Structural behaviour of FRP reinforced concrete slabs in fire

The durability of reinforced concrete (RC) structures is a fundamental issue that engineers address in design procedures. A relatively new structural typology replaces traditional steel reinforcing bar with fiber reinforced polymers (FRP), which is a material less prone to corrosion. On the other hand, these materials have disadvantages, among which construction issue (the FRP rebar cannot be easily bent on site) and mechanical susceptibility to fire. Several studies have shown that high temperatures cause the matrix decomposition (i.e. the resin that surrounds the fibers), which precludes the shear transfer between FRP bars and concrete. Authors built a 3D finite element model to investigate this second issue, considering both geometric and material non-linearities. Once the finite element model was validated based on the outcomes of experimental tests performed on glass FRP-RC slabs exposed to ISO834 standard fire, a parametric analysis has been carried out by varying (i) the reinforcement type (i.e. steel, GFRP, CFRP) (ii) redundant boundary conditions that prevent the thermal expansion and (iii) number and length of the spans.