in order to evaluate the capacity of reinforced concrete （RC） structures subjected to blast Ioadings, the damaged plasticity model for concrete was used in the analysis of the dynamic responses of blast-loaded RC st...in order to evaluate the capacity of reinforced concrete （RC） structures subjected to blast Ioadings, the damaged plasticity model for concrete was used in the analysis of the dynamic responses of blast-loaded RC structures, and all three failure modes were numerically simulated by the finite element software ABAQUS. Simulation results agree with the experimental observations. It is demonstrated that the damaged plasticity model for concrete in the finite element software ABAQUS can predict dynamic responses and typical flexure, flexure-shear and direct shear failure modes of the blast-loaded RC structures.展开更多
A conventional method of damage modeling by a reduction in stiffness is insufficient to model the complex non-linear damage characteristics of concrete material accurately.In this research,the concrete damage plastici...A conventional method of damage modeling by a reduction in stiffness is insufficient to model the complex non-linear damage characteristics of concrete material accurately.In this research,the concrete damage plasticity constitutive model is used to develop the numerical model of a deck beam on a berthing jetty in the Abaqus finite element package.The model constitutes a solid section of 3D hexahedral brick elements for concrete material embedded with 2D quadrilateral surface elements as reinforcements.The model was validated against experimental results of a beam of comparable dimensions in a cited literature.The validated beam model is then used in a three-point load test configuration to demonstrate its applicability for preliminary numerical evaluation of damage detection strategy in marine concrete structural health monitoring.The natural frequency was identified to detect the presence of damage and mode shape curvature was found sensitive to the location of damage.展开更多
Some of the current concrete damage plasticity models in the literature employ a single damage variable for both the tension and compression regimes,while a few more advanced models employ two damage variables.Models ...Some of the current concrete damage plasticity models in the literature employ a single damage variable for both the tension and compression regimes,while a few more advanced models employ two damage variables.Models with a single variable have an inherent dificulty in accounting for the damage accrued due to tensile and compressive actions in appropriately different manners,and their mutual dependencies.In the current models that adopt two damage variables,the independence of these damage variables during cyclic loading results in the failure to capture the effects of tensile damage on the compressive behavior of concrete and vice-versa.This study presents a cyclic model established by extending an existing monotonic constitutive model.The model describes the cyclic behavior of concrete under multiaxial loading conditions and considers the influence of tensile/compressive damage on the compressive/tensile response.The proposed model,dubbed the enhanced concrete damage plasticity model(ECDPM),is an extension of an existing model that combines the theories of classical plasticity and continuum damage mechanics.Unlike most prior studies on models in the same category,the performance of the proposed ECDPM is evaluated using experimental data on concrete specimens at the material level obtained under cyclic multiaxial loading conditions including uniaxial tension and confined compression.The performance of the model is observed to be satisfactory.Furthermore,the superiority of ECDPM over three previously proposed constitutive models is demonstrated through comparisons with the results of a uniaxial tension-compression test and a virtual test.展开更多
A combined dam structure using different concrete materials offers many practical benefits.There are several real-world cases where largevolume heterogeneous concrete materials have been used together.From the enginee...A combined dam structure using different concrete materials offers many practical benefits.There are several real-world cases where largevolume heterogeneous concrete materials have been used together.From the engineering design standpoint,it is crucial to understand the deformation coordination characteristics and mechanical properties of large-volume heterogeneous concrete,which affect dam safety and stability.In this study,a large dam facility was selected for a case study,and various design schemes of the combined dam structure were developed by changing the configurations of material zoning and material types for a given dam shape.Elastoplastic analysis of the damfoundation-reservoir system for six schemes was carried out under dynamic conditions,in which the concrete damaged plasticity(CDP)model,the Lagrangian finite element formulation,and a surface-to-surface contact model were utilized.To evaluate the mechanical properties of zoning interfaces and coordination characteristics,the vertical distribution of the first principal stress at the longitudinal joint was used as the critical index of deformation coordination control,and the overall deformation and damage characteristics of the dam were also investigated.Through a comparative study of the design schemes,an optimal scheme of the combined dam structure was identified:large-volume roller-compacted concrete(RCC)is recommended for the dam body upstream of the longitudinal joint,and high-volume fly ash conventional concrete(CC)for the dam body downstream of the longitudinal joint.This study provides engineers with a reference basis for combined dam structure design.展开更多
The bonding quality of the cement sheath interface decreases during well completion because of the change in the casing pressure.To explore the root cause of such phenomena,experiments on the mechanical properties and...The bonding quality of the cement sheath interface decreases during well completion because of the change in the casing pressure.To explore the root cause of such phenomena,experiments on the mechanical properties and interface bonding strength of a cement sheath have been carried out taking the LS25-1 high-temperature and high-pressure(HTHP)gas field as an example.Moreover,a constitutive model of the cement sheath has been defined and verified both by means of a full-scale HTHP cement sheath sealing integrity evaluation experiment and three-dimensional finite element simulations.The results show that the low initial cementing surface strength is the root cause of cement sheath interface bonding failure.When the pressure in the casing exceeds a certain limit,the stress caused by the change in the internal pressure in the casing is transmitted to the cement sheath,resulting in the degradation of the interface stiffness of the cement sheath.However,with an increase in the casing wall thickness,the stress transmission capacity decreases.Therefore,it is concluded that improving the interfacial cementing strength,appropriately increasing the casing wall thickness and increasing the initial stress of the cement sheath are the keys to ensuring the sealing integrity of the cement sheath in high-temperature and high-pressure gas wells.展开更多
基金Supported by National Natural Science Foundation of China (No.50638030 and 50525825)National Science and Technology Support Program (No.2006BAJ13B02).
文摘in order to evaluate the capacity of reinforced concrete （RC） structures subjected to blast Ioadings, the damaged plasticity model for concrete was used in the analysis of the dynamic responses of blast-loaded RC structures, and all three failure modes were numerically simulated by the finite element software ABAQUS. Simulation results agree with the experimental observations. It is demonstrated that the damaged plasticity model for concrete in the finite element software ABAQUS can predict dynamic responses and typical flexure, flexure-shear and direct shear failure modes of the blast-loaded RC structures.
文摘A conventional method of damage modeling by a reduction in stiffness is insufficient to model the complex non-linear damage characteristics of concrete material accurately.In this research,the concrete damage plasticity constitutive model is used to develop the numerical model of a deck beam on a berthing jetty in the Abaqus finite element package.The model constitutes a solid section of 3D hexahedral brick elements for concrete material embedded with 2D quadrilateral surface elements as reinforcements.The model was validated against experimental results of a beam of comparable dimensions in a cited literature.The validated beam model is then used in a three-point load test configuration to demonstrate its applicability for preliminary numerical evaluation of damage detection strategy in marine concrete structural health monitoring.The natural frequency was identified to detect the presence of damage and mode shape curvature was found sensitive to the location of damage.
基金The authors acknowledge the financial support of this study by the Austrian Marshall Plan Foundation,which funded the first author's short-term visit to UCLA during the course of this study.
文摘Some of the current concrete damage plasticity models in the literature employ a single damage variable for both the tension and compression regimes,while a few more advanced models employ two damage variables.Models with a single variable have an inherent dificulty in accounting for the damage accrued due to tensile and compressive actions in appropriately different manners,and their mutual dependencies.In the current models that adopt two damage variables,the independence of these damage variables during cyclic loading results in the failure to capture the effects of tensile damage on the compressive behavior of concrete and vice-versa.This study presents a cyclic model established by extending an existing monotonic constitutive model.The model describes the cyclic behavior of concrete under multiaxial loading conditions and considers the influence of tensile/compressive damage on the compressive/tensile response.The proposed model,dubbed the enhanced concrete damage plasticity model(ECDPM),is an extension of an existing model that combines the theories of classical plasticity and continuum damage mechanics.Unlike most prior studies on models in the same category,the performance of the proposed ECDPM is evaluated using experimental data on concrete specimens at the material level obtained under cyclic multiaxial loading conditions including uniaxial tension and confined compression.The performance of the model is observed to be satisfactory.Furthermore,the superiority of ECDPM over three previously proposed constitutive models is demonstrated through comparisons with the results of a uniaxial tension-compression test and a virtual test.
基金supported by the National Natural Science Foundation of China(Grant No.51879185)the Fund of the National Dam Safety Research Center(Grant No.CX2019B02).
文摘A combined dam structure using different concrete materials offers many practical benefits.There are several real-world cases where largevolume heterogeneous concrete materials have been used together.From the engineering design standpoint,it is crucial to understand the deformation coordination characteristics and mechanical properties of large-volume heterogeneous concrete,which affect dam safety and stability.In this study,a large dam facility was selected for a case study,and various design schemes of the combined dam structure were developed by changing the configurations of material zoning and material types for a given dam shape.Elastoplastic analysis of the damfoundation-reservoir system for six schemes was carried out under dynamic conditions,in which the concrete damaged plasticity(CDP)model,the Lagrangian finite element formulation,and a surface-to-surface contact model were utilized.To evaluate the mechanical properties of zoning interfaces and coordination characteristics,the vertical distribution of the first principal stress at the longitudinal joint was used as the critical index of deformation coordination control,and the overall deformation and damage characteristics of the dam were also investigated.Through a comparative study of the design schemes,an optimal scheme of the combined dam structure was identified:large-volume roller-compacted concrete(RCC)is recommended for the dam body upstream of the longitudinal joint,and high-volume fly ash conventional concrete(CC)for the dam body downstream of the longitudinal joint.This study provides engineers with a reference basis for combined dam structure design.
基金The authors gratefully acknowledge the CNOOC scientific research project“Study of risk assessment and countermeasures of well drilling and completion under ultrahigh temperature and high pressure”and“Research on development feasibility of LS25-1 gas field”(Grant Nos.YXKY-ZX-09-2021,2020FS-08).
文摘The bonding quality of the cement sheath interface decreases during well completion because of the change in the casing pressure.To explore the root cause of such phenomena,experiments on the mechanical properties and interface bonding strength of a cement sheath have been carried out taking the LS25-1 high-temperature and high-pressure(HTHP)gas field as an example.Moreover,a constitutive model of the cement sheath has been defined and verified both by means of a full-scale HTHP cement sheath sealing integrity evaluation experiment and three-dimensional finite element simulations.The results show that the low initial cementing surface strength is the root cause of cement sheath interface bonding failure.When the pressure in the casing exceeds a certain limit,the stress caused by the change in the internal pressure in the casing is transmitted to the cement sheath,resulting in the degradation of the interface stiffness of the cement sheath.However,with an increase in the casing wall thickness,the stress transmission capacity decreases.Therefore,it is concluded that improving the interfacial cementing strength,appropriately increasing the casing wall thickness and increasing the initial stress of the cement sheath are the keys to ensuring the sealing integrity of the cement sheath in high-temperature and high-pressure gas wells.
