Research Of Impact Coefficient Analysis Methods For The Rigid Frame And Continuous Beam

Currently, the research about impact coefficient of complex long-span bridge is still in exploration stage, the research carried out for the composite structure of the rigid frame and continuous beam was especially less. Almost all the researches of impact coefficient at home and abroad are confined to single factor analysis. In the General Code for Design of Highway Bridges and Culverts (JTG D60-2004), the calculation formula of impact coefficient only considers the single factor of basic structure frequency without vehicle dynamic performance and pavement unevenness. Therefore, study on the impact coefficient of composite structure of the rigid frame and continuous beam has very important academic significance and practical value.This paper based on a composite structure of the rigid frame and continuous beam in Shaanxi province, building 6 different models from 4 spans to 6 spans, which contains the effects of pier-bottom consolidation and pile-earth coupling. In order to discuss the sensitivity parameters of impact coefficient, three axes two-line suspension vehicle model has been used and the analysis of the orthogonal experiment has employed. The calculation divided into 24 conditions, contains nine factors including the axle frequency ratio, pavement unevenness, body quality, bridge span number, driving speed, vehicle driving mode, bridge stiffness, damping ratio and the substructure calculation. The analysis shows the deflection of girder control section, bending moment and horizontal displacement of main piers control section, the bending moment impact coefficient parameter sensitivity and its maximum assembly parameter. Based on the above factors, the maximum impact coefficient curves are given and impact coefficient range of composite structure of the rigid frame and continuous beam has been provided according to the analysis results in the maximum parameters load combinations condition. The result shows that the vehicle speed, basic structure frequency and pavement unevenness are main influencing factors for the impact coefficient. In the article, pavement unevenness is considered to be the sub-item standard, speed and basic structure frequency is the argument. By means of regression analysis, the impact coefficient approximate formulas are given for the first time to direct at A, B and C three surface levels for the girder and main piers of the composite structure of the rigid frame and continuous beam, and the formula is compared with prescripts and standards of other countries to obtain its advantages and disadvantages.The research conclusions can be used for the design of the rigid frame and continuous beam, and also can be used as reference for dynamic analysis in other bridges.