In this study, the influence of confined concrete models on the response of reinforced concrete structures is investigatedat member and global system levels. The commonly encountered concrete models such as Modified K...In this study, the influence of confined concrete models on the response of reinforced concrete structures is investigatedat member and global system levels. The commonly encountered concrete models such as Modified Kent-Park, Saatçioğlu-Razvi, and Mander are considered. Two moment-resisting frames designed according to thepre-modern code are taken into consideration to reflect the example of an RC moment-resisting frame in thecurrent building stock. The building is in an earthquake-prone zone located on Z3 Soil Type. The inelasticresponse of the building frame is modelled by considering the plastic hinges formed on each beam and columnelement for different concrete classes and stirrups spacings. The models are subjected to non-linear static analyses.The differences between confined concrete models are comparatively investigated at both reinforced concretemember and system levels. Based on the results of the comparative analysis, it is revealed that the column behaviouris mostly influenced by the choice of model, due to axial loads and confinement effects, while the beams areless affected, and also it is observed that the differences exhibited in the moment-curvature response of columncross-sections do not significantly affect the overall behaviour of the global system. This highlights the critical roleof model selection relative to the concrete strength and stirrup spacing of the member.展开更多
The control criteria for structural deformation and the evaluation of operational safety performance for large-diameter shield tunnel segments are not yet clearly defined.To address this issue,a refined 3D finite elem...The control criteria for structural deformation and the evaluation of operational safety performance for large-diameter shield tunnel segments are not yet clearly defined.To address this issue,a refined 3D finite element model was established to analyze the transverse deformation response of a large-diameter segmental ring.By analyzing the stress,deformation,and crack distribution of large-diameter segments under overload conditions,the transverse deformation of the segmental ring could be divided into four stages.The main reasons for the decrease in segmental ring stiffness were found to be the extensive development of cracks and the complete formation of four plastic hinges.The deformation control value for the large-diameter shield tunnel segment is chosen as 8%o of the segment's outer diameter,representing the transverse deformation during the formation of the first semi-plastic hinge(i.e.,the first yield point)in the structure.This control value can serve as a reinforcement standard for preventing the failure of large-diameter shield tunnel segments.The flexural bearing capacity characteristic curve of segments was used to evaluate the structural strength of a large-diameter segmental ring.It was discovered that the maximum internal force combination of the segment did not exceed the segment ultimate bearing capacity curve(SUBC).However,the combination of internal force at 9°,85°,and 161°of the joints,and their symmetrical locations about the 0°-180°axis exceeded the joint ultimate bearing capacity curve(JUBC).The results indicate that the failure of the large-diameter segment lining was mainly due to insufficient joint strength,leading to an instability failure.The findings from this study can be used to develop more effective maintenance strategies for large-diameter shield tunnel segments to ensure their long-term performance.展开更多
Global failure mechanism, i.e., the strong-column weak-beam mechanism, can provide higher total energy dissipation capacity with less ductility demand on components than other failure modes, and results in a more unif...Global failure mechanism, i.e., the strong-column weak-beam mechanism, can provide higher total energy dissipation capacity with less ductility demand on components than other failure modes, and results in a more uniform story drift distribution and higher resistance to earthquake loads at the system level. However, the current code-based elastic design method cannot guarantee the global failure mechanism of frame structures under severe earthquakes. In this paper, a simple, but practical design procedure is proposed to ensure the global failure mechanism of reinforced concrete(RC) frame structures by redesigning the columns using the column tree method(CTM). CTM considers the yield limit state of all beams and column bases. The code-based design is firstly carried out to determine the section information of all beams and base columns. Then, the internal force demands applied on the column tree can be derived. Lastly, the column moments, shear forces and axial forces are determined according to the free-body diagram of CTM to finish the column redesign. Two RC frame structures with 6 and 12 stories are illustrated to verify the design procedure. The analytical results demonstrate the proposed approach can realize the global failure mechanism.展开更多
文摘In this study, the influence of confined concrete models on the response of reinforced concrete structures is investigatedat member and global system levels. The commonly encountered concrete models such as Modified Kent-Park, Saatçioğlu-Razvi, and Mander are considered. Two moment-resisting frames designed according to thepre-modern code are taken into consideration to reflect the example of an RC moment-resisting frame in thecurrent building stock. The building is in an earthquake-prone zone located on Z3 Soil Type. The inelasticresponse of the building frame is modelled by considering the plastic hinges formed on each beam and columnelement for different concrete classes and stirrups spacings. The models are subjected to non-linear static analyses.The differences between confined concrete models are comparatively investigated at both reinforced concretemember and system levels. Based on the results of the comparative analysis, it is revealed that the column behaviouris mostly influenced by the choice of model, due to axial loads and confinement effects, while the beams areless affected, and also it is observed that the differences exhibited in the moment-curvature response of columncross-sections do not significantly affect the overall behaviour of the global system. This highlights the critical roleof model selection relative to the concrete strength and stirrup spacing of the member.
基金supported by the National Natural Science Foundation of China(Nos.52122807,52090082,and 51938005)the Youth Science and Technology Innovation Talent Project of Hunan Province(No.2021RC3043),China。
文摘The control criteria for structural deformation and the evaluation of operational safety performance for large-diameter shield tunnel segments are not yet clearly defined.To address this issue,a refined 3D finite element model was established to analyze the transverse deformation response of a large-diameter segmental ring.By analyzing the stress,deformation,and crack distribution of large-diameter segments under overload conditions,the transverse deformation of the segmental ring could be divided into four stages.The main reasons for the decrease in segmental ring stiffness were found to be the extensive development of cracks and the complete formation of four plastic hinges.The deformation control value for the large-diameter shield tunnel segment is chosen as 8%o of the segment's outer diameter,representing the transverse deformation during the formation of the first semi-plastic hinge(i.e.,the first yield point)in the structure.This control value can serve as a reinforcement standard for preventing the failure of large-diameter shield tunnel segments.The flexural bearing capacity characteristic curve of segments was used to evaluate the structural strength of a large-diameter segmental ring.It was discovered that the maximum internal force combination of the segment did not exceed the segment ultimate bearing capacity curve(SUBC).However,the combination of internal force at 9°,85°,and 161°of the joints,and their symmetrical locations about the 0°-180°axis exceeded the joint ultimate bearing capacity curve(JUBC).The results indicate that the failure of the large-diameter segment lining was mainly due to insufficient joint strength,leading to an instability failure.The findings from this study can be used to develop more effective maintenance strategies for large-diameter shield tunnel segments to ensure their long-term performance.
基金supported by the National Natural Science Foundation of China(Grant Nos.51261120376 and 91315301)Scholarship Award for Excellent Doctoral Student granted by Ministry of Education of China
文摘Global failure mechanism, i.e., the strong-column weak-beam mechanism, can provide higher total energy dissipation capacity with less ductility demand on components than other failure modes, and results in a more uniform story drift distribution and higher resistance to earthquake loads at the system level. However, the current code-based elastic design method cannot guarantee the global failure mechanism of frame structures under severe earthquakes. In this paper, a simple, but practical design procedure is proposed to ensure the global failure mechanism of reinforced concrete(RC) frame structures by redesigning the columns using the column tree method(CTM). CTM considers the yield limit state of all beams and column bases. The code-based design is firstly carried out to determine the section information of all beams and base columns. Then, the internal force demands applied on the column tree can be derived. Lastly, the column moments, shear forces and axial forces are determined according to the free-body diagram of CTM to finish the column redesign. Two RC frame structures with 6 and 12 stories are illustrated to verify the design procedure. The analytical results demonstrate the proposed approach can realize the global failure mechanism.
