Seismic Pounding And Mitigation Of Bridge Structures With Precast Segmental Columns

Bridge structures are the crucial fundamental traffic infrastructures in society,whose design concept and construction technology have always been the focus of research personnel and construction staff.Traditional reinforced concrete bridges usually use on-site concrete pouring,and there are many drawbacks in the construction method(a large number of mechanical equipment and construction templates;long construction period;impact on existing traffic and natural environment,etc.).The traditional construction technology is more difficult to adapt to the needs of modern industrial society to accelerate bridge construction.In order to accelerate bridge construction and reduce construction disturbances,in recent years,the accelerated bridge construction technology which prefabricated components in factory and assembled on site has received extensive attention.The quality of segmental assembly bridges can be effectively controlled due to prefabrication in the factory.Rapid installation on the construction site also greatly shortens the construction period.Compared with the traditional construction method,although the cost of manufacturing and transportation has been improved,it has obviously avoided the various drawbacks of the traditional cast-in-place bridge operation,and the maintenance,repair and the replacement of components are more convenient.However,the previous bridge prefabricated segment assembly technology is mainly applied to the bridge superstructure.As the main load-bearing components of the bridges,the bridge piers are still cast-in-place to ensure its good integrity.Compared with the traditional monolithic column supported bridge,this paper investigates the seismic performance of pre-stressed segmental column supported bridges under different kinds of earthquake loadings.The main work and achievements are as follows:(1)The related researches at home and abroad are collated,and three theoretical analysis methods for exploring the seismic performance of prefabricated segmental concrete columns are discussed: analytical method,fiber-based element method and concentrated mass plastic hinge method.The advantages and disadvantages of various theoretical analysis methods and their scope of application are summarized.By comparing with the existing test results,the correctness and accuracy of the pseudo-static behavior of various methods in the simulation of prefabricated prestressing segmental columns are verified.(2)Based on the fiber element method,the influence of material strength and structural details on the seismic behavior indexes of the prestressed prefabricated segmental bridge piers including hysteretic curves,energy dissipation capacity and minimum residual displacement are discussed,and the seismic failure mechanism of the column is clarified.Comparing the similarities and differences of pseudo-static behavior between prestressing segmental concrete columns and corresponding traditional monolithic reinforced concrete columns,it is found that the application of prestressing prefabricated segmental bridge piers may bring more violent seismic pounding effect to the whole bridge structure.(3)Taking a five-span cantilever beam bridge as the research background,the seismic pounding effect and self-centering performance of the traditional monolithic bridge and the prefabricated segmental bridge under uniform ground motions,spatially varying ground motions,far-fault and near-fault ground motions were compared.The influence of structural details(reserved joint opening gap size,adjacent structure frequency ratio),spatially varying ground motion(wave passage velocity and coherency loss),near-fault ground motions(pulse effect,peak ground velocity and acceleration ratio PGV/PGA)on the key parameters of the two types of bridges including the peak displacement of the main girder,the residual displacement of the pier,the maximum pounding force,the number of pounding,and the peak joint opening displacement were discussed.(4)Taking the existing five-span prefabricated concrete continuous girder bridge as an example,the application of the seismic mitigation measures such as the friction pendulum isolation bearing,the rubber absorber pad and the steel restrainers in the traditional monolithic-column supported bridge and the prefabricated segmental-column supported bridge were investigated.It is found that although the prefabricated segmental-column supported bridge has better self-centering performance,it needs additional seismic mitigation measures to reduce seismic pounding force,excessive expansion joint opening displacment,etc.,which may cause severe seismic damage due to the poor energy dissipation capacity and overall integrity.