Three Dimensional Seismic Responses Study Of Concrete Self-anchored Suspension Bridges

As a particular kind of suspension bridge, and preserving the exquisite configuration of conventional suspension bridge, self-anchored suspension bridge has made an appeal in field of engineering by its elegant and picturesque disorder figure. It has become a competitive design scheme in middle, and small-span bridges in cities. However, due to complexity of its structure, from the document that has existed, there is little research of dynamic behavior for self-anchored suspension bridge, especially concrete self-anchored suspension bridge. The dynamic behavior and seismic response of self-anchored suspension bridge are investigated in this paper. The main research work covers the following aspects:(1) Based on Large-displacement Non-linear Elastic Generalized Variational Principle, coupling effect of axial and flexural action, shearing strain energy, torsional strain energy of stiffening girder being considered, the large-displacement incomplete generalized potential energy functional of space coupling free vibration of a three-span concrete self-anchored suspension bridge is presented. By constraint variation, fundamental differential equations of vertical flexural vibration, lateral flexural vibration, and longitudinal vibration are formulated, and the linear free vibration differential equation is obtained when the nonlinear items are discarded. In this paper, a concrete self-anchored suspension bridge with the main of span 240m is an example for the analytic solution of frequency of vertical free vibration. Compared with numerical solution, the results inosculate well. This approach provides theoretical basis for analysis of natural vibration character of concrete self-anchored suspension bridges.(2) Dynamic behaviors of concrete self-anchored suspension bridge mainly include natural vibration frequency and principal mode, which is the base and precondition of dynamic analysis for self-anchored suspension bridge. Lan Qi Songhua River Bridge, a concrete self-anchored suspension bridge with the main span of 240m, is taken for example, and the first 20 frequencies and corresponding vibration modes are given by using space finite element model. At the same time, effects caused by varieties of dead load, rigidity of stiffing girder, stiffness of tower, rise-span ratio are computed. The results are compared with those of an earth-anchored suspension bridge with the same span and structure parameter. The influence regulations are discussed in detail.(3) According to the preparatory estimate report of seismic effect on the Lan Qi Songhua River Bridge, following the fortifying demand of three-level seismic resistance, under the effect of two earthquake probability P1 and P2, the seismic response of Lan Qi Songhua River Bridge is analyzed by the Response Spectrum Method. Two kinds of seismic combinational modes, which are longitudinal vibration plus vertical vibration, and transverse plus vertical vibration are considered. According to the Seismic Resistance Design Specification of Highway Bridges, vertical response spectrum is 2/3 that of horizontal. In order to ensure the precision, the CQC ( Complete Quadratic Combination) approach is applied. The method and conclusion can conduct the preliminary design of similar bridge.(4) Multiple-support excitation, traveling wave effect and the nonlinear of the structure taken into account, four group of artificial seismic waves are utilized to study on the seismic response of concrete self-anchored suspension bridge under vertical, longitudinal, and lateralAbstractseismic excitation. In the condition of multiple-support linear uniform, nonlinear uniform and traveling wave effect excitation, the response time histories of internal force and displacement of controlling section such as main beam, tower, side pier, are analyzed and compared. The effect regulation is discussed in detail. Since the HPD(High Precision Direct integration) method is applied in time domain analysis, the results are more accurate.(5) Based on Large-displacement Incomplete Generalized Po...