Seismic collapse capacity assessment of SDOF systems incorporating duration and instability effects

Abstract

This paper presents a detailed investigation into the seismic response of non-deteriorating and deteriorating single degree-of-freedom systems controlled by P − Δ effects, with due account for the influence of earthquake duration. In order to isolate the effect of duration from other ground motion characteristics, 77 pairs of records with equivalent spectral shapes are considered in the study. The structural characteristics examined include the structural period, applied gravity loading, post-yield stiffness, viscous damping, material hysteretic behaviour, as well as the level of cyclic deterioration within the pinching systems. Detailed incremental dynamic analyses are carried out, considering an intensity measure corresponding to the spectral acceleration at the structural period of vibration of the system. Based on the incremental dynamic analysis results, predictive relationships are proposed for determining the structural collapse capacity, accounting for the influence of key parameters including instability and duration effects. The median and dispersion of the collapse capacity distribution embedded in the predictive models are also presented. The effect of duration is shown to increase with longer structural periods and to decrease with higher P − Δ levels. The more rapid instigation of dynamic instability in relatively stiff systems is also shown to reduce their comparative sensitivity to variations in ground motion characteristics. Overall, it is indicated that disregarding the influence of duration could lead to over-estimations of up to 50% in the collapse capacity. The paper concludes with a discussion of other sources of structural damage that instigate collapse when using records with equivalent spectral shape but without especial consideration for duration effects.

Stability Consideration in Design of Steel Structures: A Review

“…Instability of a steel structure are caused by several reasons which includes neglecting of stability design, human error during construction phase, degradation of steel due to fire and failures due to seismic event (Alpsten, 2017;Bravo-Haro et al, 2020;Xu et al, 2018). To avoid these issues as mentioned, the consideration of stability should be improved to ensure better structural integrity.…”

Seismic collapse capacity and dispersion spectra for self‐centering braced frames considering uncertainty propagation

“…To identify the influence of system parameters on the collapse capacity, single‐degree‐of‐freedom (SDOF) systems are regarded as an effective approach with relatively small computational efforts. Comprehensive studies for assessment of structural collapse associated with typical peak‐oriented, pinched and bilinear hysteretic behaviors through SDOF analysis have been conducted 23–27 . As for the SC systems, however, the collapse capacity has not been systematically evaluated in the previous studies.…”

“…As for the SC systems, however, the collapse capacity has not been systematically evaluated in the previous studies. Besides, the P‐Δ effect also plays an important role in the sideway collapse, which may reduce lateral load‐carrying capacity and effective lateral stiffness, and lead to dynamic instability 24,27 . Therefore, the estimation of the collapse capacity of SC systems, especially in SDOF analysis, may be unreliable if the P‐Δ effect is not properly considered.…”

“…Comprehensive studies for assessment of structural collapse associated with typical peak-oriented, pinched and bilinear hysteretic behaviors through SDOF analysis have been conducted. [23][24][25][26][27] As for the SC systems, however, the collapse capacity has not been systematically evaluated in the previous studies. Besides, the P-Δ effect also plays an important role in the sideway collapse, which may reduce lateral load-carrying capacity and effective lateral stiffness, and lead to dynamic instability.…”

“…Besides, the P-Δ effect also plays an important role in the sideway collapse, which may reduce lateral load-carrying capacity and effective lateral stiffness, and lead to dynamic instability. 24,27 Therefore, the estimation of the collapse capacity of SC systems, especially in SDOF analysis, may be unreliable if the P-Δ effect is not properly considered. Meantime, recalling that the collapse potential of SC systems is mainly controlled by the inelastic deformability of components, pulse-like near-fault ground motions can further amplify the deformation demand of SC systems and hence increase the collapse risk.…”