| Fatigue failure is one of the main failure modes in steel bridges, and there have been an amount of cases in which the steel bridges are damaged because of the fatigue failure in China and the world. In order to prevent fatigue failure problems on steel bridges, the Specification for Design of Highway Steel Bridge has been implemented in our country since December 1, 2015; Compare with previous edition of steel bridge design specification, the fatigue design part in the new specification has been thoroughly amended and begin to at the same stage with the current fatigue design specification for steel bridge overseas. Because the specification was published not long ago, so there is no any published research to calculate reliability index inhering in the fatigue design method in the new specification.So, basing on reliability theory, this dissertation has calibrated the resistance factor of Fatigue Design Method Ⅱ in the Specification for Design of Highway Steel Bridge,the main works in this dissertation is shown as below:(1) The required resistance factors of the Fatigue Design Method Ⅱ in the Specification for Design of Highway Steel Bridge is calculated with reliability theory when it is applied to the design of simple supported beam bridge with single-lane. Base on the assumption that the actual stress ranges obey Rayleigh distribution, the dissertation has studied the variation trend of the fatigue resistance with different parameters.(2) Based on statistical data of actual vehicle loads in Hebei and Zhejiang, the dissertation has calculated the statistical data of stress ranges with the method of influence line, and then values of the resistance factors were calculated using the formula used for calculating the resistance factors when bridge span, design life, mass limit of heavy vehicle are set at different values, and the variation trends of the fatigue resistance with these three parameters have been studied the.(3) In order to take vehicles’ dynamic effect into account, a compute program of vehicle-bridge coupled model has been developed in this dissertation to calculate the statistical data of dynamic stress range acted on bridge. Basing on the results of calculations, the influence of pavement roughness and vehicles’ speed on the fatigue resistance has been studied.(4) By analyzing the result of fatigue resistance calculation, the conclusion below has been made: The required fatigue resistance varies from region to region; The fatigue resistance value derived from the Hebei province is obviously higher than that derived from Zhejiang province. For Hebei, the result is higher than the value specified in the Specification for Design of Highway Steel Bridge. For Zhejiang province, when bridge’s span is short or road roughness coefficient is relatively high, the result is also higher than the value specified in the specification. |
PDF Full Text Request