Achievements are presented for truss models of RC structures developed in previous years: 1. Two constitutive models, biaxial and triaxial, are based on regular trusses, with bars obeying nonlinear uniaxial σ-ε laws...Achievements are presented for truss models of RC structures developed in previous years: 1. Two constitutive models, biaxial and triaxial, are based on regular trusses, with bars obeying nonlinear uniaxial σ-ε laws of material under simulation;both models have been compared with test results and show a dependence of Poisson ratio on curvature of σ-ε law. 2. A truss finite element has been used in the nonlinear static and dynamic analysis of plane RC frames;it has been compared with test results and describes, in a simple way, the formation of plastic hinges. 3. Thanks to the very simple geometry of a truss, the equilibrium equations can be easily written and the stiffness matrix can be easily updated, both with respect to the deformed truss, within each step of a static incremental loading or within each time step of a dynamic analysis, so that to take into account geometric nonlinearities. So the confinement of a RC column is interpreted as a structural stability effect of concrete. And a significant role of the transverse reinforcement is revealed, that of preventing, by its close spacing and sufficient amount, the buckling of inner longitudinal concrete struts, which would lead to a global instability of the RC column. 4. The proposed truss model is statically indeterminate, so it exhibits some features, which are not met by the “strut-and-tie” model.展开更多
There are many cracked concrete structures worldwide. Although there have been numerous efforts to eliminate cracks, some cracks are very harmful and should be repaired as soon as possible. On the other hand, some cra...There are many cracked concrete structures worldwide. Although there have been numerous efforts to eliminate cracks, some cracks are very harmful and should be repaired as soon as possible. On the other hand, some cracks are almost harmless. So, a good guideline regarding how to deal with cracks in concrete structures is needed. In this guideline, the practical investigation, repair and strengthening method of cracked concrete structures is discussed. And the detecting subjects are cracks generated immediately after casting and during the service time. This guideline targets on the owners （including managers） of concrete structure and the engineers working for the maintenance of concrete structure. JCI （Japan Concrete Institute） published first version of ＂Practical Guideline for Investigation and Repair of Cracked Concrete Structures＂ in 1980, and then the fourth version titled ＂Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures--2009＂ was published. This guideline is very practical when cracks are observed in existing concrete structures, in any other countries as well as in Japan. These three authors led the establishment of this guideline.展开更多
There are many cracked concrete structures, although there have been numerous efforts to eliminate cracks. Some cracks are very harmful and should be repaired as soon as possible. On the other hand, the other cracks a...There are many cracked concrete structures, although there have been numerous efforts to eliminate cracks. Some cracks are very harmful and should be repaired as soon as possible. On the other hand, the other cracks are almost harmless. So, a good guideline about how to deal with cracks in concrete structures had been needed. JCI （Japan Concrete Institute） published the first version of ＂Practical Guideline for Investigation and Repair of Cracked Concrete Structures＂ in 1980, the second version in 1987, the third version in 2003, and then the fourth version titled ＂Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures-2009＂ was published. This Guideline is very practical, when cracks are observed in existed concrete structures, in any other countries as well as in Japan.展开更多
Pulse-prepump Brillouin optical time domain analysis (PPP-BOTDA) is a novel technique for distributed strain measurements, in which a pre-pump pulse is inputted in front of the measuring pump pulse to stimulate the ph...Pulse-prepump Brillouin optical time domain analysis (PPP-BOTDA) is a novel technique for distributed strain measurements, in which a pre-pump pulse is inputted in front of the measuring pump pulse to stimulate the phonon, so that higher spatial resolution and measurement precision can be obtained. Principle, methodologies and technical parameters of the PPP-BOTDA are presented and the influence of temperature on measurements is discussed. Applications are made in the bond test of steel rebars and the bending test of concrete girders. Test results show that the PPP-BOTDA can provide a precise description on the strain distribution of steel rebar and concrete, exhibiting the ability for crack detection. Moreover, structural deformation can be obtained indirectly by accumulating the distributed strains along the optical fiber, thus the deflection curves of the concrete girder during the loading process are obtained. Suggestions with regards to the application of the PPP-BOTDA in strain measurements and crack monitoring for civil infrastructures are given.展开更多
文摘Achievements are presented for truss models of RC structures developed in previous years: 1. Two constitutive models, biaxial and triaxial, are based on regular trusses, with bars obeying nonlinear uniaxial σ-ε laws of material under simulation;both models have been compared with test results and show a dependence of Poisson ratio on curvature of σ-ε law. 2. A truss finite element has been used in the nonlinear static and dynamic analysis of plane RC frames;it has been compared with test results and describes, in a simple way, the formation of plastic hinges. 3. Thanks to the very simple geometry of a truss, the equilibrium equations can be easily written and the stiffness matrix can be easily updated, both with respect to the deformed truss, within each step of a static incremental loading or within each time step of a dynamic analysis, so that to take into account geometric nonlinearities. So the confinement of a RC column is interpreted as a structural stability effect of concrete. And a significant role of the transverse reinforcement is revealed, that of preventing, by its close spacing and sufficient amount, the buckling of inner longitudinal concrete struts, which would lead to a global instability of the RC column. 4. The proposed truss model is statically indeterminate, so it exhibits some features, which are not met by the “strut-and-tie” model.
文摘There are many cracked concrete structures worldwide. Although there have been numerous efforts to eliminate cracks, some cracks are very harmful and should be repaired as soon as possible. On the other hand, some cracks are almost harmless. So, a good guideline regarding how to deal with cracks in concrete structures is needed. In this guideline, the practical investigation, repair and strengthening method of cracked concrete structures is discussed. And the detecting subjects are cracks generated immediately after casting and during the service time. This guideline targets on the owners （including managers） of concrete structure and the engineers working for the maintenance of concrete structure. JCI （Japan Concrete Institute） published first version of ＂Practical Guideline for Investigation and Repair of Cracked Concrete Structures＂ in 1980, and then the fourth version titled ＂Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures--2009＂ was published. This guideline is very practical when cracks are observed in existing concrete structures, in any other countries as well as in Japan. These three authors led the establishment of this guideline.
文摘There are many cracked concrete structures, although there have been numerous efforts to eliminate cracks. Some cracks are very harmful and should be repaired as soon as possible. On the other hand, the other cracks are almost harmless. So, a good guideline about how to deal with cracks in concrete structures had been needed. JCI （Japan Concrete Institute） published the first version of ＂Practical Guideline for Investigation and Repair of Cracked Concrete Structures＂ in 1980, the second version in 1987, the third version in 2003, and then the fourth version titled ＂Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures-2009＂ was published. This Guideline is very practical, when cracks are observed in existed concrete structures, in any other countries as well as in Japan.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 50608017, 50725828)
文摘Pulse-prepump Brillouin optical time domain analysis (PPP-BOTDA) is a novel technique for distributed strain measurements, in which a pre-pump pulse is inputted in front of the measuring pump pulse to stimulate the phonon, so that higher spatial resolution and measurement precision can be obtained. Principle, methodologies and technical parameters of the PPP-BOTDA are presented and the influence of temperature on measurements is discussed. Applications are made in the bond test of steel rebars and the bending test of concrete girders. Test results show that the PPP-BOTDA can provide a precise description on the strain distribution of steel rebar and concrete, exhibiting the ability for crack detection. Moreover, structural deformation can be obtained indirectly by accumulating the distributed strains along the optical fiber, thus the deflection curves of the concrete girder during the loading process are obtained. Suggestions with regards to the application of the PPP-BOTDA in strain measurements and crack monitoring for civil infrastructures are given.
