方钢管混凝土柱-外环板式组合梁节点在地震损伤后的耐火性能分析

为研究方钢管混凝土柱-外环板式组合梁节点在地震损伤后的耐火性能，该文建立了有限元数值模型，并用其他研究者完成的试验数据对模型进行了验证。在此基础上分别建立了震损后组合梁节点在三种受火工况下耐火极限计算模型，分析了组合梁节点柱防火保护层在滞回加载中的脱落位置及脱落程度和三种受火工况对节点耐火极限、破坏模态的影响。结果表明:经历柱端往复荷载作用的节点随着损伤程度的不断加重，钢管应力值及变形程度明显增大；当节点在楼板以下区域受火时，随着受火时间的增长，栓钉由底部至顶部的温度梯度较明显，楼板混凝土由于栓钉的影响，温度场分布呈现波浪形；不同损伤程度及不同受火工况对节点破坏模态均影响显著，但有无考虑防火保护层脱落的节点在三种受火工况下的破坏模态均没有较大差别；在楼板以下区域受火及楼板以上区域受火两种工况下，防火层脱落对重度损伤节点的耐火极限影响显著。在楼板上下区域均受火的工况下，防火层脱落对节点的耐火极限没有显著影响。

ANALYSIS ON THE FIRE RESISTANCE OF SQUARE CONCRETE-FILLED STEEL TUBULAR COLUMN TO COMPOSITE BEAM WITH OUTER RING PLATE CONNECTIONS AFTER EARTHQUAKE DAMAGE

To study the fire resistance of the square concrete-filled steel tubular column to composite beam with outer ring plate connections after earthquake damage, finite element numerical models were established and verified by experimental data of other researchers. The finite element models for the fire resistance of composite beam joints under three fire conditions after earthquakes were established. The impact of the shedding position and degree of the fire protection layer of the column in hysteretic loading and three fire conditions on the fire resistance and failure modes was analyzed. The results indicate that the stress value and deformation degree of the steel tube increased obviously with the increase of the damage degree of the joint under the hysteretic loading at the column end. When the joint was exposed to fire in the area below the RC slab, the temperature gradient of the stud from the bottom to the top was obvious with the increase of the fire time. The temperature field distribution of the RC slab was wavy due to the influence of the stud. Different damage degrees and different fire conditions had significant effects on the failure modes. However, there was no significant difference on the failure modes with or without the fire protection layer falling off under the three fire conditions. Under the two fire conditions in the area below the RC slab and the area above the RC slab, the shedding fire layer had a significant influence on the fire resistance of severely damaged joints. Under the condition that both the upper and lower areas of the RC slab were under fire, the shedding fire layer had no significant influence on the fire resistance of the joints.