Wind turbines are growing used to transform wind energy into electric energy given that wind energy is becoming more popular as a renewable resource, unlike fossil fuels, and does not pollute the environment. However, in this technology, a reliable and stable structure is necessary while taking into account the economics of the project. Building the structure and connecting it to the grid account for, respectively, 25 and 75% of the total project costs and, therefore, reducing the building costs help economically justify the project. Steel lattice truss structures with single- and double-angle bolted connections significantly reduce the weight of the consumed steel and, therefore, the transportation and assembly costs, thus reducing the total structural costs by 30%. Bolted connections in such structures give rise to joint slip, which in turn increases the tower displacement. Indeed, using the results of this project and entering them into the software can lead to a better understanding of the wind-turbine tower behavior, which helps eliminate the factor of safety that is taken into consideration in design due to being unable to forecast the behavior. Unlike the earlier studies that have been only carried out on single angles, the present study investigated double angles. The fact that single angles are mostly used in x-shaped and bracing components and double angles are mostly used in piers of lattice wind-turbine towers was the key factor to the necessity of this research. This study investigated double-angle lattice tower members. The experiments were conducted on a total of 9 bolted double-angle connections, and the force–displacement curves were presented for each. The equations derived to estimate the behavior of double angles were consistent with the existing equations for single angles. These equations were derived based on the different variables affecting the joint behavior, such as the number of bolts, bolt diameter, angle specifications, area of bolts, and the net cross-sectional area, offering a maximum error of 10% compared to the experimental results. The behavior of the wind turbine members was, therefore, estimated for both single and double types using these equations, which is indicative of their ability to estimate the behavior of all bolted connections in lattice wind turbine structures based on the size and number of angles and the number of bolts. This study can help the design of lattice wind turbine structures by providing the designer with a more accurate behavior of the structure

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