| Research on the impact result from vehicles traveling on bridge has caught muchattention of Bridge System Engineers. However, referring to JTG D60-2004, aformula for calculating coefficient of impact has only taken the bridge basalfrequency into consideration. Few have concluded a multifactor formula of impactcoefficient focus on simply-supported girder bridge, although countless people hasconducted numerous researches and projects on such kind of bridge by car impactedand drawn conclusions that both the vehicle characteristics and the bridgecharacteristics could be influential in it. In this paper, the dominant factors thatpossibly have an effect on impact coefficient of simply-supported girder bridge willbe taken into account and the modified Formula with Comprehensive considerationwill be put forward, so that the reasonable results can be used for reference to bridgedesign. The main contents are as follows:1.By using ANSYS the model of a simply supported girder bridge was beenmodeled, and the first three frequencies could be obtained by ANSYS. The model inthis paper is proved to be correct after comparing the numerical results with thetheoretical solution.2.After establishing the half vehicle model, the vehicle vibration equation wasderived and it could be solved by using MATLAB, the vertical vibration displacement,velocity and acceleration curve under the vehicle was running were concluded.3.Based on a simply-supported girder bridge, simulate curve of different levelsof bridge deck geometric irregularities which was built from MATLAB Self-compiledProgram.and bridge deck geometric irregular sequence could be used as the wheel’sdisplacements to stimulate the bridge deck geometric irregularity.And build avehicle-bridge coupled model according to displacement-based simultaneous equationof vehicle-bridge touch point and the interaction force between them. And the modelwas verified, and proves the correctness of the vehicle-bridge coupled model in thispaper.4.Take6factors that might influence number of strokes on simply-supportedgirder bridge into account, including bridge deck geometric irregularity, vehiclerunning velocity, bridge basal frequency, vehicle spring stiffness, vehicle springdamping and car load. Then apply ANSYS to obtain the dynamic analysis ofvehicle-bridge coupled model as well as the displacement time-history curve of nodeon medium span of the simply-supported girder bridge in various situations, and the impact coefficient could be figured out. Moreover, it can be shown by the Result andanalysis that levels of bridge deck geometric irregularity, vehicle running velocity,vehicle weight and bridge basal frequency are principal elements which havesignificant effect on impact coefficient.5.Taking bridge deck level as clausal standard, vehicle running speed and bridgebasal frequency as independent variable, we have fitted the approximate formula ofsimply-supported girder bridge impact coefficient on Level A、Level B and Level Cthese three bridge deck levels respectively by means of multiple linear regressionanalysis. Comparing the equation to relevant information in JTG D60-2004, theconclusion goes as follow:①The calculated value of impact coefficient which is onlyconsidered the bridge basal frequency in code, is only applied to a certain speed andfundamental frequency range in the bridge deck level, and in the bridge deck level ofgrade A、grade B, it’s relatively small under high speed, large under low speed, largeunder low frequency, small under high frequency; it’s generally small in the bridgedeck level of grade C, and large under low frequency and low speed, small under highfrequency and high speed;②when designing a bridge, levels of bridge deck, vehiclerunning speed and bridge basal frequency are supposed to be taken into account toascertain the impact coefficient. |
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