Naturally deposited soils are always found in the complex three-dimensional stress state.Constitutive models developed for modeling the three-dimensional mechanical behavior of soils should obey the basic laws of ther...Naturally deposited soils are always found in the complex three-dimensional stress state.Constitutive models developed for modeling the three-dimensional mechanical behavior of soils should obey the basic laws of thermo-mechanical principles.Based on the incremental dissipation function,a new deviatoric shift stress is derived and then introduced into the existing constitutive models to describe the yield behavior in the deviatoric plane for geomaterials.By adopting the proposed shift stress,the relationship between dissipative stress tensors and true stress tensors can be established.Therefore,the threedimensional plastic strain can be calculated reasonably through the associated flow rule in the three-dimensional dissipative stress space.At the same time,three methods that are conventionally adopted for generalizing constitutive models to model the three-dimensional stress-strain relationships are examined under the thermo-mechanical framework.The TS(transformed stress)method is shown to obey the thermo-mechanical rules and the TS space adopted in TS method is actually a translational three-dimensional dissipative stress space.However,it is illustrated that the other two approaches,the method of using failure criterion directly and the method of using g()function,violate the basic rules of thermo-mechanical theories although they may bring convenience and simplicity to numerical analysis for geotechnical engineering.Comparison between model predictions and experimental data confirms the validity of the proposed three-dimensional dissipative stress space.展开更多
Over the past 2 decades,tight restriction has been imposed on strength criteria of concrete by the combination of plasticity and damage in one theory.The present study aims at constructing plastic/damage loading funct...Over the past 2 decades,tight restriction has been imposed on strength criteria of concrete by the combination of plasticity and damage in one theory.The present study aims at constructing plastic/damage loading functions for elastoplastic damage models for concrete that can perform more satisfactorily in 3D stress states.Numerous strength criteria of concrete are reorganized according to their simplest representations as Cartesian,cylindrical,mixed cylindrical-Cartesian,and other forms,and the homogeneity of loading functions discussed.It is found that under certain supplementary conditions from physical meanings,an unambiguous definition of the cohesion in a strength criterion,which is demanded in an elastoplastic damage model,is usually available in an explicit or implicit form,and in each case the loading function is still homogeneous.To apply and validate the presented theory,we construct the respective homogeneous damage and plastic loading functions and implant them into some widely used elastoplastic damage models for concrete,and their performances in triaxial compression prove to have improved significantly.展开更多
基金supported by the National Natural Science Foundation of China (Grants Nos. 11072016,51179003,11272031,51209002)
文摘Naturally deposited soils are always found in the complex three-dimensional stress state.Constitutive models developed for modeling the three-dimensional mechanical behavior of soils should obey the basic laws of thermo-mechanical principles.Based on the incremental dissipation function,a new deviatoric shift stress is derived and then introduced into the existing constitutive models to describe the yield behavior in the deviatoric plane for geomaterials.By adopting the proposed shift stress,the relationship between dissipative stress tensors and true stress tensors can be established.Therefore,the threedimensional plastic strain can be calculated reasonably through the associated flow rule in the three-dimensional dissipative stress space.At the same time,three methods that are conventionally adopted for generalizing constitutive models to model the three-dimensional stress-strain relationships are examined under the thermo-mechanical framework.The TS(transformed stress)method is shown to obey the thermo-mechanical rules and the TS space adopted in TS method is actually a translational three-dimensional dissipative stress space.However,it is illustrated that the other two approaches,the method of using failure criterion directly and the method of using g()function,violate the basic rules of thermo-mechanical theories although they may bring convenience and simplicity to numerical analysis for geotechnical engineering.Comparison between model predictions and experimental data confirms the validity of the proposed three-dimensional dissipative stress space.
基金supported by the National Natural Science Foundation of China-National Science Foundation Joint Project(Grant No.51261120374)the National Natural Science Foundation of China(Grant Nos.51108336 and 51378377)
文摘Over the past 2 decades,tight restriction has been imposed on strength criteria of concrete by the combination of plasticity and damage in one theory.The present study aims at constructing plastic/damage loading functions for elastoplastic damage models for concrete that can perform more satisfactorily in 3D stress states.Numerous strength criteria of concrete are reorganized according to their simplest representations as Cartesian,cylindrical,mixed cylindrical-Cartesian,and other forms,and the homogeneity of loading functions discussed.It is found that under certain supplementary conditions from physical meanings,an unambiguous definition of the cohesion in a strength criterion,which is demanded in an elastoplastic damage model,is usually available in an explicit or implicit form,and in each case the loading function is still homogeneous.To apply and validate the presented theory,we construct the respective homogeneous damage and plastic loading functions and implant them into some widely used elastoplastic damage models for concrete,and their performances in triaxial compression prove to have improved significantly.
