高温下钢筋混凝土框架梁抗剪性能研究

Research on shear behavior of reinforced concrete frame beams at high temperature

为了研究高温下钢筋混凝土框架梁的抗剪性能,建立了框架梁的非线性有限元分析模型,采用恒载升温的方式,对高温下钢筋混凝土框架梁的抗剪性能进行模拟,分析了不同混凝土强度、剪跨比及混凝土保护层厚度对钢筋混凝土框架梁抗剪性能的影响。结果表明:减小剪跨比和增大混凝土保护层厚度能显著提高框架梁高温下的抗剪性能,在相同条件下,剪跨比为1.5的框架梁的耐火极限比剪跨比为2.3的框架梁的提高45%,剪跨比为2.3的框架梁的耐火极限比剪跨比为3.0的框架梁的提高50%;混凝土保护层厚度每增加10 mm,框架梁的耐火极限约提高20%。随着混凝土强度的增加,框架梁高温下的抗剪性能得到提高,但提高效果不够明显。工程设计时,适当提高混凝土强度、减小剪跨比、增大混凝土保护层厚度是提高钢筋混凝土梁抗剪性能的有效措施。

In order to study the shear behavior of RC frame beams at high temperature,a nonlinear finite element model is developed. The shear behavior of the beams at high temperature is simulated by heating the model under constant load. The parameters,including concrete strength,shear span to depth ratios and thickness of concrete cover of the fire-damaged RC beams are analyzed. The results show that with the decrease of shear span to depth ratios or the increase of thickness of concrete cover,the shear capacity of fire-damaged RC beam is obviously improved. Under the same conditions,the duration of fire resistance of the beam with a shear span to depth ratio of 1. 5 is improved by forty-five percent than that of the beam with a shear span to depth ratio of 2. 3,and the duration of fire resistance of the beam with a shear span to depth ratio of 2. 3 is improved by fifty percent than that of the beam with a shear span to depth ratio of 3. 0. With the increase of every 10 mm in thethickness of concrete cover,the duration of fire resistance of the frame beam is approximately improved by twenty percent. With the increase of concrete strength,the shear capacity of the fire-damaged RC beam is also improved,but the improvement is not obvious. In engineering design,the increase of concrete strength,decrease of shear span to depth ratio and increase of thickness of concrete cover are effective measures to improve the shear behavior of RC beam.