In this study,the seismic stability of arch dam abutments is investigated within the framework of the probabilistic method.A large concrete arch dam is considered with six wedges for each abutment.The seismic safety o...In this study,the seismic stability of arch dam abutments is investigated within the framework of the probabilistic method.A large concrete arch dam is considered with six wedges for each abutment.The seismic safety of the dam abutments is studied with quasi-static analysis for different hazard levels.The Londe limit equilibrium method is utilized to calculate the stability of the wedges in the abutments.Since the finite element method is time-consuming,the neural network is used as an alternative for calculating the wedge safety factor.For training the neural network,1000 random samples are generated and the dam response is calculated.The direction of applied acceleration is changed within 5-degree intervals to reveal the critical direction corresponding to the minimum safety factor.The Latin hypercube sampling(LHS)is employed for sample generation,and the safety level is determined with reliability analysis.Three sample numbers of 1000,2000 and 4000 are used to examine the average and standard deviation of the results.The global sensitivity analysis is used to identify the effects of random variables on the abutment stability.It is shown that friction,cohesion and uplift pressure have the most significant effects on the wedge stability variance.展开更多
We present a 3-D finite element (FE) approach to find the optimal distribution of seismic reinforcement force to secure high arch dam-abutment structures against certain earthquake actions. Nonlinear FE time history a...We present a 3-D finite element (FE) approach to find the optimal distribution of seismic reinforcement force to secure high arch dam-abutment structures against certain earthquake actions. Nonlinear FE time history analysis is performed on the structure to find the seismic responses, using the associated elastic-perfectly plastic material description. The concept of plastic complementary energy is introduced to structural dynamics to quantify the structure's resistance against the seismic action throughout the time history and to indicate the critical moments when extreme extents of dynamic failure occur. Meanwhile the distributions of the unbalanced force at these critical moments reveal the dominant patterns of the dynamic failure. By the principle of minimum plastic complementary energy, the unbalanced force is just the counterforce of optimal reinforcement force to secure the self-unsupportable structure against the earthquake, which makes the seismic design more targeted and effective. Seismic design analysis is performed on Maji high arch dam-abutment structure. The results could to a large extent guide the seismic design, showing that several structural surfaces lying at the upper abutment are the most seismically vulnerable. This application indicates good applicability of this approach to large-scale projects.展开更多
文摘In this study,the seismic stability of arch dam abutments is investigated within the framework of the probabilistic method.A large concrete arch dam is considered with six wedges for each abutment.The seismic safety of the dam abutments is studied with quasi-static analysis for different hazard levels.The Londe limit equilibrium method is utilized to calculate the stability of the wedges in the abutments.Since the finite element method is time-consuming,the neural network is used as an alternative for calculating the wedge safety factor.For training the neural network,1000 random samples are generated and the dam response is calculated.The direction of applied acceleration is changed within 5-degree intervals to reveal the critical direction corresponding to the minimum safety factor.The Latin hypercube sampling(LHS)is employed for sample generation,and the safety level is determined with reliability analysis.Three sample numbers of 1000,2000 and 4000 are used to examine the average and standard deviation of the results.The global sensitivity analysis is used to identify the effects of random variables on the abutment stability.It is shown that friction,cohesion and uplift pressure have the most significant effects on the wedge stability variance.
基金supported by China National Key Research Program (Grant No. 90715041)China National Funds for Distinguished Young Scientists (Grant No. 50925931)
文摘We present a 3-D finite element (FE) approach to find the optimal distribution of seismic reinforcement force to secure high arch dam-abutment structures against certain earthquake actions. Nonlinear FE time history analysis is performed on the structure to find the seismic responses, using the associated elastic-perfectly plastic material description. The concept of plastic complementary energy is introduced to structural dynamics to quantify the structure's resistance against the seismic action throughout the time history and to indicate the critical moments when extreme extents of dynamic failure occur. Meanwhile the distributions of the unbalanced force at these critical moments reveal the dominant patterns of the dynamic failure. By the principle of minimum plastic complementary energy, the unbalanced force is just the counterforce of optimal reinforcement force to secure the self-unsupportable structure against the earthquake, which makes the seismic design more targeted and effective. Seismic design analysis is performed on Maji high arch dam-abutment structure. The results could to a large extent guide the seismic design, showing that several structural surfaces lying at the upper abutment are the most seismically vulnerable. This application indicates good applicability of this approach to large-scale projects.
