Local stiffeners affect the behaviour of thin-walled beams (TWBs). An in-house code based on a one-dimensional model proved effective in several instances of compressive buckling of TWBs but gave counterintuitive results for locally stiffened TWBs. To clarify the matter, we investigated TWBs with multi-symmetric double I cross-section, widely used in practical applications where high bending stiffness is required. Several samples were manufactured and stiffened on purpose, closing them over a small portion of the axis at different places. The samples were tested with end constraints accounting for various warping conditions. The experimental and numerical outputs from a commercial FEM code gave a key to overcome the unexpected results by the in-house code, paving the way for further studies.

局部加劲肋会影响薄壁梁（TWB）的性能。基于一维模型的内部代码在几种形式的TWB压缩屈曲中被证明是有效的，但对于局部变硬的TWB却给出了违反直觉的结果。为了澄清这个问题，我们研究了具有多对称双I截面的TWB，这些TWB被广泛用于需要高弯曲刚度的实际应用中。特制了一些样品并进行了加硬处理，在不同位置将它们沿轴的一小部分封闭。在考虑各种翘曲条件的最终约束条件下对样品进行了测试。商业FEM代码的实验和数字输出为克服内部代码带来的意外结果提供了关键，这为进一步研究铺平了道路。