配筋钢管混凝土短柱中环向箍筋的受力机理

Load Transfer Mechanism of Lateral Hoops in Reinforced Concrete Filled Steel Tubular Column

通过轴压试验和数值模拟手段,研究了箍筋对配筋钢管混凝土轴压短柱(R-CFST)力学性能的影响机理及承载力计算方法,旨在提出R-CFST设计方法和了解R-CFST施工时能否适当减少箍筋用量以降低成本。试验参数有平行式和螺旋式两种箍筋形式,其中,平行式箍筋有3种间距,共准备4组、8根R-CFST和3根钢管混凝土试件。试件在受力性能、承载力、断裂韧性、延性、套箍效应和破坏模式等方面的分析结果表明:构件在最大荷载前的受力特性和承载力与箍筋间距和形式无关,承载力计算时可不予考虑;平行式箍筋纵向间距的变化不会对构件的力学性能产生明显影响,因而推荐使用较大的箍筋间距以获得较好的经济效益;螺旋式箍筋有助于提高构件最大荷载后的受力性能,尤其是对延性的提高作用更为显著,因而推荐使用螺旋式箍筋以获得构件较好的延性和抗震性能。在试验结果的基础上,进行了数值分析研究,提出了可靠和有效的核心混凝土本构方程和此类构件的数值模拟方法,结合模拟结果进一步验证了试验结论的准确性。最后,研究了R-CFST的承载力计算方法,发现美国规范给出的公式过于保守,提出了与中国规范的设计习惯相匹配的R-CFST承载力计算公式,与试验结果对比分析表明提出的公式可以用于工程设计。

In order to propose a design method and understand if it is possible to reduce the amount of lateral hoops and then construction cost of reinforced concrete filled steel tubular column(R-CFST)subjected to axial force,investigations were performed respectively on the ultimate strength evaluation-equation and the influence of lateral hoops on the mechanical performance of R-CFST,by means of both compression test and numerical simulation.The test variables included the patterns and spacing of lateral hoops.Two patterns with flat and spiral hoops and three different spacing of flat hoops were used.8 R-CFSTs in 4 groups and 3 concrete filled steel tube(CFST)specimens were prepared.Analyses results on load-transfer performance,ductility,confinement and composite effect,and failure mode indicated that:before-ultimate loading performance and ultimate load-bearing capacity of the member were not relevant to the patterns of lateral hoops;differences in spacing of flat hoops would not cause significant changes in mechanical performance of member,and thus larger spacing was recommended to obtain a time and work saving construction process;spiral hoops would bring improvement to ductility and post-ultimate loading performance of the member,and thus spiral hoops were recommended when the ductility or seismic performance was the main concern.Based the experimental results,the numerical simulation method for R-CFST was investigated and a constitutive equation for its concrete core was proposed.Simulation results showed a good agreement with test results,which further confirmed the reliability of the test.At the end,investigations on prediction methods of ultimate load-bearing capacity of R-CFST were conducted.As results,the equation from US code was found to be conservative,and equations which were modified based on the Chinese code were proposed.Verification results against known experimental data indicated that the equations proposed were applicable in engineering design of R-CFST member subjected axial load.