In order to study the performances of high-strength concrete beams including steel fibers and large-particle recycled aggregates,four different beams have been designed,tested experimentally and simulated numerically....In order to study the performances of high-strength concrete beams including steel fibers and large-particle recycled aggregates,four different beams have been designed,tested experimentally and simulated numerically.As varying parameters,the replacement rates of recycled coarse aggregates and CFRP(carbon fiber reinforced polymer)sheets have been considered.The failure mode of these beams,related load deflection curves,stirrup strain and shear capacity have been determined through monotonic loading tests.The simulations have been conducted using the ABAQUS finite element software.The results show that the shear failure mode of recycled concrete beams is similar to that of ordinary concrete beams.The shear carrying capacity of high-strength concrete beams including steel fibers and large-particle recycled coarse aggregates grows with an increase in the replacement rate of recycled coarse aggregates.Reinforcement with CFRP sheets can significantly improve the beam’s shear carrying capacity and overall resistance to deformation.展开更多
With the application of X-ray computed tomography（CT） technology of C80 high-strength concrete with polypropylene fiber at elevated temperatures, the microscopic damage evolution process observation and image buildi...With the application of X-ray computed tomography（CT） technology of C80 high-strength concrete with polypropylene fiber at elevated temperatures, the microscopic damage evolution process observation and image building could be obtained, based on the statistics theory and numerical analysis of the combination of concrete internal defects extension and evolution regularity of microscopic structure. The expermental results show that the defect rate has changed at different temperatures and can determine the concrete degradation threshold temperatures. Also, data analysis can help to establish the evolution equation between the defect rate and the effect of temperature damage, and identify that the addition of polypropylene fibers in the high strength concrete at high temperature can improve cracking resistance.展开更多
In this study,an experimental study and numerical calculations using fiber model were conducted for four high-strength concrete shear walls with boundary columns under low cyclic load.The boundary column and shear wal...In this study,an experimental study and numerical calculations using fiber model were conducted for four high-strength concrete shear walls with boundary columns under low cyclic load.The boundary column and shear wall were divided into fiber elements,and PERFORM-3D finite element analysis software was used to carry out push-over analysis on the test specimens.The results show that the finite element analysis results were in good agreement with the experimental results.The proposed analysis method could perform elasto-plastic analysis on the high-strength concrete shear wall with boundary columns without distinguishing the categories of frame column and shear wall.The seismic performance of high-strength concrete shear wall with boundary columns was analyzed using the following parameters:axis compression ratio,height to width ratio,ratio of vertical reinforcement,and ratio of longitudinal reinforcement in the boundary column.The results show that the increase in the axial compression ratio causes the bearing capacity of the shear wall to increase at first and then to decrease and causes the ductility to decrease.The increase in the height to width ratio causes the bearing capacity of the shear wall to decrease and its ductility to increase.The ratio of vertical reinforcement was found to have little effect on the bearing capacity and ductility.The increase in the ratio of longitudinal reinforcement in boundary column resulted in a significant increase in the bearing capacity and caused the ductility to decrease at first and then to slowly increase.展开更多
Background:Multiple techniques are commonly used for posterior cruciate ligament(PCL)reconstruction.However,the optimum method regarding the fixation of PCL reconstruction after PCL tears remains debatable.The purpose...Background:Multiple techniques are commonly used for posterior cruciate ligament(PCL)reconstruction.However,the optimum method regarding the fixation of PCL reconstruction after PCL tears remains debatable.The purpose of this study was to compare the biomechanical properties among three different tibial fixation procedures for transtibial single-bundle PCL reconstruction.Methods:Thirty-six porcine tibias and porcine extensor tendons were randomized into three fixation study groups:the interference screw fixation(IS)group,the transtibial tubercle fixation(TTF)group,and TTF+IS group(n=12 in each group).The structural properties of the three fixation groups were tested under cyclic loading and load-to-failure.The slippage after the cyclic loading test and the stiffness and ultimate failure load after load-to-failure testing were recorded.Results:After 1000 cycles of cyclic testing,no significant difference was observed in graft slippage among the three groups.For load-to-failure testing,the TTF+IS group showed a higher ultimate failure load than the TTF group and the IS group(876.34±58.78 N vs.660.92±77.74 N[P<0.001]vs.556.49±65.33 N[P<0.001]).The stiffness in the TTF group was significantly lower than that in the IS group and the TTF+IS group(92.77±20.16 N/mm in the TTF group vs.120.27±15.66 N/m in the IS group[P=0.001]and 131.79±17.95 N/mm in the TTF+IS group[P<0.001]).No significant difference in the mean stiffness was found between the IS group and the TTF+IS group(P=0.127).Conclusions:In this biomechanical study,supplementary fixation with transtibial tubercle sutures increased the ultimate failure load during load-to-failure testing for PCL reconstruction.展开更多
基金the Natural Science Foundation of Shandong Province[Grant Nos.ZR2015EQ017,ZR2018MEE044]the Key Laboratory Open Project of the Ministry of Education of Beijing University of Technology[Grant No.2020B03].
文摘In order to study the performances of high-strength concrete beams including steel fibers and large-particle recycled aggregates,four different beams have been designed,tested experimentally and simulated numerically.As varying parameters,the replacement rates of recycled coarse aggregates and CFRP(carbon fiber reinforced polymer)sheets have been considered.The failure mode of these beams,related load deflection curves,stirrup strain and shear capacity have been determined through monotonic loading tests.The simulations have been conducted using the ABAQUS finite element software.The results show that the shear failure mode of recycled concrete beams is similar to that of ordinary concrete beams.The shear carrying capacity of high-strength concrete beams including steel fibers and large-particle recycled coarse aggregates grows with an increase in the replacement rate of recycled coarse aggregates.Reinforcement with CFRP sheets can significantly improve the beam’s shear carrying capacity and overall resistance to deformation.
基金Funded by the National Natural Science Foundation of China(No.51278325)the Shanxi Province Natural Science Foundation(No.2011011024-2)
文摘With the application of X-ray computed tomography（CT） technology of C80 high-strength concrete with polypropylene fiber at elevated temperatures, the microscopic damage evolution process observation and image building could be obtained, based on the statistics theory and numerical analysis of the combination of concrete internal defects extension and evolution regularity of microscopic structure. The expermental results show that the defect rate has changed at different temperatures and can determine the concrete degradation threshold temperatures. Also, data analysis can help to establish the evolution equation between the defect rate and the effect of temperature damage, and identify that the addition of polypropylene fibers in the high strength concrete at high temperature can improve cracking resistance.
基金supported by the National Natural Science Foundation of China(No.51708209)Hunan Provincial Natural Science Foundation of China(No.2019JJ50209)National Student‘s Program for Innovation and Entrepreneurship(No.201912658001)。
文摘In this study,an experimental study and numerical calculations using fiber model were conducted for four high-strength concrete shear walls with boundary columns under low cyclic load.The boundary column and shear wall were divided into fiber elements,and PERFORM-3D finite element analysis software was used to carry out push-over analysis on the test specimens.The results show that the finite element analysis results were in good agreement with the experimental results.The proposed analysis method could perform elasto-plastic analysis on the high-strength concrete shear wall with boundary columns without distinguishing the categories of frame column and shear wall.The seismic performance of high-strength concrete shear wall with boundary columns was analyzed using the following parameters:axis compression ratio,height to width ratio,ratio of vertical reinforcement,and ratio of longitudinal reinforcement in the boundary column.The results show that the increase in the axial compression ratio causes the bearing capacity of the shear wall to increase at first and then to decrease and causes the ductility to decrease.The increase in the height to width ratio causes the bearing capacity of the shear wall to decrease and its ductility to increase.The ratio of vertical reinforcement was found to have little effect on the bearing capacity and ductility.The increase in the ratio of longitudinal reinforcement in boundary column resulted in a significant increase in the bearing capacity and caused the ductility to decrease at first and then to slowly increase.
文摘Background:Multiple techniques are commonly used for posterior cruciate ligament(PCL)reconstruction.However,the optimum method regarding the fixation of PCL reconstruction after PCL tears remains debatable.The purpose of this study was to compare the biomechanical properties among three different tibial fixation procedures for transtibial single-bundle PCL reconstruction.Methods:Thirty-six porcine tibias and porcine extensor tendons were randomized into three fixation study groups:the interference screw fixation(IS)group,the transtibial tubercle fixation(TTF)group,and TTF+IS group(n=12 in each group).The structural properties of the three fixation groups were tested under cyclic loading and load-to-failure.The slippage after the cyclic loading test and the stiffness and ultimate failure load after load-to-failure testing were recorded.Results:After 1000 cycles of cyclic testing,no significant difference was observed in graft slippage among the three groups.For load-to-failure testing,the TTF+IS group showed a higher ultimate failure load than the TTF group and the IS group(876.34±58.78 N vs.660.92±77.74 N[P<0.001]vs.556.49±65.33 N[P<0.001]).The stiffness in the TTF group was significantly lower than that in the IS group and the TTF+IS group(92.77±20.16 N/mm in the TTF group vs.120.27±15.66 N/m in the IS group[P=0.001]and 131.79±17.95 N/mm in the TTF+IS group[P<0.001]).No significant difference in the mean stiffness was found between the IS group and the TTF+IS group(P=0.127).Conclusions:In this biomechanical study,supplementary fixation with transtibial tubercle sutures increased the ultimate failure load during load-to-failure testing for PCL reconstruction.
