In-situ load testing and finite element analysis of a damaged reinforced concrete flat plate slab in a tall building

Abstract This study provides a detailed case analysis of a reinforced concrete flat plate slab with localized damage in a 25-story high-rise. A poorly hardened concrete layer under the soffit raised immediate concerns about structural safety, prompting a thorough evaluation in accordance with ACI 318-25. A controlled 24-h monotonic load test was conducted using sandbags, with real-time deflection data recorded. Results indicated a maximum deflection of 5.70 mm and a residual deflection of 0.62 mm—both within acceptable limits per code. No crack growth or signs of ongoing deterioration were seen during visual checks after the test. Nonlinear finite element analyses in ABAQUS used the concrete damaged plasticity model with test-based concrete properties and no calibration. On the actual supports, the analysis gave 4.66 mm at full load against 5.12 mm measured, whereas clamped panel edges gave only 0.89–2.19 mm. Although the slab performed well during testing, repair of the deteriorated soffit is advised to address possible long-term issues. This case study offers insights into evaluating flat plate systems with localized damage, linking field diagnostics with analytical models.