高温后钢筋混凝土梁剩余承载性能试验研究

通过对7根高温后钢筋混凝土简支梁试件和3根常温对比梁试件的静力试验，研究受火时间、剪跨比、配箍率、楼板翼缘对钢筋混凝土梁剩余受剪性能和剩余受弯性能的影响。利用有限元程序，分析ISO 834标准升降温全过程对混凝土梁截面内各点最高过火温度的影响，提出了三面受火后钢筋混凝土梁受剪承载力的计算方法。研究结果表明：高温作用使梁的受弯承载力和受剪承载力降低、挠度增大；楼板翼缘对梁的受弯承载力具有一定的提高作用，但对受剪承载力影响不大；降温段对截面内部混凝土曾经历的最高过火温度影响较大，梁截面宽度250 mm、高度400 mm的混凝土矩形截面按ISO 834标准曲线三面受火1h、2h后，是否考虑降温段可使截面内最高过火温度最大相差283、251℃；提出的高温后钢筋混凝土梁受剪承载力计算式具有一定的安全保证率。

Experimental study on residual performance of reinforced concrete beams after fire

Based on the static load tests of seven reinforced concrete (RC) beams after fire and three contrastive specimens at ambient temperature, the effects of fire exposure time, shear span ratio, reinforcement ratio and flange on the residual shear behavior and the residual flexural behavior of beams were analyzed. Using a finite element program, the effects of ISO 834 standard fire with rising and cooling phases on the peak temperature in the RC section were analyzed and a practical calculation method for the shear strength of RC beams after fire was suggested. The results show that the fire can decrease the bending capacity and shear capacity, and increase the deflection of RC beam on the whole. The flange has a positive influence on the improvement of residual flexural capacity but has little effect on the shear capacity of RC beam after fire. The cooling phase of fire has significant effects on the peak temperature in the section, and whether it is considered can lead to a peak temperature with the biggest difference of 283℃ and 251℃ in a section of 250 mm width and 400 mm height after exposure to ISO 834 standard fire for 1h and 2h, respectively. The proposed formula for the residual shear capacity of RC beams after fire has certain safety margin ratio, and can be used to assess the shear performance of structural member after fire.