Wind loads can cause significant vibrations in circular section members, resulting in serious structural hazards. In order to control the vibration of the structure and mitigate the hazards, this study investigates the optimal design and carries out a performance evaluation of a tuned mass damper inerter (TMDI) designed for the vibration control of circular section members in structures. The TMDI system is a novel vibration reduction device that utilizes an inerter based on a tuned mass damper (TMD). The main structure is a simplified Euler beam made up of circular section members, and the mass of the TMDI is coupled to the main structure by a spring and damper, as well as to the ground via an inerter. The optimization objectives are to minimize the displacement variance and maximize the energy dissipation index (EDI), and two different optimization schemes are designed. In addition to the comparative analysis of the results obtained from the different optimization schemes, a sensitivity analysis of the design parameters is also performed, and the results show that TMDI not only effectively reduces the additional mass but also has better vibration control performance and robustness than the TMD.

To investigate vibration control and optimal design of transmission lines with tuned-mass-damper-inerter (TMDI), the motion equation of transmission lines with TMDI is established in the paper, and the closed-form solutions of the response spectrum of transmission line displacement are derived by the frequency domain analysis method. The design parameters of TMDI are optimized by fixed-point theory, and the vibration control performance of TMDI is discussed. The results show that the increase in apparent mass ratio has a positive effect on the vibration control performance of TMDI; the vibration control performance is greatly affected by frequency ratio and limited by damping ratio; the increase in both mass ratio and apparent mass ratio reduces the peak values of the displacement response spectra of transmission line with TMDI; however, blindly increasing the apparent mass and mass ratio (β > 0.2 or μ > 0.4) has a limited effect on improving the vibration control performance of TMDI; compared with conventional TMD, the peak values of the controlled displacement response spectrum of the transmission line with TMDI can be reduced by about 12%, and TMDI has a better vibration suppression effect on the transmission lines.

Downburst is one of the high-intensity winds that cause transmission tower failures. The regulations of transmission tower-line systems under downburst wind loads cannot meet the design requirements at present. In this paper, the calculation formulas of the background and resonant components of transmission tower under downburst wind loads are obtained, based on the modal analysis theory of non-stationary wind for the single-degree-of-freedom system in the frequency domain. The effects of structural dynamic characteristics, damping ratio, and mean wind speed vertical profile on dynamic effect on structural response are discussed. Then the equivalent static wind load (ESWL) is obtained according to the maximum response and compared with the finite element method (FEM) in the time domain. Applications of these formulas are addressed to the cases from the empirical model of Holmes and field record of a rear flank downdraft (RFD). The results show that the maximum responses obtained by the current formulas match well with those from the modal decomposition method and dynamic analysis with FEM. The internal forces of tower members calculated by ESWL based on maximum response are closer to the results from FEM than those calculated by downburst loads recommended in ASCE guidelines. The presented framework can be used to assist the wind-resistant design of transmission towers considering downburst wind load.

A downburst is one of the high-intensity winds that cause transmission tower failures. In recent years, downbursts have brought great disasters to the economies and lives of people all around the world. In this paper, the dynamic stability of the transmission tower-line system under a downburst is analyzed. The deterministic-random mixed model is used to generate the downburst wind field and ANSYS software is employed to establish the finite element model of the transmission tower-line system. The response characteristics of the transmission tower-line system in the downburst and the atmospheric boundary layer (ABL) wind fields are compared through time history analysis. The displacement response of the transmission tower is analyzed with different Z_max values and attack angles. Based on the Budiansky–Roth criterion and dynamic incremental method, the dynamic stability of the transmission tower system under the action of the downburst wind field is studied, and the corresponding wind speed conditions when the transmission tower-line system is unstable are obtained. The results show that the top displacement of the tower-line system under the action of a downburst is 1.83 times that under the ABL wind. The tower top acceleration under the downburst is 1.57 times that under ABL wind. The most unfavorable wind attack angle for a transmission tower-line system is 90°. When Z_max is within the height range of the transmission tower, the influence on the displacement of the transmission tower increases with the increase in Z_max. When Z_max exceeds the height range of the transmission tower, the influence on the displacement of the transmission tower decreases. Under the most unfavorable wind attack angle, the influence of the conductor on the stability of the transmission tower is obvious.