Microtremor measurements and 3D dynamic soil–structure interaction analysis for a historical masonry arch bridge under the effects of near- and far-fault earthquakes

For rational solutions against seismic excitations of masonry bridges, the capability of 3D soil–structure interaction (SSI) modeling with experimental evidence has been insufficiently researched up to now. This is also valid for the effects of near- and far-fault earthquakes. Hence, the spectral responses measured by microtremors have been compared with the ones of 3D SSI analysis under the effects of near- and far-fault earthquakes for a historical masonry arch bridge in this article. The 3D SSI modeling of bridge and substructure soil was built with elastic finite element model using solid element and viscous boundary. The SSI analysis has been performed by direct approach using time-history analysis. The earthquake motions (near fault, far fault) were selected in accordance with the tectonic setting of the bridge’s region. From the study, it is possible to confirm that microtremors are able to detect spectral responses of the bridge by the presence of SSI influences. By the evidence of amplifications and soil–structure resonance, the microtremor measurements experimentally promise that: (i) the bridge can be adequately identified by SSI analysis compared to fixed base, (ii) the elastic model can satisfactorily provide information about the bridge’s responses (amplitudes, spectral response, stress distribution) under earthquake effect, and (iii) the far-fault motion especially due to SSI modeling is significant for the seismic responses. The study indicates that regarding the SSI influences into seismic computation has become quite efficient for determination of a possibility of various adverse effects (high displacements, critical stresses, resonance). Moreover, diagnosing the historical bridge well as a result of microtremors together with SSI modeling strongly proposes protection of the bridge with an appropriate retrofitting.