The tension cable-supported power transmission structure (TC-PTS) is a new type of power transmission structure suitable for mountainous terrain, and is sensitive to wind load. In this regard, a nonlinear finite element analysis model of wind-induced vibration is proposed for the TC-PTS, and the wind-induced vibration response of the structure is analyzed. Firstly, the tangent stiffness matrix of the three-dimensional truss element for the supporting suspension cable and transmission line, considering the geometric nonlinearity of structures, is derived through the relationship between the element elastic energy and its displacement. Subsequently, the element mass matrix and damping matrix of the supporting suspension cable and transmission line, as well as the element nodal load vector obtained from wind load equivalence, are given. Then, based on the nonlinear finite element theory, the nonlinear dynamic equation of wind-induced vibration is established for the TC-PTS and solved using the Newmark-β method combined with the Newton–Raphson iterative method. Furthermore, the rain-flow counting method and Miner’s linear fatigue cumulative damage theory were used for wind-induced fatigue damage assessment. Finally, a two-span TC-PTS was selected as an example, and the wind-induced nonlinear vibration and fatigue damage assessment were analyzed through the proposed model. The results show that the proposed model has high computational accuracy and efficiency. The first three order vibration modes of the supporting-conductor part of the two-span TC-PTS were antisymmetric vertical bending, symmetric side bending, and antisymmetric side bending. With the increase in wind speed and wind direction angle, the maximum lateral displacement and tension of the supporting suspension cable and transmission line increased, and their degree of increase showed a nonlinear trend. In terms of the wind-induced fatigue analysis results of TC-PTS, the fatigue damage at the end of the supporting-conductor suspension cable was greater than the fatigue damage at its midpoint. Compared to the fatigue damage at the midpoint of the conductor, the fatigue damage at the end of the conductor was less affected by the wind direction angle, and both were more significantly affected by the wind speed.

The time-variant system reliability analysis is a challenging and significant topic, which also faces the common obstacles of traditional system reliability methods such as combination explosion and unclear correlation information. In this paper, the probability density evolution method (PDEM) for two types of time-variant system reliability analysis is proposed. First, the system reliability is classified into two types, and the corresponding equivalent performance functions are given, which are further extended to time-variant structural systems. Second, based on the single equivalent performance function, the generalized density evolution equation (GDEE) for time-variant structural system is derived in two different ways. Third, the GDEE is solved by the Dirac sequence method and the time-variant system reliability is evaluated. Finally, several numerical examples are investigated to illustrate the accuracy and effectiveness of proposed method.

In mountainous areas, the installation of steel towers was the major obstacle to the construction of transmission lines. In long-span cross-rope suspension (CRS) structures, the conductors are supported by hundreds-meters-long suspension cables crossing valleys instead of steel towers. Though long-span CRS is an innovative structural system, its structural performance needs to be clarified. Firstly, an assembled FE model was established based on initial deformed components for long-span cross-rope suspension structure. The wind load response of long-span cross-rope suspension structure with different lengths or number of spans was established and analyzed. Vortex-induced vibration (VIV), which was the major factor regarding fatigue and service life, and its controlling by Stockbridge damper for a long-span CRS were discussed. The numerical simulation results showed that the tensile force of the suspension cable increased with the length and number of spans of the conductor. In addition, considering the ice covering the transmission line, the interaction between the wind load and ice load induced the nonlinear lateral deformation characteristics of the conductor. Moreover, the vibration characteristics of the conductor in the long-span CRS were studied and compared with the traditional tower-line system. An analysis of the long-span CRS with a Stockbridge damper showed that additional dampers were essential for controlling the maximum dynamic bending stress of conductors at both ends.

The transmission tower is an important infrastructure for transmission lines. To secure the operation of the power grid, it is particularly important to evaluate the safety of the in-service transmission tower under the action of random wind loads throughout their entire life cycle. Thus, this paper firstly establishes the time-varying equivalent performance function of the in-service transmission tower under the action of random wind loads. Then, in order to address the shortcomings of the traditional maximum entropy method, the high-order moments-based improved maximum entropy method (HM-IMEM) is proposed and extended to assess the wind resistance global reliability of the in-service transmission tower. Finally, the effectiveness of the proposed method is demonstrated evaluating the wind resistance global reliability of an in-service transmission tower in an engineering setting. Analytic results indicate that: (1) The proposed method can ensure a balance between calculation accuracy and efficiency. Compared with Monte Carlo simulation (MCS) method, the relative error is only 0.11% and the computational cost is much lower than that of the MCS method. (2) The reliability of the in-service transmission tower significantly decreased over time. In order to guide maintenance and reinforcement by predicting the time-varying performance of in-service transmission towers, it is of great engineering value to evaluate the wind resistance global reliability of the in-service transmission tower.

With the extensive construction of ultra-high voltage (UHV) transmission lines, the fatigue damage of steel tube members caused by vortex-induced vibration (VIV) in tubular towers has received growing attention. Although some progress has been made in the research of the VIV of steel tubes in uniform flow, there is still relatively scarce research on the VIV of steel tubes at various inflow conditions. In this paper, a series of wind tunnel tests are conducted to investigate the VIV of the steel tube subjected to uniform, turbulent, and oblique flows. Three turbulence intensities (I_u = 5.9%, 9.7%, and 12.6%), and four yaw angles (α = 10°, 20°, 30°, and 40°) are considered. The results show that the VIV response of the steel tube in the in-line (IL) direction is negligible compared to that in the cross-flow (CF) direction. The displacement amplitude gradually decreases as the turbulence intensity increases, accompanied by a more unstable response. For the inclined steel tube, the VIV maximum amplitude almost remains constant when α ≤ 20°, while it sharply decreased in the case of α = 30° and α = 40°. Furthermore, it was found that the so-called independent principle is applicable for α ≤ 10°.