By means of fracture testing on roller-compacted concrete （RCC） three-point bending beams with two different specimen sizes, the P-CMOD complete curve for RCC was gained. Furthermore, by applying double-K fracture t...By means of fracture testing on roller-compacted concrete （RCC） three-point bending beams with two different specimen sizes, the P-CMOD complete curve for RCC was gained. Furthermore, by applying double-K fracture theory, KiniⅠC,KunⅠC, as well as the critical effective crack length and the critical crack tip opening displacement, were evaluated. Based on the double-K fracture parameters above, the calculation model of equivalent strength for induced crack was established, thus the calculation method on its initiation, stable propagation and unstable fracture was ascertained. Moreover, the finite element simulation analysis of stress field in ShaPai arch dam and the on-site observational splaying points of induced crack at different altitudes validated the reliability of the model. Finally, crack inducer′s optimal setting in RCC arch dam was studied. It improves the design level of induced crack in RCC arch dam and satisfies the necessity of engineering practice.展开更多
A finite element analysis method was used to simulate the stamping process of the blade of a large concrete-mixer truck. The updated Lagrange method and the elasto-plastic constitutive equation were adopted to solve t...A finite element analysis method was used to simulate the stamping process of the blade of a large concrete-mixer truck. The updated Lagrange method and the elasto-plastic constitutive equation were adopted to solve the large strain and displacement deformation of the blade. A modified Coulomb friction model was used to solve the sliding contact between the blade and the dies. The von Mises stress distribution in the blade, the spatial displacement variation and the spring-back of the typical node were investigated in the simulation. The von Mises stress in the blade where the spring-back occurs is lowered from 463.0MPa to 150.0MPa before and after the spring-back. A typical node in the blade has a 3.33mm spring-back in Z direction. The results of the (experiments) agree well with the simulation. The analysis results are valuable for designing optimal tool dies.展开更多
The construction of Three Gorges Project (TGP) is characterized by large construction scale,high construction intensity and complexity in technology.In view of various technical difficulties such as navigation in cons...The construction of Three Gorges Project (TGP) is characterized by large construction scale,high construction intensity and complexity in technology.In view of various technical difficulties such as navigation in construction period,two river closures,high-intensity concrete and earth-rock construction,high-intensity construction and demolition of RCC (roller compacted concrete) cofferdam in stage III and immediate navigation of double-line five-step shiplock after impoundment of reservoir,the scheme of river diversion during construction is adopted,namely "diversion in 3 stages,open channel navigation and cofferdam power generation".The practice and innovation achievements in river diversion during construction as well as earth-rock and concrete construction are presented emphatically.展开更多
According to the characteristics of thin-layer rolling and pouting construction technology and the complicated mechanical behavior of the roller compacted concrete dam （RCCD） construction interface, a constitutive m...According to the characteristics of thin-layer rolling and pouting construction technology and the complicated mechanical behavior of the roller compacted concrete dam （RCCD） construction interface, a constitutive model of endochronic damage was established based on the endochronic theory and damage mechanics. The proposed model abandons the traditional concept of elastic-plastic yield surface and can better reflect the real behavior of rolled control concrete. Basic equations were proposed for the fluid-solid coupling analysis, and the relationships among the corresponding key physical parameters were also put forward. One three-dimensional finite element method （FEM） program was obtained by studying the FEM type of the seepage-stress coupling intersection of the RCCD. The method was applied to an actual project, and the results show that the fluid-solid interaction influences dam deformation and dam abutment stability, which is in accordance with practice. Therefore, this model provides a new method for revealing the mechanical behavior of RCCD under the coupling field.展开更多
Two large explosion trials (5 000 kg TNT and 500 kg ANFO) were conducted in Woomera, Australia in April/May 2006. Advance Protective Technologies for Engineering Structures (APTES) group tested 2 large single-storey c...Two large explosion trials (5 000 kg TNT and 500 kg ANFO) were conducted in Woomera, Australia in April/May 2006. Advance Protective Technologies for Engineering Structures (APTES) group tested 2 large single-storey concrete modules with individual components such as doors, windows and tiled panels. A description of the trial and details of various modules tested in these trials are presented in the paper. Numerical modelling and simulations are performed using computer programs, CONWEP, AIR3D and AUTODYN. A comparison of the pressure time histories obtained using these codes is made along with the concluding remarks.展开更多
The adaptive neuro-fuzzy inference systems(ANFIS)are widely used in the concrete technology.In this research,the compressive strength of light weight concrete was determined.To this end,the scoria percentage and curin...The adaptive neuro-fuzzy inference systems(ANFIS)are widely used in the concrete technology.In this research,the compressive strength of light weight concrete was determined.To this end,the scoria percentage and curing day variables were used as the input parameters,and compressive strength and tensile strength were used as the output parameters.In addition,100 patterns were used,70%of which were used for training and 30%were used for testing.To assess the precision of the neuro-fuzzy system,it was compared using two linear regression models.The comparisons were carried out in the training and testing phases.Research results revealed that the neuro-fuzzy systems model offers more potential,flexibility,and precision than the statistical models.展开更多
Based on the construction property of rolled compacted concrete, three-dimensional finite element relocating mesh method was developed in simulating construction process and computing temperature and stress field. Usi...Based on the construction property of rolled compacted concrete, three-dimensional finite element relocating mesh method was developed in simulating construction process and computing temperature and stress field. Using this method, the temperature and the thermal stress fields developed in the RCC gravity dam of the Longtan project with or without a longitudinal joint during construction and operation are calculated so as to simulate the construction process. The computation results show that the value of the thermal stresses developed in the dam even, without any longitudinal joint, could meet the design criteria provided the placement temperature is adequately controlled.展开更多
The applied technology of high roller-compacted concrete(RCC) dams is quite complicated because of various risk factors, including the weather condition, supply of concrete aggregate, efficiency of transport machinery...The applied technology of high roller-compacted concrete(RCC) dams is quite complicated because of various risk factors, including the weather condition, supply of concrete aggregate, efficiency of transport machinery and dam surface machinery, and so on. In order to ensure the comprehensiveness, accuracy and objectivity of construction schedule risk analysis, a mathematical model called improved correlated schedule risk analysis model(CSRAM) is proposed in this paper. This model takes into account not only the construction features of high RCC dams, but also the stochastic variations of risk factors with the construction schedule, as well as their comprehensive effects. Using Monte Carlo method to solve this model enables the completion probability of a high RCC dam construction within plan time, and uncertainty analysis of risk factors. Compared with the conventional CSRAM, the improved CSRAM has higher completion probability and more convergent distribution of a simulation period, making analysis results more accurate and closer to actual engineering conditions. Among the ten risk factors selected, efficiency of dam surface machinery and proficiency of workers are found to be of the maximum uncertainty.展开更多
文摘By means of fracture testing on roller-compacted concrete （RCC） three-point bending beams with two different specimen sizes, the P-CMOD complete curve for RCC was gained. Furthermore, by applying double-K fracture theory, KiniⅠC,KunⅠC, as well as the critical effective crack length and the critical crack tip opening displacement, were evaluated. Based on the double-K fracture parameters above, the calculation model of equivalent strength for induced crack was established, thus the calculation method on its initiation, stable propagation and unstable fracture was ascertained. Moreover, the finite element simulation analysis of stress field in ShaPai arch dam and the on-site observational splaying points of induced crack at different altitudes validated the reliability of the model. Finally, crack inducer′s optimal setting in RCC arch dam was studied. It improves the design level of induced crack in RCC arch dam and satisfies the necessity of engineering practice.
基金Project(2002A1040703) supported by the Science and Technology Fund of Guangdong Province
文摘A finite element analysis method was used to simulate the stamping process of the blade of a large concrete-mixer truck. The updated Lagrange method and the elasto-plastic constitutive equation were adopted to solve the large strain and displacement deformation of the blade. A modified Coulomb friction model was used to solve the sliding contact between the blade and the dies. The von Mises stress distribution in the blade, the spatial displacement variation and the spring-back of the typical node were investigated in the simulation. The von Mises stress in the blade where the spring-back occurs is lowered from 463.0MPa to 150.0MPa before and after the spring-back. A typical node in the blade has a 3.33mm spring-back in Z direction. The results of the (experiments) agree well with the simulation. The analysis results are valuable for designing optimal tool dies.
文摘The construction of Three Gorges Project (TGP) is characterized by large construction scale,high construction intensity and complexity in technology.In view of various technical difficulties such as navigation in construction period,two river closures,high-intensity concrete and earth-rock construction,high-intensity construction and demolition of RCC (roller compacted concrete) cofferdam in stage III and immediate navigation of double-line five-step shiplock after impoundment of reservoir,the scheme of river diversion during construction is adopted,namely "diversion in 3 stages,open channel navigation and cofferdam power generation".The practice and innovation achievements in river diversion during construction as well as earth-rock and concrete construction are presented emphatically.
基金Projects(51139001,51179066,51079046,50909041) supported by the National Natural Science Foundation of ChinaProject(NCET-10-0359) supported by the Program for New Century Excellent Talents in UniversityProjects(2009586012,2009586912,2010585212)supported by the Special Fund of State Key Laboratory of China
文摘According to the characteristics of thin-layer rolling and pouting construction technology and the complicated mechanical behavior of the roller compacted concrete dam （RCCD） construction interface, a constitutive model of endochronic damage was established based on the endochronic theory and damage mechanics. The proposed model abandons the traditional concept of elastic-plastic yield surface and can better reflect the real behavior of rolled control concrete. Basic equations were proposed for the fluid-solid coupling analysis, and the relationships among the corresponding key physical parameters were also put forward. One three-dimensional finite element method （FEM） program was obtained by studying the FEM type of the seepage-stress coupling intersection of the RCCD. The method was applied to an actual project, and the results show that the fluid-solid interaction influences dam deformation and dam abutment stability, which is in accordance with practice. Therefore, this model provides a new method for revealing the mechanical behavior of RCCD under the coupling field.
文摘Two large explosion trials (5 000 kg TNT and 500 kg ANFO) were conducted in Woomera, Australia in April/May 2006. Advance Protective Technologies for Engineering Structures (APTES) group tested 2 large single-storey concrete modules with individual components such as doors, windows and tiled panels. A description of the trial and details of various modules tested in these trials are presented in the paper. Numerical modelling and simulations are performed using computer programs, CONWEP, AIR3D and AUTODYN. A comparison of the pressure time histories obtained using these codes is made along with the concluding remarks.
文摘The adaptive neuro-fuzzy inference systems(ANFIS)are widely used in the concrete technology.In this research,the compressive strength of light weight concrete was determined.To this end,the scoria percentage and curing day variables were used as the input parameters,and compressive strength and tensile strength were used as the output parameters.In addition,100 patterns were used,70%of which were used for training and 30%were used for testing.To assess the precision of the neuro-fuzzy system,it was compared using two linear regression models.The comparisons were carried out in the training and testing phases.Research results revealed that the neuro-fuzzy systems model offers more potential,flexibility,and precision than the statistical models.
文摘Based on the construction property of rolled compacted concrete, three-dimensional finite element relocating mesh method was developed in simulating construction process and computing temperature and stress field. Using this method, the temperature and the thermal stress fields developed in the RCC gravity dam of the Longtan project with or without a longitudinal joint during construction and operation are calculated so as to simulate the construction process. The computation results show that the value of the thermal stresses developed in the dam even, without any longitudinal joint, could meet the design criteria provided the placement temperature is adequately controlled.
基金supported by the Innovative Research Groups of the National Natural Science Foundation of China(Grant No.51321065)the National Basic Research Program of China("973"Project)(Grant No.2013CB035906)the National Natural Science Foundation of China(Grant No.51339003)
文摘The applied technology of high roller-compacted concrete(RCC) dams is quite complicated because of various risk factors, including the weather condition, supply of concrete aggregate, efficiency of transport machinery and dam surface machinery, and so on. In order to ensure the comprehensiveness, accuracy and objectivity of construction schedule risk analysis, a mathematical model called improved correlated schedule risk analysis model(CSRAM) is proposed in this paper. This model takes into account not only the construction features of high RCC dams, but also the stochastic variations of risk factors with the construction schedule, as well as their comprehensive effects. Using Monte Carlo method to solve this model enables the completion probability of a high RCC dam construction within plan time, and uncertainty analysis of risk factors. Compared with the conventional CSRAM, the improved CSRAM has higher completion probability and more convergent distribution of a simulation period, making analysis results more accurate and closer to actual engineering conditions. Among the ten risk factors selected, efficiency of dam surface machinery and proficiency of workers are found to be of the maximum uncertainty.
