Research On Seismic Performance Gradient GFRP Bar-reinforced Concrete Bridge Pier

By observing the damage characteristics of the existing bridges in China over the past years of earthquakes,it can be found that most existing bridges of reinforced concrete structures show the characteristics of large rigidity of the upper beam and softer piers of the lower piers.Serious damage and even overall collapse have become the main characteristics of this type of bridge earthquake damage.The destruction of the bridge pier will cause the collapse of the upper supporting structure,in addition to causing huge economic losses,it will also seriously hinder traffic and affect the development of post-disaster rescue and reconstruction work.Existing cantilever bridge pier plastic hinge areas generally only occur at the bottom of the pier.The rotation and displacement ductility of the pier plastic hinge have a significant impact on the seismic performance of the pier.Bridges are the key nodes in the entire transportation system,and the consequences of earthquake damage to bridges are also huge.It is particularly important to improve the seismic performance of bridges.This paper mainly takes concrete cantilever piers as the research object,and proposes a new type of concrete bridge piers with performance gradients to improve the ductility of bridge piers.The following aspects are specifically studied:(1)This paper analyzes the domestic and foreign bridge pier damage manifestations,the application of fiber-reinforced composite materials in actual engineering,and the status of plastic hinges.At the same time,the finite element simulation of the experimental assumptions is performed,and the mechanical properties of the steel and GFRP reinforcement materials are analyzed.Characteristics,a scheme of using GFRP bars and steel bars to form a performance gradient was proposed.(2)Three concrete bridge pier test pieces with a loading height of 2700 mm and a cross-section size of 250 mm × 250 mm were designed and manufactured.Comparative test piece A is a conventionally configured steel bar test piece,and B and C test pieces are mixed with GFRP bars and steel bars.By changing the reinforcement height of GFRP bars,three gradient seismic performances are formed in the pier.The main research performance is The process and mechanism of gradient formation and its influence on the seismic capacity of bridge pier.(3)The experiment adopts the experimental research scheme of monotonic loading of pushover,and the dual-channel actuator is used for loading,and the shear force-displacement data curve of the loading point is collected.A large number of strain measurement points,displacement measurement points,and NDI measurement points are arranged,and data such as strain,displacement,and curvature are collected.The experimental crack width and phenomenon are recorded in detail.The strain-load curve,displacement curvature,and crack width are obtained through analysis.The distribution curve of the height along the pier.(4)Based on the experimental data,the ductility of the plastic hinge displacement and corner is calculated through theoretical analysis.The influence of different GFRP reinforcement heights on the bearing capacity and deformation capacity of the plastic hinge is discussed,and based on the formation of the plastic hinge of the concrete bridge pier Regularly,the change of the position of plastic hinge at different heights of GFRP tendons is analyzed.(5)The finite element simulation of the concrete bridge piers was performed using the finite element analysis software ABAQUS,and the pushover curve of the concrete bridge piers was obtained,which is in good agreement with the experimental loading curve.Then,based on the strain analysis of concrete and tendons,the experimental results Conclusion.