【摘要】 处于整体结构中的构件受到相邻结构构件的约束作用,其火灾中的反应与单个构件具有明显差异。采用约束框架模拟整体结构为组合梁提供约束作用,通过2个组合梁试件研究简支组合梁和连续组合梁的火灾反应。试验表明,在整个火灾过程中,组合梁轴力、挠度及其抵抗弯距相互影响和转化,共同抵抗外荷载作用。在火灾初始阶段,组合梁轴力为压力,削弱了组合梁抗火能力;在火灾中后期,组合梁轴力发展为拉力,挠度可达跨度的1/15,产生的悬链线效应有效提高了组合梁极限抗火能力。简支组合梁和连续组合梁均发生了下翼缘屈曲,下翼缘屈曲是组合梁轴力由压力向拉力的转折点。依据功能原理建立了组合梁下翼缘屈曲的屈服线模型和计算方法,计算结果与试验结果吻合良好。更多还原

【Abstract】 Because of the restraint from the neighbouring component,the behavior of members under fire in the redundant structure is different from that of isolated member.Two fire tests were conducted to study the behavior of composite beams under fire.The restraint was provided by an additional steel frame.It was found that the axial force,deflection and moment were coupled together and interacting to each other when fire was growing.At the beginning stage of the fire,the composite beam was under compression,resulting in a decrease in the fire-resistance capacity.With the growing of the fire,the axial force of composite beam became tension which,with the large deflection(about 1/15 times of span),induced the catenary action and enhanced the fire-resistance capacity.The bottom flange buckling happened at the bottom flange near the connection regardless of simply supported connection or rigid connection.The compression force of the beam reached the ultimate value when buckling happened.The mechanical model and theoretical method were set up to calculate the temperature when buckling happened.The results based on the theory are found to be in good agreement with the experiment.更多还原