Study On Safety Performance Of Slant Leeged Rigid-frame Bridge Under Earchquakeand Discussion On Buckling-restrained Brace In Bridge Reinforcement

As the steel structure has the advantages of light weight, high strength and itssupport frame horizontal stiffness is bigger, in the seismic region the steel braced frameis often adopted to meet the design requirements. But common brace’s problem is thecompression buckling under severe earthquakes，and the degradation of such braces instiffness and strength caused by buckling aggravated the damage to the steel frames.The Buckling-Restrained Brace is proved based on common brace.The compressionand tension loads are designed to be carried only by the core by means of unboundedlayer to allow the free slip between the core and the surrounding concrete. TheBuckling-Restrained Brace can reach and retain fully sectional yielding of the coreunder compression, and exhibits stable hysteretic behavior when cyclically loaded.Accordingly, based on the Japanese rigid-frame bridge the Sisraqka bridge project,using the TDAPⅢ finite element software, the dynamic characteristics and seismicperformance of the bridge is analyzed. According to its damage reinforcement schemeis determined comparing the bridge’s seismic response and damage situation with andwithout soil reinforcement, this paper summit the damping effect ofBuckling-Restrained Brace under severe earthquakes. The main research contents andresults are as follows:Firstly, the related theory and method are researched. Through comparingadvantages and disadvantages of various seismic analysis methods, the time-historyanalysis is selected as the research method in this thesis.Secondly,3D space model is established. TDAPⅢ software is used, and the3Dspace model of Sisraqka bridge is established for considering nonlinearity of piers basedon various finite elements.Thirdly, based on the established simulation model, the study on dynamiccharacteristics of Sisraqka Bridge is carried out. The result shows that: the first modeshows that the beam is bended with symmetric and vertical forms. The modal isintensive, and the tensional vibration mode appeared relatively late. Rayleigh dampingis employed to establish the damping matrix and the problem that how to determine thedamping coefficient is discussed. It pointed out that the vibration mode and effectivemass ratio should be considered while the modes are selected.Fourthly, through analyzing the internal force of main truss member, the mechanical characteristics of the bridge is definited. and the key points analyzed in thisthesis are the pier’s brace location, the arch foot and the arch part. Through bendingproofread, shear proofread, deformation, and the hysteresis curve of those key parts, itshows that: horizontal structure of the arch part and the arch foot are damaged, P1pieroccurs bending-destroy, the ductility of piers is not enough.Fifthly, according to the specific damage this paper adopts externally bondedreinforced concrete as the pier reinforcement, and adopts Buckling-Restrained Brace asreinforcement measures of the arch part.Through the analysis on bridge’s deformation and the displacement of the keypoint and acceleration comparison, it shows that the Buckling-Restrained Brace playeda good hysteretic performance. And in the seismic waves along the transverse directionof the bridge excitation, it reduces the effect of earthquake on the bridge by making alarge deformation...