In consideration that behavior of curvature ductility of interior support directly influences the degree of moment modification of unbonded prestressed concrete (UPC) continuous structures, constitutive relationships ...In consideration that behavior of curvature ductility of interior support directly influences the degree of moment modification of unbonded prestressed concrete (UPC) continuous structures, constitutive relationships of concrete, non-prestressed reinforcement and prestressed reinforcement used for nonlinear analysis are given. Through simulation analysis on simple beams subjected to single loading at the middle of the span, the law of factors influencing curvature ductility, such as global reinforcing index, prestressing degree, effective prestress, strength of concrete and grade of non-prestressed reinforcement are explored. Based on these researches, calculating formula of curvature ductility coefficient of UPC beams is established, which provides basic data for further research on plastic design of UPC indeterminate structures.展开更多
The earthquake forces used in design codes of buildings should be theoretically determinable. This work examines the seismic force modification factor R based on elastic-plastic time-history earthquake analysis of SDO...The earthquake forces used in design codes of buildings should be theoretically determinable. This work examines the seismic force modification factor R based on elastic-plastic time-history earthquake analysis of SDOF systems, wherein the hys-teresis models are elastic-perfectly-plastic (EPP), elastic-linearly-hardening (ELH), shear-slipped and bilinear-elastic. The latter two models are analysed for separating the effect of the ductility and the energy-dissipating capacity. Three-hundred eighty-eight earthquake records from different site conditions are used in analysis. The ductility is taken to be 2, 3, 4, 5 and 6, with the damping ratio being 0.02, 0.035 and 0.05 respectively. The post-yield stiffness ratios 0.0, 0.1 and 0.2 are used in the analysis. The R spectra are standardized by the characteristic period of the earthquake records, which leads to a much smaller scatter in averaged numerical results. It was found that the most important factor determining R is the ductility. R increases more than linearly with ductility. The energy-dissipating capacity, damping and the post-yield stiffness are the less important factors. The energy dissipating capacity is important only for structures with short period and moderate period (0.3≤T/Tg<5.0). For EPP and ELH models, R for 0.05 damping is 10% to 15% smaller than for 0.02 damping. For EPP and ELH models, greater post-yield stiffness leads to greater R, but the influence of post-yield stiffness is obvious only when the post-yield stiffness is less than 10% of the initial stiffness. By means of statistical regression analysis the relation of the seismic force modification factor R with the natural period of the system and ductility for EPP and ELH models were established for each site and soil condition.展开更多
The research presented in this paper deals with the seismic protection of existing frame structures by means of passive energy dissipation. An iterative displacement-based procedure, based on capacity spectrum, to des...The research presented in this paper deals with the seismic protection of existing frame structures by means of passive energy dissipation. An iterative displacement-based procedure, based on capacity spectrum, to design dissipative bracings for seismic retrofitting of the frame structures is described, and some applications are discussed. The procedure can be used with any typology of dissipative device and for different performance targets. In this work, the procedure has been applied, with both traditional pushover （load profile proportional to first mode） and multimodal pushover, to an existing RC （reinforced concrete） frame building. In the application, the buckling restrained braces have been used in order to prevent damages to both the structure and non structural elements. The use of multimodal pushover proves to be more effective than pushover based on single mode in case of medium rise RC frame building （higher than 30 m） but, once this building is retrofitted, and therefore regularized, with a bracing system, the difference between using monomodal or multimodal pushover becomes insignificant.展开更多
The earthquake demand spectrum is often assumed as the average spectrum in the seismic design code or based upon probabilistic models to take into account the uncertainties of ground motion. The average spectrum can n...The earthquake demand spectrum is often assumed as the average spectrum in the seismic design code or based upon probabilistic models to take into account the uncertainties of ground motion. The average spectrum can not deal with the uncertainty of earthquake excitation. Furthermore, results of probabilistic analysis are suspicious when information describing the uncertainty is inadequate. Considering the uncertainties of peak acceleration of ground motion and characteristic period of response spectra using a double bounded convex set model, the bounds of the design spectrum and the demand spectrum were obtained based on Chinese seismic code. Then the convex analysis method was integrated into the capacity spectrum procedure to study the bound characteristics of target displacement. Finally, the target displacement was derived with an interval, and it is more objective and robust with respect to probabilistic perspective.展开更多
Standard finite element approaches are still ineffective in handling extreme material deformation, such as cases of large deformations and moving discontinuities due to severe mesh distortion. Among meshfree methods d...Standard finite element approaches are still ineffective in handling extreme material deformation, such as cases of large deformations and moving discontinuities due to severe mesh distortion. Among meshfree methods developed to overcome the ineffectiveness, Reproducing Kernel Particle Method (RKPM) has demonstrated its great suitability for structural analysis.This paper presents applications of RKPM in elasto-plastic problems after a review of meshfree methods and an introduction to RKPM. A slope stability problem in geotechnical engineering is analyzed as an illustrative case. The corresponding numerical simulations are carried out on an SGI Onyx3900 supercomputer. Comparison of the RKPM and the FEM under identical conditions showed that the RKPM is more suitable for problems where there exists extremely large strain such as in the case of slope sliding.展开更多
In this paper, through the investigation and research on some representative art academies, the difference between art academies and general institutions of higher learning in campus environment is explored in depth. ...In this paper, through the investigation and research on some representative art academies, the difference between art academies and general institutions of higher learning in campus environment is explored in depth. Hopefully, the specific characteristics of the design for campus environments of art academies as well as all sorts of factors causing the characteristics can be discovered, including the specific characteristics of campus subjects, the originality of campus buildings, and the novelty of campus sculpture.展开更多
文摘In consideration that behavior of curvature ductility of interior support directly influences the degree of moment modification of unbonded prestressed concrete (UPC) continuous structures, constitutive relationships of concrete, non-prestressed reinforcement and prestressed reinforcement used for nonlinear analysis are given. Through simulation analysis on simple beams subjected to single loading at the middle of the span, the law of factors influencing curvature ductility, such as global reinforcing index, prestressing degree, effective prestress, strength of concrete and grade of non-prestressed reinforcement are explored. Based on these researches, calculating formula of curvature ductility coefficient of UPC beams is established, which provides basic data for further research on plastic design of UPC indeterminate structures.
文摘The earthquake forces used in design codes of buildings should be theoretically determinable. This work examines the seismic force modification factor R based on elastic-plastic time-history earthquake analysis of SDOF systems, wherein the hys-teresis models are elastic-perfectly-plastic (EPP), elastic-linearly-hardening (ELH), shear-slipped and bilinear-elastic. The latter two models are analysed for separating the effect of the ductility and the energy-dissipating capacity. Three-hundred eighty-eight earthquake records from different site conditions are used in analysis. The ductility is taken to be 2, 3, 4, 5 and 6, with the damping ratio being 0.02, 0.035 and 0.05 respectively. The post-yield stiffness ratios 0.0, 0.1 and 0.2 are used in the analysis. The R spectra are standardized by the characteristic period of the earthquake records, which leads to a much smaller scatter in averaged numerical results. It was found that the most important factor determining R is the ductility. R increases more than linearly with ductility. The energy-dissipating capacity, damping and the post-yield stiffness are the less important factors. The energy dissipating capacity is important only for structures with short period and moderate period (0.3≤T/Tg<5.0). For EPP and ELH models, R for 0.05 damping is 10% to 15% smaller than for 0.02 damping. For EPP and ELH models, greater post-yield stiffness leads to greater R, but the influence of post-yield stiffness is obvious only when the post-yield stiffness is less than 10% of the initial stiffness. By means of statistical regression analysis the relation of the seismic force modification factor R with the natural period of the system and ductility for EPP and ELH models were established for each site and soil condition.
文摘The research presented in this paper deals with the seismic protection of existing frame structures by means of passive energy dissipation. An iterative displacement-based procedure, based on capacity spectrum, to design dissipative bracings for seismic retrofitting of the frame structures is described, and some applications are discussed. The procedure can be used with any typology of dissipative device and for different performance targets. In this work, the procedure has been applied, with both traditional pushover （load profile proportional to first mode） and multimodal pushover, to an existing RC （reinforced concrete） frame building. In the application, the buckling restrained braces have been used in order to prevent damages to both the structure and non structural elements. The use of multimodal pushover proves to be more effective than pushover based on single mode in case of medium rise RC frame building （higher than 30 m） but, once this building is retrofitted, and therefore regularized, with a bracing system, the difference between using monomodal or multimodal pushover becomes insignificant.
文摘The earthquake demand spectrum is often assumed as the average spectrum in the seismic design code or based upon probabilistic models to take into account the uncertainties of ground motion. The average spectrum can not deal with the uncertainty of earthquake excitation. Furthermore, results of probabilistic analysis are suspicious when information describing the uncertainty is inadequate. Considering the uncertainties of peak acceleration of ground motion and characteristic period of response spectra using a double bounded convex set model, the bounds of the design spectrum and the demand spectrum were obtained based on Chinese seismic code. Then the convex analysis method was integrated into the capacity spectrum procedure to study the bound characteristics of target displacement. Finally, the target displacement was derived with an interval, and it is more objective and robust with respect to probabilistic perspective.
文摘Standard finite element approaches are still ineffective in handling extreme material deformation, such as cases of large deformations and moving discontinuities due to severe mesh distortion. Among meshfree methods developed to overcome the ineffectiveness, Reproducing Kernel Particle Method (RKPM) has demonstrated its great suitability for structural analysis.This paper presents applications of RKPM in elasto-plastic problems after a review of meshfree methods and an introduction to RKPM. A slope stability problem in geotechnical engineering is analyzed as an illustrative case. The corresponding numerical simulations are carried out on an SGI Onyx3900 supercomputer. Comparison of the RKPM and the FEM under identical conditions showed that the RKPM is more suitable for problems where there exists extremely large strain such as in the case of slope sliding.
文摘In this paper, through the investigation and research on some representative art academies, the difference between art academies and general institutions of higher learning in campus environment is explored in depth. Hopefully, the specific characteristics of the design for campus environments of art academies as well as all sorts of factors causing the characteristics can be discovered, including the specific characteristics of campus subjects, the originality of campus buildings, and the novelty of campus sculpture.
