钢管混凝土加固钢筋混凝土方形截面偏压短柱受力性能分析

Mechanical behavior of square RC columns strengthened with concrete filled steel tube under eccentric load

对8根钢管混凝土加固柱试件和1根未加固钢筋混凝土方形截面短柱试件进行偏心受压试验，试验结果表明： 采用钢管混凝土加固法能显著提高原柱的承载力和变形能力；随着钢管壁厚的增大，加固柱试件的承载力和变形能力显著提高; 随着后浇混凝土强度的提高，加固柱试件的承载力有所提高，但延性降低。在试验研究的基础上，采用通用有限元软件ANSYS对加固柱试验进行全过程受力分析，与试验结果对比后发现，二者吻合良好，有限元分析的承载力最大相差为6%。有限元分析结果表明：弯曲内侧受压的后浇混凝土会受到明显的约束作用，最大约束应力可达10MPa，而弯曲外侧的后浇混凝土受拉，不受约束作用；钢筋混凝土原柱各处混凝土受到的约束力大致相同，在2.0~2.5MPa之间；由于外套圆钢管对受压侧原柱混凝土和后浇混凝土提供有效约束作用，其最大应力可明显高于其单轴抗压强度。

Eight RC columns strengthened with concrete filled steel tube and one unstrengthened RC column were tested under eccentric load. The results show that the strengthening method significantly improves the ultimate bearing capacity and the ductility of the original RC columns. With the wall thickness of steel tube increasing, the strengthened columns show an increasing trend in the bearing capacity and the ductility. With the compressive strength of strengthening concrete increasing, the strengthened columns show a slightly increasing trend in the bearing capacity but a significantly decreasing trend in ductility. Based on the experimental results, the mechanical properties of the strengthened columns under eccentric load were analyzed by ANSYS. Comparative results with the experimental results indicate that the numerical model is effective, and the maximum error of calculated strengths is 6%. The analysis results of the finite element method show that the inside strengthened concrete is obviously confined by the steel tube and the maximum confining stress is up to 10 MPa, while the outside strengthened concrete is under tension and is not confined. Moreover, the confining stress of original concrete is roughly similar everywhere and is between 2. 0 MPa and 2.5 MPa. Because of the effective confinement provided by the circular steel tube, the maximum stresses of original concrete and strengthening concrete are more than their uniaxial compressive strength.