关键词: 超高强混凝土, 轴心受压, 箍筋约束, 承载力修正公式, 约束混凝土

Abstract:

To study the effect of stirrup confinement on the axial compressive bearing capacity of ultra-high-strength concrete (UHSC) precast columns, this paper first conducted an axial compression contrast experiment between full-size UHSC column and ordinary column, and investigated the difference of crack development, failure pattern and ultimate bearing capacity of these two type columns. Based on the experimental results, further finite element analysis was conducted to simulate 36 full-scale UHSC columns. The study focused on analyzing the effects of stirrup configuration, stirrup spacing, and stirrup diameter on the axial compressive performance of UHSC columns. Combining the experimental findings and parametric analysis results, a modified calculation formula for the axial compressive bearing capacity of UHSC columns considering stirrup confinement was proposed. The proposed formula was then compared with the calculation formula in the current Code for Design of Concrete Structures. The results show that: the ultimate bearing capacity of equal-strength designed UHSC column is higher than that of ordinary concrete column, but it is more brittle than ordinary concrete, especially when reaching the ultimate bearing capacity; the confinement effect of stirrups on the core concrete enhances the axial compressive bearing capacity of UHSC columns. Changes in stirrup configuration, stirrup spacing, and stirrup diameter have a significant impact on the ultimate bearing capacity and peak compressive strain of UHSC columns; the proposed axial compressive bearing capacity correction formula for UHSC columns incorporates the differences between UHSC columns and ordinary concrete columns, considering the confinement effect of stirrups on the core concrete. Compared to the calculation formula provided in the code, which does not account for stirrup confinement and is primarily applicable to ordinary concrete columns, this formula better utilizes the material’s potential while ensuring safety margins. It can serve as a useful reference for practical engineering design.

Key words: ultra-high-strength concrete, axial compression, constraint of stirrup, modified bearing capacity formula, confined concrete