A method for strengthening damaged tubular steel T-joints under axial compression by wrapping them with carbon fiber-reinforced polymer (CFRP) sheets was proposed and evaluated. The influence of the CFRP strengthening on the failure mode and load capacity of T-joints with different degrees of damage was investigated using experiments and finite element analyses. Five T-joints were physically tested: one bare joint to obtain the peak load and corresponding displacement (Δ_1m), two reinforced joints to provide a reference, and two pre-damaged then retrofitted joints to serve as the primary research objects. The ratio of the pre-loaded specimen chord displacement to the value of Δ_1m was considered to be the degree of damage of the two retrofitted joints, and was set to 0.80 and 1.20. The results demonstrate that the maximum capacity of the retrofitted specimen was increased by 0.83%–15.06% over the corresponding unreinforced specimens. However, the capacity of the retrofitted specimen was 2.51%–22.77% lesser compared with that of the directly reinforced specimens. Next, 111 numerical analysis models (0.63 ⩽ β ⩽ 0.76, 9.70 ⩽ γ ⩽ 16.92) were established to parametrically evaluate the effects of different geometric and strengthening parameters on the load capacity of strengthened tubular T-joints under different degrees of damage. The numerical analysis results revealed that the development of equivalent plastic strain at the selected measuring points was moderated by strengthening with CFRP wrapping, and indicated the optimal CFRP strengthening thickness and wrapping orientation according to tubular T-joint parameters. Finally, reasonable equations for calculating the load capacity of CFRP-strengthened joints were proposed and demonstrated to provide accurate results. The findings of this study can be used to inform improved CFRP strengthening of damaged tubular steel structures.

提出并评估了一种在轴向压缩下用碳纤维增强聚合物（CFRP）板包裹受损的T型钢管的方法。通过实验和有限元分析，研究了CFRP加固对T型接头不同破坏程度的破坏模式和承载能力的影响。对五个T型接头进行了物理测试：一个裸露的接头获得峰值载荷和相应的位移（_Δ1m），两个加固的接头提供参考，两个预先损坏然后进行改装的接头作为主要研究对象。预载样本弦位移与_Δ1m值之比被认为是两个改型接头的损坏程度，并设置为0.80和1.20。结果表明，与未加固的标本相比，改造后的标本的最大承载能力提高了0.83％–15.06％。但是，与直接加固的标本相比，改造后的标本的承载能力要低2.51％–22.77％。接着，111个的数值分析模型（0.63⩽ β ⩽0.76，9.70⩽ γ⩽16.92）的建立是为了通过参数评估不同几何和加固参数在不同程度的破坏下对管状T形接头的承载能力的影响。数值分析结果表明，通过CFRP包裹加固可以缓和选定测量点的等效塑性应变的发展，并根据管状T形接头参数确定了最佳CFRP加固厚度和包裹方向。最后，提出了计算CFRP加固节点承载力的合理方程式，并证明了该方程式可提供准确的结果。这项研究的发现可用于为受损的管状钢结构的CFRP加固提供信息。