LAUSR

To explore the influence of the loading conditions and fire exposure time on the residual mechanical properties of concrete T-beams, 10 concrete T-shaped beams were designed and manufactured. Three levels of loading were applied to the concrete T-beams during fire tests, namely, unloaded, loaded without concrete cracking and normal service conditions. The fire test durations were 60 min, 90 min, and 120 min. After the fire tests, static loading tests were carried out on the fire-damaged T-beams to determine the residual flexural capacity. The test results showed that with an increase in load ratio and fire time, the maximum temperature experienced by the concrete and steel bar increased. For example, for the specimens that underwent 120 minutes of fire exposure, the temperature of the specimen with a load ratio of 0.44 was larger than that with load ratios of 0.12 and 0, and the difference was 60°C and 80°C, respectively. During the fire tests, the mid-span deflection also increased significantly with an increase in load ratio and fire duration. In addition, the flexural load-bearing capacity after fire exposure decreased with an increase in load ratio and fire time. Compared with the bearing capacity, the degradation of the flexural rigidity was more obvious. For example, when the fire exposure time was 120 minutes, the bending capacity of the beam with a load ratio of 0.44 was approximately 4.5% lower and 5.1% lower than that with a load ratio of 0.12 and 0, respectively, and the reduction in flexural rigidity became 6.8% and 15%, respectively. Considering the effect of cracking, ANSYS was used to analyze the temperature field, deflection, and bearing capacity of the T-beams. It was determined that the calculation model that considers the effects of cracks was more accurate than the calculation model that disregards the appearance of cracks. This study can provide a basis for the assessment of fire damage and the repair of concrete structures.