Seismic influence of P-Δ effect is the subject of this study.First,it is pointed out that the elastic static amplification factor shall be isolated in formulating the dynamic inelastic second order effect.An amplific...Seismic influence of P-Δ effect is the subject of this study.First,it is pointed out that the elastic static amplification factor shall be isolated in formulating the dynamic inelastic second order effect.An amplification factor for the static inelastic P-Δ effect is derived.Seismic force reduction factors(SFRF)for given ductility and stability coefficients are computed for one-story,one-span frames.The P-Δ amplification factors for seismic base shears are obtained by dividing SFRFs with and without P-Δ effect.Both P-Δ amplification factors and SFRFs are presented separately with two kinds of period abscissas.The P-Δ amplification factors are dependent on periods with the maximum occurring at about 0.75 s for site type C and approach to the static inelastic counterpart at long periods.Post-yield stiffness cannot fully counteract the adverse impact of the P-Δ effect.Formulas for seismic P-Δ amplification factors are proposed and compared to results of others.Collapse capacity spectra(CCS)are reviewed and their application in codes discussed.Available CCSs are compared with SFRFs with finite ductility computed for two ensembles of seismic records.A comparison reveals that the SFRFs are affected by seismic records,and available CCSs do not always provide upper limits for the SFRFs when stability coefficients are greater than 0.1 for frame models.展开更多
The main purpose of this paper is to study the collapse capacity of single degree of freedom(SDOF)systems and to produce fragility curves as well as collapse capacity spectra while considering a broad range of structu...The main purpose of this paper is to study the collapse capacity of single degree of freedom(SDOF)systems and to produce fragility curves as well as collapse capacity spectra while considering a broad range of structural parameters,including system degradation,the P-Δeffect,ductility capacity and the post-capping stiffness ratio.The modified Ibarra-Krawinkler deterioration model was used to consider hysteretic behavior.A comprehensive study was conducted to extract the collapse capacity spectrum of SDOF systems with a wide range of periods,varying from 0.05 to 4 s,to cover short,intermediate and long periods.Incremental dynamic analysis(IDA)was performed for SDOF systems to identify the condition in which the collapse capacity of the system is determined.The IDAs were performed using different sets of seismic ground motions.The ground motion records were categorized into different sets based on three spectral shape parameters,including the epsilon,SaRatio and N_(p).The collapse fragility curves of SDOF systems with different periods were extracted to illustrate the collapse capacity at different probability levels.The results show that structural degradation and ductility as well as the spectral shape parameters significantly affect the collapse capacity of SDOF systems.On the other hand,the post-capping stiffness ratio and small levels of the P-Δeffect do not remarkably change collapse capacity.Also,the collapse capacity of SDOF systems is more sensitive to the records categorized based on SaRatio and N_(p)than those classified based on epsilon.展开更多
文摘Seismic influence of P-Δ effect is the subject of this study.First,it is pointed out that the elastic static amplification factor shall be isolated in formulating the dynamic inelastic second order effect.An amplification factor for the static inelastic P-Δ effect is derived.Seismic force reduction factors(SFRF)for given ductility and stability coefficients are computed for one-story,one-span frames.The P-Δ amplification factors for seismic base shears are obtained by dividing SFRFs with and without P-Δ effect.Both P-Δ amplification factors and SFRFs are presented separately with two kinds of period abscissas.The P-Δ amplification factors are dependent on periods with the maximum occurring at about 0.75 s for site type C and approach to the static inelastic counterpart at long periods.Post-yield stiffness cannot fully counteract the adverse impact of the P-Δ effect.Formulas for seismic P-Δ amplification factors are proposed and compared to results of others.Collapse capacity spectra(CCS)are reviewed and their application in codes discussed.Available CCSs are compared with SFRFs with finite ductility computed for two ensembles of seismic records.A comparison reveals that the SFRFs are affected by seismic records,and available CCSs do not always provide upper limits for the SFRFs when stability coefficients are greater than 0.1 for frame models.
文摘The main purpose of this paper is to study the collapse capacity of single degree of freedom(SDOF)systems and to produce fragility curves as well as collapse capacity spectra while considering a broad range of structural parameters,including system degradation,the P-Δeffect,ductility capacity and the post-capping stiffness ratio.The modified Ibarra-Krawinkler deterioration model was used to consider hysteretic behavior.A comprehensive study was conducted to extract the collapse capacity spectrum of SDOF systems with a wide range of periods,varying from 0.05 to 4 s,to cover short,intermediate and long periods.Incremental dynamic analysis(IDA)was performed for SDOF systems to identify the condition in which the collapse capacity of the system is determined.The IDAs were performed using different sets of seismic ground motions.The ground motion records were categorized into different sets based on three spectral shape parameters,including the epsilon,SaRatio and N_(p).The collapse fragility curves of SDOF systems with different periods were extracted to illustrate the collapse capacity at different probability levels.The results show that structural degradation and ductility as well as the spectral shape parameters significantly affect the collapse capacity of SDOF systems.On the other hand,the post-capping stiffness ratio and small levels of the P-Δeffect do not remarkably change collapse capacity.Also,the collapse capacity of SDOF systems is more sensitive to the records categorized based on SaRatio and N_(p)than those classified based on epsilon.
