Dynamic Response of a Road Viaduct to a Mining Tremor Using Multiple Support Response Spectrum Method

In this study the dynamic response analysis of a concrete road viaduct subjected to a mining shock is presented. The dynamic analysis was performed using different methods of analysis, i.e. the Time History Analysis (THA), the Response Spectrum Analysis (RSA) and the Multiple Support Response Spectrum Analysis (MSRS). On the basis of analyses, the effectiveness and the suitability of these methods in case of non-uniform kinematic excitation were determined. For the analysis of dynamic response, a real road structure was chosen. The object is a three-span bridge, 40 m long. The structure was subjected to a real, representative mining shock as a kinematic excitation. The typical shock from Upper Silesian Coal Basin was taking into account. The dynamic calculation of the viaduct to the mining shock were performed using the THA, RSA and MSRS methods. For the THA method two kinds of ground motion models were used: the uniform and non-uniform model. For the non-uniform excitation model two wave velocities were taken into account: 500 and 1000 m/s. For the RSA and MSRS analysis the spectral curves, created on the basis of the mining shock acceleration, were used. In the RSA method, the same spectra were used at each supports. In the MSRS method, the response spectra were modified, due to the occurring non-uniformity of excitation effects. For the MSRS analysis the wave passage effect, the attenuation effect and the incoherence effect were taken into account. As the results of the analysis, principal stresses in representative points were determined. To compare the obtained solutions, the results of each analysis were correlated. This comparison clearly presents the significant influence of the non-uniformity effects. On the basis of the results obtained for chosen elements it was easy to notice that the non-uniform excitation model results in much greater values of stresses than the uniform excitation model. The presented results also prove that the MSRS analysis led to significantly greater values of stresses than the RSA method. The conducted response spectrum analysis has shown that the RSA method may lead to underestimation of the dynamic response of structures, whereas the MSRS method provides the proper quasi-static way to estimate the stress level in a structure subjected to a nonuniform kinematical excitation. The key conclusion of this studies is that the non-uniformity effects has important influence on the dynamic behaviour of multiple-support structures. Neglecting of these effects may results in underestimation the maximum response of a structure. In addition, the comparison of results obtained by different methods shows that the MSRS method may be used in estimation of the dynamic response of large-dimensional structure subjected to non-uniform mining shock. (paper)