Key Technological Study Of Long Span Continuous Composite Box Girder Bridges

This dissertation addresses key technological issues of long span continuous composite box girder bridges. Based on existing theoretical research and practical experience, the research uses the Shanghai Yangtze River Bridge as a case study and focuses primarily on numerical analysis and design. Using methods such as structural finite element analysis and model loading tests, the following issues are investigated specifically for long span continuous composite box girder bridges:1, Key questions' study of conceptual designA comprehensive overview and analysis of the structural performance, engineering practice and design experience of long span continuous composite box girder bridges are provided. Major technical problems related to conceptual design are brought forward. Clarification is provided for overall design principles, negative moment region design, key structure detailed design, and construction methods. These considerations are important for improving structural performance and reducing cost.2, Study on optimization methods of design and construction Various design and construction optimization methods are analyzed, with specific focus on structural performance characteristics, applicability, constructibility, and cost. Their importance to the design and construction of long span continuous composite box girder bridges are then evaluated and reasonable recommendations provided.3, Structural performance and methods of analysisAnalysis of and comparison between the 2-D model, the 3-D model, no slipping model and slipping model for the connector are conducted to better understand structural performance under different stages of construction and occupancy, as well as the applicability of various analysis methods and standard design practice. A comprehensive precision 3-D numerical analysis model, taking into account the complete process of construction and occupancy, is created to investigate the characteristics and main structural requirements of long span composite girders. The stability characteristics of composite steel girders and the applicability of related code standards are studied through contrasting analysis of basic stability theory, code standards, and related experimental research. Structural performance characteristics and optimized design and analysis methods are delineated.4, Connecting technique between steel girder and deck slabComplete solid 3-D analysis model and partial structural precision submodels are created. Precision analysis taking into account shear studs and plates with holes are performed. The influence and performance requirements of different connector layouts are studied. Investigation targeting the up-tensioned force exerted by long span wide deck composite box girder bridges on shear studs is carried out, which elucidates the combined effects of tension and shear force on shear studs, studies connection design methods, proposes measures to reduce or limit tension, and improves numerical analysis and design of connectors and connections.5, Connector and connection model loading testsThrough model loading tests, the tensile, shear, and combined tension-shear resistances and related design parameters are studied for shear studs of different length and for different plates with holes. The tensile force distribution and the amount of de-bonding between the deck slab and the steel girder are investigated for connections with different connector layout. The study indicates that the layout of shear studs should be designed to limit deck debonding and tensile force in the shear studs. Methods to reduce or limit shear stud tensile force are proposed. This fills a void in current research, improves the reliability of wide deck composite box girder bridge design, and contributes to the development of related design theories and methods.