| It may pose adverse effects on safety performance and service life of theoperational bridge under the external dynamic loads, especially the moving vehicleloads. However, it’s impossible to identify the moving vehicle excitations ofoperational bridge by accurate measurement directly. Therefore, an effective way canbe found to identify the vehicle moving loads through the vibration response oflimited measurement points on the bridge.It’s a random loads identification problem to determine the moving vehicle loadson the bridge. According to the plate girder theory, multiples of researches have beendone to invert bridge structure loads through the optimization method, consideringthe effects of the vehicle moving loads movement. Such method, focusing on specificinteraction between vehicle and bridge in the process of analysis, can be used todetermine the spatial location of the loads and the time domain process with theaccurate finite element model. While the analysis process would be affectedsignificantly by the analysis singularity.Firstly, this paper deals with modal experiments. It adopts modal force hammerfor beaming slab, collects the vibration acceleration signal of each measuring point,then uses Matlab for programming analysis of each measuring point of theacceleration signal. Therefore, we can calculate modal parameters of the beam slabstructure and each order formation. On this basis, by running vehicle dynamic loadidentification experiment in the laboratory, we can calculate the modal dynamicstiffness of each slab. Meanwhile, according to Zhang Xin[1], who puts forward theexperimental modal method of bridge crane incentives in the running state, we canhave a filter analysis of the acceleration response to every measuring point, obtain theinstantaneous amplitude of each order modal and finally identify beam slab of F1calendar and the incentive mode of driving load spectrum composition. Besides,according to the acceleration sensor placed on the driving car, we can collect theacceleration signal caused by actual vibration. Based on this, we can work out the time domain and frequency domain of the modal load F2in the process of driving.Finally, on the theory of random vibration, under the same test period and mode, wecan calculate the roots of the variance of the two modal loads respectively. Bynumerical comparison of the root of variance, we can draw the following conclusions:Under the influence of environmental factors and experiment conditions, the roots ofthe variance of the above two kinds of loads about numerical difference are bigger.But for two different points, the same modal of the ratio of loads to the root of thevariance of numerical size is stable. Results show that the experimental conditionsand external environment remain unchanged, under the same modal. The basic rootsof variance ratio of the identification modal load F1and the measured modal load F2keep unchanged. However, we want to understand various influencing factors of theexternal environment and experimental conditions on the influence degree of theexperimental results. We need to make a large number of experiments to compare andanalyze. Finally, on the premise of all the factors, we can identify the bridge structureto a great extent in the process of running on the road excitation loads; provide goodtechnology to prolong its service life and maintain the health of the bridge operation.In this paper, the experimental results show that, if the experimental conditionsand external environment factors such as the premise of basic remain the same, wecan use the method that Zhang Xin[1]proposed for identifying the vehicle movingloads on the bridge. The method can overcome the uncertainty of the analysis ofsingularity that dues to the loads identification process. It is easy to operate and issuitable for application in bridge structure health monitoring system. |
