钢筋混凝土预损伤梁的火灾行为相似性研究

Similarity on fire behavior of reinforced concrete beams with pre-damage

为研究不同比例钢筋混凝土预损伤梁火灾行为的相似性,在已有缩尺模型明火试验的相似理论基础上,对不同几何尺寸比例的3根钢筋混凝土无损梁和9根因经历常温静载试验而产生不同程度预损伤的梁开展明火试验。试验结果表明:采用热辐射模型确定不同比例梁明火试验的升温曲线,可以较好地实现不同比例梁在相应时间点截面温度分布相似;明火试验前形成的宽度在2 mm以下的裂缝对不同比例梁温度场的相似性影响不大,仅影响局部混凝土温度,明火试验前梁上已有的残余变形对其耐火极限影响不大;将不同比例梁受火时间的相似比由几何比例的平方调整为几何比例的1.8次方,可以实现预损伤程度相同的不同比例钢筋混凝土梁挠度变化以及耐火极限相似,从而实现由缩尺模型梁的火灾下力学行为预测足尺原型梁的火灾力学行为。

To investigate the similarity on fire behavior of scaled reinforced concrete beams with different levels of pre-damage, based on the existing similarity theory for fire testing of reduced-scale structural models, three scaled reinforced concrete beams without pre-damage and nine scaled beams with different levels of pre-damage were tested in fire. The pre-damage was induced by static load tests at room temperature. The test results show that similar temperature distribution in different scaled beams can be achieved by using the thermal radiation model to determine the temperature-time curves of beams under fire tests. Cracks formed on the beam prior to the fire test, with a maximum width of less than 2 mm have no significant effect on the similarity of temperature field of beams with different scales, but have an influence on local concrete temperature. The existing residual deformation on beams before fire test has little effect on the fire resistance of the beams. By modifying the time scale power index from 2 to 1.8, different scaled reinforced concrete beams with the same level of pre-damage show good agreement in the prototype deflection-time curves and fire resistance, so that the fire behavior of full-scale prototype beams can be predicted through that of scaled model beams.