Numerical simulation of post fire-behaviour of high strength lightweight reinforced concrete beams strengthened with basalt fiber-reinforced polymer grid and engineered cementitious composites jacket

This study examined a new composite strengthening method using a basalt fiber-reinforced polymer (BFRP) grid combined with engineered cementitious composites (ECC) matrix to recover the strength of deteriorated lightweight high-strength concrete beams after burning. The experiment involved testing eight lightweight high-strength concrete beams(HSLWC), including control beams (not exposed to fire), fire-exposed beams for one hour and strengthened beam specimens with BFRP grid and ECC jacket were further prepared and tested under two-point loading in the lab to evaluate ductility, stiffness, and failure modes and make experimental comparisons for the results. This work considered various parameters such as the lightweight concrete beam covers and jacket thickness (20 and 30 mm) with a 1 hour fire duration. During testing, the BFRP-ECC composite and LWC substrate showed good bonding performance, capable of preventing the extension of diagonal cracks in the shear/bending moment zones and exhibiting flexural crack modes with rupture of the BFRP grid for all strengthened beams. Additionally, finite element analyses studies using ABAQUS/Standard software were employed to develop analytical estimations to verify the tested beam results. The ultimate load, deflection, load- displacement curves, stress distribution, and time–temperature distribution from the finite element models agreed well with the data obtained from the experimental beam results in this investigation.