直角角钢横截面的两主惯性矩之比约为4:1，60度角钢横截面的两主惯性矩之比约为4:3。尽管60度角钢可克服直角角钢绕横截面两主惯性轴的抗失稳能力相差3倍的缺点，但60度角钢及其结构力学特性的研究则很少。我们对60度角钢及其三角形铁塔进行了初步研究，发现60度角钢及其三角形铁塔的承载能力远比相同重量的直角角钢及其四边形铁塔的承载能力高。本申请项目的主要研究内容包括：1）60度角钢局部屈曲和整杆失稳与角钢尺寸比例的关系；2）60角钢与直角角钢的优缺点比较；3）单肢连接和双肢连接对60度角钢局部屈曲和整杆失稳的影响；4）60度角钢的三角形铁塔承载（尤其是冲击载荷）能力远大于重量相同的直角角钢的四边形铁塔承载能力的原因；5）通过实验测量和有限元模拟，比较60度角钢的三角形铁塔与直角角钢的四边形铁塔在大变形时的力学特性。本申请项目的研究成果可望为60度角钢及其三角形铁塔在输电工程中应用提供理论基础。

The ratio of two principal moments of inertia in a transverse cross section of 90 angle steels is about 4:1. The ratio of two principal moments of inertia in a transverse cross section of 60 angle steels is about 4:3. Although 60 angle steels can overcome the shortcoming that the anti-instabilities of 90 angle steels about two principal inertia axes have 3 times difference, people rarely study mechanical properties of 60 angle steels and their structures. We have conducted the preliminary study to 60 angle steels and their triangle iron towers. We find that the load bearing capacities of 60 angle steels and their triangle iron towers are higher than those of 90 angle steels and their quadrangle iron towers with the same weights. The main research contents of this project include: 1) the relationship among local buckling, entire pole instability, and size proportions of 60 angle steels; 2) the advantages and the shortcomings of 60 angle steels and 90 angle steels; 3) the effects of connections by one leg and two legs to local buckling and entire pole instability of 60 angle steels; 4) explain why the load bearing capacity (particular impact load) of triangle iron tower with 60 angle steels is higher than that of the same weight quadrangle iron tower with 90 angle steels; 5) compare mechanical properties of triangle iron towers of 60 angle steels with those of quadrangle iron towers of 90 angle steels under large deformation by experimental measurements and FEM simulations. The results of the project may become the theoretical foundation of 60 angle steel's triangle iron towers in power transmission engineering.