三面受火胶合竹梁耐火极限的试验研究

Experimental study on fire endurance of laminated bamboo beams exposed to three-side fire

通过5根胶合竹梁的耐火极限试验，对三面受火胶合竹梁的升温规律和耐火极限进行了研究，试验参数包括截面和荷载比。研究表明：未受火对比胶合竹梁经历弹性阶段、弹塑性阶段后，发生脆性断裂破坏；跨中截面应变符合平截面假定。耐火极限试验试件各测点温度随受火时间的增加而升高，且停火之后温度下降较慢；测点离胶合竹截面表面距离越近，温度越高；不同试件距边缘相同距离测点的温度随受火时间变化规律基本相似。相同截面胶合竹梁耐火极限随荷载比增大而减小，相同荷载比胶合竹梁耐火极限随截面尺寸增大而增加。100×225截面胶合竹梁荷载比为0．2，0．35，0．5时，耐火极限分别为30，22，10min。

The temperature development law and fire endurance of laminated bamboo beams exposed to three-side fire were studied through fire endurance tests of 5 laminated bamboo beams. The parameters included cross-section and load ratio. Results show that the control specimen experiences elastic phase and elastic-plastic phase before brittle rupture. The strain distribution across the mid-span cross-section is basically conformed to plane cross-section assumption. Temperature of thermocouples set in specimens increases with the increase of fire exposure time and decreases very slowly after the fire is stopped. The closer the thermocouples to the surface of laminated bamboo beam are, the higher their temperature is. For the thermocouples at different specimens with the same distance to the surface of laminated bamboo beam, temperature varies similarly with the fire exposure time. It is observed that for the laminated bamboo beams with the same cross-section, the fire endurance decreases with the increase of load ratios, while for the laminated bamboo beams subjected to the same load ratios, the fire endurance increases with the increase of cross-section. The fire endurance of laminated bamboo beams with the 100×225 cross-section tested under the load ratio of 0.2, 0.35 and 0. 5 are 30, 22 and 10 min respectively.