圆不锈钢管超高性能混凝土短柱轴压性能研究

STUDY ON AXIAL-COMPRESSION PERFORMANCE OF CIRCULAR ULTRA-HIGH PERFORMANCE CONCRETE -FILLED SATAINLESS STELL TUBE COLUMN

  • 摘要: 该文对6根超高性能混凝土填充不锈钢管(UHPC-filled circular stainless steel tubular, UFCSST)短柱、3根普通混凝土填充不锈钢管(Concrete-filled stainless steel tubular columns, CFSST)短柱以及3根不锈钢管进行轴压试验,试件参数包括不锈钢管壁厚和核心混凝土强度等级。观察了试件的受力破坏过程及形态,获取了荷载-位移曲线,通过试件受力过程的破坏形态、荷载-位移曲线、荷载-应变曲线、混凝土贡献率和强度提高系数对UFCSST轴压力学性能进行了分析。结果表明:UFCSST短柱失效模型与套箍系数相关,当套箍系数大于1.03时,核心混凝土由剪切型破坏向横向膨胀转变。荷载-位移曲线在峰值荷载后的变化趋势依据套箍系数大小可分为三类:一是存在下降段,后再缓慢回升至峰值荷载;二是平稳发展;三是缓慢上升。不锈钢管厚度一定时,UHPC等级对承载力影响较小,最大能提升承载力14.8%。由于UHPC强度高且内部含有钢纤维减缓UHPC内部裂缝和变形的发展,导致UHPC的混凝土贡献率比普通混凝土贡献率高81.6%,而由于UHPC自收缩性和混凝土多轴力学特性,UHPC的强度提高系数比普通混凝土低46.4%。国外部分规范计算结果较试验结果偏于保守,最大偏差可达22.4%,而国内CECS 28: 2012的计算结果较试验承载力高出10.4%。基于统一强度理论提出了UFCSST承载力理论计算模型。

     

    Abstract: In this paper, 6 short columns of ultra-high performance concrete filled stainless steel tubes (UFCSST), 3 short columns of ordinary concrete filled stainless steel tubes (CFSST), and 3 stainless steel tubes are tested under axial compression. The test parameters were stainless steel tube wall thickness and core concrete strength. The failure process and morphology of the specimen was observed, and the load-displacement curves were obtained. The axial-compressive properties of UFCSST were analyzed through the failure morphology, load-displacement curve, load-strain curve, concrete contribution rate and strength improvement coefficient of the specimen. The results show that the failure model of UFCSST short columns is related to the confinement coefficient. When the confinement coefficient is greater than 1.03, the core concrete changes from shear failure to lateral expansion. The change trend of load-displacement curve after the peak load can be divided into three categories according to the value of confinement coefficient: an initial descending section followed by slow increase to the peak load, stable development, and slow increase. When the thickness of stainless steel tube is fixed, the UHPC grade has little influence on the bearing capacity, and the maximum bearing capacity can be increased by 14.8%. The high strength of UHPC and the inclusion of steel fibers inside would slow down the development of cracks and inside deformation, causing the concrete contribution rate of UHPC 81.6% higher than that of ordinary concrete; however, due to the autogenous shrinkage of UHPC and the multiaxial mechanical properties of concrete, the strength improvement coefficient of UHPC is 46.4% lower than that of ordinary concrete. The calculation results of some foreign codes are more conservative than the test results, with the maximum deviation of 22.4%, while the calculation results of CECS 28: 2012 in China are 10.4% higher than the test bearing capacity. Based on the unified strength theory, a theoretical calculation model of UFCSST bearing capacity is proposed.

     

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