圆钢管混凝土柱轴压破坏行为与尺寸效应理论研究

Failure behavior and size effect theory of circular concrete-filled steel tubular columns under axial compression

当前混凝土材料层次的尺寸效应理论已较为完备,而对钢管混凝土构件层次的尺寸效应理论研究则远远不足.针对圆钢管混凝土柱,考虑混凝土细观非均质性及钢管-混凝土相互作用,建立了研究其轴压破坏行为的三维细观数值分析模型.在模拟结果与已有试验结果吻合良好的基础上,基于细观模拟方法研究了不同横向约束作用(以套箍系数来表征)及不同尺寸下钢管混凝土柱的轴压破坏机理与失效模式,揭示了钢管横向约束作用对混凝土柱名义轴压强度及其尺寸效应的影响规律.最后,结合钢管对混凝土柱轴压强度的影响机制——"强度增强效应"与"尺寸效应削弱效应",在材料层次尺寸效应律的基础上,建立了能反映横向约束作用的混凝土柱轴压强度的尺寸效应理论公式,并验证了理论公式的准确性和合理性.

Although great progress has been made in the research of size effect laws of concrete materials,little attention has been paid on the size effect theory of concrete-filled steel tube components.In this study,a three-dimensional mesoscopic numerical analysis model is established to explore the axial compressive failure of circular concrete-filled steel tubular columns,considering concrete heterogeneity and interaction between the steel tube and concrete.A good agreement between our simulation results and the existing experimental results is achieved.Also,the axial compressive failure mechanism and failure modes of concrete-filled steel tubular columns under different lateral constraints(represented by confinement coefficients)and different structural sizes are studied by using the mesoscopic simulation method.In addition,the effect of horizontal confinement on the nominal axial compressive strength of concrete columns and the corresponding size effect are revealed.Finally,by applying the influencing mechanism of steel tube to the axial compressive strength of concrete columns,causing the strength enhancement effect and size effect weakening effect,based on the size effect law of material level,a theoretical formula of size effect reflecting the axial compressive strength of concrete columns under lateral constraint is established.The accuracy and rationality of the derived theoretical formula are verified.