A numerical method was used in order to establish the constitutive relationship of sands under different stress paths, Firstly, based on the numerical method modeling the constitutive law of sands, the elastoplastic c...A numerical method was used in order to establish the constitutive relationship of sands under different stress paths, Firstly, based on the numerical method modeling the constitutive law of sands, the elastoplastic constitutive relationship of sand was established for three paths： the constant proportion of principle stress path, the conventional triaxial compression （CTC） path, and the p=constant （TC） path. The yield lines of plastic volumetric strain and plastic generalized shear strain were given. Through visualization, the three dimensional surface of the stress-strain relationship in the whole stress field （p, q） obtained under the three paths was plotted. Also, by comparing the stress-strain surfaces and yield locus of the three stress paths, the differences were found to be obvious, which demonstrates that the influence of the stress paths on constitutive law was not neglected. The numerical modeling method overcame the difficulty of finding an analytical expression for plastic potential. The results simulated the experimental data with an accuracy of 90% on average, so the constitutive model established in this paper provides an effective constitutive equation for this kind of engineering, reflecting the effect of practical stress paths that occur in sands.展开更多
Ten specimens were tested in this paper in order to study the bond behavior and the process of force transfer when bars adhered to mortar. The development of the bond stress between bars and mortar was calculated. Tes...Ten specimens were tested in this paper in order to study the bond behavior and the process of force transfer when bars adhered to mortar. The development of the bond stress between bars and mortar was calculated. Test results show that the maximum bond-stress is not influenced by the bar bond length and increases as the increased splitting strength of mortar for block. The local bond stress-slip curve was obtained. Then,based on the regressive analysis of test data,two bond shearing stress-slip constitutive models between bars and mortar were proposed. The models can be used in the numerical simulation or finite element analysis and provide references for the improvement of the corresponding design codes.展开更多
Engineered bamboo has recently received lots of attention of civil engineers and professional researchers due to its better mechanical performance than that of softwood timber.Parallel strand bamboo is one important p...Engineered bamboo has recently received lots of attention of civil engineers and professional researchers due to its better mechanical performance than that of softwood timber.Parallel strand bamboo is one important part of engineered bamboo for its excellent durable performance compared to the laminated veneer bamboo.The required curing temperature in hot-pressing process is usually higher than 120°C to reduce the content of nutri-tional ingredients and hemy cellulose,and to avoid the decay from the environment and insects.Nonetheless,the appearance of engineered bamboo gets darker with the increase of temperature during the hot-pressing process.In order to minimize the color deepening while maintaining the durability,a high-durable parallel strand bamboo(HPSB)with relative high hot-pressing temperature(140°C)was produced and tested.The present study inves-tigates the mechanical performance through tension,compression,shear and bending tests.The experimental behavior of the specimens was identified,including the failure mode and load-displacement relationship.It was demonstrated that the HPSB material had better mechanical performance parallel to grain,making it as a considerable structural material.The average elastic modulus parallel to grain was 14.1 GPa,and the tensile and compressive strengths were 120.7 MPa and 121.0 MPa,respectively.The tension perpendicular to grain should be avoided in the practical application due to the lower strength and elastic modulus.Two stress-strain relationships of tension and compression parallel to grain,including three-linear and quadratic function models,were proposed and compared with the experimental results.The three-linear model was then applied to the finite element model.The finite element analysis using ANSYS software was conducted to validate the feasibility of the constitutive relationship.The quadratic function model showed better agreement with the experimental results,but the three-linear relationship was also precise enough to analyze the bending tests of HPSB material,whereas being less accurate to describe the elastic-plastic compression behavior.展开更多
The mechanical properties of the sand of Takelamagan desert in Xinjiang under moving vehicle are studied by soil dynamic triaxial test apparatus. The nonlinear elastic constitutive model of the sand under moving vehic...The mechanical properties of the sand of Takelamagan desert in Xinjiang under moving vehicle are studied by soil dynamic triaxial test apparatus. The nonlinear elastic constitutive model of the sand under moving vehicle is established first. These results lay the foundations for studying the interaction between vehicle running gear and the sand of Takelamagan desert in Xinjiang. and developing sand vehicle.展开更多
The representative elementary watershed (REW) approach proposed by Reggiani et al. was the first attempt to develop scale adaptable equations applicable directly at the macro scale. Tian et al. extended the initial de...The representative elementary watershed (REW) approach proposed by Reggiani et al. was the first attempt to develop scale adaptable equations applicable directly at the macro scale. Tian et al. extended the initial definition of REW for simulating the energy related processes, and re-organized the deriving procedure of balance equations so that additional sub-regions and substances could be easily incorpo-rated. The resultant ordinary differential equation set can simulate various hydro-logical processes in a physically reasonable way. However, constitutive and geo-metric relationships have not been developed for Tian et al.'s equation set, which are necessary for the thermodynamic watershed hydrological model to apply in hydrological modeling practice. In this work, the constitutive equations for mass exchange terms and momentum exchange terms were developed as well as geo-metric relationships. The closed ordinary differential equation set with nine equa-tions was finally obtained.展开更多
为了探究单轴受压下石粉-钢渣混凝土的本构关系,根据正交试验方案配制了不同掺量钢渣砂(30%、40%、50%)、钢渣石(30%、40%、50%)、石粉(0%、7.5%、15%)的石粉-钢渣混凝土,对石粉-钢渣混凝土的应力-应变关系进行了实验研究,建立了单轴受...为了探究单轴受压下石粉-钢渣混凝土的本构关系,根据正交试验方案配制了不同掺量钢渣砂(30%、40%、50%)、钢渣石(30%、40%、50%)、石粉(0%、7.5%、15%)的石粉-钢渣混凝土,对石粉-钢渣混凝土的应力-应变关系进行了实验研究,建立了单轴受压下石粉-钢渣混凝土的本构关系模型。实验结果表明:当受到单轴压力时,石粉-钢渣混凝土的破坏模式与普通混凝土相似,表现出斜剪切的特征。石粉-钢渣混凝土峰值应力、峰值应变及弹性模量随着钢渣骨料掺量的增加而提高。为了更好地模拟无量纲应力-应变曲线,本工作采用了Carreira and Chu模型的上升段和过镇海模型的下降段进行了分段拟合。结果表明,实验曲线与分段模型曲线吻合较好。展开更多
Hardfill is a new type of artificially cemented material for dam construction works,with a wide application prospect.Its mechanical behavior lies between concrete and rockfill materials.A series of large-scale triaxia...Hardfill is a new type of artificially cemented material for dam construction works,with a wide application prospect.Its mechanical behavior lies between concrete and rockfill materials.A series of large-scale triaxial tests are performed on hardfill specimens at different ages,and the stress-strain behavior of hardfill is further discussed.The strength and stress-strain relationship of hardfill materials show both frictional mechanism and cohesive mechanism.An age-related constitutive model of hardfill is developed,which is a parallel model consisting of two components,rockfill component and cementation component.Moreover,a comparison is made between the simulated and the experimental results,which shows that the parallel model can reflect the mechanical characteristics of both rockfill-like nonlinearity and concrete-like age relativity.In addition,a simplified method for the determination of parameters is proposed.展开更多
To predict correctly the rut depths in asphalt pavements,a new nonlinear viscoelastic-elastoplastic constitutive model of permanent deformation in asphalt pave-ments is presented. The model combines a generalized Maxw...To predict correctly the rut depths in asphalt pavements,a new nonlinear viscoelastic-elastoplastic constitutive model of permanent deformation in asphalt pave-ments is presented. The model combines a generalized Maxwell model with an elasto-plastic one. Then from the creep theory,the linear and nonlinear constitutive equations of the generalized Maxwell model are obtained. From the nonlinear finite element method for the rutting of the asphalt pavement,the rut depths of 4 asphalt-aggregate mixtures are obtained. And the results are compared with the ones from the finite element method by SHRP and the experiments by SWK/UN. The results in this paper are better than the ones by SHRP,and agree with the ones of the experiment by SWK/UN. This shows that the nonlinear viscoelastic-elastoplastic constitutive model,which is presented in this paper for the rutting of the asphalt pavement,is effective. The properties,such as nonlinear elastic-ity,plasticity,viscoelasticity and nonlinear viscoelasticity,which affect the rutting of an asphalt pavement,can be shown in the model. And the characteristics of the permanent deformation of the asphalt pavement can be presented entirely in the model.展开更多
文摘A numerical method was used in order to establish the constitutive relationship of sands under different stress paths, Firstly, based on the numerical method modeling the constitutive law of sands, the elastoplastic constitutive relationship of sand was established for three paths： the constant proportion of principle stress path, the conventional triaxial compression （CTC） path, and the p=constant （TC） path. The yield lines of plastic volumetric strain and plastic generalized shear strain were given. Through visualization, the three dimensional surface of the stress-strain relationship in the whole stress field （p, q） obtained under the three paths was plotted. Also, by comparing the stress-strain surfaces and yield locus of the three stress paths, the differences were found to be obvious, which demonstrates that the influence of the stress paths on constitutive law was not neglected. The numerical modeling method overcame the difficulty of finding an analytical expression for plastic potential. The results simulated the experimental data with an accuracy of 90% on average, so the constitutive model established in this paper provides an effective constitutive equation for this kind of engineering, reflecting the effect of practical stress paths that occur in sands.
基金Sponsored by the National Science and Technology Pillar Program during the 11th Five-Year Plan Period of China(Grant No. 2009BAK58B03-03 and 2006BAJ03A01-05)the Key Laboratory of Structural Engineering of Shenyang Jianzhu University,China(Grant No. JG200705)the Science & Re-search Program of Shenyang,China(Grant No. 1091064-A-00)
文摘Ten specimens were tested in this paper in order to study the bond behavior and the process of force transfer when bars adhered to mortar. The development of the bond stress between bars and mortar was calculated. Test results show that the maximum bond-stress is not influenced by the bar bond length and increases as the increased splitting strength of mortar for block. The local bond stress-slip curve was obtained. Then,based on the regressive analysis of test data,two bond shearing stress-slip constitutive models between bars and mortar were proposed. The models can be used in the numerical simulation or finite element analysis and provide references for the improvement of the corresponding design codes.
基金The authors acknowledge funding supported by the Fundamental Research Funds for the Central Universities of China(No.BLX201706)supported by Major Science and Technology Program for Water Pollution Control and Treatment(No.2017ZX07102-001)supported by the National Natural Science Foundation of China(Nos.51908038 and 31770602)。
文摘Engineered bamboo has recently received lots of attention of civil engineers and professional researchers due to its better mechanical performance than that of softwood timber.Parallel strand bamboo is one important part of engineered bamboo for its excellent durable performance compared to the laminated veneer bamboo.The required curing temperature in hot-pressing process is usually higher than 120°C to reduce the content of nutri-tional ingredients and hemy cellulose,and to avoid the decay from the environment and insects.Nonetheless,the appearance of engineered bamboo gets darker with the increase of temperature during the hot-pressing process.In order to minimize the color deepening while maintaining the durability,a high-durable parallel strand bamboo(HPSB)with relative high hot-pressing temperature(140°C)was produced and tested.The present study inves-tigates the mechanical performance through tension,compression,shear and bending tests.The experimental behavior of the specimens was identified,including the failure mode and load-displacement relationship.It was demonstrated that the HPSB material had better mechanical performance parallel to grain,making it as a considerable structural material.The average elastic modulus parallel to grain was 14.1 GPa,and the tensile and compressive strengths were 120.7 MPa and 121.0 MPa,respectively.The tension perpendicular to grain should be avoided in the practical application due to the lower strength and elastic modulus.Two stress-strain relationships of tension and compression parallel to grain,including three-linear and quadratic function models,were proposed and compared with the experimental results.The three-linear model was then applied to the finite element model.The finite element analysis using ANSYS software was conducted to validate the feasibility of the constitutive relationship.The quadratic function model showed better agreement with the experimental results,but the three-linear relationship was also precise enough to analyze the bending tests of HPSB material,whereas being less accurate to describe the elastic-plastic compression behavior.
文摘The mechanical properties of the sand of Takelamagan desert in Xinjiang under moving vehicle are studied by soil dynamic triaxial test apparatus. The nonlinear elastic constitutive model of the sand under moving vehicle is established first. These results lay the foundations for studying the interaction between vehicle running gear and the sand of Takelamagan desert in Xinjiang. and developing sand vehicle.
基金the National Natural Science Foundation of China (Grant No. 50509013)
文摘The representative elementary watershed (REW) approach proposed by Reggiani et al. was the first attempt to develop scale adaptable equations applicable directly at the macro scale. Tian et al. extended the initial definition of REW for simulating the energy related processes, and re-organized the deriving procedure of balance equations so that additional sub-regions and substances could be easily incorpo-rated. The resultant ordinary differential equation set can simulate various hydro-logical processes in a physically reasonable way. However, constitutive and geo-metric relationships have not been developed for Tian et al.'s equation set, which are necessary for the thermodynamic watershed hydrological model to apply in hydrological modeling practice. In this work, the constitutive equations for mass exchange terms and momentum exchange terms were developed as well as geo-metric relationships. The closed ordinary differential equation set with nine equa-tions was finally obtained.
文摘为了探究单轴受压下石粉-钢渣混凝土的本构关系,根据正交试验方案配制了不同掺量钢渣砂(30%、40%、50%)、钢渣石(30%、40%、50%)、石粉(0%、7.5%、15%)的石粉-钢渣混凝土,对石粉-钢渣混凝土的应力-应变关系进行了实验研究,建立了单轴受压下石粉-钢渣混凝土的本构关系模型。实验结果表明:当受到单轴压力时,石粉-钢渣混凝土的破坏模式与普通混凝土相似,表现出斜剪切的特征。石粉-钢渣混凝土峰值应力、峰值应变及弹性模量随着钢渣骨料掺量的增加而提高。为了更好地模拟无量纲应力-应变曲线,本工作采用了Carreira and Chu模型的上升段和过镇海模型的下降段进行了分段拟合。结果表明,实验曲线与分段模型曲线吻合较好。
基金supported partially by the National Natural Science Foundation of China (Grant No. 10932012)the China-Europe Science and Technology Cooperation Program (Grant No. 0820)European Commission (Grant No. FP7-NMP-2007-LARGE-1)
文摘Hardfill is a new type of artificially cemented material for dam construction works,with a wide application prospect.Its mechanical behavior lies between concrete and rockfill materials.A series of large-scale triaxial tests are performed on hardfill specimens at different ages,and the stress-strain behavior of hardfill is further discussed.The strength and stress-strain relationship of hardfill materials show both frictional mechanism and cohesive mechanism.An age-related constitutive model of hardfill is developed,which is a parallel model consisting of two components,rockfill component and cementation component.Moreover,a comparison is made between the simulated and the experimental results,which shows that the parallel model can reflect the mechanical characteristics of both rockfill-like nonlinearity and concrete-like age relativity.In addition,a simplified method for the determination of parameters is proposed.
文摘To predict correctly the rut depths in asphalt pavements,a new nonlinear viscoelastic-elastoplastic constitutive model of permanent deformation in asphalt pave-ments is presented. The model combines a generalized Maxwell model with an elasto-plastic one. Then from the creep theory,the linear and nonlinear constitutive equations of the generalized Maxwell model are obtained. From the nonlinear finite element method for the rutting of the asphalt pavement,the rut depths of 4 asphalt-aggregate mixtures are obtained. And the results are compared with the ones from the finite element method by SHRP and the experiments by SWK/UN. The results in this paper are better than the ones by SHRP,and agree with the ones of the experiment by SWK/UN. This shows that the nonlinear viscoelastic-elastoplastic constitutive model,which is presented in this paper for the rutting of the asphalt pavement,is effective. The properties,such as nonlinear elastic-ity,plasticity,viscoelasticity and nonlinear viscoelasticity,which affect the rutting of an asphalt pavement,can be shown in the model. And the characteristics of the permanent deformation of the asphalt pavement can be presented entirely in the model.
