Browsing by Author "Desroches, Reginald"

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    Empirical Fragility Analysis of Haitian Reinforced Concrete and Masonry Buildings
    (MDPI, 2024) Laguerre, Marc-Ansy; Salehi, Mohammad; Desroches, Reginald
    This study develops empirical fragility curves for concrete and masonry buildings in Haiti, utilizing data from the 2021 earthquake. A dataset of 3527 buildings from the StEER database, encompassing a diverse range of building types, is used. These buildings types include reinforced concrete structures with masonry infills, confined masonry buildings, reinforced masonry bearing walls, and unreinforced masonry bearing walls. Shakemaps from the USGS are utilized to assess the earthquake’s intensity at each building, with the peak ground acceleration (PGA) as the intensity measure. Damage is classified into five distinct states: no damage, minor, moderate, severe, and partial or total collapse. For each of these states, the corresponding probabilities of exceedance are calculated, and log-normal cumulative distribution functions were fitted to those data to produce empirical fragility curves. The results show a notable similarity in performance among the four types, each having high probability of failure even under low-intensity earthquakes. Total fragility curves (including all four building types) are developed subsequently and they are convolved to the probabilistic seismic hazard map of Haiti to assess the seismic risk. This includes estimating the annual probability of partial/total collapse and the probability of partial/total collapse in the event of 475-year and 2475-year earthquakes. The results indicate a significant risk, with up to 64% probability of collapse in certain areas for the 2475-year earthquake and a probability of collapse of 15% for a 475-year earthquake. These findings underscore the critical vulnerability of Haiti’s buildings to seismic events and the urgent need for their retrofit.
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    Seismic Retrofitting of Low-Rise Reinforced Concrete (RC) Structures: a Multi-Faceted Evaluation
    (2024-04-23) Laguerre, Marc-Ansy; Desroches, Reginald; Padgett, Jamie; Duno-Gottberg, Luis; Duenas-Osorio, Leonardo
    The threat of seismic activity is a major concern for countries worldwide, and many have invested significant resources into researching the seismic retrofit of reinforced concrete (RC) structures. As a result, building codes and retrofit strategies have been enhanced to strengthen vulnerable structures. However, Haiti remains a country with limited knowledge about the vulnerability of RC buildings to seismic events and retrofitting solutions. This study aims to address this knowledge gap by conducting a comprehensive analysis of Haitian RC structures and evaluating multiple retrofit methods to enhance their seismic performance. This study examines the retrofitting of RC buildings in Haiti using deterministic and probabilistic approaches, followed by a Life-Cycle Cost-Benefit (LCCB) analysis to determine the optimal techniques. The study first analyzes Haitian construction norms and practices before selecting building prototypes: R1 (residential 1-story), R2 (residential 2-story), NR2 (non-residential 2-story), and NR3 (non-residential 3-story). These prototypes' columns and beams are designed according to the BAEL (Beton Aux Etats Limites) guidelines, a French construction code widely used for engineered buildings in Haiti before 2010. For the deterministic analysis, a two-phase numerical modeling method is used. Initially, continuum-based finite element models on LS-DYNA are used to validate and derive hysteretic curves of the column joints. Following this, a macroscopic model, which is calibrated from the results from LS-DYNA, is used for non-linear time history analysis of the building's 2D frames using OpenSees. Five retrofit strategies are then added to the original frames: RC shear walls (used for non-residential models), steel braces (used for residential models), buckling-restrained braces (used for non-residential models), prestressed tendons (used for residential models), and RC jackets (used for all models). These retrofits were designed such that the frames do not reach the life safety (LS) objectives of FEMA for a hazard of the return period of 2475 years. A total of 10 ground motions, which include motion recorded in Haiti, are chosen to run the time history analysis and evaluate the retrofit methods' efficiency. It was observed that the using of RC jackets with each of the global retrofits is able to enhance the building's performance to meet chosen performance objectives. This research also assessed retrofitting solutions through probabilistic analysis, generating fragility curves. Initially, empirical fragility curves were derived using post-earthquake data and the shakemap from Haiti's 2021 earthquake, confirming the high vulnerability of Haitian RC buildings. Analytical fragility curves were subsequently developed for the four models representing these structures. Using continuum-based models on LS-DYNA, four damage states (minor, moderate, severe, and collapse) were used and investigated through pushover analyses. The results were then used for a multiple linear regression to predict the drift limit states. A probabilistic seismic demand regression was further derived via time history analysis on a 2D OpenSees model. The resulting analytical fragility curves revealed that incorporating RC jackets and a global retrofit substantially improved building resilience. Finally, a LCCB analysis was conducted to assess the financial implications of the retrofits. By integrating hazard and fragility data with the estimated costs for building repair, replacement, and retrofitting, the benefit of implementing the retrofits was evaluated. The analysis revealed that retrofitting with RC jackets offers significant benefits. However, these benefits are notably higher when RC jackets are combined with steel braces in residential buildings, and with shear walls in non-residential buildings, thus optimizing the structural resilience and financial viability of the retrofitting strategies.