To solve the problem that the overlapping parts of a retractable pier column are prone to damage,this paper proposed the reinforcing measure of setting a stiffener ring at the bottom of the steel pipe.To study how the...To solve the problem that the overlapping parts of a retractable pier column are prone to damage,this paper proposed the reinforcing measure of setting a stiffener ring at the bottom of the steel pipe.To study how the stiffener-ring parameters influence the mechanical properties of the pier column.12 scale model specimens(including nine specimens with stiffener-ring widths of 40,50,and 60 mm and three unstiffened comparison specimens)were tested under axial compression.Based on the test results,the specimen load-displacement,load-deflection,and load-strain curves were analyzed,and a finite-element model of a pier column under axial compression was established to determine the optimal stiffener size.The results show that setting a stiffener ring enhances the cooperative working ability between the steel pipe and the internal filling material and restrains the lateral deformation of the pier column,thereby improving the ultimate bearing capacity and overall stability of the pier column.The ultimate bearing capacity of the pier column is related to the width and thickness of the stiffener ring.The optimal size of the stiffener ring of the model pier column is 70 mm in width and 4 mm in thickness.The present research results provide a reference for designing compressible pier columns and column stiffening in mines and have important practical significance.展开更多
Considering the desirable behavior of concrete filled steel tube(CFT)columns and the complicated behavior of segmental double-column piers under cyclic loads,three post-tensioned precast segmental CFT double-column pi...Considering the desirable behavior of concrete filled steel tube(CFT)columns and the complicated behavior of segmental double-column piers under cyclic loads,three post-tensioned precast segmental CFT double-column pier specimens were tested to extend their application in moderate and high seismicity areas.The effects of the number of CFT segments and the steel endplates as energy dissipaters on the seismic behavior of the piers were evaluated.The experimental results show that the segmental piers exhibited stable hysteretic behavior with small residual displacements under cyclic loads.All the tested specimens achieved a drift ratio no less than 13%without significant damage and strength deterioration due to the desirable behavior of CFT columns.Since the deformation of segmental columns was mainly concentrated at the column-footing interfaces,the increase of the segment numbers for each column had no obvious effects on the loading capacity but reduced the initial stiffness of the specimens.The use of steel endplates improved the bearing capacity,stiffness and energy dissipation of segmental piers,but weakened their self-centering capacity.Fiber models were also proposed to simulate the hysteretic behavior of the tested specimens,and the influences of segment numbers and prestress levels on seismic behavior were further studied.展开更多
Double-column bridge piers are prone to local damage during earthquakes,leading to the destruction of bridges.To improve the earthquake resistance of double-column bridge piers,a novel swing column device(SCD),consist...Double-column bridge piers are prone to local damage during earthquakes,leading to the destruction of bridges.To improve the earthquake resistance of double-column bridge piers,a novel swing column device(SCD),consisting of a magnetorheological(MR)damper,a current controller,and a swing column,was designed for the present work.To verify the seismic energy dissipation ability of the SCD,a lumped mass model for a double-column bridge pier with the SCD was established according to the low-order modeling method proposed by Steo.Furthermore,the motion equation of the double-column bridge pier with the SCD was established based on the D′Alembert principle and solved with the use of computational programming.It was found that the displacement response of the double-column bridge pier was effectively controlled by the SCD.However,due to rough current selection and a time delay,there is a significant overshoot of the bridge acceleration using SCD.Hence,to solve the overshoot phenomenon,a current controller was designed based on fuzzy logic theory.It was found that the SCD design based on fuzzy control provided an ideal shock absorption effect,while reducing the displacement and acceleration of the bridge pier by 36.43%‒40.63%and 30.06%‒33.6%,respectively.展开更多
文摘To solve the problem that the overlapping parts of a retractable pier column are prone to damage,this paper proposed the reinforcing measure of setting a stiffener ring at the bottom of the steel pipe.To study how the stiffener-ring parameters influence the mechanical properties of the pier column.12 scale model specimens(including nine specimens with stiffener-ring widths of 40,50,and 60 mm and three unstiffened comparison specimens)were tested under axial compression.Based on the test results,the specimen load-displacement,load-deflection,and load-strain curves were analyzed,and a finite-element model of a pier column under axial compression was established to determine the optimal stiffener size.The results show that setting a stiffener ring enhances the cooperative working ability between the steel pipe and the internal filling material and restrains the lateral deformation of the pier column,thereby improving the ultimate bearing capacity and overall stability of the pier column.The ultimate bearing capacity of the pier column is related to the width and thickness of the stiffener ring.The optimal size of the stiffener ring of the model pier column is 70 mm in width and 4 mm in thickness.The present research results provide a reference for designing compressible pier columns and column stiffening in mines and have important practical significance.
基金National Natural Science Foundation of China under Grant Nos.51978656 and 51478459the Key Research and Development Project of Xuzhou under Grant No.KC22282the Open Fund of Jiangsu Key Laboratory of Environmental Impact and Structural Safety in Civil Engineering,China University of Mining and Technology under Grant No.KFJJ202004。
文摘Considering the desirable behavior of concrete filled steel tube(CFT)columns and the complicated behavior of segmental double-column piers under cyclic loads,three post-tensioned precast segmental CFT double-column pier specimens were tested to extend their application in moderate and high seismicity areas.The effects of the number of CFT segments and the steel endplates as energy dissipaters on the seismic behavior of the piers were evaluated.The experimental results show that the segmental piers exhibited stable hysteretic behavior with small residual displacements under cyclic loads.All the tested specimens achieved a drift ratio no less than 13%without significant damage and strength deterioration due to the desirable behavior of CFT columns.Since the deformation of segmental columns was mainly concentrated at the column-footing interfaces,the increase of the segment numbers for each column had no obvious effects on the loading capacity but reduced the initial stiffness of the specimens.The use of steel endplates improved the bearing capacity,stiffness and energy dissipation of segmental piers,but weakened their self-centering capacity.Fiber models were also proposed to simulate the hysteretic behavior of the tested specimens,and the influences of segment numbers and prestress levels on seismic behavior were further studied.
文摘Double-column bridge piers are prone to local damage during earthquakes,leading to the destruction of bridges.To improve the earthquake resistance of double-column bridge piers,a novel swing column device(SCD),consisting of a magnetorheological(MR)damper,a current controller,and a swing column,was designed for the present work.To verify the seismic energy dissipation ability of the SCD,a lumped mass model for a double-column bridge pier with the SCD was established according to the low-order modeling method proposed by Steo.Furthermore,the motion equation of the double-column bridge pier with the SCD was established based on the D′Alembert principle and solved with the use of computational programming.It was found that the displacement response of the double-column bridge pier was effectively controlled by the SCD.However,due to rough current selection and a time delay,there is a significant overshoot of the bridge acceleration using SCD.Hence,to solve the overshoot phenomenon,a current controller was designed based on fuzzy logic theory.It was found that the SCD design based on fuzzy control provided an ideal shock absorption effect,while reducing the displacement and acceleration of the bridge pier by 36.43%‒40.63%and 30.06%‒33.6%,respectively.
