Capacity Parametric Model and Damage Index for Steel Buildings. a Probabilistic Approach

Abstract eng:
The capacity and expected seismic damage of several types of steel buildings are assessed. Nonlinear static structural analysis and incremental dynamic analysis (IDA) by means of a probabilistic approach with Monte Carlo Simulation are used. For static analysis, an important contribution of this paper is to extend the parametric models and damage index that were previously proposed for reinforced concrete buildings to steel buildings. Thus, the parametric model is used to fit capacity curves and the expected damage is assessed by means of this new damage index. In this parametric model, the linear and non-linear parts of the capacity curve are separated. The linear part is defined by the initial stiffness and the nonlinear part can be parameterized by the integral of a cumulative lognormal function; the ultimate capacity point provides the two last parameters of the five ones that fully define this new capacity model. The damage index is defined as a combination of the energy dissipation and the tangent stiffness degradation. The analyzed buildings are typical of Mexico City and the seismic actions are selected so that they are compatible with the design spectra provided in the seismic code. The results show that, on average, the Park-Ang index, calculated by the IDA, is well fitted by the combination of the contributions to damage index of the stiffness degradation (66-71%) and the one of the energy loss (29-34%); with the advantage that this index can be obtained in an easy, fast and straightforward way from capacity curves. The obtained results show that the parametric model and the damage index are powerful tools for probabilistic assessments of seismic risk.

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