Study On Mechanical Performance And Design Method Of Concrete-filled Steel-plate Composite Towers

Bridge towers are important load-bearing components in cable bridges,especially cable-stayed bridges,which have high requirements on the stiffness and strength of the tower.The concrete-filled steel-plate composite bridge tower(referred as CSC bridge tower)is a new choice of bridge tower structure,which is of great significance for solving key engineering problems such as insufficient tower stiffness in a multi-tower cablestayed bridge.In this dissertation,the CSC bridge tower is invesgated from interface connection level,tower wall level to tower level.Based on model tests,numerical method,and theoretical analysis,the main results and achievements of the research are presented as follows:(1)A set of single-hole and tri-hole thin-rib perfobond connectors on the interface of CSC bridge tower were designed for pull-out tests.The pull-out performance and mechanism of the connector specimens were systematically analyzed.Based on the theoretical derivation and experimental calibration,the accurate formula and simplified design formula for predicting the pull-out strength of thin-rib perfobond connectors were proposed.(2)The fine numerical model,simplified numerical model of the thin-rib perfobond connector were established and verified by the test results.Based on the simplified numerical model,the parameter analysis of the pull-out stiffness of the thin-rib perfobond connectors was performed with 1,000 cases.A spring model of the connector was established to calculate the pull-out stiffness,and the stiffness calculation formula was derived.A simplified spring constitutive model for the thin-rib perfobond connector was proposed.(3)A set of full-scale tower wall four-point bending specimens were designed and the compatible functioning of CSC tower was studied.The test included two composite specimens TL1,TL2 and concrete specimen TL3.Based on the loading process,failure mode,and measured mechanical performance parameters,the design suggestions,such as plane assumption,for the composite tower wall were proposed.(4)A method for fine numerical modeling of composite tower wall specimens was proposed.The experimental results were compared and expanded based on this method,which verified the fine numerical modeling method.The parameter analysis of the composite tower wall specimens was carried out based on the fine numerical modeling method,and the influence of the parameters of concrete,steel plate and connector on the performance of the composite tower wall specimen was studied.The pull-out capacity design formula of the connector based on the strength-stiffness relationship to ensure the compatible functioning of the composite tower wall was derived,and the design process was proposed.(5)A multi-scale model was established to conduct the nonlinear time-history analysis of a multi-tower cable-stayed bridge with composite towers to investigate the seismic performance of the composite tower.The comprehensive design method of the composite bridge tower was proposed,and the composite bridge tower,concrete bridge tower,and steel bridge tower were compared.The proposed connector pull-out design method was compared with existing design method.Specific design suggestions for composite bridge towers and connector were summarized.