The mechanical behavior of plastic concrete used in the cut-off walls of earth dams has been studied. Triaxial compression tests on the specimens in various ages and mix designs under different confining pressures hav...The mechanical behavior of plastic concrete used in the cut-off walls of earth dams has been studied. Triaxial compression tests on the specimens in various ages and mix designs under different confining pressures have been done and the stress-strain behavior of such materials and their strength parameter changes have been experimentally investigated. It has been observed that increasing the confining pressures applied on the specimens causes the material behavior to be alike the more ductile materials and the compressive strength increases considerably as well. Moreover, a parametric study has been carded out to investigate the influence of essential parameters on the shear strength parameters of these materials. According to the research, increasing the coarse to fine aggregates ratio leads to the increase of compressive strength of the specimens as well as the increase of the cohesion and internal friction angle of the materials. Furthermore, the bentonite content decrease and the cement factor increase result in an increase of the cohesion parameter of plastic concretes and decrease of the internal friction angle of such materials.展开更多
Split Hopkinson Pressure Bar(SHPB) test was simulated to investigate the distribution of the first principal stress and damage zone of specimen subjected to dynamic compressive load. Numerical models of plate-type spe...Split Hopkinson Pressure Bar(SHPB) test was simulated to investigate the distribution of the first principal stress and damage zone of specimen subjected to dynamic compressive load. Numerical models of plate-type specimen containing cracks with inclined angles of 0°,45° and 90° were also established to investigate the crack propagation and damage evolution under dynamic loading. The results show that the simulation results are in accordance with the failure patterns of specimens in experimental test. The interactions between stress wave and crack with different inclined angles are different; damage usually appears around the crack tips firstly; and then more damage zones develop away from the foregoing damage zone after a period of energy accumulation; eventually,the damage zones run through the specimen in the direction of applied loading and split the specimen into pieces.展开更多
The static tests of nine traditional and bird beak square hollow structure(SHS) T-joints with different β values and connection types under axial compression at brace end were carried out. Experimental test schemes, ...The static tests of nine traditional and bird beak square hollow structure(SHS) T-joints with different β values and connection types under axial compression at brace end were carried out. Experimental test schemes, failure modes of specimens, jack load-vertical displacement curves, jack load-deformation of chord and strain intensity distribution curves of joints were presented. The effects of β and connection types on axial compression property of joints were studied. The results show that the ultimate axial compression capacity of common bird beak SHS T-joints and diamond bird beak SHS T-joints is larger than that of traditional SHS T-joint specimens with big values of β. The ultimate axial compression capacity of diamond bird beak SHS T-joints is larger than that of common bird beak SHS T-joints. As β increases, the increase of the ultimate axial compression capacity of diamond bird beak SHS T-joints over that of common bird beak joints grows. The ultimate axial compression capacity and the initial axial stiffness of all kinds of joints increase as β increases, and the initial axial stiffness of the diamond bird beak SHS T-joints is the largest. The ductilities of common bird beak and diamond bird beak SHS T-joints increase as β increases, but the ductility of the traditional SHS T-joints decreases as β increases.展开更多
The RMB-150B rock mechanics test system was employed to obtain the complete stress-strain test curves under confining pressures of 0-30MPa for marble samples from Ya'an ,Sichuan province. On the basis of former st...The RMB-150B rock mechanics test system was employed to obtain the complete stress-strain test curves under confining pressures of 0-30MPa for marble samples from Ya'an ,Sichuan province. On the basis of former study and the convention triaxial pressure test results ,the complete procedures curves which described the relationships between yielding strength、 peak strength、 residual strength and confining pressure was obtained. Taking the strain softening of rock into account, the bilinear elastic-linear softening-residual perfect plasticity four-linear model was put forward in this paper on the basis of the test results and theory of plasticity. This model was adopted to describe the behaviors of marble in different phases under triaxial compression with the constitutive equation of strain softening phase as focus. The results indicated that the theoretic model fitted in well with the test results.展开更多
在环境腐蚀介质作用下,普通碳钢管混凝土柱构件的承载力和延性会出现明显的下降,从而危害整个结构体系的安全。为了使钢管混凝土柱在耐腐蚀、承载力和延性方面具有更好的表现,本文提出采用双相型不锈钢管超高性能混凝土柱(UFSST)代替普...在环境腐蚀介质作用下,普通碳钢管混凝土柱构件的承载力和延性会出现明显的下降,从而危害整个结构体系的安全。为了使钢管混凝土柱在耐腐蚀、承载力和延性方面具有更好的表现,本文提出采用双相型不锈钢管超高性能混凝土柱(UFSST)代替普通碳钢管混凝土柱,并对12根矩形短柱试件进行轴心受压试验。通过对试件破坏模式、荷载-位移曲线和荷载-应变行为规律的研究,讨论了3种混凝土强度等级和3种钢管壁厚对矩形UFSST短柱试件轴压承载力性能影响,以及双相不锈钢与超高性能混凝土(UHPC)之间的相互作用。结果表明:矩形UFSST短柱试件破坏模式可分为腰鼓屈曲和剪切破坏,两类破坏均具有良好的变形能力;试件极限承载力随钢管壁厚和混凝土强度增加而提升,钢管约束效应使试件荷载在峰值后随轴向位移增加仍保持相对平稳发展。对比试验结果与现行规范承载力设计公式计算结果发现:在未考虑钢管约束效应的规范中,欧洲规范BS EN 1994-1-1计算结果均值与试验结果最接近且偏于安全,可直接用于矩形UFSST短柱承载力估算;考虑了钢管约束效应的中国技术规程T/CECS 952—2021承载力公式计算结果偏于不安全。基于矩形钢管对混凝土的非均匀约束作用,对中国技术规程T/CECS 952—2021公式进行了修正,修正公式的计算结果与试验结果吻合较好,可用于矩形UFSST短柱承载力估算。展开更多
文摘The mechanical behavior of plastic concrete used in the cut-off walls of earth dams has been studied. Triaxial compression tests on the specimens in various ages and mix designs under different confining pressures have been done and the stress-strain behavior of such materials and their strength parameter changes have been experimentally investigated. It has been observed that increasing the confining pressures applied on the specimens causes the material behavior to be alike the more ductile materials and the compressive strength increases considerably as well. Moreover, a parametric study has been carded out to investigate the influence of essential parameters on the shear strength parameters of these materials. According to the research, increasing the coarse to fine aggregates ratio leads to the increase of compressive strength of the specimens as well as the increase of the cohesion and internal friction angle of the materials. Furthermore, the bentonite content decrease and the cement factor increase result in an increase of the cohesion parameter of plastic concretes and decrease of the internal friction angle of such materials.
基金Projects(50534030, 50674107, 50490274) supported by the National Natural Science Foundation of ChinaProject(06JJ3028) supported by the Provincial Natural Science Foundation of Hunan, China
文摘Split Hopkinson Pressure Bar(SHPB) test was simulated to investigate the distribution of the first principal stress and damage zone of specimen subjected to dynamic compressive load. Numerical models of plate-type specimen containing cracks with inclined angles of 0°,45° and 90° were also established to investigate the crack propagation and damage evolution under dynamic loading. The results show that the simulation results are in accordance with the failure patterns of specimens in experimental test. The interactions between stress wave and crack with different inclined angles are different; damage usually appears around the crack tips firstly; and then more damage zones develop away from the foregoing damage zone after a period of energy accumulation; eventually,the damage zones run through the specimen in the direction of applied loading and split the specimen into pieces.
基金Projects(51278209,51478047)supported by the National Natural Science Foundation of ChinaProject(2014FJ-NCET-ZR03)supported by the Program for New Century Excellent Talents in Fujian Provincial Universities,China+1 种基金Project(JA13005)supported by the Incubation Program for Excellent Young Science and Technology Talents in Fujian Provincial Universities,ChinaProject(ZQN-PY110)supported by the Young and Middle-aged Academic Staff of Huaqiao University,China
文摘The static tests of nine traditional and bird beak square hollow structure(SHS) T-joints with different β values and connection types under axial compression at brace end were carried out. Experimental test schemes, failure modes of specimens, jack load-vertical displacement curves, jack load-deformation of chord and strain intensity distribution curves of joints were presented. The effects of β and connection types on axial compression property of joints were studied. The results show that the ultimate axial compression capacity of common bird beak SHS T-joints and diamond bird beak SHS T-joints is larger than that of traditional SHS T-joint specimens with big values of β. The ultimate axial compression capacity of diamond bird beak SHS T-joints is larger than that of common bird beak SHS T-joints. As β increases, the increase of the ultimate axial compression capacity of diamond bird beak SHS T-joints over that of common bird beak joints grows. The ultimate axial compression capacity and the initial axial stiffness of all kinds of joints increase as β increases, and the initial axial stiffness of the diamond bird beak SHS T-joints is the largest. The ductilities of common bird beak and diamond bird beak SHS T-joints increase as β increases, but the ductility of the traditional SHS T-joints decreases as β increases.
文摘The RMB-150B rock mechanics test system was employed to obtain the complete stress-strain test curves under confining pressures of 0-30MPa for marble samples from Ya'an ,Sichuan province. On the basis of former study and the convention triaxial pressure test results ,the complete procedures curves which described the relationships between yielding strength、 peak strength、 residual strength and confining pressure was obtained. Taking the strain softening of rock into account, the bilinear elastic-linear softening-residual perfect plasticity four-linear model was put forward in this paper on the basis of the test results and theory of plasticity. This model was adopted to describe the behaviors of marble in different phases under triaxial compression with the constitutive equation of strain softening phase as focus. The results indicated that the theoretic model fitted in well with the test results.
文摘在环境腐蚀介质作用下,普通碳钢管混凝土柱构件的承载力和延性会出现明显的下降,从而危害整个结构体系的安全。为了使钢管混凝土柱在耐腐蚀、承载力和延性方面具有更好的表现,本文提出采用双相型不锈钢管超高性能混凝土柱(UFSST)代替普通碳钢管混凝土柱,并对12根矩形短柱试件进行轴心受压试验。通过对试件破坏模式、荷载-位移曲线和荷载-应变行为规律的研究,讨论了3种混凝土强度等级和3种钢管壁厚对矩形UFSST短柱试件轴压承载力性能影响,以及双相不锈钢与超高性能混凝土(UHPC)之间的相互作用。结果表明:矩形UFSST短柱试件破坏模式可分为腰鼓屈曲和剪切破坏,两类破坏均具有良好的变形能力;试件极限承载力随钢管壁厚和混凝土强度增加而提升,钢管约束效应使试件荷载在峰值后随轴向位移增加仍保持相对平稳发展。对比试验结果与现行规范承载力设计公式计算结果发现:在未考虑钢管约束效应的规范中,欧洲规范BS EN 1994-1-1计算结果均值与试验结果最接近且偏于安全,可直接用于矩形UFSST短柱承载力估算;考虑了钢管约束效应的中国技术规程T/CECS 952—2021承载力公式计算结果偏于不安全。基于矩形钢管对混凝土的非均匀约束作用,对中国技术规程T/CECS 952—2021公式进行了修正,修正公式的计算结果与试验结果吻合较好,可用于矩形UFSST短柱承载力估算。
