Seismic Response Analysis Of Lanqi Songhua River Bridge In Jilin City

With the scale of cable-stayed bridge enlarging, more and more attention is paid for the aseismatic capability of cable-stayed bridge. Lanqi Songhua River Bridge in Jilin City is a concrete cable-stayed bridge with double towers and single cable plane, which is 240 meter. The earthquake intensity of the situation of this bridge is VII and the system of this bridge is peculiar. So analyzing the earthquake response of this bridge is significant. The dynamic behavior and seismic response of Lanqi Songhua River Bridge in Jilin City are investigated in this paper. The main research work covers the following aspects:(1) After investigating the properties of cable-stayed bridge component, i.e. the cables deck and joints in detail, the bridge model with reference to Lanqi Songhua cable-stayed bridge for seismic analysis is established. The advanced analysis program ANSYS is used to get the 15 frequencies and corresponding vibration modes.(2) The standard seismic response spectrum is inputted from longitudinal, transverse and vertical direction respectively. Two kinds of seismic combinational modes, which are longitudinal vibration plus vertical vibration and transverse plus vertical vibration are considered. In order to ensure the precision, the CQC (Complete Quadratic Combination) approach is applied.(3) Because of the half floating structural system, the basal period of Lanqi Songhua River Bridge is comparative long. The seismic response of the structure with long period will be over estimated, if the standard spectrum or the design spectrum given by seismic risk analysis is applied. So this paper amends the design spectrum and analyzes the influence of long period response spectrum on dynamic character and seismic response.(4) The aseismatic capability of cable-stayed bridge lies on the selected structural system. So several structural systems are analyzed and a sort of elastic restriction structural system composed of towers and beams is selected. This paper also analyzes the influence of longitudinal elastic restriction on dynamic character and seismic response.(5) The spectral analysis is linear so the nonlinear factors can not be taken into account. The dynamic properties of Lanqi Songhua River Bridge are calculated also with dynamic time-history analysis considering the nonlinear factors. The earthquake response is gained according to the calculation results of the two methods.These laws can be used as the basis of seismic design of the Lanqi Songhua River Bridge and is useful for directing seismic response analysis of such kind bridge.