Experimental Study on the Fire Behavior of Restrained R/C Beams Strengthened with Carbon Fiber Sheet

摘要

This paper presents an experimental study on the fire behavior of seven restrained RC beams strengthened with carbon fiber sheet (CFS) and provided with fire insulation. The influence of some parameters (i.e., axial and rotational restraint stiffness, thickness of the fire insulation, and load ratio) on the deformations and internal forces of the beams is analyzed. The test results indicate that: (a) for a restrained beam in fire, the maximum axial elongation decreases with increasing stiffness of the axial restraint, and increasing thickness of the fire insulation, while the maximum additional axial force increases with increasing stiffness of the axial restraint, and decreasing thickness of fire insulation. The maximum additional bending moment at the beam ends increases with decreasing thickness of the fire insulation, but on the whole the influence of the thickness of the fire insulation within the investigated range (10-20 mm [0.394-0.787 in]) is rather limited; (b) the additional axial force in a restrained beam recovers slightly during the cooling phase, while the additional bending moment at beam end of a restrained beam recovers significantly in the cooling phase; (c) the peak value of the bending moment of a strengthened and insulated beam occurs much later than in the case of an ordinary RC beam (i.e., without strengthening and fire insulation), while the maximum additional bending moment at beam end is lower; and (d) the influence of the rotational restraint stiffness on the maximum additional bending moments at beam ends is rather limited.