## 1 Introduction  
Lattice towers are widely used for power transmission, telecommunication, wind turbine, and observation towers, etc. Tall lattice towers usually have relatively low natural frequencies and small damping ratios, which may result in large amplitude vibration under dynamic excitation such as wind loads [1; 2]. The excessive vibration may diminish the serviceability of the towers, and cause fatigue damage, joint bolt looseness and even structural failure [3; 4; 5; 6; 7]. The lattice transmission tower employed in transmission line systems is an important type of lattice tower. Many collapse accidents happened to transmission towers under strong winds [8; 9; 10], as shown in Figure 1. The failure of the tower may cause massive blackouts, which results in a lot of economic loss and secondary disasters. With rapid development of power industry, many high-voltage transmission towers with greater height and span were constructed, especially in China. For example, the world's highest transmission tower currently is located at Zhoushan in China, with a height of 380 m. These tall transmission towers, which are prone to large vibrations, pose new challenges to engineering design. Hence, improving the performance of wind resistance to ensure the structural safety of the tower has become an important issue, and has attracted great attention. There are two main countermeasures to improve the wind resistance of lattice towers. The first is to increase structural stiffness by enlarging the size of the members or adding secondary members. However, this may significantly increase the material consumption and the project cost, which compromises the advantage of the low self-weight of lattice towers. The second countermeasure is to install vibration control devices to suppress the vibration. In this way, the dynamic response of the internal forces of the members can be mitigated. Consequently, small size members can meet the requirement, which means a lower cost. Various types of control devices installed on structures were studied, such as tuned mass dampers (TMD) [11; 12; 13; 14; 15; 16; 17; 18; 19], tuned liquid dampers (TLD) [20], liquid column vibration absorbers (LCVA) [5], friction dampers [21], etc. Among these control devices, using TMD in tower vibration control seems to be a promising solution due to its efficiency, convenience and low cost [14]. A TMD typically consists of a mass, a spring and a damper. The control effectiveness of a TMD depends on its parameters, such as mass, frequency and damping ratio. Hence, it is of great significance to obtain the optimal parameters for the TMD [15; 16; 17]. For TMDs on lattice towers under wind loads, theoretical or numerical studies on it were conducted. [PERSON] and [PERSON] [18] performed a three dimensional (3D) finite element (FE) analysis of a truss-type telecommunication tower with a TMD installed, and the TMD effectiveness was found to be favorable in case of wind load. [PERSON] and [PERSON] [19] conducted a parametric study of tuned mass dampers for a long span transmission tower-line system under wind load, and the influence of TMD parameters on TMD effectiveness was presented. Though the effectiveness of TMD can be evaluated theoretically or numerically, wind tunnel test is still an important method for physical verification. For high-rise structures under wind loads, the effectiveness of TMD was experimentally examined [22; 23; 24; 25], whereas the experimental studies on lattice towers with TMD installed are scarce [26]. [PERSON] et al. [23] studied the along-wind and across-wind performance of a TMD-installed building under different wind speeds and wind directions, and their results clearly show the effectiveness of the TMD. [PERSON] et al. [26] performed wind tunnel tests for a transmission tower-line system with TMDs installed, and the control effectiveness in either along-wind or across-wind direction was favorable under different wind speeds.