Research On Continuous Rigid Frame Bridge Girder Design Parameter Optimization Base On Orthogonal Experiment Method

As a kind of bridge, the prestressed reinforced concrete is famous for its excellent behavior and beautiful shape, such as nice wholeness, bearing property, comfortable driving condition, moderate cost. All advantages of common continuous beam bridge and "T "shape frame bridge can be found in this one, because no expansion joints except for those at the two ends, no bearer and construction convenience, with good seismic performance. The main beam connect with the pier rigidly, so more negative moment will be found at the joint, and smaller positive moment will go to the middle of the long span. In this way, the continuous rigid frame bridge can go across a longer span than the common continuous beam bridge. In a long time, this kind of bridge is complicated to design for its structure analysis is complex with a space effect and too many design factors. In this case, the optimization for the bridge is depend on the experience without scientific optimization method. Orthogonal experimental design is a scientific optimization method, with a clear concept, easy operatetion. Applied to continuous rigid frame bridge girder design parameters optimization, it only need a small number tests, with a good test results. In this paper, four design parameters will be research, and a building long span continuous frame bridge will be the engineering Background, which is being constructed in Sichuan. The main work is summarized as follow:(1) This paper introduces the development of the prestressed continuous rigid frame bridge and the research status, a comprehensive analysis to design parameters of the existing bridge is done for getting four orthogonal level of test parameters about the side-span ratio, the high-span ratio at root of the beam, central beam high cross-ratio and the beam bottom curve equal-power.(2) A reasonable orthogonal design table is selected, space beam elements are applied to built 16 bridges test model for the finite element analysis. A indicator on the basis of the strength, deflection, concrete volume as well as the impact factor is defined for the four key parameters optimization, then individual indicators and parameter value combinations are got.(3) On the basis of static force test model, a three Victor modal response spectrum analysis is carried out under earthquake El, the control moment orthogonal test for three key nodes, the Pier bottom, the main beam—pier section, mid—span section, obtained the optimization parameter combination and the parameter values in favor of reducing the moment value.(4) On this basis of static optimization and dynamic optimization of the earthquake, it found that the same optimal design parameters for the main beam cannot both meet the requirements of the bridge static and dynamic requirements. Therefore, girder design should consider static and dynamic needs in the same time, or focused on one of them.