Study On Seismic Behavior Of Concrete Filled Steel Tubular Arch Bridges

With the high bearing capacity, strong spanning ability, good seismic behavior and convenience of construction, concrete filled steel tubular (CFST) arch bridges develop rapidly. Up to now there have been over one hundred bridges constructed in China, and the large economic benefit is getting in practical engineering. China has a big earthquake area, where CFST arch bridges will be applied more and more. However no one has experienced a strong earthquake because of the short construction history. Now the study on seismic theory for CFST arch bridges just begins and design system is not perfect, there is no special design standard for them. Therefore, studying on the seismic behavior, establishing the model of dynamic time-history analysis and determining the method of seismic design are very urgent for bridge engineers.By the help of State Key Laboratory for disaster Reduction in Civil Engineering, CFST arch bridges were researched in this paper in order to present a referenced method for seismic design and to found a base for development of design theory. Main works done in this paper are as follows.1. The shaking table dynamic test of CFST arch bridge was carried out for first time to know the mechanic characteristics and failure forms under the earthquake loading and get the credible dynamic properties and seismic responses. The test supplied a gap of dynamic behavior test for CFST arch bridge structures. By the results the 3D model of nonlinear time-history analysis was verified. The basic datawere given for CFST arch bridges seismic design study.2. A 3D model of elastic-plastic time-history analysis was established. The yield equation including the interaction of bending moment, torsion and axial force for CFST material was formulated. By the elastic-plastic theory the constitutive relation and stiffness matrix were established. It becomes possible for nonlinear time-history analysis of CFST arch bridges. It is benefit to know the seismic responses of CFST arch bridges under earthquake loading.3. According to the mechanic characteristics of CFST component, a constitutive model for triaxial-loading concrete was presented. The calculation criterion of the cracking and crushing for concrete were determined and the stress releasing in the 3D-stress space when concrete cracked was formulated. By the model, the force-deformation curve of CFST components can be calculated and the ultimate bearing capacity and ductile behavior can be determined.4. By the use of current advanced seismic ideal, it was presented for the seismic design principles, standards and methods in two stages of CFST arch bridges. After analyzing dynamic properties of CFST arch bridges, seismic concepts were given for the design of the bridge shape. The seismic design theory system was founded initially in this paper.