Nonlinear Seismic Response Analysis Of Concrete Arch Bridge With Steel Webs

Long span arch bridge in China has a highly competitive and wide range ofapplications. It is a key issue to make self-weight of arch as light as possible for theevolution of large-span concrete arch bridge. Concrete arch bridge with steel webs is aninnovative composite structure, in which the cross-section is composed of concrete flangesand planar or corrugated steel webs. Existing researches show that compared withtraditional concrete arch bridges, this new type of bridge has many advantages: it caneffectively reduce the weight of the main ring structure, lower arch axial force and shortenthe construction period. To further demonstrate its feasibility in engineering applications, itis necessary to understand the nonlinear seismic characteristics of this new type of archbridge, but due to the complexity of the seismic response of long span arch bridge itself,the current researches are inadequate. To address this problem, this thesis carried out thefollowing research:(1) Taking Lingdou Bridge in Fujian as a prototype, calculation for trial-design ofconcrete arch bridge with steel webs is carried out in the thesis. The mechanical behaviorof this new type of bridge is calculated and the results show that the strength, stability,stiffness of the main ring and shear strength of steel webs and other technical indicators areto meet the requirements of the original design specifications.(2) Based on a double nonlinear finite element program-NLBeam3D (Nonlinearanalysis program of Beam3D), the paper established three-dimensional FE models ofLingdou bridge (the reinforced concrete arch bridge) and two trial-design arch bridges.Then the natural vibration characteristics of three arch bridges are analyzed and compared.(3) When subjected to T111seismic wave in the out-of-plane direction, the nonlinearseismic responses of three arch bridges are much larger than those in the longitudinaldirection. Unlike the reinforced concrete arch bridge, the maximum strain generated on thefeet of the concrete arch bridges with steel webs are almost as same as those generated inthe out-of-plane direction. Therefore, the effect of the combined out-of-plane andlongitudinal excitations could not be considered when taking a seismic design for this newtype of concrete arch bridges.(4) When subjected to T211seismic wave in the combined out-of-plane and longitudinal directions, the maximum strain generated on the feet of the concrete archbridge with corrugated steel webs and concrete arch bridge with planar steel webs areseparately3.30times and2.40times as those generated in the out-of-plane direction. So,the effect of the combined out-of-plane and longitudinal excitations should be consideredwhen this new type of concrete arch bridges is subjected to T211seismic wave. Comparedwith T111seismic wave, the nonlinear response to the out-of-plane direction aroused byT211is smaller. But the case is opposite in longitudinal direction.