Abstract
An efficient optimization approach is described to calibrate load factors used for designing of structures. The load factors are calibrated so that the structural reliability index is as close as possible to a target reliability value. The optimization procedure is applied to find optimal load factors for designing of structures in accordance with the new version of the Mexico City Building Code (RCDF). For this aim, the combination of factors corresponding to dead load plus live load is considered. The optimal combination is based on a parametric numerical analysis of several reinforced concrete elements, which are designed using different load factor values. The Monte Carlo simulation technique is used. The formulation is applied to different failure modes: flexure, shear, torsion, and compression plus bending of short and slender reinforced concrete elements. Finally, the structural reliability corresponding to the optimal load combination proposed here is compared with that corresponding to the load combination recommended by the current Mexico City Building Code.
Highlights
The structural design guidelines can be based on different reliability formats [1], for example, (a) the semiprobabilistic approach [2], (b) first-order and second moments, FOSM [3,4,5], and (c) load and resistance factor design (LRFD) [6, 7], based on hazard analysis [8, 9] or based on optimization [10,11,12,13]
An efficient optimization procedure is described to find the optimal load factors that will appear in the new version of the Mexico City Building Code
It is proposed that the load factors obtained here be included in the new version of the Mexico City Building Code (RCDF04) [21]
Summary
The structural design guidelines can be based on different reliability formats [1], for example, (a) the semiprobabilistic approach [2], (b) first-order and second moments, FOSM [3,4,5], and (c) load and resistance factor design (LRFD) [6, 7], based on hazard analysis [8, 9] or based on optimization [10,11,12,13]. Most of the design codes in the world, including the Mexico City Building Code 2004 (RCDF from its acronym in Spanish), use the load and resistance factor design (LRFD) approach. The calibration procedure can be seen as a specific optimization process where the control variables are the partial factors of a design code. An efficient optimization procedure is described to find the optimal load factors that will appear in the new version of the Mexico City Building Code. It is proposed that the load factors obtained here be included in the new version of the Mexico City Building Code (RCDF04) [21]. The calibration procedure is applied to estimate the optimal combination of load factors corresponding to the RCDF-04, based on a target reliability value. ∗γ values should be equal to 1.5 for the design of important constructions
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