Approximate Seismic Performance Uncertainty Estimation Using Static Pushover Methods

Abstract eng:
An approximate method based on the static pushover is introduced to estimate the seismic performance uncertainty of structures having uncertain parameters. Performance uncertainty is one of the driving forces behind modern seismic guidelines (e.g. FEMA-350) and it is arguably an essential ingredient of Performance-Based Earthquake Engineering (PBEE). We propose a methodology that uses a minimum of static nonlinear analyses and is capable of accurately estimating the demand and capacity epistemic uncertainty. As a testbed, the well-known nine-story LA9 steel frame is employed using beam-hinges with uncertain backbone properties. These range from simple elastic-perfectly plastic backbones with kinematic hardening to full quadrilinear backbones with pinching hysteresis, including an elastic, a hardening, a negative stiffness and a residual plateau branch, terminating with a final drop to zero strength. The properties of the backbone can be fully described by six parameters which are considered uncertain with given mean and standard deviation values. Using latin hypercube sampling with classic Monte Carlo simulation, the pushover curve is shown to be a powerful tool that can accurately estimate the uncertainty in the seismic performance. Coupled with the SPO2IDA tool, such estimates can be applied at the level of the results of nonlinear dynamic analysis, allowing the evaluation of seismic capacity uncertainty even close to global dynamic instability. In summary, the method presented can inexpensively supply the uncertainty in the seismic performance of first-mode dominated buildings, offering for the first time an estimator of the accuracy of typical performance calculations.

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