Analysis Of Seismic Behavior Of Rocking Self-Centering Double-deck Bridge Bents Under Vertical Earthquake Ground Motions

Double-deck bridge bents can effectively solve the problem of traffic congestion and road traffic in complex geological environment,and the viaduct with double-deck bridge bents as the main vertical load-bearing component is used more and more in bridge engineering at home and abroad.However,the earthquake damage shows that the double-deck bridge bents based on the ductive design were severely damaged and can not be repaired quickly after an earthquake.The rocking self-centering(RSC)system can greatly reduce the residual displacement of the bridge after an earthquake and reduce the damage to the structures by relaxing the constraints at both ends of the bridge column and using the resilience provided by the self-weight and pre-stressed tendons to enable the bridge to react under a strong earthquake.Ensure the rapid restoration of bridge function after an earthquake.In general,the vertical component of earthquake ground motion has little effect on structures compared with the horizontal component and is always neglected.However,with the further study,it is found that within a certain range of near faults,part of the vertical acceleration magnitude is close to or even greater than the horizontal acceleration amplitude,which exceeds the design of the current seismic design specifications.Therefore,it is very important to study the effect of vertical earthquake ground motion on the behavior of bridge structure.In the current study,the seismic behavior of RSC double-deck bridge bents considering the vertical earthquake ground motion is studied by using the OpenSees platform.The main work and conclusions are summarized as follows:1.From the literature review at home and abroad,studies on the seismic performance of the double-deck bridge bents under the near-fault earthquake ground motion were summarized.The development of the RSC structural system and the research progress at home and abroad were studied.The research purpose and research content of this dissertation were proposed.2.Based on a double-deck bridge bents in Gansu Province and the OpenSees platform,two double-deck bridge bent models for the RSC and RC bents were built.The modeling process and material model were introduced in detail.The modal analysis was conducted for both the RSC and RC bents,and the accuracy of the model is verified by the shake table test results for the RSC bent.3.Two kinds of the RSC double-deck bridge bent models were built.The first one was named as RSC-X model,for which one the behavior under the horizontal component of the near-fault earthquake ground motion was studied.The second one was named as RSC-XZ model,for which one the behavior under both the horizontal and vertical components of the near-fault earthquake ground motion was studied.It is found that the following parameters of the RSC-XZ model is larger than of the RSC-X model: drift ratio,residual drift ratio,the maximum stress of the longitudinal reinforcement,the maximum stress of the prestressing tendons and deformation of external energy-dissipation angle steel.The angle steel would yield and absorb seismic energy,while no rupture damage was found.The deformation of the RSC bent model will concentrated on the top floor.4.Two kinds of the RC double-deck bridge bent models were built.The first one was named as the RC-X model,for which only the horizontal component of the near-fault earthquake ground motion was used for the analysis.The second one was named as the RC-XZ model,for which both the horizontal and vertical compoments of the near-fault earthquake ground motion was used for the analysis.It is found that the deformation of the RC bent model is concentrated on the top floor.The top floor deformation of the RC bent model is smaller than that of the RSC bent.The RC-XZ model has larger drift ratio,residual drift ratio,and the maximum stress of the longitudinal reinforcement than that of the the RC-X model.The maximum top floor drift ratio of the RSC bent model is slightly larger than that of the RC bent model,and while the residual drift ratio of the RSC bent model is only 1.5% of that of the RC bent model.