钢筋活性粉末混凝土柱高温全过程受力性能试验研究

在高温试验炉中对大尺寸钢筋活性粉末混凝土（RPC）柱和普通混凝土柱开展了高温试验，以及高温后的抗压试验，获取了柱高温下的截面温度场与轴向变形发展，分析了控制温度与轴压荷载对高温后钢筋RPC柱受压性能的影响。结果表明：掺入体积分数为2%的钢纤维和0.3%的PP纤维，避免了RPC高温爆裂的发生，且有利于提高钢筋RPC柱的高温抗裂能力；轴压荷载有效抑制了钢筋RPC柱高温下的膨胀与高温后收缩裂缝的产生，但高温与荷载的耦合作用降低了钢筋RPC柱高温后的剩余承载力与变形能力；钢筋RPC柱在经历600 ℃和800 ℃高温作用后，其承载力分别下降了39%和68%，轴向刚度分别下降了68%和83%；相比于普通钢筋混凝土柱，钢筋RPC柱高温后的承载力降低幅度更大，但其剩余截面强度相对更高；基于材料试验获得的温度-强度相关关系，提出了钢筋RPC柱高温后的剩余承载力计算式，预测值与试验值较为接近。

Experimental research on mechanical behavior of reinforced reactive powder concrete columns at whole process of high temperature

The large-scale reinforced reactive powder concrete (RPC) columns and a reinforced normal concrete (NC) column were examined via elevated temperature tests in an electric furnace in this study. The cross-sectional temperature field and the axial deformation development of the columns were measured under elevated temperature. The influences of the control temperature and axial load on the compressive properties were also analyzed through compression test on the specimens after high temperature. The results show that explosive spall phenomenon is not observed in the large-scale RPC columns during testing, which means that mixing 2% steel fiber and 0.3% polypropylene fiber (volume dosage) in RPC mixture can suppress the fire spalling of RPC. The steel fibers are also beneficial to the cracking resistance of the reinforced RPC columns at elevated temperature. Pre-loading on reinforced RPC column decreases the thermal expansion at elevated temperature and reduces the shrink cracking after high temperature. However, the coupling of high temperature and axial load decreases the residual load carrying capacity and deformability of the reinforced RPC column after high temperature. After reinforced RPC columns were subjected to high temperature of 600℃ and 800℃, the bearing capacity is decreased by 39% and 68%, and the axial stiffness is decreased by 68% and 83% respectively. The RPC column exhibits relatively more severe reduction in the load carrying capacity after exposure to high temperature compared with the NC columns, while the former has much higher residual cross-sectional strength. Based on the existing relationship between strength of RPC and high temperature, a calculation method was proposed to predict the residual load carrying capacity of the reinforced RPC columns after exposure to high temperatures, and the proposed method was validated against the experimental results.