Residual bond strength in steel reinforced concrete columns after fire exposure

Steel reinforced concrete columns have been widely used in many countries. The effect of fire exposure on the residual bond strength between the encased steel section and concrete is investigated in this paper. A total of 11 specimens, including 3 unheated specimens and 8 specimens which had been exposed to ISO 834 standard fire for 90 min or 180 min, were tested to investigate the influence of the following parameters: (a) fire exposure time, (b) thickness of concrete cover, (c) concrete strength, and (d) tie arrangement. A comparison is made between the measured bond stress–slip curves and predictions of an existing model.

► Significant bond strength deterioration was observed after fire exposure.
► Long time fire exposure may lead to bond strength recovery.
► The influence of the thickness of concrete cover on residual bond strength is minor.
► Lateral reinforcement is effective for concrete experienced long fire exposure.