配筋对方钢管再生混凝土短柱轴压性能的影响

Axial compressive behavior of reinforced and recycled aggregate concrete-filled square steel tube short column

为了明确再生粗骨料100%替代率下配筋对方钢管再生混凝土短柱(recycled aggregate concrete-filled tube,RACFST)轴压性能的提高作用,进行了试验研究。以5种配筋率为变化参数设计了5组配筋方钢管再生混凝土(reinforcement and recycled aggregate concrete-filled steel tube,R-RACFST)试件,同时设计相应的钢管混凝土(concrete-filled steel tube,CFST)与钢管再生混凝土(RACFST)试件作为对照组。通过分析配筋率对破坏模式、受力性能、延性、刚度退化和屈强比等关键力学特性的影响规律,发现钢筋笼对核心混凝土产生二次套箍效应,因而明显改善核心再生混凝土的脆性;在一定配筋率范围内,配筋对提高构件极限承载力和延性等力学性能有显著贡献,并在一定程度上延缓再生混凝土的刚度退化。结果表明:配置适量钢筋可将再生粗骨料替代率提高到100%并能保证R-RACFST具有较好的结构适用性;推荐配筋率合理范围为1.34%~3.02%;现行规程可计算再生粗骨料100%取代率下的R-RACFST承载力,但计算结果过于保守;修正得到R-RACFST承载力计算公式,其结果与试验值更吻合,结果稳定可靠。

The experimental investigation was conducted to determine the improving mechanism of reinforcements on the overall performance of square-section reinforced and recycled aggregate concrete-filled steel tube short column(R-RACFST)with 100%replacement ratio of recycled coarse aggregates under axial loading.Taking replacement ratio as variable,five groups of R-RACFST with five different replacement ratios and corresponding CFST and RACFST as control groups were fabricated.The effect of reinforcement ratio on key mechanical indexes such as failure mode,load transfer performance,ductility,stiffness degradation and yield-strength ratio were analyzed.The analysis indicated the brittle failure of RAC core was relieved due to the secondary confinement effect of reinforcements,Within a range of reinforcement ratio,reinforcements could significantly contribute to the ultimate bearing capacity and ductility and delay the stiffness degradation to some extent.It is concluded that configuring appropriate amount of reinforcements can increase the replacement ratio of recycled coarse aggregate to 100%and ensure the applicability of R-RACFST,the reinforcement ratio,1.34%3.02%,is reasonable and recommended.The predicting method of current code can be used to predict the bearing capacity of R-RACFST with 100%replacement ratio,but it is too conservative;the modified predicting method is more reliable and stable.