Force Transfer Mechanism In Main Cable Anchorage Zone Of Composite Girder Self-anchored Suspension Bridge

Self-anchored suspension bridge has got very rapid developments in recent years while the bridge type is becoming more and more diversified.As a new type of bridge structure,steel-concrete composite girders have been used in self-anchored suspension bridges that which most were made of steel or concrete structures in the past.With the increase of self-anchored suspension bridges and unique mechanical performance of steel-concrete composite girders,thus the research of transfer mechanism of main cable force in anchorage zone have been extensively investigated.Combined with the Yellow River Binghe Bridge,the self-anchored suspension bridge with steel-concrete composite girders was studied in this thesis.The main research achievements are as following:(1)Based on the field-test of the stress,the distribution law of the internal force of the main girder has been analyzed,whole bridge beam-column and local finite element model of anchorage zone were established,according to previous research results to accurately simulate the connection between steel and concrete,the correctness of the model is verified by comparing the results of calculated with the test.(2)Stress distribution in anchorage zone of main cable,relative slips between steel and concrete and the axial force sharing ratio of each component,were investigated by the results of finite element method,the transmission path of the main cable force in the anchorage zone is clear,the mechanical performance of the main girder under multiple load is analyzed,the ultimate limit state of anchorage zone of main cable is studied,the failure mode of anchorage zone is obtained.(3)Based on the analysis of the transmission path of the main cable and the ultimate limit state of main girder,the influence of different design parameters on the mechanical performance of anchoring zone is compared,discussed on the design method of the steel-concrete composite girders on the basis.The results indicate that:the girder longitudinal compression and plane bending under the main cable anchoring force,the longitudinal force transferred to the web plate and the top plate through the welding seam of the reinforcing part of the main girder;the axial force on the roof spreads inward at an angle of 45°,and a portion is transferred to the concrete bridge deck by the upper shear pin above the web,and the remainder is transferred to the stringer's web;the axial force spread from both sides to the middle under the action of crossbeam,the force transmission process until 20 meters from the end of the girder to end.The concrete bridge deck slips over the end crossbeam and crack at the position that oblique web and outer web close to the department,resulting in failure of the shear pin and main girder.Reducing the width of the end crossbeam and encrypting the common crossbeams can optimize the main cable force transfer;due to the smaller shearing force on the crossbeams,a cluster arrangement can be used for construction.