Geometry Parameters Research Of Continuous Rigid Frame Bridge

The prestressed reinforced concrete continuous rigid frame bridge is widely used in long-span bridges, and as a kind of complicated structure system, selecting the reasonable geometric parameters is very important in bridge design. In this paper, the geometric parameters of double thin-wall piers continuous rigid frame bridge were analyzed. Through the analysis of the parameters, the reasonable range was obtained. Taking the practical engineering as the basis, the single factor analysis of the parameters were carried out using the finite element model and the regularity of stress and deformation in the key section with parameter variation was obtained. In this foundation, the sensitivity and sensitivity sequence about parameters to the stress and deformation was got through multi factor sensitivity analysis about parameters using orthogonal experiment and the conclusions obtained have a certain referential value to the similar bridge design in the future. The main work is summarized as follow:1. Through single factor analysis of the parameters, it is obtained that the reasonable value range of bottom curves of box-girder is1.5to2, and adopting higher power of bottom curve is beneficial for deadweight reduction, In favor of light structure. The reasonable value range of side to middle span ratio is0.5to0.7, mainly concentrated in about0.55and the change of it has a huge effect on the stress and deformation in the side span section. The height-span ratio of box-girder is generally0.05to0.06, most of them in0.055or so. The main dimensions of box-girder:the top board is generally25cm to28cm. The bottom board is generally variable thickness and is generally20cm to40cm in middle span. The thickness of ventral board is generally changing from the cross to root by40cm to70cm. The increase of space between the double thin-wall piers can reduce the stress in middle section but will increase the stress in the root section. And it also can effectively reduce the structural deformation.2. Through multi factor sensitivity analysis of the parameters, it is obtained that when the stress as a control index, the bottom curves of box-girder sensitivity is maximum, side to middle span ratio sensitivity followed and the height sensitivity of thin-wall piers is minimum. When the middle span deformation as a control index, the side to middle span ratio sensitivity is maximum under the weight but under the lane load the space sensitivity of double thin-wall piers is maximum. In the design of continuous rigid frame bridge, one index can’t take as the control index. Therefore, it is necessary to distinguish the sensitivity of the factors influencing the control index, in determining the optimal scheme. For the strong sensitivity main factor, it should be selected the optimal level according to the requirement in favor of index. And for the secondary factors of which sensitivity isn’t strong, it can be selected the other level according to the requirement in favor of other indexes (such as economy, convenience of construction).