Effect of P-delta uncertainty on the seismic collapse capacity and its variability of single-degree-of freedom systems

This study assesses the effect of parameter uncertainty of non-deteriorating P-delta vulnerable single-degree-of-freedom systems on the median and dispersion of the collapse capacity. The post-yielding negative slope is a necessary condition of P-delta induced collapse that dominates the failure mode, and thus, it is the primary system parameter to be considered as a random variable. The parameter uncertainty on the collapse capacity is quantified with the first-order-second-moment method, and verified with the Latin hypercube sampling (LHS) technique. The total variability of the collapse capacity is estimated by combining the parameter uncertainty with record-to-record variability according to the square-root-of-sum-of-squares rule. Alternatively, the total variability of the collapse capacity is obtained from LHS realizations that simultaneously account for uncertainty of the post-yielding negative stiffness ratio and the earthquake excitation. The importance of uncertain post-yielding negative slope on the collapse capacity is underlined, and the main observations of the parameter uncertainty and total uncertainty of the collapse capacity are discussed.