Effect of fire-induced restraint forces on fire behavior of reinforced and prestressed concrete beams

This paper presents results from a set of numerical studies on the effect of fire-induced restraint forces on the response of prestressed concrete (PC) beams. The main parameters studied are the effect of cross-sectional shape, support conditions, and level of prestress. The numerical studies are conducted using a validated three-dimensional (3D) finite-element (FE) based numerical model which accounts for critical governing factors such as magnitude and location of restraint forces, cracking and crushing of concrete, material, and geometric nonlinearity, and spalling. Especially, the model accounts for varying fire-induced restraint forces throughout fire exposure using a new efficient spring idealization framework for connections. The effect of fire-induced restraint forces on the fire response of PC beams is compared with equivalent RC beams to identify key differences in the fire behavior of PC and RC beams. Results from the advanced numerical studies show that significant restraint forces develop in PC and RC beams under fire exposure and these forces vary with fire exposure duration. Further the results show that the fire-induced restraint forces significantly alter the structural response of the beam.