为探讨方钢管覆板加强节点的轴向受压承载机理，对表面覆板加强节点进行静力加载试验，分析了节点的破坏形态和荷载－变形曲线; 建立了覆板加强节点的有限元模型并进行有限元参数分析，揭示了覆板对节点的加强机理; 文中还采用塑性铰线法建立了覆板加强节点的承载力设计公式，并提出了覆板加强的设计建议．结果表明: 增加覆板厚度能显著提高节点的抗压承载力，覆板宽度和长度对节点承载力的影响不明显; 覆板尺寸相同时，支管－主管宽度比( β) 越小，则覆板的加强比越高; 覆板对节点的加强机理为覆板与主管表面共同屈服，但当 β≥0．8 或覆板厚度较大时，加强节点容易发生主管侧壁屈曲，造成覆板屈服不能完全发展; 文中公式计算结果与试验及参数分析结果吻合较好．

In order to reveal the bearing mechanism of doubling plate- reinforced square tubular joints under axial compression,monotonic loading tests of the joints were carried out,and the failure modes as well as the load-deformation curves of the specimens were analyzed.Then,a finite element model of the joints was constructed,and the corresponding model parameters were analyzed,through which the reinforcement mechanism of doubling plate for joints was revealed.Moreover,the formulas of bearing capacity of doubling plate- reinforced joints were deduced based on the yield line method,and some design proposals were suggested for the doubling plate reinforce-ment.The results show that (1) the compression capacity of the joint significantly improves with the thickness of the doubling plate but changes a little with the plate width and length; (2) the reinforcement ratio of doubling plate increases with the decrease in brace- chord width ratio β; (3) the doubling plate improves the compression capacity by yielding together with the chord flange; (4) when β≥0.8 or when the plate thickness exceeds a certain range,the yield of doubling plate may be incomplete due to the buckling of chord web; and (5) the deduced design formulas accord well with the results of experiments and parameter analyses.