摘要
为提升混凝土柱复杂环境下的受力性能,提出超高性能钢纤维混凝土(UHPFRC)外管约束普通混凝土(NSC)内柱的组合短柱,并采用宏微观试验和理论计算分析其全截面轴压性能。对高度300 mm的6根NSC短柱(直径104 mm,设计强度20、35、50 MPa)和18根UHPFRC-NSC组合短柱(直径150 mm,外管厚23 mm,钢纤维体积掺量2%)开展轴压试验,发现后者峰值应力比前者最大提高238%,峰值应变比前者最大提高77%,且掺端钩钢纤维比平直钢纤维对峰值应力和峰值应变提升效果更好。为揭示内部破坏机理,开展了缩尺UHPFRC-NSC(强度等级C50)组合短柱的原位微观X光CT加载试验(像素精度35μm)。采用数字体积相关技术获得三维应变演化全过程,发现外管为劈裂-剪切破坏,先于内柱的剪切破坏。基于弹性力学理论和外管-内柱界面径向位移协调条件,推导出界面压力的计算式,结果表明外管-内柱界面作用力较小,约束作用较弱。根据UHPFRC和NSC受压本构关系,得到组合柱轴压应力-应变计算方法,计算结果与试验结果吻合良好。
To enhance the mechanical performance of concrete columns in complex environments,a composite short column composed of ultra high performance fiber reinforced concrete(UHPFRC)outer tubes and wrapped normal strength concrete(NSC)inner columns was proposed and studied under full-section axial compression by macro and micro-scale experiments and theoretical calculations.Six NSC columns with a height of 300 mm,a diameter of 104 mm(designed compressive strength of 20 MPa,35 MPa and 50 MPa)and 18 UHPFRC-NSC composite columns(diameter of 150 mm,outer tube thickness of 23 mm and high-strength steel fiber volume fraction of 2%)were tested.It is found that the peak stress and strain of the composite columns with fibers in outer tubes are improved by up to 238%and 77%respectively compared with the NSC columns,and the end-hook fibers show better effects than the straight ones.To investigate the failure mechanisms,in-situ micro X-ray computed tomography(μXCT)tests were conducted on two half-sized UHPFRC-NSC(concrete strength grade C50)columns.The digital volume correlation technique was employed to the acquired series of 35μm CT images to calculate 3D strain field evolution.It is observed that the outer tube exhibits splitting-shear failure before the shear failure occurs to the inner column.Additionally,based on the elasticity theory and the radial displacement compatibility condition at the interface between the outer tube and the inner column,the interfacial force equation was derived.The results demonstrate that the interfacial force is minimal and the constraint effect is negligible.According to the UHPFRC and NSC compression constitutive models,a design equation of compressive stress and strain was proposed for composite columns,whose results agree well with the experimental data.
作者
姜韬
彭程明
田彤
杨贞军
JIANG Tao;PENG Chengming;TIAN Tong;YANG Zhenjun(School of Civil Engineering,Wuhan University,Wuhan 430072,China;Hubei Provincial Key Laboratory of Geotechnical and Structural Safety,Wuhan University,Wuhan 430072,China;The First Branch of Beijing Construction Engineering Co.,Ltd,Beijing 100054,China)
出处
《建筑结构学报》
北大核心
2025年第2期122-131,140,共11页
Journal of Building Structures
基金
国家自然科学基金项目(52173300)。
关键词
超高性能钢纤维混凝土
组合柱
X光计算断层扫描
原位加载试验
约束作用
ultra high performance fiber reinforced concrete(UHPFRC)
composite column
micro X-ray computed tomography
in-situ loading test
confinement effect
