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چکیده
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This study presents a robust design optimization (RDO) approach for 2D steel moment-resisting frames, addressing uncertainties in material properties and external loads. The study considers special moment frames with high ductility capacity (R=8) designed according to American Institute of Steel Construction Load and Resistance Factor Design (AISC-LRFD) specifications. The objective is to minimize both structural weight and the robustness index, defined as the standard deviation of roof displacement. The Enhanced Vibrating Particles System (EVPS) algorithm is employed to solve the optimization problem, while Monte Carlo simulation (MCS) is used to model uncertainties. Three benchmark frames (10, 15, and 24 stories) demonstrate the effectiveness of the proposed methodology. Results show a 50-60% reduction in roof displacement variability compared to deterministic optimization, with only a 20-30% increase in structural weight. For the 10-story frame with β=0.4, the approach achieved a 67% reduction in standard deviation (from 0.484 to 0.159) with a 74% weight increase (from 63,848 lb to 111,701 lb). The robustness index coefficient (β) is identified as a key parameter for controlling the weight-robustness trade-off, allowing designers to tailor solutions based on project requirements. The study provides a practical framework for improving steel frame reliability under real-world conditions.
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