Shear performance of prestressed hollow-core slabs strengthened with CFRP: Finite element modeling and parametric insights

This study investigates the shear performance of prestressed hollow-core (HC) slabs strengthened with externally bonded carbon fiber-reinforced polymer (CFRP) sheets using finite element modeling (FEM). Three-dimensional FEM models, developed in Abaqus and validated against experimental data, accurately replicate the web-shear failure mode and shear capacity of five full-scale HC slabs under shear-dominated loading, with deviations of less than 5%. A comprehensive parametric study examines the influence of CFRP configuration (bonded length and number of layers), concrete compressive strength, prestressing level, and slab geometry (depth and void shape). The results confirm that CFRP strengthening significantly enhances shear capacity, with optimal performance achieved using two to three layers at a bonded length of 450 mm. Higher concrete strength further amplifies the effectiveness of CFRP, while increased prestressing levels tend to reduce shear capacity due to additional stresses in the web region. Slabs with greater depths and non-circular voids exhibit more pronounced improvements, especially when full-height CFRP strengthening is applied. Comparisons with ACI 318-19 and ACI 440.1R-15 reveal notable discrepancies, emphasizing the limitations of current design provisions and the need for refined analytical approaches. The findings offer practical insights into the design and strengthening of HC slabs and contribute to the development of more accurate and reliable design guidelines.