A reinforced concrete slit shear wall is a new breed of earthquake resistant structure recently proposed by the authors. In this paper, the seismic responses of the slit shear walls under the shake of earthquake exci...A reinforced concrete slit shear wall is a new breed of earthquake resistant structure recently proposed by the authors. In this paper, the seismic responses of the slit shear walls under the shake of earthquake excitation have been dealt with. Based on a simplified structural model, which is shown to have a sufficient accuracy for the real slit shear wall structure, the analysis focuses on the influence of nonlinear behavior of the connecting beams between the slits on the dynamic performance of the whole slit shear wall structure. It has been found that the yielding of connecting beams in a slit shear wall can provide significant improvement in reducing the structural responses, and by choosing an appropriate strength value for the connecting beams, it is possible to optimize the seismic response of the slit shear wall.展开更多
Specimens of steel fiber reinforced concrete (SFRC) in volume ratios of 0%, 0.5%, 1% and 1.5% were prepared to study the supporting effect of SFRC at these diffterent volume ratios in a deep soft rock tunnel. Experi...Specimens of steel fiber reinforced concrete (SFRC) in volume ratios of 0%, 0.5%, 1% and 1.5% were prepared to study the supporting effect of SFRC at these diffterent volume ratios in a deep soft rock tunnel. Experiments with mechanical properties of compressive strength in cubic specimens, cleave strength in cylindrical specimens and four-point flexure strength of sheet metal specimens were carded out. The experimental results indicate that SFRC in a volume ratio of 1% is superior in ranking to other volume ratios in terms of technique and economics. By means of a numerical simulation, given the characteristics of soft rock deformation and damage at great depth, a new support substitution scheme of SFRC to replace plain concrete is proposed. The results of an industrial trial show that the support provided by SFRC can withstand large deformations of the surrounding rock. Good resuits have been obtained in a practical anplication.展开更多
To retrofit and strengthen existing unreinforced masonry (URM) structures to resist the potential earthquake damages has become an important issue in Australia. In order to secure the performance of URM under seismic ...To retrofit and strengthen existing unreinforced masonry (URM) structures to resist the potential earthquake damages has become an important issue in Australia. In order to secure the performance of URM under seismic loading in the future, a research project was carried out aimed at developing a simple and high strength seismic retrofitting technique for masonry structures. A series of experimental testing on URM walls retrofitted with an innovative technique by cable system have been conducted. The results indicated that both the strength and ductility of the tested speci-mens were significantly enhanced with the technique. An analytical model which is based on Dis-tinct Element Method (DEM) has also been developed to simulate the behaviour of URM walls be-fore and after retrofitting. The model is then further developed by applying a seismic wave to the wall to simulate the wall behavior under earthquake loads before and after retrofitting.展开更多
Past earthquake disasters in Greece, during the last thirty years, demonstrate that the severity of destruction is not only due to the intensity of the seismic event but also to the urbanization of the affected region...Past earthquake disasters in Greece, during the last thirty years, demonstrate that the severity of destruction is not only due to the intensity of the seismic event but also to the urbanization of the affected region and the vulnerability of certain types of buildings. Considerable damage was sustained by both old unreinforced masonry structures as well as by relatively new multistory reinforced concrete structures with "soft story" at their ground floor level. The most important observations made during six past earthquake disasters are presented in a summary form and discussed. The most remarkable case of extensive structural damage was caused from the resent Athens 1999 earthquake. The consequent discussion focuses on the following issues: (1) Classification of structural damage and their underlying causes. (2) Repair and strengthening of damaged structures. (3) Upgrade the seismic design. (4) Plans for earthquake preparedness. (5) Assessing the vulnerability of certain type of structures (schools, hospitals, public buildings etc). (6) Education specialized in earthquake engineering. (7) The enrichment of the strong motion data base.展开更多
In several parts of the world, disposal of waste materials such as fly ash is a great problem. Application of waste materials as structural fills in foundations is one of the best solutions to disposal problems, becau...In several parts of the world, disposal of waste materials such as fly ash is a great problem. Application of waste materials as structural fills in foundations is one of the best solutions to disposal problems, because wastes can be used in large volumes in such applications. There may be difficulty due to poor load-bearing capacity of fly ash, especially when footing rests on the top of the fly ash fill slope. Inclusion of polymeric reinforcements as horizontal sheets within the fill may be one of the most viable solutions to improving the load-bearing capacity of reinforced fly ash slope, and it is particularly important for the situations where foundations need to be located either on the top of a slope or on slope itself. The present work is aimed at investigating the efficacy of a single layer of reinforcement in improving the lo, ad-bearing capacity when it gets incorporated within the body of a model fly ash embankment slope. An increase in load bearing capacity due to the incorporation of reinforcement in the model slope was found by conducting laboratory tests. Experimental results were compared by numerical values obtained using software GEO5 and PLAXIS.展开更多
The reinforced two layered foundation bed considered for study consists of a layer of granular fill overlying soft non-homogeneous clay with inclusion or reinforcement (geosymhetic strips, grids or sheets) in single...The reinforced two layered foundation bed considered for study consists of a layer of granular fill overlying soft non-homogeneous clay with inclusion or reinforcement (geosymhetic strips, grids or sheets) in single layer at soil-granular fill interface A method is developed to estimate the bearing capacity of a strip footing on the surface of a reinforced foundation bed over a finite layer of clay whose undrained strength increases linearly with depth incorporating the contribution of axial resistance of the reinforcement together with those of granular fill and soft ground. Parametric studies presented quantify the improvement in bearing capacity.展开更多
Timber bridges can provide an economical alternative to concrete and steel structures, particularly in rural areas where vehicle traffic is light to moderate. The wooden components of bridges have historically been pr...Timber bridges can provide an economical alternative to concrete and steel structures, particularly in rural areas where vehicle traffic is light to moderate. The wooden components of bridges have historically been preserved with either an oil type or waterborne preservative system to protect the wood from decay in order to maintain required performance standards for an extended period of time. The focus of this paper is to describe some of the key preservatives, research and case studies that support use of preserved wood, and some important steps to follow for the appropriate and safe use of preserved wood when the planned application will be in or over aquatic and wetland environments. A wealth of scientific information has been collected and analyzed that clearly suggests the use of preserved wood does not present a significant adverse effect on aquatic and wetland environments. This conclusion is based on two decades of empirical research and case study evaluating the environmental fate and effects of preserved wood, level of migration of contaminates into aquatic and marine environments, and the preserved wood environment. This is particularly true when risks are properly assessed on a project site, the appropriate preservative is selected and the wood is preserved to the Western Wood Preservers Institute's BMPs (best management practices), along with properly installing and maintaining the preserved material. To assist with the assessment process, peer-reviewed risk assessment models for 11 commonly used preservatives have been developed that provide for streamlined data entry by users and allow for evaluation of a structure above and below water. A companion preliminary screening level assessment tool is also available. When these measures are properly utilized engineers, biologists and other responsible officials can be confident that the service life of the preserved wood components will more than likely meet the required performance standards in an environmentally safe manner for up to 50 or more years on a majority of timber bridge projects.展开更多
In order to investigate the seismic performance of geosynthetic reinforced and pile supported(GRPS) embankment under seismic loads, an input method for three-dimensional oblique incidence of P wave was proposed. This ...In order to investigate the seismic performance of geosynthetic reinforced and pile supported(GRPS) embankment under seismic loads, an input method for three-dimensional oblique incidence of P wave was proposed. This method is based on the explicit finite element method while considering the viscous-spring artificial boundary(VSAB) condition. Using the proposed method, a numerical study was conducted, and the influence of oblique incidence on the seismic response of GRPS embankment under the oblique incident P waves was analyzed. The results indicate that in comparison with vertical incidence, the oblique incidence can significantly increase the displacement, velocity and acceleration of key locations in the GRPS embankment. The existence of geosynthetics can alleviate the impact of seismic load on the response of the embankment to a certain degree. Moreover, the number of reinforcement layers and modulus of geogrid also greatly influence the seismic performance of GRPS embankment.展开更多
The present work discusses the outcomes of recent experimental tests and numerical simulations carried out on full scale reinforced concrete (RC) non-ductile frames retrofitted with dissipative steel braces, i.e. in...The present work discusses the outcomes of recent experimental tests and numerical simulations carried out on full scale reinforced concrete (RC) non-ductile frames retrofitted with dissipative steel braces, i.e. innovative buckling restrained braces (BRBs). Experimental tests were performed on two sample full scale RC framed buildings designed for gravity loads only. Such frames were subjected to cyclic pushovers to investigate their structural performance under different levels of earthquake loadings. The outcomes of the performed experimental tests demonstrate the efficiency and reliability of utilizing BRBs to retrofit non ductile RC frames. These outcomes were confirmed by refined non linear static and response history analyses carried out on an existing RC school framed building designed without seismic details and retrofitted with BRBs similar to those adopted for the tested full-scale frame. In such sample building the BRBs are placed along the perimeter of the existing frames to minimize the interruption of the functionality of the school and for easy of maintenance in the aftermath of major earthquake ground motions. The seismic performance assessment of the retrofitted structural system is illustrated in a detailed manner. Local and global response quantities are presented. The values of the global overstrength Ω for the case study vary between 2.14 and 2.54 for the retrofitted framed building. The translation ductility μ△-values range between 2.07 and 2.36. The response modification factor (or behaviour factor, namely R- or q-factor) is on average equal to 5.0. Additionally, the estimated maximum axial ductility of the BRBs is about 10. Finally, the cost-effectiveness of the adopted retrofitting scheme is emphasized and further needs for the application of BRBs are highlighted.展开更多
Based on a series of previous studies, an experiment on the integral seismic behavior of a 1/3 scaled model of two-bay and three-story reinforced concrete frame with split columns at lower two stories is performed und...Based on a series of previous studies, an experiment on the integral seismic behavior of a 1/3 scaled model of two-bay and three-story reinforced concrete frame with split columns at lower two stories is performed under cyclic loading. The original columns at lower two stories of the model frame are short columns and they are replaced by the split columns. The hysteresis curves between the horizontal cyclic load and the lateral displacement at the top of the model frame, indicate that under the cyclic loading, the model frame undergoes the process of cracking, yielding, and maximum loading before being destroyed at the ultimate load. They also indicate that the model frame has better ductility, and the ratio of the ultimate displacement to the yielding displacement, reaches 6.0. The yielding process of the model frame shows that for the frame with split columns, plastic hinges are generated at the ends of beams and then the columns begin yielding while the frame still possesses the bearing and deformation capacity. The design idea of directly changing the short column to long one in the reinforced concrete frame may be realized by replacing the short column with the split one.展开更多
The subject structure was consisted of a proto-type house with plan dimensions of 8 m ×4 m. A variety of materials was used to the construction, with special emphasis on using environmentally friendly non-toxic m...The subject structure was consisted of a proto-type house with plan dimensions of 8 m ×4 m. A variety of materials was used to the construction, with special emphasis on using environmentally friendly non-toxic materials. The structure's core consisted of reinforced concrete frames with masonry infill walls. Inside faces of the walls and the roof's outside face were covered with proprietary composite panels, which are manufactured with a mixture of cement, volcanic ash, and local sawmill waste. These panels were analyzed for their physical and chemical properties, as well as for their resistance to decay and insects when subjected to extreme conditions for 15 years. The panels have also shown to provide thermal insulation and nonflammable when in direct contact with fire. The roof surface was further covered with a blend of local drought-resistant succulents and cacti. This study provides a detailed review of the construction process and materials employed.展开更多
To investigate the mechanical behavior of segmental lining, a three-dimensional numerical analysis and test using three actual segments were used to analyze the effects of axial force and reinforcement ratio on the fa...To investigate the mechanical behavior of segmental lining, a three-dimensional numerical analysis and test using three actual segments were used to analyze the effects of axial force and reinforcement ratio on the failure mechanism and ultimate bearing capacity of segmental lining. Both numerical and test results confirmed that the cracking load, yield and ultimate load were strongly influenced by axial force, and it was also proved that the yield and ultimate load would increase with the increase of reinforcement ratio, but the cracking load was almost not affected. The cracking load, yield and ultimate load are about 28.7%, 500% and 460% larger due to the effect of axial force respectively. The comparison between numerical calculation and test results showed that the finite element analysis resuits were in good agreement with the test results.展开更多
In many seismically active regions of the world there are large numbers of masonry buildings. Most of these buildings have not been designed for seismic loads. Recent earthquakes have shown that many of these building...In many seismically active regions of the world there are large numbers of masonry buildings. Most of these buildings have not been designed for seismic loads. Recent earthquakes have shown that many of these buildings are seismically vulnerable and should be considered for retrofitting. Different conventional and unconventional retrofitting techniques are available to increase the strength and/or ductility of unreinforced masonry (URM) walls. This paper reviews and discusses seismic retrofitting of masonry walls with emphasis on the conventional techniques. Retrofitting procedures are discussed with regard to a case study: a stone masonry building in lrpinia region, damaged by the 1980 earthquake. The interventions are evaluated by means of finite elements with a macroelement obtained with a homogenization technique. Linear and nonlinear procedures are compared, and peculiarities of each procedure are shown.展开更多
To evaluate the coupling pounding-friction effect between bridge girders and retainers and its influence on bridge seismic response, a reinforced concrete (RC) continuous bridge is selected as the research object. T...To evaluate the coupling pounding-friction effect between bridge girders and retainers and its influence on bridge seismic response, a reinforced concrete (RC) continuous bridge is selected as the research object. Three bridge finite element (FE) models were built using OpenSees, in which the longitudinal and transverse pounding elements, as well as the transverse failure element of bearings were introduced. Based on this, tire seismic response analysis considering the coupling pounding-friction effect was conducted for the continuous bridge subjected to bi-directional ground motions. Furthermore, the influential parameters were analyzed. The analysis results indicate that the coupling pounding-friction effect can alter the internal force distribution of the bridge structure and generate additional torsional force to bridge columns. The friction coefficient and longitudinal pounding gap size are two important factors. The appropriate friction coefficient and longitudinal pounding gap size can significantly reduce seismic response of girders, and effectively transfer part of the girder inertia force from the fixed columns to the sliding columns, which can reduce the seismic demands of the fixed columns and improve the seismic performance of continuous bridge structures.展开更多
The risk during construction and in the operation of the underground gas storage (UGS) was analyzed. One of most important risk which should be prevented is large deformation or destruction of the steel lining. The ...The risk during construction and in the operation of the underground gas storage (UGS) was analyzed. One of most important risk which should be prevented is large deformation or destruction of the steel lining. The specific deformation of the steel lining needs to be inside the acceptable value. This paper presents lined rock cavern (LRC) concept and specific deformations, which can occur under operation of underground gas storage. Analysis is performed with different (3D model and axis symmetrical) FEM models and analytical model. We made a comparison between analytical calculation and FEM calculation. Concrete wall is mechanically not regarded as reinforced concrete structure which means that concrete will crack. Finally, we determined the minimum value of Young's modulus, which satisfies the condition of maximum deformation of steel lining.展开更多
文摘A reinforced concrete slit shear wall is a new breed of earthquake resistant structure recently proposed by the authors. In this paper, the seismic responses of the slit shear walls under the shake of earthquake excitation have been dealt with. Based on a simplified structural model, which is shown to have a sufficient accuracy for the real slit shear wall structure, the analysis focuses on the influence of nonlinear behavior of the connecting beams between the slits on the dynamic performance of the whole slit shear wall structure. It has been found that the yielding of connecting beams in a slit shear wall can provide significant improvement in reducing the structural responses, and by choosing an appropriate strength value for the connecting beams, it is possible to optimize the seismic response of the slit shear wall.
基金Project 50490274 supported by the National Natural Science Foundation of China
文摘Specimens of steel fiber reinforced concrete (SFRC) in volume ratios of 0%, 0.5%, 1% and 1.5% were prepared to study the supporting effect of SFRC at these diffterent volume ratios in a deep soft rock tunnel. Experiments with mechanical properties of compressive strength in cubic specimens, cleave strength in cylindrical specimens and four-point flexure strength of sheet metal specimens were carded out. The experimental results indicate that SFRC in a volume ratio of 1% is superior in ranking to other volume ratios in terms of technique and economics. By means of a numerical simulation, given the characteristics of soft rock deformation and damage at great depth, a new support substitution scheme of SFRC to replace plain concrete is proposed. The results of an industrial trial show that the support provided by SFRC can withstand large deformations of the surrounding rock. Good resuits have been obtained in a practical anplication.
文摘To retrofit and strengthen existing unreinforced masonry (URM) structures to resist the potential earthquake damages has become an important issue in Australia. In order to secure the performance of URM under seismic loading in the future, a research project was carried out aimed at developing a simple and high strength seismic retrofitting technique for masonry structures. A series of experimental testing on URM walls retrofitted with an innovative technique by cable system have been conducted. The results indicated that both the strength and ductility of the tested speci-mens were significantly enhanced with the technique. An analytical model which is based on Dis-tinct Element Method (DEM) has also been developed to simulate the behaviour of URM walls be-fore and after retrofitting. The model is then further developed by applying a seismic wave to the wall to simulate the wall behavior under earthquake loads before and after retrofitting.
文摘Past earthquake disasters in Greece, during the last thirty years, demonstrate that the severity of destruction is not only due to the intensity of the seismic event but also to the urbanization of the affected region and the vulnerability of certain types of buildings. Considerable damage was sustained by both old unreinforced masonry structures as well as by relatively new multistory reinforced concrete structures with "soft story" at their ground floor level. The most important observations made during six past earthquake disasters are presented in a summary form and discussed. The most remarkable case of extensive structural damage was caused from the resent Athens 1999 earthquake. The consequent discussion focuses on the following issues: (1) Classification of structural damage and their underlying causes. (2) Repair and strengthening of damaged structures. (3) Upgrade the seismic design. (4) Plans for earthquake preparedness. (5) Assessing the vulnerability of certain type of structures (schools, hospitals, public buildings etc). (6) Education specialized in earthquake engineering. (7) The enrichment of the strong motion data base.
文摘In several parts of the world, disposal of waste materials such as fly ash is a great problem. Application of waste materials as structural fills in foundations is one of the best solutions to disposal problems, because wastes can be used in large volumes in such applications. There may be difficulty due to poor load-bearing capacity of fly ash, especially when footing rests on the top of the fly ash fill slope. Inclusion of polymeric reinforcements as horizontal sheets within the fill may be one of the most viable solutions to improving the load-bearing capacity of reinforced fly ash slope, and it is particularly important for the situations where foundations need to be located either on the top of a slope or on slope itself. The present work is aimed at investigating the efficacy of a single layer of reinforcement in improving the lo, ad-bearing capacity when it gets incorporated within the body of a model fly ash embankment slope. An increase in load bearing capacity due to the incorporation of reinforcement in the model slope was found by conducting laboratory tests. Experimental results were compared by numerical values obtained using software GEO5 and PLAXIS.
文摘The reinforced two layered foundation bed considered for study consists of a layer of granular fill overlying soft non-homogeneous clay with inclusion or reinforcement (geosymhetic strips, grids or sheets) in single layer at soil-granular fill interface A method is developed to estimate the bearing capacity of a strip footing on the surface of a reinforced foundation bed over a finite layer of clay whose undrained strength increases linearly with depth incorporating the contribution of axial resistance of the reinforcement together with those of granular fill and soft ground. Parametric studies presented quantify the improvement in bearing capacity.
文摘Timber bridges can provide an economical alternative to concrete and steel structures, particularly in rural areas where vehicle traffic is light to moderate. The wooden components of bridges have historically been preserved with either an oil type or waterborne preservative system to protect the wood from decay in order to maintain required performance standards for an extended period of time. The focus of this paper is to describe some of the key preservatives, research and case studies that support use of preserved wood, and some important steps to follow for the appropriate and safe use of preserved wood when the planned application will be in or over aquatic and wetland environments. A wealth of scientific information has been collected and analyzed that clearly suggests the use of preserved wood does not present a significant adverse effect on aquatic and wetland environments. This conclusion is based on two decades of empirical research and case study evaluating the environmental fate and effects of preserved wood, level of migration of contaminates into aquatic and marine environments, and the preserved wood environment. This is particularly true when risks are properly assessed on a project site, the appropriate preservative is selected and the wood is preserved to the Western Wood Preservers Institute's BMPs (best management practices), along with properly installing and maintaining the preserved material. To assist with the assessment process, peer-reviewed risk assessment models for 11 commonly used preservatives have been developed that provide for streamlined data entry by users and allow for evaluation of a structure above and below water. A companion preliminary screening level assessment tool is also available. When these measures are properly utilized engineers, biologists and other responsible officials can be confident that the service life of the preserved wood components will more than likely meet the required performance standards in an environmentally safe manner for up to 50 or more years on a majority of timber bridge projects.
基金Projects(41202220,41472278,51478438)supported by the National Natural Science Foundation of ChinaProjects(20120022120003,20134101120009)supported by the Research Fund for the Doctoral Program of Higher Education,China+1 种基金Project(2652012065)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(14A560014)supported by the Key Project of Education Department in Henan Province,China
文摘In order to investigate the seismic performance of geosynthetic reinforced and pile supported(GRPS) embankment under seismic loads, an input method for three-dimensional oblique incidence of P wave was proposed. This method is based on the explicit finite element method while considering the viscous-spring artificial boundary(VSAB) condition. Using the proposed method, a numerical study was conducted, and the influence of oblique incidence on the seismic response of GRPS embankment under the oblique incident P waves was analyzed. The results indicate that in comparison with vertical incidence, the oblique incidence can significantly increase the displacement, velocity and acceleration of key locations in the GRPS embankment. The existence of geosynthetics can alleviate the impact of seismic load on the response of the embankment to a certain degree. Moreover, the number of reinforcement layers and modulus of geogrid also greatly influence the seismic performance of GRPS embankment.
文摘The present work discusses the outcomes of recent experimental tests and numerical simulations carried out on full scale reinforced concrete (RC) non-ductile frames retrofitted with dissipative steel braces, i.e. innovative buckling restrained braces (BRBs). Experimental tests were performed on two sample full scale RC framed buildings designed for gravity loads only. Such frames were subjected to cyclic pushovers to investigate their structural performance under different levels of earthquake loadings. The outcomes of the performed experimental tests demonstrate the efficiency and reliability of utilizing BRBs to retrofit non ductile RC frames. These outcomes were confirmed by refined non linear static and response history analyses carried out on an existing RC school framed building designed without seismic details and retrofitted with BRBs similar to those adopted for the tested full-scale frame. In such sample building the BRBs are placed along the perimeter of the existing frames to minimize the interruption of the functionality of the school and for easy of maintenance in the aftermath of major earthquake ground motions. The seismic performance assessment of the retrofitted structural system is illustrated in a detailed manner. Local and global response quantities are presented. The values of the global overstrength Ω for the case study vary between 2.14 and 2.54 for the retrofitted framed building. The translation ductility μ△-values range between 2.07 and 2.36. The response modification factor (or behaviour factor, namely R- or q-factor) is on average equal to 5.0. Additionally, the estimated maximum axial ductility of the BRBs is about 10. Finally, the cost-effectiveness of the adopted retrofitting scheme is emphasized and further needs for the application of BRBs are highlighted.
基金Supported by National Science Fund for Distinguished Young Scholars of China( No. 50425824
文摘Based on a series of previous studies, an experiment on the integral seismic behavior of a 1/3 scaled model of two-bay and three-story reinforced concrete frame with split columns at lower two stories is performed under cyclic loading. The original columns at lower two stories of the model frame are short columns and they are replaced by the split columns. The hysteresis curves between the horizontal cyclic load and the lateral displacement at the top of the model frame, indicate that under the cyclic loading, the model frame undergoes the process of cracking, yielding, and maximum loading before being destroyed at the ultimate load. They also indicate that the model frame has better ductility, and the ratio of the ultimate displacement to the yielding displacement, reaches 6.0. The yielding process of the model frame shows that for the frame with split columns, plastic hinges are generated at the ends of beams and then the columns begin yielding while the frame still possesses the bearing and deformation capacity. The design idea of directly changing the short column to long one in the reinforced concrete frame may be realized by replacing the short column with the split one.
文摘The subject structure was consisted of a proto-type house with plan dimensions of 8 m ×4 m. A variety of materials was used to the construction, with special emphasis on using environmentally friendly non-toxic materials. The structure's core consisted of reinforced concrete frames with masonry infill walls. Inside faces of the walls and the roof's outside face were covered with proprietary composite panels, which are manufactured with a mixture of cement, volcanic ash, and local sawmill waste. These panels were analyzed for their physical and chemical properties, as well as for their resistance to decay and insects when subjected to extreme conditions for 15 years. The panels have also shown to provide thermal insulation and nonflammable when in direct contact with fire. The roof surface was further covered with a blend of local drought-resistant succulents and cacti. This study provides a detailed review of the construction process and materials employed.
基金Supported by National Natural Science Foundation of China (No. 10902073)
文摘To investigate the mechanical behavior of segmental lining, a three-dimensional numerical analysis and test using three actual segments were used to analyze the effects of axial force and reinforcement ratio on the failure mechanism and ultimate bearing capacity of segmental lining. Both numerical and test results confirmed that the cracking load, yield and ultimate load were strongly influenced by axial force, and it was also proved that the yield and ultimate load would increase with the increase of reinforcement ratio, but the cracking load was almost not affected. The cracking load, yield and ultimate load are about 28.7%, 500% and 460% larger due to the effect of axial force respectively. The comparison between numerical calculation and test results showed that the finite element analysis resuits were in good agreement with the test results.
文摘In many seismically active regions of the world there are large numbers of masonry buildings. Most of these buildings have not been designed for seismic loads. Recent earthquakes have shown that many of these buildings are seismically vulnerable and should be considered for retrofitting. Different conventional and unconventional retrofitting techniques are available to increase the strength and/or ductility of unreinforced masonry (URM) walls. This paper reviews and discusses seismic retrofitting of masonry walls with emphasis on the conventional techniques. Retrofitting procedures are discussed with regard to a case study: a stone masonry building in lrpinia region, damaged by the 1980 earthquake. The interventions are evaluated by means of finite elements with a macroelement obtained with a homogenization technique. Linear and nonlinear procedures are compared, and peculiarities of each procedure are shown.
基金The National Natural Science Foundation of China(No.51678141)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX17_0128)the Fundamental Research Funds for the Central Universities
文摘To evaluate the coupling pounding-friction effect between bridge girders and retainers and its influence on bridge seismic response, a reinforced concrete (RC) continuous bridge is selected as the research object. Three bridge finite element (FE) models were built using OpenSees, in which the longitudinal and transverse pounding elements, as well as the transverse failure element of bearings were introduced. Based on this, tire seismic response analysis considering the coupling pounding-friction effect was conducted for the continuous bridge subjected to bi-directional ground motions. Furthermore, the influential parameters were analyzed. The analysis results indicate that the coupling pounding-friction effect can alter the internal force distribution of the bridge structure and generate additional torsional force to bridge columns. The friction coefficient and longitudinal pounding gap size are two important factors. The appropriate friction coefficient and longitudinal pounding gap size can significantly reduce seismic response of girders, and effectively transfer part of the girder inertia force from the fixed columns to the sliding columns, which can reduce the seismic demands of the fixed columns and improve the seismic performance of continuous bridge structures.
文摘The risk during construction and in the operation of the underground gas storage (UGS) was analyzed. One of most important risk which should be prevented is large deformation or destruction of the steel lining. The specific deformation of the steel lining needs to be inside the acceptable value. This paper presents lined rock cavern (LRC) concept and specific deformations, which can occur under operation of underground gas storage. Analysis is performed with different (3D model and axis symmetrical) FEM models and analytical model. We made a comparison between analytical calculation and FEM calculation. Concrete wall is mechanically not regarded as reinforced concrete structure which means that concrete will crack. Finally, we determined the minimum value of Young's modulus, which satisfies the condition of maximum deformation of steel lining.