the construction process is convenient and reliable.