受火方式和防火层对梁柱全焊节点抗火性能影响分析

梁柱节点作为钢结构的重要组成部分,在火灾下极易遭到破坏。全焊节点具有较好的塑性变形能力,且抗震性能较好,在高烈度地震地区广泛应用。采用有限元法对梁柱全焊节点抗火性能进行数值模拟,研究不同受火方式下全焊节点的力学行为,揭示不同受火方式时梁柱各节点处温度变化规律,并对比分析有无防火层对全焊节点温度的影响规律。研究结果表明:不同受火方式对全焊节点温度影响较大。节点全部受火时节点各处温度变化曲线基本接近,结构各部位温差较小,整体处于高温状态;梁柱两面受火时受火面温度马上升高,远离受火位置的节点温度升高缓慢,节点各处温差较大。将节点全部受火与不受火进行对比发现,节点全部受火时节点各处应力明显大于不受火情况,温度升高使节点承载能力下降。在柱内壁和梁下侧施加防火层,升温最快的是防火层区域,且有防火层区域节点温度整体低于无防火层节点,对节点施加防火层可以有效降低整体结构升温。

Influence of bearing fire mode and fire protection layer to fire resistance performance of beam-to-column welded connection joint

The beam-to-column joint is a very important component of steel framed structure which may be destroyed easily in fire hazards. Because of the better capacity of plastic deformation and earthquake-resistance, welded connection joint is extensively used in highly seismic regions. In this paper, the finite element method is adopted to simulate the fire resistance performance of welded connection joint to beam-to-column, and the mechanical behavior of welded connection joint under different bearing fire modes is studied. The temperature of welded connection joint is investigated for different bearing fire modes, and the influence of fire protection layer on the temperature of a welded connection joint is analyzed. The results indicate that the bearing fire mode has marked impact on the temperature of the welded connection joint. The temperature variation curves of welded joints are very close when the all the welded joints bear the fire entirely, with little temperature difference for different regions in the steel structure, for which the whole structure suffers high temperature. When two sides of beam-to-column bear a fire, the temperatures of bearing fire surfaces rise immediately, while that of joints far from bearing fire position rise slowly, causing significant temperature difference in different regions. It is found that the stress of a joint bearing fire entirely is obviously higher than that of a joint which does not bear the fire, and the temperature increase reduces the bearing capacity of the welded joint. When a fire protection layer is applied to a column inside and a beam underside, the temperature of fire protection layer region rises quickly, and the joint temperature in the fire protection layer is lower than that when there is no fire protection layer. It is concluded that use of a fire protection layer to the joints can decrease the temperature rise of the whole structure.