## 1 Introduction  
Latticed steel angle towers are widely used in lifeline engineering structures such as communication towers, transmission towers, and television towers due to their advantages of regular structural form, uniform stiffness changes, and simple processing technology [1; 2; 3; 4; 5]. As an important component of large and complex lifeline systems, safety issues directly affect the production and construction of the country and the living order of the people. There are approximately 2 million communication towers in China, most of which are lattice steel angle towers. Due to extreme weather conditions such as strong winds, ice cover, and earthquakes, insufficient consideration is given to design wind loads, especially with the emergence of new technologies such as 5G, which require a large number of additional equipment to be installed on existing communication towers [4], and other reasons [6; 7; 8; 9; 10; 11; 12], resulting in loads exceeding the bearing capacity of existing steel angle towers and causing structural damage or even collapse. Due to the fact that the cost of constructing new steel angle towers is much higher than the cost of strengthening existing steel angle towers,telecom operators attach great importance to strengthening them in order to achieve higher economic benefits [13; 14; 15; 16]. At present, there are three main types of reinforcement methods for lattice towers in engineering: one is to increase the transverse diaphragm or auxiliary materials, reduce the calculated length of the members, and improve the buckling bearing capacity. For example, [PERSON] et al. [17] added a series of partition supports in the middle of slender members, which can achieve significant load-bearing capacity improvement. [PERSON] and [PERSON] [18] strengthened the diagonal steel tower by adding diaphragms, and the overall bearing capacity of the tower was increased by about 18% after reinforcement. The second is to paste a fiber-reinforced polymer layer on the original components to improve the cross-sectional strength. For example, [PERSON] [19] proposed a renovation plan that utilizes high-modulus carbon fiber polymer as a reinforcement mechanism for communication towers. After reinforcement, the strength and stiffness of the cross-section were increased by 20-50%. [PERSON] et al. [20] studied using fiberglass-reinforced plastic (GFRP) plates to reinforce existing communication towers. [PERSON] et al. [21] proposed an unbonded CFRP reinforcement method to improve the axial bearing capacity of components. The third is to improve the structural bearing capacity by connecting other components in parallel based on the existing members. For example, [PERSON] et al. [22] conducted a study on the reinforcement method of a cross-shaped double steel angle; in the experiment, the bearing capacity of the reinforced tower increased by 54-105%, and the reinforcement effect was significant. [PERSON] et al. [23] examined three different forms of cross-shaped steel angle reinforcement components (one-way connection with filled plates, staggered connection with filled plates, and steel angle connection), and the results showed that the angle steel connection method was the best. [PERSON] et al. [24] studied the reinforcement methods of cross joints and splice joints on the legs of transmission towers. [PERSON] et al. [25] designed a reinforcement method that prevents lateral torsion and weak axial buckling of single-angle section members through a casing and achieved good results overall. [PERSON] et al. [26; 27] conducted an experimental and numerical study on the reinforcement method of anisotropic cross-shaped components in the legs of lattice transmission or communication towers, effectively improving the overall strength of the structure. [PERSON] et al.