In this study, the damage-plasticity model for concrete that was verified by the model experiment was used to calculate the damage to a spiral case structure based on the damage mechanics theory. The concrete structur...In this study, the damage-plasticity model for concrete that was verified by the model experiment was used to calculate the damage to a spiral case structure based on the damage mechanics theory. The concrete structure surrounding the spiral case was simulated with a three-dimensional finite element model. Then, the distribution and evolution of the structural damage were studied. Based on investigation of the change of gap openings between the steel liner and concrete structure, the impact of the non-uniform variation of gaps on the load-beating ratio between the steel liner and concrete structure was analyzed. The comparison of calculated results of the simplified and simulation algorithms shows that the simulation algorithm is a feasible option for the calculation of spiral case structures. In addition, the shell-spring model was introduced for optimization analysis, and the results were reasonable.展开更多
In order to understand the effect of hardening ductility parameters and softening ductility parameters of the concrete damage plastic model in LS-DYNA,a sensitivity and reliability analysis of these parameters through...In order to understand the effect of hardening ductility parameters and softening ductility parameters of the concrete damage plastic model in LS-DYNA,a sensitivity and reliability analysis of these parameters through a convenient cube unit test was conducted. The results showed that the peak strength strain was independent of the hardening ductility parameter DH,but affected by AH,BH,and CH. The softening ductility was mainly related to the softening ductility parameter AS,but not affected by the damage ductility exponent BS. In case that the model with default parameters failed to match the AS-controlled damage softening phase,an optimized model with an AS correction was developed. The corrected model with the AS value of 2 matched well with the code model,and exhibited good feasibility in predicting the stress-strain curve of different grades of concrete. Moreover,the practicability of the corrected model was further validated by the conventional triaxial test. The simulated curve exhibited favorable consistence with the trial curve. Therefore,the model with parameter correction could provide a prospective reference for predicting the mechanical properties of concrete.展开更多
In the present work,important aspects of time-dependent nonlinear 3D finite element(FE)models for deep tunnel advance by the New Austrian Tunneling Method(NATM),characterized by repeated sequences of excavation,securi...In the present work,important aspects of time-dependent nonlinear 3D finite element(FE)models for deep tunnel advance by the New Austrian Tunneling Method(NATM),characterized by repeated sequences of excavation,securing,and idle periods,are discussed on the example of a 3D finite element model of a stretch of the Brenner Base Tunnel,which is currently constructed between Austria and Italy.Nonlinear material models are utilized for representing the surrounding rock mass and the shotcrete shell.Based on the finite element model,strategies for the efficient implementation into a parallel distributed memory numerical code are proposed.They are essential to achieve reasonable computation times for numerical simulations of tunneling based on large 3D FE models.In particular,the implementation of the construction procedure,parallel computing and communication specific details,and efficient linear solvers for the global equation system within the incremental-iterative Newton–Raphson scheme are addressed.Furthermore,possible extensions of the material models for rock mass and shotcrete,used in the 3D FE model,are presented.They concern(i)a gradient-enhanced model for transversely isotropic rock and rock mass,taking into account hardening and softening behavior and(ii)the extension of the shotcrete model to nonlinear creep and damage due to creep.The possible benefits of the model extensions in numerical simulations of tunneling by the NATM are discussed.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 51079020)the He'nan Provincial Research Foundation for Basic and Advanced Technology (Grant No. 122300410001)the Foundation of He'nan Educational Committee (Grant No. 13A570715)
文摘In this study, the damage-plasticity model for concrete that was verified by the model experiment was used to calculate the damage to a spiral case structure based on the damage mechanics theory. The concrete structure surrounding the spiral case was simulated with a three-dimensional finite element model. Then, the distribution and evolution of the structural damage were studied. Based on investigation of the change of gap openings between the steel liner and concrete structure, the impact of the non-uniform variation of gaps on the load-beating ratio between the steel liner and concrete structure was analyzed. The comparison of calculated results of the simplified and simulation algorithms shows that the simulation algorithm is a feasible option for the calculation of spiral case structures. In addition, the shell-spring model was introduced for optimization analysis, and the results were reasonable.
基金Supported by the National Natural Science Foundation of China(10272109)
文摘In order to understand the effect of hardening ductility parameters and softening ductility parameters of the concrete damage plastic model in LS-DYNA,a sensitivity and reliability analysis of these parameters through a convenient cube unit test was conducted. The results showed that the peak strength strain was independent of the hardening ductility parameter DH,but affected by AH,BH,and CH. The softening ductility was mainly related to the softening ductility parameter AS,but not affected by the damage ductility exponent BS. In case that the model with default parameters failed to match the AS-controlled damage softening phase,an optimized model with an AS correction was developed. The corrected model with the AS value of 2 matched well with the code model,and exhibited good feasibility in predicting the stress-strain curve of different grades of concrete. Moreover,the practicability of the corrected model was further validated by the conventional triaxial test. The simulated curve exhibited favorable consistence with the trial curve. Therefore,the model with parameter correction could provide a prospective reference for predicting the mechanical properties of concrete.
基金Partial financial support for Alexander Dummer and Thomas Mader by the Tyrolean Science Fund(TWF),Austria(Project Nos.F.18719 and F.18712)is gratefully acknowledged.
文摘In the present work,important aspects of time-dependent nonlinear 3D finite element(FE)models for deep tunnel advance by the New Austrian Tunneling Method(NATM),characterized by repeated sequences of excavation,securing,and idle periods,are discussed on the example of a 3D finite element model of a stretch of the Brenner Base Tunnel,which is currently constructed between Austria and Italy.Nonlinear material models are utilized for representing the surrounding rock mass and the shotcrete shell.Based on the finite element model,strategies for the efficient implementation into a parallel distributed memory numerical code are proposed.They are essential to achieve reasonable computation times for numerical simulations of tunneling based on large 3D FE models.In particular,the implementation of the construction procedure,parallel computing and communication specific details,and efficient linear solvers for the global equation system within the incremental-iterative Newton–Raphson scheme are addressed.Furthermore,possible extensions of the material models for rock mass and shotcrete,used in the 3D FE model,are presented.They concern(i)a gradient-enhanced model for transversely isotropic rock and rock mass,taking into account hardening and softening behavior and(ii)the extension of the shotcrete model to nonlinear creep and damage due to creep.The possible benefits of the model extensions in numerical simulations of tunneling by the NATM are discussed.
