Behaviours and residual-flexural stiffness of T-shaped prefabricated composite reinforced-concrete beams after fire exposure

Abstract

The performance of T-shaped–prefabricated-composite–reinforced-concrete (T-PCRC) beams under fire exposure differs from that of T-shaped–reinforced-concrete (T-RC) beams. Fourteen T-PCRC and seven T-RC beams were cast to analyse the damage progression in T-PCRC beams under fire and the stiffness attenuation after exposure. Dynamic tests were conducted under fire, follow by static load tests after exposure. First, dynamic tests under fire were conducted in accordance with the ISO-834 standard. The analysis focused on the impact of fire-exposure time, load ratio, and superposition coefficient on the dynamic response of T-PCRC beams. The vertical displacement of the specimens was also measured to aid in analysing the damage and crack development under fire. Static tests were conducted post-fire exposure. The effects of the fire-exposure time, load ratio, and superposition coefficient on the attenuation of section flexural stiffness were thoroughly analysed. Notably, a method for calculating the residual-flexural stiffness of T-PCRC after fire exposure was established. This method is based on the existing stiffness calculation method for T-RC beams and the corresponding finite-element model of T-PCRC beams, which was verified using tests. The validity of the proposed stiffness calculation method was experimentally verified. The research results showed that as increase in fire-exposure time, the vibration frequency gradually decayed, while deflection increased. The presented stiffness calculation method offers a valuable reference, exhibiting a 10% margin of error between the tests and simulations. This method can be employed as a foundation for assessing damage and implementing reinforcement repairs for T-PCRC beams post-fire event.