受火后方钢管约束钢筋再生混凝土轴压短柱力学分析

Research on the axial compression performance of square tubed reinforced recycled aggregate concrete stub columns after exposure to fire

利用ABAQUS软件建立了火灾后方钢管约束钢筋再生混凝土轴压短柱非线性有限元模型,在确定混凝土和钢材的本构基础上,对其火灾后轴压性能进行了数值计算,并与已有相关试验数据进行了对比验证。分析了升温时间、基体混凝土强度、再生粗集料取代率、截面尺寸、含钢率等参数对火灾后轴压性能的影响规律。结果表明:随着升温时间的增加,试件截面角部对中心区域的约束效果逐渐减弱,截面应力逐渐降低且分布趋向均匀;基体混凝土强度和截面直径是影响试件剩余承载力和初始损伤的主要因素,集料取代率和含钢率影响较小,所有试件的损伤发展过程较为相似;各试件的耗能能力随升温时间的增加呈现先提高后降低的趋势;提出了此类试件火灾后相关评价指标的简化计算公式,可为工程实际应用提供参考。

This paper studies the axial compression performanceof square tubued reinforced recycled aggregate concrete （STRAC） stub columns after exposure to fire. In terms of the thermal and mechanical properties of materials, a finite element （FE） model is established with the software ABAQUS. The reliability of the FE model is validated by the good agreement between the theoretical results and the experimental data. The axial compression performance of the STRAC columns is analyzed based on the FE model, and the parameters investigated include fire exposure time, concrete strengths, recycled aggregate replacement percentage, diameter of cross section and steel ratio. It is revealed that with the increase of fire exposure time, the constraint effect on the central area is gradually weakened, and the stress distribution of the section is more uniform, with similar development trends of energy consumption capacity of specimens.The strength of concrete and diameter of cross section are the main factors which influence the residual bearing capacity and the initial failure condition of specimens. The aggregate replacement percentage has no obvious effect on the damage evolution process. Simplified formulas are proposed to predict the evaluating indicators of STRAC columns after exposure to fire, which may be a reference of this kind of columns used in practical engineering.