Study Of Seismic Behavior Of Innovative Resilient Reinforced Concrete Precast Bridge Columns Using Composite And Traditional Materials

Self-centering(SC)system is one of the systems proposed for use in reinforced concrete(RC)bridge piers.Extensive researches have been performed to investigate the lateral performance of the SC precast bridge piers.The results of these researches declare that the use of SC system in RC bridge piers can significantly overcome many obstacles of existing traditional systems.However,such system displays much lower hysteretic energy dissipation(ED)capacity than conventional monolithic concrete system.In literature,several supplementary energy dissipators have been proposed to improve the ED capacity of SC precast bridge piers.In which,internal ED bars and external ED devices have been introduced.Based on the best author’s knowledge,the existing energy dissipators cannot fully achieve the desired resilience performance of precast bridge piers after severe earthquake actions.Therefore,additional studies are required to improve the available energy dissipators or develop innovative ED systems that can be used in RC bridges in moderate and high seismic regions,and can be generally applied with different precast bridge pier systems(single-column pier,wall pier,and multi-column pier).For the first chapters of the thesis(Chapter 1,and Chapter 2),the construction technique,structural system,and seismic response of typical SC precast bridge pier are presented.In addition,a summary of the main findings of previous studies on the influence of various design parameters on the damping capacity of the typical SC precast bridge pier system have been discussed.After that,the available proposed energy dissipators are fully addressed in the light of the conducted experimental studies.Where the energy dissipators of the SC precast bridge pier are classified into two groups(i.e.,internal ED bars and external ED devices),and the deficiencies of each type of the energy dissipator have been cautiously determined.Accordingly,the body of the thesis introduces an innovative concept,which is to use precast RC elements as ED system for SC RC bridge piers in moderate and high seismic regions.An innovative resilience system for precast segmental RC bridge columns has been proposed for application in moderate seismic regions.The proposed system consists of a typical precast hollow core RC segmental column and an energy dissipation(ED)element.The ED element is a precast RC column partially filling the hollow core of the segmental column.As a new damage control component,the ED element(the hidden column)is adopted to provide the system with adequate ED capacity.Using commercial finite element(FE)software,a threedimensional(3D)model of experimentally tested precast segmental columns was developed.After validating the results of the FE model,the model was used to systematically investigate the behavior of the proposed system under lateral cyclic loads.The parametric study is related to the design details of the hidden column with respect to the main column(the precast segmental column): column height ratio,and cross-sectional area ratio.In addition,concrete compressive strength,main reinforcement yield strength,and longitudinal reinforcement ratio were examined.In order to ensure a resilience lateral performance for high seismic regions,the proposed system for precast segmental bridge columns has been developed by replacing the emulative hidden column with a hybrid precast column system(SC hidden column).Where the SC hidden column combines post-tensioned tendons and bonded mild steel bars.During seismic actions,the SC hidden column allows the rocking mechanism,and dissipates the energy by mild steel bars.To investigate the lateral behavior of the developed precast bridge column system,a parametric study was performed.The parametric study is related to the design details of the SC hidden column.Where the influence of reinforcement ratio;posttensioned force level;and unbonded length on the lateral performance of the proposed column were investigated.In addition,three different confinement thicknesses of FRP jackets were examined to improve the damage tolerance of the SC hidden column.Moreover,under the influence of successive earthquakes,repeated cyclic loading scenarios were applied to the proposed system.Finally,a general application of precast RC fuse units as a replaceable ED structural system was adopted for precast bridge pier systems including precast wall pier system,and precast multi-column bridge pier system.The precast ED fuse units were adopted with the main SC system in two forms to popularize the application of the proposed system in moderate and high seismic areas.The first form consists of precast RC column made of well-known traditional materials(i.e.,steel bars and concrete),while the second type combines mild steel reinforcement with posttensioned tendons(hybrid precast system).Using commercial FE software,3D-FE models were created and verified for precast wall piers and precast doublecolumn bridge piers to investigate the lateral performance of the proposed system under cyclic loads.The study focused on the effect of SC coefficient in controlling the lateral performance of the proposed system.Discussion and summary of several interesting findings and general recommendations on the SC coefficient of the proposed concept are drawn.At the end of the thesis,a summary of this investigation and the overall conclusions based on the numerical results have been presented.Moreover,some recommendations for further research work are also included.