Flexural Capacity of NSM FRP Strengthened RC Beams at Elevated Temperature

Abstract

This paper presents the thermal and the mechanical analyses, simulating the experimental tests conducted in the recent past on reinforced concrete beams strengthened with the Near Surface Mounted (NSM) FRP system. The thermal analyses were conducted through the software ABAQUS, whereas the mechanical analyses were carried out through the iterative-incremental procedure Moment- Curvature. The aim of these analyses is, firstly, assess the ability of simulating the experimental results of non-standard fire tests (local and global heating using propanefired radiant panels) and, then, generalise the experimental results providing a standard time of fire exposure that might lead to the un-effectiveness of the strengthening system due to debonding failure. The results of the numerical analyses (2D) cross-sectional finite element model (FEM) and 3D FEM were compared with the temperature recorded by the thermocouples during the tests, in order to assess the reliability of the FEM simulating the experimental results. The results of the 3D FEM model enabled also the evaluation of the heat transfer from the exposed to the unexposed zone and, therefore, to assess the length of the effective cold end-anchorage. Finally, thermal analyses of a 3D FEM of the NSM FRP strengthened RC beam, subjected to the standard ISO834 curve, were conducted in order to define useful fire safety design criteria for this investigated structural typology. The effect of the passive protection of the end-anchorage was also investigated, analyzing the structural element protected at both ends through a fire rated plasterboard with thickness ranging between ten and thirty millimeters.