Seismic Behavior Of Box Section Steel Bridge Pier With Recoverable Function

With the quick development of urbanization in China and the increase number of fly-over crossways,the box section steel bridge pier have been widely used.The traditional piers were reinforced concrete structure,however,the reinforced concrete bridge pier have the following drawbacks: heavy self-weight,weak ductility and long term of construction work.In the course of urbanization in China,a large number of people crowded into cities,thus,the traffic volume is growing heavily which leads to the high traffic pressure of public transportation.The long traffic control due to the construction about the bridge pier will cause severe traffic jam,bringing inconvenience to people.Therefore,it is urgent to develop a type of new-model pier which conforms to the Green Building Concept and needs less construction time.This paper develops a type of box section steel bridge pier.It has a replaceable energy consumption area and some features of sound seismic behavior,assimilability and the possibilities of rapid repairing after quakes.In terms of the stress characteristics of box section steel bridge pier,the root area of the box section steel piers’ test specimens were equipped replaceable energy consumption area with high-strength bolts and energy-consumption siding with bucking restrained splints,namely,the outside steel plates were connected to both inside and outside of the lower-yield-point energy-consumption sidings by highstrength bolts.For one thing,the function of box section steel piers can be restored by replacing the bucking restrained splints in the energy-consumption area after small earthquake;for the other,the whole box section steel piers can be replace to recover its function after big earthquake.The paper aims to explore the seismic behavior and failure mechanism of the box section steel bridge pier with the recoverable function,equipped with bucking restrained splints,under axial pressure(or eccentric compression)and reciprocating horizontal load on the top of the column.The main parameters are bucking restrained splints,axial compression ratio and eccentrically of pressure.Two groups of 7 test pieces in total were designed for quasi-static testing.The data of the load-displacement hysteretic curve,skeleton curve,bearing capacity,ductility coefficient,the degradation characteristics of stiffness and strength,and energy consumption characteristics of the test specimen were obtained.The data were used to analyze those factors’ influence to the seismic performance of box section steel piers.The finite full-scale element model of the box section steel bridge pier is established.The test justified the accuracy of the model and conducted the further analysis.34 test specimens were used for calculating the data.The load-displacement hysteretic curve,skeleton curve and bearing capacity were analyzed to explore the influence of the seismic performance of box section steel piers with bucking restrained splints by researching axial compression ratio,the strength of middle plate in the bucking restrained splints,axial compression ratio,thicknesses of middle plate in the bucking restrained splints and the different eccentricity.The research findings are as follow: firstly,the box section steel bridge pier with bucking restrained splints have stronger bearing capacity,deformation capacity and ductility;therefore the seismic behavior and energy-dissipating capacity are better.Secondly,axial compression ratio and eccentricity are the main parameters which affect the seismic behavior of the box section steel bridge pier with bucking restrained splints.The smaller number of either axial compression ratio or eccentricity,the greater the bearing capacity and ductility are and the slower the stiffness degradation and strength degradation become.Fourthly,the stronger or thicker middle plate in the bucking restrained splints are,the greater the yield capacity and peak value of axial compressive force are,and the faster the stiffness degradation and strength degradation become.In addition,the distance of the transverse stiffener has little influence on the seismic behavior of the box section steel bridge pier with bucking restrained splints.Lastly,based on the results of tests and finite element analysis,this paper proposes some practical designs of the new type of the box section steel bridge pier for seismic behavior and the simplified formulae.