Chloride-induced corrosion of the reinforcement is considered as one of the major mechanisms resulting in the reduction of structural resistance of reinforced concrete structural elements located in marine and other a...Chloride-induced corrosion of the reinforcement is considered as one of the major mechanisms resulting in the reduction of structural resistance of reinforced concrete structural elements located in marine and other aggressive environments. A study of reinforced concrete structures located at the Fangcheng dock in the Beibu Gulf port, China, was present. The result from field survey indicates that the concrete cover depth and chloride diffusion coefficient fit best normal distribution and lognormal distribution, respectively. The service life of structure is about 55 a, while initiation time is 45 a. Sensitivity analysis indicates that the most influential factor of the structure service life prediction is concrete cover, followed by diffusion coefficient, diffusion decay index, critical chloride concentration, surface chloride concentration, current density and localized pitting corrosion. Finally, the effects of diffusion decay index and critical chloride concentration on structure service life prediction are discussed.展开更多
Monitoring the service condition of concrete structures requires the quantitative assessment of properties and corrosion rate of structural steels surrounded by concrete.A multi-cell sensor system that included a refe...Monitoring the service condition of concrete structures requires the quantitative assessment of properties and corrosion rate of structural steels surrounded by concrete.A multi-cell sensor system that included a reference electrode,a chloride content sensor,a macrocell current unit and an electrical resistance measurement unit was developed.This system provided the following important electrochemical data in the cover-zone concrete on site:open circuit potential,macrocell current from anodes to cathode,chloride profile,concrete resistance and corrosion rate of built-in anodes.The experimental results show that the macrocell current increases when the chloride content in concrete is higher.Thus,monitoring the chloride content is a good method for monitoring the corrosion state.The chloride ion content and cover depth are the key factors that affect the electrical resistance of concrete.Without considering the temperature and time,a simplified model of the instantaneous corrosion rate of steel rebar in a concrete structure based on the measured chloride contents and concrete resistance was proposed.The test results further prove the reliability of this simplified predicting model.展开更多
Super-highly reinforced concrete tube in tube structure is a developing structure system of high-rise building. The more reasonable derivation process of the multi-vertical-line-element model stiffness matrix is given...Super-highly reinforced concrete tube in tube structure is a developing structure system of high-rise building. The more reasonable derivation process of the multi-vertical-line-element model stiffness matrix is given.On the premise of pointing out the problems of present multi-spring element model, combined with present multivertical-line-element model for analyzing on shear wall, the model is expanded to spatial one, and the stiffness matrix of which is derived. Combined with hysteretic axial model and hysteretic shear model, it is suitable for columns,wall limbs and beams with all kinds of section form. Some examples are calculated and compared with test results,which shows that the models have relatively good accuracy. On the base of the experimental phenomenon and failure mechanism for tube in tube structure specimen, nonlinear seismic responses analysis program on the basis of the advantaged element model for tube in tube structure is developed. Calculation results are in good agreement with those of the pseudo-dynamic tests and the failure mechanism can be well reflected.展开更多
Reinforced concrete(RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthqu...Reinforced concrete(RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthquakes, but also more economical. The effect of progressive collapse caused by removal of load bearing elements, in various positions in plan and stories of the RC load bearing wall system was evaluated by nonlinear dynamic and static analyses. For this purpose, three-dimensional model of 10-story structure was selected. The analysis results indicated stability, strength and stiffness of the RC load-bearing wall system against progressive collapse. It was observed that the most critical condition for removal of load bearing walls was the instantaneous removal of the surrounding walls located at the corners of the building where the sections of the load bearing elements were changed. In this case, the maximum vertical displacement was limited to 6.3 mm and the structure failed after applying the load of 10 times the axial load bored by removed elements. Comparison between the results of the nonlinear dynamic and static analyses demonstrated that the "load factor" parameter was a reasonable criterion to evaluate the progressive collapse potential of the structure.展开更多
In order to get the formulae for calculating the equivalent frame width coefficient of reinforced concrete hollow slab-column structures with edge beam,the finite element structural program was used in the elastic ana...In order to get the formulae for calculating the equivalent frame width coefficient of reinforced concrete hollow slab-column structures with edge beam,the finite element structural program was used in the elastic analysis of reinforced concrete hollow slab-column structure with different dimensions to study internal relationship between effective beam width and the frame dimensions.In addition,the formulas for calculating the increasing coefficient of edge beam were also obtained.展开更多
The compositions, technical principles and construction equipments of a new piling method used for ground improvement plastic tube cast-in-place concrete pile were introduced. The results from static load tests on sin...The compositions, technical principles and construction equipments of a new piling method used for ground improvement plastic tube cast-in-place concrete pile were introduced. The results from static load tests on single piles with different forms of pile shoes and on their composite foundations were analyzed. The distribution patterns of axial force, shaft friction and toe resistance were studied based on the measurements taken from buried strain gauges. From the point of engineering application, the pile has merits in convenient quality control, high bearing capacity and reliable quality, showing higher reasonability, advancement and suitability than other ground improvement methods. The pile can be adopted properly to take place of ordinary ground improvement method, achieving greater economical and social benefits.展开更多
Social infrastructures such as dams are likely to be exposed to high risk of terrorist and military attacks,leading to increasing attentions on their vulnerability and catastrophic consequences under such events.This ...Social infrastructures such as dams are likely to be exposed to high risk of terrorist and military attacks,leading to increasing attentions on their vulnerability and catastrophic consequences under such events.This paper tries to develop advanced deep learning approaches for structural dynamic response prediction and dam health diagnosis.At first,the improved long short-term memory(LSTM)networks are proposed for data-driven structural dynamic response analysis with the data generated by a single degree of freedom(SDOF)and the finite numerical simulation,due to the unavailability of abundant practical structural response data of concrete gravity dam under blast events.Three kinds of LSTM-based models are discussed with the various cases of noise-contaminated signals,and the results prove that LSTM-based models have the potential for quick structural response estimation under blast loads.Furthermore,the damage indicators(i.e.,peak vibration velocity and domain frequency)are extracted from the predicted velocity histories,and their relationship with the dam damage status from the numerical simulation is established.This study provides a deep-learning based structural health monitoring(SHM)framework for quick assessment of dam experienced underwater explosions through blastinduced monitoring data.展开更多
In this study,a nonlinear three-dimensional hydrocode numerical simulation was carried out using AUTODYN-3D to investigate the effect of blasting of a high explosive material(TNT)against several configurations of the ...In this study,a nonlinear three-dimensional hydrocode numerical simulation was carried out using AUTODYN-3D to investigate the effect of blasting of a high explosive material(TNT)against several configurations of the composite structure.Several numerical models were carried out to study the effect of varying the thickness of the walls and the effect of adding an air layer or aluminum foam layer inside two layers of concrete in mitigating the effect of blast waves on the structure walls.The results showed that increasing the thickness of walls has a good effect on mitigating the effect of blast waves.When a layer of air was added,the effect of blast waves was exaggerated,while when a layer of aluminum foam was added the blast wave effects were mitigated with a reasonable percentage.展开更多
A nonlinear finite element model of the nut post reinforced concrete （RC） structure of the safety mechanism in the Three Gorges Project （TGP） ship lift was built by ANSYS software. Some irregular structures such a...A nonlinear finite element model of the nut post reinforced concrete （RC） structure of the safety mechanism in the Three Gorges Project （TGP） ship lift was built by ANSYS software. Some irregular structures such as the nut post and the rotary rod were divided by curved surface into a series of regular parts, and the structures were all meshed to hexahedron. Constraint equations were defined between two interfaces with different element sizes and mesh patterns. PRETS179 elements were used to simulate the preload in the tendons and the pre-stressed screws, and the loss of prestressing force was calculated. Five extreme load cases were analyzed. The stress of each part in the structure was obtained. The results indicate that the maximum compressive stress of concrete C35 is 24.13 MPa, so the concrete may be partially crushed; the maximum tensile stress of the grouting motar is 6.73 MPa, so the grouting motar may partially fracture; the maximum yon Mises stress of the rotary rod is 648.70 MPa, therefore the rotary rod may partially yield.展开更多
Steel-tube-confined concrete(STCC) targets are provided with excellent anti-penetration performance over semi-infinite concrete(SIC) targets since the steel tube imposes passive restraint on the in-filled concrete dur...Steel-tube-confined concrete(STCC) targets are provided with excellent anti-penetration performance over semi-infinite concrete(SIC) targets since the steel tube imposes passive restraint on the in-filled concrete during the penetration process. Grid STCC system with square steel tubes is a potential solution to protective structures. In this paper, experiments of 9-cell grid STCC targets penetrated by 12.7 mm Armor Piercing Projectile(APP) were performed. The influence of side length and thickness of steel tube,steel ratio and impact velocity on anti-penetration performance were taken into account. Additionally,single-cell square STCC targets were also designed and tested for comparison with the 9-cell grid STCC targets. Damage modes and parameters of the tested targets were measured and discussed. Moreover,the stiffness of radial confinement of grid STCC targets is achieved according to the elastic solution of infinite cylindrical shell in Winkler medium. Furthermore, the penetration resistance and depth of penetration(DOP) for grid STCC targets are obtained on the basis of the dynamic finite spherical cavityexpansion(FSCE) models including radial confinement effect. It is shown that the 9-cell grid STCC targets with optimal dimension match of thickness and side length of steel tube can reduce the DOP by about17 % and 23 % in comparison with the SIC targets and single-cell square STCC targets, respectively, due to both the confinement of square steel tube to concrete in the impacted cell and the additional confinement of the surrounding cells to the impacted cell;the penetration resistance and DOP of the grid and cellular STCC targets with similar steel ratio is close, and thus the grid STCC targets with simpler manufacturing process and excellent in-plane expandability are preferred in engineering practice;moreover, the predicted results of DOP model based on the FSCE models agree well with the tested results with the maximum disparity less than 12 % and the proposed model is more applicable to the grid and cellular STCC targets with high radial confinement.展开更多
基金Project(41274012) supported by the National Natural Science Foundation of China
文摘Chloride-induced corrosion of the reinforcement is considered as one of the major mechanisms resulting in the reduction of structural resistance of reinforced concrete structural elements located in marine and other aggressive environments. A study of reinforced concrete structures located at the Fangcheng dock in the Beibu Gulf port, China, was present. The result from field survey indicates that the concrete cover depth and chloride diffusion coefficient fit best normal distribution and lognormal distribution, respectively. The service life of structure is about 55 a, while initiation time is 45 a. Sensitivity analysis indicates that the most influential factor of the structure service life prediction is concrete cover, followed by diffusion coefficient, diffusion decay index, critical chloride concentration, surface chloride concentration, current density and localized pitting corrosion. Finally, the effects of diffusion decay index and critical chloride concentration on structure service life prediction are discussed.
基金Project(200632800003-11) supported by Western Communications Construction Scientific and Technological Project in China
文摘Monitoring the service condition of concrete structures requires the quantitative assessment of properties and corrosion rate of structural steels surrounded by concrete.A multi-cell sensor system that included a reference electrode,a chloride content sensor,a macrocell current unit and an electrical resistance measurement unit was developed.This system provided the following important electrochemical data in the cover-zone concrete on site:open circuit potential,macrocell current from anodes to cathode,chloride profile,concrete resistance and corrosion rate of built-in anodes.The experimental results show that the macrocell current increases when the chloride content in concrete is higher.Thus,monitoring the chloride content is a good method for monitoring the corrosion state.The chloride ion content and cover depth are the key factors that affect the electrical resistance of concrete.Without considering the temperature and time,a simplified model of the instantaneous corrosion rate of steel rebar in a concrete structure based on the measured chloride contents and concrete resistance was proposed.The test results further prove the reliability of this simplified predicting model.
文摘Super-highly reinforced concrete tube in tube structure is a developing structure system of high-rise building. The more reasonable derivation process of the multi-vertical-line-element model stiffness matrix is given.On the premise of pointing out the problems of present multi-spring element model, combined with present multivertical-line-element model for analyzing on shear wall, the model is expanded to spatial one, and the stiffness matrix of which is derived. Combined with hysteretic axial model and hysteretic shear model, it is suitable for columns,wall limbs and beams with all kinds of section form. Some examples are calculated and compared with test results,which shows that the models have relatively good accuracy. On the base of the experimental phenomenon and failure mechanism for tube in tube structure specimen, nonlinear seismic responses analysis program on the basis of the advantaged element model for tube in tube structure is developed. Calculation results are in good agreement with those of the pseudo-dynamic tests and the failure mechanism can be well reflected.
文摘Reinforced concrete(RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthquakes, but also more economical. The effect of progressive collapse caused by removal of load bearing elements, in various positions in plan and stories of the RC load bearing wall system was evaluated by nonlinear dynamic and static analyses. For this purpose, three-dimensional model of 10-story structure was selected. The analysis results indicated stability, strength and stiffness of the RC load-bearing wall system against progressive collapse. It was observed that the most critical condition for removal of load bearing walls was the instantaneous removal of the surrounding walls located at the corners of the building where the sections of the load bearing elements were changed. In this case, the maximum vertical displacement was limited to 6.3 mm and the structure failed after applying the load of 10 times the axial load bored by removed elements. Comparison between the results of the nonlinear dynamic and static analyses demonstrated that the "load factor" parameter was a reasonable criterion to evaluate the progressive collapse potential of the structure.
文摘In order to get the formulae for calculating the equivalent frame width coefficient of reinforced concrete hollow slab-column structures with edge beam,the finite element structural program was used in the elastic analysis of reinforced concrete hollow slab-column structure with different dimensions to study internal relationship between effective beam width and the frame dimensions.In addition,the formulas for calculating the increasing coefficient of edge beam were also obtained.
基金Project (2007H03) supported by Communications Department of Zhejiang Province
文摘The compositions, technical principles and construction equipments of a new piling method used for ground improvement plastic tube cast-in-place concrete pile were introduced. The results from static load tests on single piles with different forms of pile shoes and on their composite foundations were analyzed. The distribution patterns of axial force, shaft friction and toe resistance were studied based on the measurements taken from buried strain gauges. From the point of engineering application, the pile has merits in convenient quality control, high bearing capacity and reliable quality, showing higher reasonability, advancement and suitability than other ground improvement methods. The pile can be adopted properly to take place of ordinary ground improvement method, achieving greater economical and social benefits.
基金supported by a grant from the National Natural Science Foundation of China(Grant No.52109163 and 51979188).
文摘Social infrastructures such as dams are likely to be exposed to high risk of terrorist and military attacks,leading to increasing attentions on their vulnerability and catastrophic consequences under such events.This paper tries to develop advanced deep learning approaches for structural dynamic response prediction and dam health diagnosis.At first,the improved long short-term memory(LSTM)networks are proposed for data-driven structural dynamic response analysis with the data generated by a single degree of freedom(SDOF)and the finite numerical simulation,due to the unavailability of abundant practical structural response data of concrete gravity dam under blast events.Three kinds of LSTM-based models are discussed with the various cases of noise-contaminated signals,and the results prove that LSTM-based models have the potential for quick structural response estimation under blast loads.Furthermore,the damage indicators(i.e.,peak vibration velocity and domain frequency)are extracted from the predicted velocity histories,and their relationship with the dam damage status from the numerical simulation is established.This study provides a deep-learning based structural health monitoring(SHM)framework for quick assessment of dam experienced underwater explosions through blastinduced monitoring data.
文摘In this study,a nonlinear three-dimensional hydrocode numerical simulation was carried out using AUTODYN-3D to investigate the effect of blasting of a high explosive material(TNT)against several configurations of the composite structure.Several numerical models were carried out to study the effect of varying the thickness of the walls and the effect of adding an air layer or aluminum foam layer inside two layers of concrete in mitigating the effect of blast waves on the structure walls.The results showed that increasing the thickness of walls has a good effect on mitigating the effect of blast waves.When a layer of air was added,the effect of blast waves was exaggerated,while when a layer of aluminum foam was added the blast wave effects were mitigated with a reasonable percentage.
基金Project (SPKJ 016-06) supported by the Key Research Project of State Power CorporationProject (2004AC101D31) supported the Key Scientific Research Project of Hubei Province, China
文摘A nonlinear finite element model of the nut post reinforced concrete （RC） structure of the safety mechanism in the Three Gorges Project （TGP） ship lift was built by ANSYS software. Some irregular structures such as the nut post and the rotary rod were divided by curved surface into a series of regular parts, and the structures were all meshed to hexahedron. Constraint equations were defined between two interfaces with different element sizes and mesh patterns. PRETS179 elements were used to simulate the preload in the tendons and the pre-stressed screws, and the loss of prestressing force was calculated. Five extreme load cases were analyzed. The stress of each part in the structure was obtained. The results indicate that the maximum compressive stress of concrete C35 is 24.13 MPa, so the concrete may be partially crushed; the maximum tensile stress of the grouting motar is 6.73 MPa, so the grouting motar may partially fracture; the maximum yon Mises stress of the rotary rod is 648.70 MPa, therefore the rotary rod may partially yield.
基金the projects supported by the Natural Science Foundation of Hunan Province, China (No. 2018JJ2470 and 2021JJ30776)。
文摘Steel-tube-confined concrete(STCC) targets are provided with excellent anti-penetration performance over semi-infinite concrete(SIC) targets since the steel tube imposes passive restraint on the in-filled concrete during the penetration process. Grid STCC system with square steel tubes is a potential solution to protective structures. In this paper, experiments of 9-cell grid STCC targets penetrated by 12.7 mm Armor Piercing Projectile(APP) were performed. The influence of side length and thickness of steel tube,steel ratio and impact velocity on anti-penetration performance were taken into account. Additionally,single-cell square STCC targets were also designed and tested for comparison with the 9-cell grid STCC targets. Damage modes and parameters of the tested targets were measured and discussed. Moreover,the stiffness of radial confinement of grid STCC targets is achieved according to the elastic solution of infinite cylindrical shell in Winkler medium. Furthermore, the penetration resistance and depth of penetration(DOP) for grid STCC targets are obtained on the basis of the dynamic finite spherical cavityexpansion(FSCE) models including radial confinement effect. It is shown that the 9-cell grid STCC targets with optimal dimension match of thickness and side length of steel tube can reduce the DOP by about17 % and 23 % in comparison with the SIC targets and single-cell square STCC targets, respectively, due to both the confinement of square steel tube to concrete in the impacted cell and the additional confinement of the surrounding cells to the impacted cell;the penetration resistance and DOP of the grid and cellular STCC targets with similar steel ratio is close, and thus the grid STCC targets with simpler manufacturing process and excellent in-plane expandability are preferred in engineering practice;moreover, the predicted results of DOP model based on the FSCE models agree well with the tested results with the maximum disparity less than 12 % and the proposed model is more applicable to the grid and cellular STCC targets with high radial confinement.
