不同保护措施下CFRP加固混凝土梁耐火性能试验

Experimental study on fire performance of CFRP-strengthened reinforced concrete beams with different protection schemes

摘要:

由于碳纤维增强复合材料(carbon fiber reinforced polymer，CFRP)在火灾中易燃烧，未采取防火保护措施的CFRP加固混凝土构件的耐火性能不能满足防火规范要求.为深入研究CFRP加固钢筋混凝土梁在不同防火保护措施下的耐火性能，在本课题组以往研究基础上，设计了9根相同截面和配筋的混凝土梁，采取不同加固方式和防火保护措施，通过ISO834标准火灾试验，详细分析了不同CFRP锚固方法(无锚固/机械锚固/U形箍锚固)、不同防火材料(超薄型防火涂料/厚型防火涂料/普通水泥砂浆)以及分区防火保护方法对CFRP加固钢筋混凝土梁温度场分布和高温变形的影响.结果表明:在本文试验条件下, 相比于机械锚固，端部碳纤维U形箍锚固在试件挠度控制方面具有更好的效果；超薄型防火涂料与普通水泥砂浆配合使用的防火保护措施可行; 采用20 mm普通水泥砂浆和2 mm超薄型防火涂料组合的防火效果好于20 mm厚型防火涂料保护的防火效果.

Abstract:

The reinforced concrete (RC) components strengthened with carbon fiber-reinforced polymer (CFRP) without fire protection measures are difficult to meet the standard requirements of fire resistance rating due to the flammability of CFRP. To study the fire performance of CFRP-strengthened RC beams based on the previous studies, nine RC beams with the same geometry and steel reinforcement were prepared with different strengthening methods and fire insulation schemes and tested under the ISO 834 standard fire. The test variables included various anchorage systems for externally bonded (EB) CFRP sheets (no anchorage, mechanical anchorage and U-wrap CFRP sheets), different fire insulation materials (intumescent fire-retardant coatings, cement-based fire protection mortar and cement mortar) and different thicknesses of fire insulation layers for different zones along the span direction. The temperature distributions and the deflection responses of these specimens under fire exposure were recorded and compared. It has demonstrated under this test condition that: U-wrap CFRP sheets used as the anchorage system are more efficient in limiting the deflection responses compared to the mechanical anchorage system; the combined use of the intumescent fire-retardant coatings and the cement mortar is practicable to protect the specimen from fire damage; the fire insulation provided by the 20 mm cement mortar and 2 mm intumescent fire-retardant coatings is better than that of 20 mm thick fire protection mortar.