Optimizing Retrofit Strategies for Irregular Structures under Seismic Loads: A Performance-Based Risk Approach

Resumo

Irregular structures often exhibit inadequate behavior under seismic loads, resulting in higher levels of damage when compared to regular structures. This represents a challenge that underscores the necessity of exploring strategies to enhance their performance and reduce associated risks. One promising solution corresponds to developing effective retrofit alternatives to optimize structural behavior and minimize expected losses. This work aims to assess the seismic performance of irregular structures using braces as a retrofit strategy. The primary goal is to determine the optimal brace cross-sectional area that balances construction and repair costs, achieving a cost-effective solution. The methodology integrates Performance-Based Earthquake Engineering (PBEE) principles with a novel Performance-Based Risk Optimization (PBRO) framework. A surrogate modeling approach is employed to model Engineering Demand Parameters (EDPs), leveraging a Kriging metamodel. This metamodel estimates the median and standard deviation of the EDPs, assuming a lognormal distribution, to capture the variability and uncertainty in seismic responses. The proposed approach is validated through a case study of an irregular steel building. The study evaluates the structure's performance both with and without the retrofit braces. Then, a multi-objective optimization process is conducted to identify the cross-sectional area of the braces that minimizes the combined costs of construction and expected repairs. The optimization framework incorporates the FEMA P-58 [1] methodology, ensuring a comprehensive evaluation of seismic performance and associated risks. The findings contribute to advancing the understanding of irregular structures subjected to seismic actions. The results provide a practical guide for identifying cost-effective retrofit solutions, offering valuable insights for practitioners and researchers in the field of earthquake engineering.[1] Applied Technology Council, & National Earthquake Hazards Reduction Program (US). (2012). FEMA P-58-1: Seismic performance assessment of buildings. Federal Emergency Management Agency.