Seismic Response Analysis Of Long Span Curved Box Girder Bridge In Cantilever Construction Process

With the rapid development of Chinese transportation industry, the application of curved bridges in practical engineering is much more than ever before. The Large span curved bridge’s features of linear fluid, long span, strong adaptability to the environment make it able to adapt to a variety of unfavorable terrain. Characteristics of large span, long construction period, plane curve complexity make seismic response analysis of large span curved box girder bridges in construction process become particularly important, while the study of domestic and foreign scholars in this area is relatively scarce.This paper in the background of Jin Ma Ren River Bridge firstly establishes a finite element model in every construction stage considering the interaction of pile and soil. And then a comprehensive analysis of earthquake response to structure in the construction process is presented through the analysis of structure itself vibration characteristics, response spectrum, time history etc. The aim is to get the change law of dynamic characteristics in the construction process and determine the maximum seismic response of sectional position for reference for design and construction. The main research results are as follows:(1)Along with the increase of cantilever’s length in construction process and the fundamental period of the structure, the structure becomes more and more soft and along the bridge direction, the transverse direction and torsional stiffness decreases gradually, resulting the basic cycle of the state bridge in the construction phase reduced.(2)The proportion of the torsional and vertical shift mode in the low order modes under each construction phase condition is very high, while the state of the bridge is very low. Through the first order statistics of the main vibration type, it is concluded that the cross bridge stiffness with construction has increased, and torsional stiffness is more and more small. However, with increase of state bridge, the longitudinal stiffness becomes weakest in the early and middle construction stages while the vertical stiffness has been larger and will decrease with the increase of construction, but will not account for the main role.(3)Under all the construction conditions, the cross bridge to translational and along the bridge to the horizontal and vertical shift mode are controlled by low order type of vibration. The torsion vibration type is controlled by the higher modes in the early stages of construction, and the control model order will reduce in the late construction stage.(4)When the most unfavorable earthquake input direction is obtained, the results of the response spectrum and time history analysis show that the long span curved box girder bridge seismic response of the most unfavorable conditions may occur in the construction process. Through the peak seismic response analysis of the beam and pier’s model nodes, elements, then a decision can be made about the maximum seismic responses of node and element for structure in each construction stage, which will select the seismic effect analysis of the control section, and that is the innovation of this paper.(5)The comparison of time history analysis results and response spectrum analysis shows that the structure internal force is similar to the displacement response rules, and the peak response is close, along with the roughly same judgment of control section which can provide a reference for the design and construction personnel.