Research On Seismic Behavior Of Recentering Socketed Segmental Precast Pier With Shape Memory Alloy And Highstrength Concrete

Segment assembled piers are widely used because of convenient construction,reliable quality and little impact on the surrounding environment and traffic.With the application of segmented bridge piers in high earthquake areas,how to improve the seismic performance of piers and reduce the large residual displacement after earthquakes,how to carry out seismic design,are currently urgent problems to be solved.Shape memory alloy(SMA),a new type of intelligent material,has been widely used in the field of civil engineering,because its yield strength is roughly the same as that of ordinary steel bar,its recoverable strain energy reaches 6% ～8%,and its superelastic properties.High-strength concrete(HSC)can solve the serious problem of concrete compression damage.This paper combines the two to make the bridge piers have better energy consumption and recentering ability.Based on the relevant domestic and foreign literature,this paper conducts numerical simulation of segmental piers based on the Open Sees,and use the fiber model to perform pseudo-static and dynamic time-history analysis.And studies the influence of segmental piers’ parameters on its seismic performance,thus forming a displacement-based seismic design method.The main research contents are as follows:(1)The research results of socket piers and segmental piers,the characteristics and constitutive relations of shape memory alloy and high strength concrete are introduced.Based on Open Sees,the fiber model modeling method is used to compare the numerical simulation results with the existing experimental results,which demonstrates the accuracy of the model and lays a foundation for the study of the seismic performance and design methods of recentering pier basis.(2)The finite element model of SMA-HSC piers was established to analyze the seismic performance indexes of pseudo-static simulation,such as hysteretic curve,skeleton curve,energy dissipation capacity and self-recentering capacity.Through parameter analysis,changing SMA reinforcement ratio and length,strength and height of high strength concrete,initial prestress and dead load axial compression ratio,the results show that increasing the initial prestress and dead load axial compression ratio can increase the horizontal bearing capacity and reduce the residual displacement.The optimized SMA-HSC piers have better energy dissipation ability and self-recentering ability compared with RC piers.(3)The dynamic time history analysis of SMA-HSC piers was carried out,and five ground motions were selected to study the peak displacement and residual displacement of the bridge piers under small and strong earthquakes.The results showed that the peak displacement of SMA-HSC piers was slightly smaller than that of RC piers.However,the residual displacement after the earthquake is almost zero,showing that the bridge pier has a good self-recentering ability in the earthquake.(4)The performance-based design method is introduced,combined with the current code regulations,four-level seismic fortification targets are proposed,and the displacement-based seismic design process of segmented piers is established,which is conducive to promoting the application of SMA-HSC piers in actual projects in areas of medium and high earthquake areas.