The Research On Seismic Response Of Concrete Filled Steel Tube Deck Arch Bridge Considering Foundation-Structure Interaction

The long-span concrete filled steel tube(CFST) arch bridge has been widely used as its advantages such as convenient construction,low cost and beautiful appearance.Now the seismic response studies of long-span CFST arch bridge mostly are based on the assumption that the arch foot is fixed without considering the foundation-structure interaction.There are a few papers on long-span CFST arch bridge seismic response considering the foundation-structure interaction,but the boundaries in these papers are very simple.The regulations on the foundation-structure interaction in the Code for Seismic Design of Highway Engineering are just about the influences of foundation deformation on the bridge period.In this paper the linear and nonlinear three dimensional viscoelastic artificial boundary and the seismic wave input methods with three dimensional viscoelastic artificial boundary were studied.The viscoelastic artificial boundary was constructed to simulate radiation damping and the elasticity recovery capacity of the medium at the far field.The full model including the bridge and foundation was made to study the seismic response of long-span CFST arch bridge with considering the foundation-structure interaction.The project background is the Zhijing River extra large bridge—deck arch bridge with 430m span.The works done in this paper are as follows:1.The research on three dimensional nonlinear viscoelastic artificial boundaryNow the viscoelastic artificial boundary is mostly studied on linear and elastic far field media.In this paper with taking the assumption that the far field medium is viscoelastic material,the three dimensional nonlinear viscoelastic artificial boundary was deduced through the elastic wave theory and viscoelastic theory.The numerical calculation results show that the conditions of force and displacement at artificial boundary are the same with those of original viscoelastic medium when the original viscoelastic medium at far field was cut and replaced with nonlinear viscoelastic artificial boundary deduced from this paper.The three dimensional nonlinear viscoelastic artificial boundary deduced from this paper can simulate the wave propagation from the computing field to the far field viscoelastic medium.2.The research on seismic wave input methods with three dimensional linear and nonlinear viscoelastic artificial boundaryThe precise seismic wave input is the premise to solve foundation-structure interaction problems.In this paper the seismic wave input methods with three dimensional linear and nonlinear viscoelastic artificial boundary were studied.The force F_B(t) applied on the viscoelastic artificial boundary to implement the seismic wave input can be expressed with the displacement(u) and velocity((?)) of input seismic wave which makes the seismic wave easy to input.3.The numerical study on CFST components mechanical behaviorThe CFST stress-strain relation suitable for beam element was deduced from three dimensional finite element method and fiber element method respectively.The numerical calculation results show that precise results can be gotten when the CFST stress-strain relation from fiber element method was used in bean element.The load-displacement hysteretic curve of CFST component was calculated with beam element.4.The research on seismic response of long-span CFST deck arch bridge with considering the foundation-structure interactionTaking the Zhijing River extra large bridge as project background,simulating radiation damping and the elasticity recovery capacity of the media at the far field with three dimensional linear and nonlinear viscoelastic artificial boundary,the linear and nonlinear seismic responses of long-span CFST deck arch bridge were studied with considering the foundation-structure interaction.The studied results show that there is bad influence on bridge seismic response if the elastic modulus of bridge foundation concrete is too large.When the bedrock is hard,the seismic response internal forces at bridge arch rib when considering the foundation-structure interaction are less than those of fixed arch foot,which shows that fixed arch foot assumption is safe in this case.When the bedrock is soft,the seismic response internal forces at bridge arch rib when considering the foundation-structure interaction are greater than those of fixed arch foot,which shows that foundation-structure interaction has bad influence on the bridge seismic response in this case.The influences of foundation-structure interaction on bridge seismic response increase with the decrease of bedrock elastic modulus.The influences of foundation-structure interaction on bridge seismic response with transverse seismic wave input are greater than those with longitudinal and vertical seismic wave inputs.In this paper the influence of traveling wave effect on bridge seismic response was also studied with considering the foundation-structure interaction which will help to know the aseismic capacity of long-span CFST arch bridge.