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
In recent years, precast segmental concrete bridge columns became prevalent because of the benefits of accelerated construction, low environmental impact, high quality and low life cycle costs. The lack of a detailed ...In recent years, precast segmental concrete bridge columns became prevalent because of the benefits of accelerated construction, low environmental impact, high quality and low life cycle costs. The lack of a detailed configuration and appropriate design procedure to ensure a comparable performance with monolithic construction has impeded this structural system from being widely used in areas of high seismicity. In this study, precast segmental bridge column cyclic loading tests were conducted to investigate the performance of unbonded post-tensioned segmental bridge columns. One monolithic and two precast segmental columns were tested. The preeast segmental column exhibited minor damage and small residual displacement after the maximum 7% cyclic drift; energy dissipation （ED） can be enhanced byadding ED bars. The experimental results were modeled by a simplified pushover method （SPOM）, as well as a fiber model （FIBM） finite element method. Forty-five cases of columns with different aspect ratios, axial load ratios and ED bar ratios were analyzed with the SPOM and FIBM, respectively. Using these parametric results, a simplified design method was suggested by regressive analysis. Satisfactory correlation was found between the experimental results and the simplified design method for preeast segmental columns with different design parameters.展开更多
An experimental investigation was conducted to study the performance of precast beam-column concrete connections using T-section steel inserts into the concrete beam and joint core,under reversed cyclic loading.Six 2/...An experimental investigation was conducted to study the performance of precast beam-column concrete connections using T-section steel inserts into the concrete beam and joint core,under reversed cyclic loading.Six 2/3-scale interior beam-column subassemblies,one monolithic concrete specimen and five precast concrete specimens were tested.One precast specimen was a simple connection for a gravity load resistant design.Other precast specimens were developed with different attributes to improve their seismic performance.The test results showed that the performance of the monolithic specimen M1 represented ductile seismic behavior.Failure of columns and joints could be prevented,and the failure of the frame occurred at the flexural plastic hinge formation at the beam ends,close to the column faces.For the precast specimens,the splitting crack along the longitudinal lapped splice was a major failure.The precast P5 specimen with double steel T-section inserts showed better seismic performance compared to the other precast models.However,the dowel bars connected to the steel inserts were too short to develop a bond.The design of the precast concrete beams with lap splice is needed for longer lap lengths and should be done at the beam mid span or at the low flexural stress region.展开更多
A beam-column joint of precast and partial steel reinforced concrete( PPSRC) is proposed for precast reinforced concrete frames. The PPSRC consists of partial steel and reinforced concrete. The partial steel is locate...A beam-column joint of precast and partial steel reinforced concrete( PPSRC) is proposed for precast reinforced concrete frames. The PPSRC consists of partial steel and reinforced concrete. The partial steel is located in the core joint region and the connections between concrete members. This paper presents an experimental study of a series of PPSRC specimens. These specimens are tested under low cyclic loading.Experimental results demonstrate that the bearing capacity of the PPSRC specimens is 3 times that of the ordinary reinforced concrete( RC) beam-column joints. The strength and stiffness degradation rates are slower compared with that of the RC beam-column joints. In addition,the strength of the core joint region and the connections is higher than other parts of the PPSRC specimens. Beam failure occurs firstly for the PPSRC specimens,followed by column failure and connections failure. The failure of the core joint region occurs finally.Test results show that the seismic performance of the PPSRC is better than that of the ordinary RC beam-column joints.展开更多
为研究预应力混凝土用钢棒(steel bar for prestressed concrete, PC钢棒)-钢筋混合配筋混凝土柱的抗震性能,设计制作了5根相同尺寸、相同纵筋配筋率、不同PC钢棒替代率的PC钢棒-钢筋混合配筋混凝土柱试件,通过拟静力试验研究了PC钢棒...为研究预应力混凝土用钢棒(steel bar for prestressed concrete, PC钢棒)-钢筋混合配筋混凝土柱的抗震性能,设计制作了5根相同尺寸、相同纵筋配筋率、不同PC钢棒替代率的PC钢棒-钢筋混合配筋混凝土柱试件,通过拟静力试验研究了PC钢棒替代率对试件抗震性能的影响规律。结果表明:随着PC钢棒替代率的提高,试件的裂缝分布高度降低,裂缝数量变少,滞回曲线的饱满程度逐渐降低,耗能能力降低,残余位移角减小,自复位能力增强;当PC钢棒的替代率不大于50%时,各试件的峰值荷载接近;当PC钢棒的替代率大于50%时,试件的峰值荷载随PC钢棒替代率的增大而提高;当加载位移角相同且不大于1.0%时,配置PC钢棒的混凝土柱的残余位移角较为接近,且明显小于未配置PC钢棒的钢筋混凝土柱的残余位移角;当加载位移角相同且大于1%时,柱的残余位移角随着PC钢棒替代率的增高而降低。展开更多
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.
基金National Natural Science Foundation of China under Grants Nos.51208268 and 51178429K.C.Wong Magna Fund in Ningbo University+1 种基金Transportation Science and Technology Project of Ningbo City under Grant No.201507Natural Science Foundation of Ningbo City under Grant No.2015A610293
文摘In recent years, precast segmental concrete bridge columns became prevalent because of the benefits of accelerated construction, low environmental impact, high quality and low life cycle costs. The lack of a detailed configuration and appropriate design procedure to ensure a comparable performance with monolithic construction has impeded this structural system from being widely used in areas of high seismicity. In this study, precast segmental bridge column cyclic loading tests were conducted to investigate the performance of unbonded post-tensioned segmental bridge columns. One monolithic and two precast segmental columns were tested. The preeast segmental column exhibited minor damage and small residual displacement after the maximum 7% cyclic drift; energy dissipation （ED） can be enhanced byadding ED bars. The experimental results were modeled by a simplified pushover method （SPOM）, as well as a fiber model （FIBM） finite element method. Forty-five cases of columns with different aspect ratios, axial load ratios and ED bar ratios were analyzed with the SPOM and FIBM, respectively. Using these parametric results, a simplified design method was suggested by regressive analysis. Satisfactory correlation was found between the experimental results and the simplified design method for preeast segmental columns with different design parameters.
文摘An experimental investigation was conducted to study the performance of precast beam-column concrete connections using T-section steel inserts into the concrete beam and joint core,under reversed cyclic loading.Six 2/3-scale interior beam-column subassemblies,one monolithic concrete specimen and five precast concrete specimens were tested.One precast specimen was a simple connection for a gravity load resistant design.Other precast specimens were developed with different attributes to improve their seismic performance.The test results showed that the performance of the monolithic specimen M1 represented ductile seismic behavior.Failure of columns and joints could be prevented,and the failure of the frame occurred at the flexural plastic hinge formation at the beam ends,close to the column faces.For the precast specimens,the splitting crack along the longitudinal lapped splice was a major failure.The precast P5 specimen with double steel T-section inserts showed better seismic performance compared to the other precast models.However,the dowel bars connected to the steel inserts were too short to develop a bond.The design of the precast concrete beams with lap splice is needed for longer lap lengths and should be done at the beam mid span or at the low flexural stress region.
文摘A beam-column joint of precast and partial steel reinforced concrete( PPSRC) is proposed for precast reinforced concrete frames. The PPSRC consists of partial steel and reinforced concrete. The partial steel is located in the core joint region and the connections between concrete members. This paper presents an experimental study of a series of PPSRC specimens. These specimens are tested under low cyclic loading.Experimental results demonstrate that the bearing capacity of the PPSRC specimens is 3 times that of the ordinary reinforced concrete( RC) beam-column joints. The strength and stiffness degradation rates are slower compared with that of the RC beam-column joints. In addition,the strength of the core joint region and the connections is higher than other parts of the PPSRC specimens. Beam failure occurs firstly for the PPSRC specimens,followed by column failure and connections failure. The failure of the core joint region occurs finally.Test results show that the seismic performance of the PPSRC is better than that of the ordinary RC beam-column joints.
文摘为研究预应力混凝土用钢棒(steel bar for prestressed concrete, PC钢棒)-钢筋混合配筋混凝土柱的抗震性能,设计制作了5根相同尺寸、相同纵筋配筋率、不同PC钢棒替代率的PC钢棒-钢筋混合配筋混凝土柱试件,通过拟静力试验研究了PC钢棒替代率对试件抗震性能的影响规律。结果表明:随着PC钢棒替代率的提高,试件的裂缝分布高度降低,裂缝数量变少,滞回曲线的饱满程度逐渐降低,耗能能力降低,残余位移角减小,自复位能力增强;当PC钢棒的替代率不大于50%时,各试件的峰值荷载接近;当PC钢棒的替代率大于50%时,试件的峰值荷载随PC钢棒替代率的增大而提高;当加载位移角相同且不大于1.0%时,配置PC钢棒的混凝土柱的残余位移角较为接近,且明显小于未配置PC钢棒的钢筋混凝土柱的残余位移角;当加载位移角相同且大于1%时,柱的残余位移角随着PC钢棒替代率的增高而降低。
