核心混凝土膨胀对钢管混凝土轴压性能的影响

Impact of core concrete expansion on axial performance of steel tube confined concrete columns

核心混凝土的收缩在钢管与混凝土之间产生空隙,降低构件性能.掺加轻集料的高强混凝土产生体积膨胀,可改善钢管与混凝土之间的密实性.推导了混凝土膨胀引起的钢管膨胀及环向应力计算公式,研究了轻集料对C50,C60两种高强混凝土力学性能、体积变形的影响以及混凝土膨胀引起的钢管环向应力、钢管混凝土轴压下的特性.研究表明,核心混凝土的膨胀在钢管内产生环向应力.核心混凝土自由条件下400～600微应变膨胀在钢管内产生70～90 MPa的环向应力.这降低了轴压下钢管的承载能力,但对钢管混凝土承载力无明显影响,此外,在不考虑材料性能因素的情况下,核心混凝土的膨胀可提高钢管混凝土的弹性模量.

Shrinkage of core concrete lead to the interspaces between steel tube and concrete, which decrease the performance of steel tube confined concrete （ STCC）. High strength contain pre - wetted lightweight aggregate expand at all age, and promote the compacting between steel tube and concrete. In this paper, functions of expansion and circumference stress of steel tube caused by core concrete expansion was derived. Influence of pre- wetted lightweight on compression strength, elastic modulus, volume deformation of high strength C50, C60 concrete and circumference strain caused by expansion of core concrete, behaviors of STCC under axial load were experimental researched. Theoretical analysis and experiments results show that expansion of core concrete lead to the circumference stress in steel tube. 400 ~ 600 micro strain expansion of core concrete without restrain arouse a 70 ~ 90 MPa circumference stress in steel tube. It diminish the carrying capacity of steel tube but have few influence on load capacity of STCC. Otherwise, despite the material performance change, expansion of core concrete improve the elastic modulus of STCC.