Analysis On Static State And Wind Resistance Performance Of The Continuous X-Arch Bridge

In the latest twenty years, lots of beautiful arch bridges are built in our nation, because of the smooth wave shape, designers are especially interested in the continuous X-arch bridges. Big span and flexible bridges’forces are complicated, so the wind loads on them may become the controllable factors in the design progress. This paper aims at describing the sea-crossing bridge in Dalian city, Puwan new district,which is a five span continuous arch bridge, and the spans are50m,170m,200m,170m,50m, the whole length is640meters and the width is48.6m. Through finite element methods, numerical simulation methods and wind tunnel tests, the bridge’s static state and natural vibrate properties, the aerostatic coefficients and the responses of the girders and arch ribs are analyzed. The main contents and conclusions are listed as follows:(1) Midas Civil software is used to modeling the X-arch bridge. In the model, several members’stresses and vertical displacements are analyzed under the constant loads and live loads, in the meantime, the static responses of the bridge under the gradient of temperature, the different temperature between the hangers and the girders, and the breaking situations of hangers are studied. As is shown, the gradient of temperature affects it less, but the different temperature between the hangers and the girders should be considered as the real bridge. The breaking of the single hanger affects3to4hangers which are on the both sides of it, and the breaking of the hangers in the position of the middle of the subordinate span has a stronger influence.(2) Analyzing on the natural vibration properties, in the meantime, the single main span and subordinate span models vibration prosperities’are compared with the continuous X-arch bridge’s, and several parameters are analyzed on the single main structure. As is studied, the vibration characteristics of them are all most the same. In the other words, the influences between the main span and the subordinate span can be ignored, and it is the theoretical evidence for the single main span and subordinate span model tests in the wind tunnel, which is to choose a bigger scale ratio model.(3) Based on the CFD numerical methods, the three component coefficients of the girders under the continuous changing of the wind attack angles are computed. This method is not identical with the traditional method which is under the discrete attack angles to get the coefficients, and it costs less time to built the numerical model, and more parameters can be got. This method provides an effective way to get the coefficients in the later days. The drag parameters of the windward and downward arch ribs under different distances of two sections, whose height and width are not the same, are studied in the wind tunnel tests. One method is traditional, which is to set different and discontinuous distances of the two arch ribs, the other is to let the distances between the two arch ribs change slowly with the help of some pulling devices; at the same time, the drag forces on the windward and downward arch ribs are measured. As is indicated, the second method is more convenient and quicker, and the accuracy is guaranteed. The drag coefficients of the windward and downward arch ribs is closely related to the ratio of the width and length of the section, and the distance between the two arch ribs. To the downward arch ribs, the results provided by the standard are safer than the results got from the experience.(4) Based on the finite element model and the static coefficients of the members, the aerostatic responses which include forces, stresses and displacements are reckoned in different initial attack angle and wind velocity. The result shows that the continuous X-arch bridge’s stiffness is strong, and it satisfies the needs for wind resistance.