Seismic response of bridge abutments on surface foundation subjected to collision forces

Bridges are important components of the roadway and railway networks, as they must remain operational in the aftermath of the seismic event. Permanent movements of the backwall and the backfill soil and rotational deformations of the abutment-backfill system are well known failure modes that potentially may incite deck unseating mechanisms. However, only a few studies dealt with the modeling of deck-abutment-backfill pounding effect. In this framework, an extended parametric study was conducted on a simplified abutment-backfill analytical model. A typical seat-type abutment was analyzed using 2D nonlinear FE model in Plaxis. Simultaneously, a refined abutment-backfill model was built in commercial software SAP2000 in view to highlight significant parameters of the interaction aiming at identifying the effect of collisions on anticipated damages of the abutment. The assessment of the deckabutment-backfill response was performed on the basis of longitudinal maximum and residual movements and rotations of the abutment that may affect both the integrity and the postearthquake accessibility of the bridge. SSI effects due to the interaction of the deck with the abutment and the backfill soil were considered; analyses showed that large seismic movements during an earthquake and permanent movements of the abutment are deemed to put in danger the abutment itself, the integrity of the end spans and finally the accessibility of the bridge. Comparison of different seat-type abutment models in Plaxis and SAP2000 revealed that modeling of bridge abutments with emphasis on the geotechnical design should be properly made. Poor design assumptions may have a serious impact in the assessment of the response of the abutment-backfill-bridge system

Seismic response of bridge abutments on surface foundation subjected to collision forces

Bridges are important components of the roadway and railway networks, as they must remain operational in the aftermath of the seismic event. Permanent movements of the backwall and the backfill soil and rotational deformations of the abutment-backfill system are well known failure modes that potentially may incite deck unseating mechanisms. However, only a few studies dealt with the modeling of deck-abutment-backfill pounding effect. In this framework, an extended parametric study was conducted on a simplified abutment-backfill analytical model. A typical seat-type abutment was analyzed using 2D nonlinear FE model in Plaxis. Simultaneously, a refined abutment-backfill model was built in commercial software SAP2000 in view to highlight significant parameters of the interaction aiming at identifying the effect of collisions on anticipated damages of the abutment. The assessment of the deckabutment-backfill response was performed on the basis of longitudinal maximum and residual movements and rotations of the abutment that may affect both the integrity and the postearthquake accessibility of the bridge. SSI effects due to the interaction of the deck with the abutment and the backfill soil were considered; analyses showed that large seismic movements during an earthquake and permanent movements of the abutment are deemed to put in danger the abutment itself, the integrity of the end spans and finally the accessibility of the bridge. Comparison of different seat-type abutment models in Plaxis and SAP2000 revealed that modeling of bridge abutments with emphasis on the geotechnical design should be properly made. Poor design assumptions may have a serious impact in the assessment of the response of the abutment-backfill-bridge system

Seismic response of an 8-story RC-building from ambient vibration analysis

In this study, we assess the dynamic characteristics of an 8-story RC-building composed by two units connected through a structural joint. This building, belonging to one of the largest hospitals in northern Greece, has been selected in the framework of an European funded project as test site for developing a structural health monitoring system and it is instrumented with a permanent strong motion network. The assessment of the dynamic characteristics is performed using ambient vibration recorded by a temporary seismic network installed inside the structure. Non-parametric identification methods, namely the peak picking and frequency domain decomposition, are applied to perform operational modal analysis and extract the natural frequencies and mode shapes of the structural system. Since the detection of changes in the shear wave velocity inside the building is relevant for health monitoring analysis, we use the ambient vibration recordings to perform a deconvolution interferometry. Moreover, a shear-beam model is considered to estimate the velocity in the first three floors, where the distribution of internal sources introduces complex patterns in the impulse response functions. The velocity for lowest part of the building is estimated by optimizing the match between the arrival times of the empirical and theoretical pulses. Finally, the velocities and quality factors estimated from ambient vibration analysis are consistent with preliminary results obtained analyzing earthquake data recorded in the same building