受火后方钢管钢筋混凝土短柱剩余承载力研究

为研究方钢管钢筋混凝土轴压短柱火灾后的剩余承载力，设计并制作18根在核心混凝土中配置纵向受力钢筋的方钢管钢筋混凝土短柱进行明火试验和承载力试验，观察试件经历火灾后的破坏形态，获取柱的极限承载力等指标。在ISO 834标准升降温曲线作用下，基于ABAQUS有限元软件建立方钢管钢筋混凝土轴压短柱温度场和火灾后力学场分析模型，分析结果得到试验结果的验证，在此基础上，利用该模型对影响方钢管钢筋混凝土轴压短柱火灾后剩余承载力的参数进行了分析。试验结果表明:受火后的方钢管钢筋混凝土短柱承载力有一定程度折减，但仍具有较高的承载能力；配置纵向钢筋对核心混凝土起到更好地约束作用，配筋率的增大对于受火后试件极限承载力的提高作用明显；影响方钢管钢筋混凝土轴压短柱火灾后剩余承载力的主要因素是升温时间和构件截面尺寸；在常用参数范围内，回归方钢管钢筋混凝土短柱火灾后剩余承载力实用计算式。

POST-FIRE BEHAVIOR OF REINFORCED CONCRETE-FILLED SQUARE STEEL TUBULAR STUB COLUMNS UNDER AXIALLY COMPRESSIVE LOADING

To study the residual load bearing capacity after fire of reinforced concrete-filled steel tube (RCFST) short columns with rectangular section under axial pressure, eighteen RCFST short columns with rectangular section were tested under loading device after exposure to standard fire. The failure modes were observed and the residual load bearing capacity was obtained. The temperature field model of RCFST short columns under heating part was built by ABAQUS. The comparison shows that the theoretical analysis results are in good agreement with the former test results. Based on that, the parametric analysis of post-fire residual load bearing capacity of RCFST column with rectangular short under axial pressure was studied. The study reveals that the RCFST short columns have high bearing capacity; longitudinal reinforcement have better restraining effect to concrete; the reinforced filled concrete can enhance the ultimate capacity of the specimens; the heating up time and sectional dimension are the main parameters influencing the fire resistance of RCFST with rectangular columns.Based on these parameters, simplified formulas of the residual load bearing capacity after fire were put forward, and the calculated results by the formulas showed well agreement with the theoretical model results.