For the evaluation of structures with known ductility demands,the constant-ductility displacement ratio spectra(CDDRS) are particularly useful for providing inelastic displacement ratios to estimate maximum lateral in...For the evaluation of structures with known ductility demands,the constant-ductility displacement ratio spectra(CDDRS) are particularly useful for providing inelastic displacement ratios to estimate maximum lateral inelastic displacement demands from maximum elastic displacement demands.The CDDRS are computed for single-degree-of-freedom systems(SDOF) by considering or ignoring P-Δ effect for different ductility levels when subjected to 344 earthquake ground motions recorded in four site classes.The modified expressions of CDDRS for P-Δ effect are proposed.It is concluded that the P-Δ effect on CDDRS is significant,and the effect increases with the increase of ductility level.In the long-period region,the CDDRS ignoring P-Δ effect almost conforms to the equal-displacement rule.But in the case of higher ductility level,the CDDRS considering P-Δ effect are much higher than 1.0,which do not conform to the equal-displacement rule.展开更多
Residual displacement,as a significant measure of structural inelasticity,is effectively used in post-earthquake seismic assessment of structures.This demand can be considered for seismic evaluation of structures unde...Residual displacement,as a significant measure of structural inelasticity,is effectively used in post-earthquake seismic assessment of structures.This demand can be considered for seismic evaluation of structures under multiple earthquakes.This study introduces a simple and novel index to predict the residual displacement of mainshock-damaged structures against subsequent aftershock.The proposed index is defined as a ratio between residual displacement of damaged structures against aftershock and peak inelastic displacement of intact structures under mainshock.In this study,constantstrength spectra based on the index are developed considering the effects of important structural characteristics and also significant seismic parameters.Moreover,analytical equations are presented to predict the proposed index for bi-linear single-degree-of-freedom(SDOF)systems considering both the effects of positive and negative polarities of aftershock.Furthermore,an equation is suggested to estimate the peak inelastic displacement of intact systems under mainshock,which is required to compute the index.展开更多
Based on the fact that the shear stress along anchorage segment is neither linearly nor uniformly distributed, the load transfer mechanism of the tension type anchor was studied and the mechanical characteristic of an...Based on the fact that the shear stress along anchorage segment is neither linearly nor uniformly distributed, the load transfer mechanism of the tension type anchor was studied and the mechanical characteristic of anchorage segment was analyzed. Shear stress?strain relationship of soil surrounding anchorage body was simplified into three-folding-lines model consisting of elastic phase, elasto-plastic phase and residual phase considering its softening characteristic. Meanwhile, shear displacement method that has been extensively used in the analysis of pile foundation was introduced. Based on elasto-plastic theory, the distributions of displacement, shear stress and axial force along the anchorage segment of tension type anchor were obtained, and the formula for calculating the elastic limit load was also developed accordingly. Finally, an example was given to discuss the variation of stress and displacement in the anchorage segment with the loads exerted on the anchor, and a program was worked out to calculate the anchor maximum bearing capacity. The influence of some parameters on the anchor bearing capacity was discussed, and effective anchorage length was obtained simultaneously. The results show that the shear stress first increases and then decreases and finally trends to the residual strength with increase of distance from bottom of the anchorage body, the displacement increases all the time with the increase of distance from bottom of the anchorage body, and the increase of velocity gradually becomes greater.展开更多
The present paper aims to establish a versatile strength theory suitable for elasto-plastic analysis of underground tunnel surrounding rock. In order to analyze the effects of intermediate principal stress and the roc...The present paper aims to establish a versatile strength theory suitable for elasto-plastic analysis of underground tunnel surrounding rock. In order to analyze the effects of intermediate principal stress and the rock properties on its deformation and failure of rock mass, the generalized nonlinear unified strength theory and elasto-plastic mechanics are used to deduce analytic solution of the radius and stress of tunnel plastic zone and the periphery displacement of tunnel under uniform ground stress field. The results show that: intermediate principal stress coefficient b has significant effect on the plastic range,the magnitude of stress and surrounding rock pressure. Then, the results are compared with the unified strength criterion solution and Mohr–Coulomb criterion solution, and concluded that the generalized nonlinear unified strength criterion is more applicable to elasto-plastic analysis of underground tunnel surrounding rock.展开更多
在统计意义上设计反应谱通常表示多条地震波反应结果的平均,利用等延性强度折减系数谱对弹性设计位移谱进行折减间接建立的弹塑性设计位移谱,在这方面与弹性设计位移谱并不能很好对应.为此基于3类场地各20条地震波的统计分析,研究了利...在统计意义上设计反应谱通常表示多条地震波反应结果的平均,利用等延性强度折减系数谱对弹性设计位移谱进行折减间接建立的弹塑性设计位移谱,在这方面与弹性设计位移谱并不能很好对应.为此基于3类场地各20条地震波的统计分析,研究了利用等延性强度折减系数谱间接建立的弹塑性位移谱与统计平均的弹塑性位移谱的偏差.结果发现前者会导致偏于危险的结果,特别是对软弱场地和位移延性系数大于4时.通过对国内外学者建议的6组等延性强度折减系数谱的比较分析,以精度较高的V id ic等建议的强度折减系数谱为准,并在间接方法中引入与位移延性系数、场地条件及结构周期相关的修正系数,建议了与弹性设计位移谱统计意义一致的弹塑性设计位移谱.展开更多
基金Supported by the National Natural Science Foundation of China(Grant No.90815014,50608024)Opening Laboratory of Earthquake Engineering and Engineering Vibration Foundation(Grant No.2007001)Opening Laboratory of Seismic Control and Structural Safety Foundation(Grant No.0808)
文摘For the evaluation of structures with known ductility demands,the constant-ductility displacement ratio spectra(CDDRS) are particularly useful for providing inelastic displacement ratios to estimate maximum lateral inelastic displacement demands from maximum elastic displacement demands.The CDDRS are computed for single-degree-of-freedom systems(SDOF) by considering or ignoring P-Δ effect for different ductility levels when subjected to 344 earthquake ground motions recorded in four site classes.The modified expressions of CDDRS for P-Δ effect are proposed.It is concluded that the P-Δ effect on CDDRS is significant,and the effect increases with the increase of ductility level.In the long-period region,the CDDRS ignoring P-Δ effect almost conforms to the equal-displacement rule.But in the case of higher ductility level,the CDDRS considering P-Δ effect are much higher than 1.0,which do not conform to the equal-displacement rule.
文摘Residual displacement,as a significant measure of structural inelasticity,is effectively used in post-earthquake seismic assessment of structures.This demand can be considered for seismic evaluation of structures under multiple earthquakes.This study introduces a simple and novel index to predict the residual displacement of mainshock-damaged structures against subsequent aftershock.The proposed index is defined as a ratio between residual displacement of damaged structures against aftershock and peak inelastic displacement of intact structures under mainshock.In this study,constantstrength spectra based on the index are developed considering the effects of important structural characteristics and also significant seismic parameters.Moreover,analytical equations are presented to predict the proposed index for bi-linear single-degree-of-freedom(SDOF)systems considering both the effects of positive and negative polarities of aftershock.Furthermore,an equation is suggested to estimate the peak inelastic displacement of intact systems under mainshock,which is required to compute the index.
基金Project(20050532021) supported by the Research Fund for the Doctoral Program of Higher Education
文摘Based on the fact that the shear stress along anchorage segment is neither linearly nor uniformly distributed, the load transfer mechanism of the tension type anchor was studied and the mechanical characteristic of anchorage segment was analyzed. Shear stress?strain relationship of soil surrounding anchorage body was simplified into three-folding-lines model consisting of elastic phase, elasto-plastic phase and residual phase considering its softening characteristic. Meanwhile, shear displacement method that has been extensively used in the analysis of pile foundation was introduced. Based on elasto-plastic theory, the distributions of displacement, shear stress and axial force along the anchorage segment of tension type anchor were obtained, and the formula for calculating the elastic limit load was also developed accordingly. Finally, an example was given to discuss the variation of stress and displacement in the anchorage segment with the loads exerted on the anchor, and a program was worked out to calculate the anchor maximum bearing capacity. The influence of some parameters on the anchor bearing capacity was discussed, and effective anchorage length was obtained simultaneously. The results show that the shear stress first increases and then decreases and finally trends to the residual strength with increase of distance from bottom of the anchorage body, the displacement increases all the time with the increase of distance from bottom of the anchorage body, and the increase of velocity gradually becomes greater.
文摘The present paper aims to establish a versatile strength theory suitable for elasto-plastic analysis of underground tunnel surrounding rock. In order to analyze the effects of intermediate principal stress and the rock properties on its deformation and failure of rock mass, the generalized nonlinear unified strength theory and elasto-plastic mechanics are used to deduce analytic solution of the radius and stress of tunnel plastic zone and the periphery displacement of tunnel under uniform ground stress field. The results show that: intermediate principal stress coefficient b has significant effect on the plastic range,the magnitude of stress and surrounding rock pressure. Then, the results are compared with the unified strength criterion solution and Mohr–Coulomb criterion solution, and concluded that the generalized nonlinear unified strength criterion is more applicable to elasto-plastic analysis of underground tunnel surrounding rock.
文摘在统计意义上设计反应谱通常表示多条地震波反应结果的平均,利用等延性强度折减系数谱对弹性设计位移谱进行折减间接建立的弹塑性设计位移谱,在这方面与弹性设计位移谱并不能很好对应.为此基于3类场地各20条地震波的统计分析,研究了利用等延性强度折减系数谱间接建立的弹塑性位移谱与统计平均的弹塑性位移谱的偏差.结果发现前者会导致偏于危险的结果,特别是对软弱场地和位移延性系数大于4时.通过对国内外学者建议的6组等延性强度折减系数谱的比较分析,以精度较高的V id ic等建议的强度折减系数谱为准,并在间接方法中引入与位移延性系数、场地条件及结构周期相关的修正系数,建议了与弹性设计位移谱统计意义一致的弹塑性设计位移谱.
