| The combined-concrete beam cable-stayed bridge adopts a unique design,with the side spans consisting of concrete beams and the middle span utilizing composite beams.The composite beams and concrete beams are connected through steel-concrete joint sections,forming this special cable-stayed bridge structure.This design has a smaller selfweight in the middle span,resulting in a larger lateral span and superior load-bearing performance compared to other types of cable-stayed bridges.It is widely used in bridge engineering projects both domestically and internationally.The joint section,as the key component connecting the composite and concrete beams,has a rather complex load transfer mechanism,primarily due to the discontinuity of materials and structures at the connection points.High-stress areas may also be generated in the joint section.Therefore,special attention should be paid to the stress situation of the joint section during the design of such mixed-beam bridges.This study focuses on the joint section,analyzing the internal force changes at the joint section’s position during the construction phase of the entire bridge,and further investigates the load transfer mechanism and load-bearing capacity of the steel chamber’s shear connection components in the joint section through numerical simulation methods.The research findings and conclusions are as follows:(1)Using the finite element analysis software Midas/Civil,a full-bridge model was constructed,and the sectional internal forces at the joint section’s location under the tower-beam synchronous construction mode were calculated and extracted.The conclusion demonstrates that,during this construction phase,the combined-concrete beam experiences stable stress in the joint section,with no significant fluctuations in internal force.This indicates that the tower-beam synchronous construction method has a certain feasibility when applied to combined-concrete beam cable-stayed bridges.(2)Utilizing the ABAQUS software,a detailed representation of the steel-reinforced concrete joint section was developed,with the most critical load combinations during the construction phase being imposed.By examining the complete deformation of the structure,internal forces,and the load transmission approach of the bearing plate,the design’s validity was confirmed,and an in-depth exploration of the joint section’s load transfer mechanism was conducted.The study concluded that the overall deformation of the joint section was relatively stable,with no significant abrupt changes.The stress distribution of the entire structure was relatively uniform;although there were localized areas of stress concentration,they did not exceed the yield strength.During the load transfer process in the joint section,the axial force of the composite beam bridge deck accounted for a higher proportion,about 65%,while the proportion of the composite beam deck and concrete was approximately 35%.(3)A standard steel grid chamber was taken out from the combined section,and a fine-grained modeling analysis of the composite shear connectors in the steel grid chamber was carried out,considering the material nonlinearity and contact nonlinearity of the connectors.And analyze mechanical characteristics during whole process on shear resistance on composite connector as well as bolt connector split out from composite connector PBL.At same time by adjusting PBL concrete strength opening plate thickness opening plate opening diameter penetrating reinforcement strength deeply understand main factors affecting PBL bearing capacity draw main conclusions as follows: among three kinds shear connectors bolt connector bearing capacity relatively small composite connector second PBL bearing capacity largest.But bolt connector has good pull-out resistance plays certain role resisting warping deformation top bottom plates steel grid room when reaching limit bearing capacity bolt connector bolt fails concrete failure not obvious.PBL has larger bearing capacity but bottom plate warping more obvious final failure stage structure all concrete tenons sheared off large amount concrete steel grid room also crushed but penetrating reinforcement did not yield.Composite connector combines advantages both although bearing capacity only about 93% PBL but damage phenomenon relatively light.In addition,through parameter analysis PBL found increasing connection piece medium concrete strength opening plate thickness opening plate opening diameter penetrating reinforcement diameter have certain influence improving connection piece bearing capacity. |
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