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This thesis investigates the post-fire residual capacity of reinforced concrete (RC) beams using a combination of finite element analysis and simplifiedmethods. Following the validation of the finite element model with experimental test data, a comprehensive parametric study was conducted to assess the effects of various key factors on the post-fire flexural capacity of RC beams. The study examined the influence of beam depth (400, 500, 600, and 700 mm), concrete cover thickness (38,
50, and 75 mm), and longitudinal rebar diameter (16, 20, and 25 mm), across different fire exposure durations (30 to 240 minutes), following the ISO 834 fire standard. In total, 36 RC beam specimens were analyzed, resulting in 324 detailed parametric simulations using the finite element software Abaqus.
The results from the parametric study demonstrated a significant reduction in post-fire moment capacity with increasing fire exposure duration and higher reinforcement ratios. Simplified methods from the literature and analytical approaches in international standards provided conservative estimates for beams with low reinforcement ratios and shorter fire durations. However, as both reinforcement ratio and fire exposure duration increased, these methods tended to overestimate the post- fire moment capacity. To address this limitation, a modification factor dependent on reinforcement ratio and fire duration was introduced and implemented into the existing simplified approach, which reduced the coefficient of variation in predictions from 0.141 to 0.07 and improved the R-squared value from 0.857 to 0.945. These findings highlight the importance of considering both reinforcement ratio and fire exposure duration in post-fire capacity evaluations. The proposed modifications enhance the reliability of simplified methods, offering engineers a more accurate tool for assessing the residual capacity of fire-damaged RC beams, ultimately improving safety evaluations and structural recovery planning. |
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