Determination of collapse load-carrying capacity of elasto-plastic material is very important in designing structure. The problem is commonly solved by elasto-plastic finite element method （FEM）. In order to deal wi...Determination of collapse load-carrying capacity of elasto-plastic material is very important in designing structure. The problem is commonly solved by elasto-plastic finite element method （FEM）. In order to deal with material nonlinear problem involving strain softening problem effectively, a new numerical method-damped Newton method was proposed. The iterative schemes are discussed in detail for pure equilibrium models. In the equilibrium model, the plasticity criterion and the compatibility of the strains are verified, and the strain increment and plastic factor are treated as independent unknowns. To avoid the stiffness matrix being singularity or condition of matrix being ill, a damping factor a was introduced to adjust the value of plastic consistent parameter automatically during the iterations. According to the algorithm, the nonlinear finite element program was complied and its numerical example was calculated. The numerical results indicate that this method converges very fast for both small load steps and large load steps. Compared with those results obtained by analysis and experiment, the predicted ultimate bearing capacity from the proposed method is identical.展开更多
Three kinds of possible structures of legged lander including monocoqe, semi-monocoqe and space frame are compared, and the lightest space frame structure is selected as the lander's structure. Then, a new lander ...Three kinds of possible structures of legged lander including monocoqe, semi-monocoqe and space frame are compared, and the lightest space frame structure is selected as the lander's structure. Then, a new lander with four-legged truss structure is proposed. In the premise of ensuring that the main and assistant structures of landing legs are not changed, six possible lander body structures of the new lander are put forward. Taking the section size of each component of lander as design variables, and taking the total mass of the structure as the objective function, the six structures are analyzed by using the software Altair. OptiStruct and the results show that the mass of the basic structure is the lightest, and it is selected as the final design scheme of lander due to its simple structure and convenient manufacture. The optimization on the selected lander structure is conducted, and the detailed results are presented.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
基金Project(2012CB026200)supported by the National Basic Research Program of ChinaProjects(50978055,50878048)supported by the National Natural Science Foundation of China
文摘Determination of collapse load-carrying capacity of elasto-plastic material is very important in designing structure. The problem is commonly solved by elasto-plastic finite element method （FEM）. In order to deal with material nonlinear problem involving strain softening problem effectively, a new numerical method-damped Newton method was proposed. The iterative schemes are discussed in detail for pure equilibrium models. In the equilibrium model, the plasticity criterion and the compatibility of the strains are verified, and the strain increment and plastic factor are treated as independent unknowns. To avoid the stiffness matrix being singularity or condition of matrix being ill, a damping factor a was introduced to adjust the value of plastic consistent parameter automatically during the iterations. According to the algorithm, the nonlinear finite element program was complied and its numerical example was calculated. The numerical results indicate that this method converges very fast for both small load steps and large load steps. Compared with those results obtained by analysis and experiment, the predicted ultimate bearing capacity from the proposed method is identical.
基金Sponsored by the Project on Absorption of Intellects by Institutions of Higher Education for Academic Disciplinary Innovations(Grant No. B07018)
文摘Three kinds of possible structures of legged lander including monocoqe, semi-monocoqe and space frame are compared, and the lightest space frame structure is selected as the lander's structure. Then, a new lander with four-legged truss structure is proposed. In the premise of ensuring that the main and assistant structures of landing legs are not changed, six possible lander body structures of the new lander are put forward. Taking the section size of each component of lander as design variables, and taking the total mass of the structure as the objective function, the six structures are analyzed by using the software Altair. OptiStruct and the results show that the mass of the basic structure is the lightest, and it is selected as the final design scheme of lander due to its simple structure and convenient manufacture. The optimization on the selected lander structure is conducted, and the detailed results are presented.
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.
