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国内外关于钢管混凝土宏观变形性能已作了较深入的研究,而对于其物理本质——核心混凝土内部微裂缝的产生和扩展过程,还没进行直接实际观测,只限于一般性的分析和推测。本文在分析钢管混凝土短柱轴压变形性能的基础上,制作了一定量试件在各变形阶段的反光切片,在光学显微镜下对微裂缝进行了实测,把构件宏观变形特征与内部结构微破坏的物理本质联系在一起,初步探讨了这种构件在荷载作用下的变形和破坏机理。在常用含钢率范围内,钢管混凝土轴压短柱即使变形很大,仍不能达到承载力极限,如何定义它的破坏荷载,是一个有争议的问题。文中依据构件的宏观变形特性和核心混凝土内部微破坏的程度,通过对变形过程中重要特征点的分析,定义了“内部结构整体性的极限荷载”,并建议以此代替传统的但实际上达不到的承载力极限作为衡量构件破坏的标准。
The in-depth study on the macro-deformation properties of concrete-filled steel tube has been made at home and abroad. However, the actual nature of the production of the micro-cracks in the core concrete has not yet been directly observed. It is limited to general analysis and speculation. In this paper, based on the analysis of axial compression behavior of concrete-filled steel tubular short columns, a series of reflective sections of specimens at various deformation stages were produced. The microcracks were measured under an optical microscope, and the macro-deformation characteristics and internal structural micro-destruction of the members were measured. The physics of nature are linked together, and the mechanism of deformation and failure of such components under load is preliminarily explored. In the range of commonly used steel ratios, even if the concrete-filled steel tubular axially compressed short column is deformed to a large extent, it cannot reach the limit of bearing capacity. How to define its failure load is a controversial issue. Based on the macroscopic deformation characteristics of the component and the degree of micro-destruction inside the core concrete, the analysis of the important feature points in the deformation process defines the “limit load of the internal structure integrity” and proposes to replace the traditional but actually achieved Less than the limit of bearing capacity as a measure of component damage.