Seismic performance and fragility assessment of ductile light non-structural components in nonlinear structures: from peak demand factors to loss estimation

Abstract

Losses resulting from the failure of non-structural components (NSCs) during earthquakes account for nearly 70–85% of total construction investment, representing the dominant share of post-earthquake economic losses. Despite this significance, conventional design approaches fail to adequately represent the varying levels of ductility of NSC attachments, relying instead on simplified empirical factors that do not explicitly consider the complex inelastic behavior of these components. To address this gap, the present thesis develops a four-step investigation aimed at simultaneously reducing seismic demands and repair costs for light ductile NSCs through performance-based design methodologies that explicitly account for component inelasticity. In the first step, ductility-based peak component modification factors (Ar/RP, IVR, and IDR) are derived and calibrated to quantify demand reductions attributable to NSC inelastic behavior. These factors are obtained from linear time-history analyses of four archetype moderately ductile reinforced concrete moment-resisting frames (3, 6, 9, 12 stories). These frames were subjected to 24 spectrally matched ground motions consistent with Montreal's Class C Uniform Hazard Spectrum. These results indicate 40–60% reductions in peak floor acceleration, velocity, and displacement demands when NSC ductility increases from μ = 1.0 to μ ≈ 2.0 under resonant conditions. In the second step, Incremental Dynamic Analysis (IDA) is employed to quantify the combined effects of structural nonlinearity and modal resonance with the first three structural modes (T₁, T₂, T₃) on NSC fragility. Results indicate that inelastic structural behavior reduces median peak floor accelerations by up to 110% relative to elastic predictions and shifts damage-state exceedance probabilities, defined per Hazus guidelines, toward higher intensity levels, particularly for components tuned to the first structural mode. In the third step, fragility functions are coupled with the FEMA-P-58 loss assessment methodology to estimate direct repair costs for two representative components: suspended ceilings installed at the roof and intermediate floors, and rooftop chillers. Enhanced attachment details, specifically multi-directional bracing for ceilings and seismic restraint devices for chillers, raise damage initiation thresholds by factors of 3-5 and 1.3, respectively. These improvements reduce expected repair costs by up to 95% for suspended ceilings and 17% for chillers at peak floor accelerations of 1.5 g peak floor acceleration. Losses concentrate near the building rooftops, where repair costs are 30-60% higher than at mid-height, and ceiling loss ratios reach 1.5-2% of total building replacement value. Chiller loss ratios remain below 0.55% of building replacement value, reflecting their smaller relative economic impact despite their critical functional role in building operations. In the fourth step, the combined effects of structural and NSC nonlinearity are investigated through nonlinear time-history analyses incorporating pushover-derived story yield 10 displacements. Building upon the elastic results from the first step, these analyses demonstrate reductions in floor acceleration demands of 67-78% for elastic NSCs and 9-64% for ductile NSCs relative to elastic structural predictions. Proposed component force factors SP values identify moderate ductility (μcomp ≈ 1.5) as the optimal design target (SP = 3.4 at roof vs. 4.0 for elastic attachments). Comparison with NBC 2020 provisions reveals that both current and the recently approved NBC 2025 formulations underestimate roof-level demands by up to 35% for mid- to high-rise buildings. Collectively, this four-step framework delivers practical performance-based design tools, including ductility-dependent modification factors, fragility functions, and component force factors that reduce NSC seismic demands by 40–60% and lower repair costs by up to 95% for ceilings and 17% for rooftop chillers, while addressing critical limitations in NBC 2020 provisions for mid- to high-rise buildings.

Date	18 Feb 2026
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Rola Assi (Supervisor)