The Research On The Effects Of Eccentric Loads Caused By Vehicle Onto Super-breadth Cable-stayed Bridges

At present in our country, it is a common way for bridge engineers to take the results calculated from the computer program based on the in-plane spar system as their basic data for design. Live load is usually disposed of in-plane with some corrections for simplification when it is necessary to take the load into account in space, for example, the vehicle load has the eccentric load factor Kp that equals to 1.15 in terms of their spatial effects. This modifying factor is determined on the basis of the analysis on some concrete box girder cantilever beam bridges with 4 lanes. With the development of communicational undertakings and urban constructions, many cable-stayed bridges with 6, 8 or even 10 lanes arise one after another. In the light of the super-breadth cable-stayed bridges those are composed of different components such as cable, tower, main beam, cross beam etc, the question whether the eccentric load factor Kp equals to 1.15 has been put forward in this thesis. By the use of the professional software MIDAS/CIVIL for spatial calculation of bridge structures, Haikou Haixin Bridge and Huai'an Wuhekou Bridge, two super-breadth cable-stayed bridges with different mechanic systems, have been analyzed in this thesis, in which the two bridge models have both taken the forms of double fishbone-typed beams so as to compare the internal forces and tresses distribution of the cables, brain beams, cross beams and towers of the bridges under the two load conditions with the vehicle load exerted fully or eccentrically. It can be seen from some conclusions of this thesis that the diversity caused by the eccentric load exists evidently in the bridges'different components, the same components at different positions and the maximum or minimum response in the same components at the same positions, therefore, when using the computer program based on the in-plane spar system for design, the way in which the eccentric load factor keep to unique value is not rigorous, and some results calculated by this way prove to be unsafe to some components. In order to simulate the real mechanic properties of super-breadth cable-stayed bridge for better results, this thesis has advanced the method of multi-factor for the eccentric load and the means by which the structures are analyzed directly in space.