Estimation of Uncertain Parameters using Static Pushover Methods

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Estimation of Uncertain Parameters using Static Pushover Methods

Michalis Fragiadakis*

Institute of Structural Analysis & Seismic Research, School of Civil Engineering, National Technical University of Athens,

Zografou Campus, Athens, 15771, Greece

Dimitrios Vamvatsikos

Department of Civil and Environmental Engineering, University of Cyprus, Nicosia 1678, Cyprus

 

ABSTRACT: Following recent guidelines (e.g. FEMA-350) seismic performance uncertainty is an essential

ingredient for performance-based earthquake engineering. Uncertainty refers to both aleatory uncertainty,

raised by the random record-to-record variability, and also to epistemic uncertainty primarily introduced by

modeling assumptions or errors. A methodology for the performance-based estimation of the dispersion introduced

by parameter uncertainties is developed. The methodology proposed provides an inexpensive alternative

to the use of tabulated values, or to performing a series of time-consuming nonlinear response history

analyses to obtain parameter uncertainty. As a testbed, the well-known 9-storey LA9 2D steel frame is employed

using beam-hinges with uncertain backbone properties. The monotonic backbone is fully described by

six parameters, which are considered as random variables with given mean and standard deviation. Using

point-estimate methods, first-order-second-moment techniques and latin hypercube sampling with Monte

Carlo simulation, the pushover curve is shown to be a powerful tool that can help accurately estimating the

uncertainty in the seismic capacity. Coupled with SPO2IDA, a powerful R-μ-T relationship, 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.

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