Shaking table tests of a 1:10 scale arch model performed to investigate the seismic behavior and resistance of concrete filled steel tubular (CFT) arch structures are described in this paper. The El-Centro record and ...Shaking table tests of a 1:10 scale arch model performed to investigate the seismic behavior and resistance of concrete filled steel tubular (CFT) arch structures are described in this paper. The El-Centro record and Shanghai artificial wave were adopted as the input excitation. The entire test process can be divided into three stages depending on the lateral brace configurations, i.e., fully (five) braced, two braces removed, and all braces removed. A total of 46 tests, starting from the elastic state to failure condition, have been conducted. The natural vibration frequencies, responses of acceleration, displacement and strain were measured. From the test results, it is demonstrated that the CFT arch structures are capable of resisting severe ground motions and that CFT arches offer a credible alternative to reinforced concrete arches, especially in regions of high seismic intensity.展开更多
An efficient computational method is suggested for the first-excursion reliability assessment of nonstationary process. In the proposed method, the nonlinear performance function is Linearized at the Hasofer-Lind poin...An efficient computational method is suggested for the first-excursion reliability assessment of nonstationary process. In the proposed method, the nonlinear performance function is Linearized at the Hasofer-Lind point obtained by an iterative algorithm. The problem of the nonstationary processes is solved by the discrete-time method, in which the precision can be controlled by choosing the steps of discretization. The derived formulae can be conveniently degraded to calculate both the first-excursion reliability with linear performance function of stationary processes and the time-independent reliability. The suggested method is useful for the analysis of components and systems with nonstationary responses in structural design where some uncertainties are represented by a vector of nonstationary processes. Examples are given to demonstrate the fast convergency and effectiveness of the presented method.展开更多
Reservoir sedimentation is an unsolved problem.In this paper,based on measured data,theoretical analysis and numerical computations,we prove that a proportion of the sediment coarser than 0.1 mm(CS) is sorted and depo...Reservoir sedimentation is an unsolved problem.In this paper,based on measured data,theoretical analysis and numerical computations,we prove that a proportion of the sediment coarser than 0.1 mm(CS) is sorted and deposited in specific reaches in the upper backwaters or in run-of-river reservoirs.The ratio of CS is usually small but it impacts the slope of deposition delta greatly and raises the backwater in later stages for a river shaped reservoir(RSR).Based on these facts,we propose to remove such CS from a fixed basin(FB) in the upper backwater by dredging and we prove that the removal of CS is effective in reducing sediment deposition and in preserving the long-term capacity of reservoirs.A numerical model computation of the Three Gorges Project(TGP) reservoir indicates that dredging 30×106-50×106 t/a of CS could reduce 20% total deposition by the end of 100th year,so that the slope of deposition can be slowed down by 25%-30%.This would be remarkable for a long extended RSR.This method of removing CS can also be applied to the Xiaolangdi reservoir(XLD) on the Yellow River(YR) to not only limit reservoir deposition but also filter out the CS from entering the Lower Yellow River(LYR) to slow down the rise of the perched LYR.It provides a new alternative to postpone the continuous siltation of the LYR.展开更多
基金This study was supported by the National Natural Science Foundation of China under Grant No.50078016Open Funding of State Key Laboratory for Disaster Reduction in Civil Engineering,China.
文摘Shaking table tests of a 1:10 scale arch model performed to investigate the seismic behavior and resistance of concrete filled steel tubular (CFT) arch structures are described in this paper. The El-Centro record and Shanghai artificial wave were adopted as the input excitation. The entire test process can be divided into three stages depending on the lateral brace configurations, i.e., fully (five) braced, two braces removed, and all braces removed. A total of 46 tests, starting from the elastic state to failure condition, have been conducted. The natural vibration frequencies, responses of acceleration, displacement and strain were measured. From the test results, it is demonstrated that the CFT arch structures are capable of resisting severe ground motions and that CFT arches offer a credible alternative to reinforced concrete arches, especially in regions of high seismic intensity.
基金The project supported by the National Natural Science Foundation of China
文摘An efficient computational method is suggested for the first-excursion reliability assessment of nonstationary process. In the proposed method, the nonlinear performance function is Linearized at the Hasofer-Lind point obtained by an iterative algorithm. The problem of the nonstationary processes is solved by the discrete-time method, in which the precision can be controlled by choosing the steps of discretization. The derived formulae can be conveniently degraded to calculate both the first-excursion reliability with linear performance function of stationary processes and the time-independent reliability. The suggested method is useful for the analysis of components and systems with nonstationary responses in structural design where some uncertainties are represented by a vector of nonstationary processes. Examples are given to demonstrate the fast convergency and effectiveness of the presented method.
基金supported by the State Key Laboratory of Hydroscience and Engineering, Tsinghua University (Grant No. 2011-KY-2)the Independent Research Plans of Tsinghua University (Grant No. 20101081780)
文摘Reservoir sedimentation is an unsolved problem.In this paper,based on measured data,theoretical analysis and numerical computations,we prove that a proportion of the sediment coarser than 0.1 mm(CS) is sorted and deposited in specific reaches in the upper backwaters or in run-of-river reservoirs.The ratio of CS is usually small but it impacts the slope of deposition delta greatly and raises the backwater in later stages for a river shaped reservoir(RSR).Based on these facts,we propose to remove such CS from a fixed basin(FB) in the upper backwater by dredging and we prove that the removal of CS is effective in reducing sediment deposition and in preserving the long-term capacity of reservoirs.A numerical model computation of the Three Gorges Project(TGP) reservoir indicates that dredging 30×106-50×106 t/a of CS could reduce 20% total deposition by the end of 100th year,so that the slope of deposition can be slowed down by 25%-30%.This would be remarkable for a long extended RSR.This method of removing CS can also be applied to the Xiaolangdi reservoir(XLD) on the Yellow River(YR) to not only limit reservoir deposition but also filter out the CS from entering the Lower Yellow River(LYR) to slow down the rise of the perched LYR.It provides a new alternative to postpone the continuous siltation of the LYR.