钢筋混凝土T形截面连续梁耐火性能试验研究及有限元分析

Experimental research and FEA of fire resistance of RC continuous T-beam

通过4根钢筋混凝土T形截面连续梁在ISO 834标准升温曲线下耐火极限的试验研究,分析不同持荷水平下三面受火T形截面连续梁的耐火极限变化规律。结果表明:未受火对比试件和受火试件均发生弯曲破坏,但出铰次序不同;持荷比分别为0.3、0.5和0.7的T形截面连续梁的耐火极限分别为160、99、58 min,即随着持荷比的增大其耐火极限显著降低,且达到耐火极限时的跨中残余变形明显增大;T形截面梁翼缘内温度分布与单面受火板相似,腹板内温度分布与三面受火矩形梁相似;在受火过程中,梁截面刚度下降是引起内力重分布的主要原因;有限元模拟能准确预测钢筋混凝土T形截面连续梁在ISO 834标准升温曲线下的耐火极限、截面温度场分布和破坏过程。

To investigate the fire endurance and resistance of RC continuous T-beams under ISO 834,four specimens at different load levels were experimentally studied and analyzed using FEM. It shows that the control specimen and the exposed specimens all collapsed with the flexural failure mode,but the sequence of plastic hinge development are opposite. The fire endurances of specimens were 160,99 and 58 min respectively when the load levels were 30%,50% and 70% of the ultimate load. It is found that the fire endurance of RC continuous T-beams exposed to fire decreases gradually when the load level is increased. The residual mid-span displacement of RC continuous T-beams after fire increases when the load level is increased. Test results show that the distribution of temperature field of the flange plate is similar to the one-side exposed RC slab,and the distribution of temperature field of the web is similar to three-side exposed RC rectangular beams. It is the main cause of the redistribution of internal force that the stiffness of the cross-section of RC continuous T-beam is decreased in the process of the fire. FEA was also conducted and its predictions of the fire endurance,the temperature field and the failure process are all in good agreement with the test results.