No abstract

A simplified calculation method is proposed for determining the peak dynamic windage yaw angle φ ^ of electricity transmission line (TL) tower suspension insulator strings (SISs). According to the rigid-body rule, the geometric stiffness matrix in the calculation of the windage yaw angle φ of SISs is dominated by the average wind loads, while the fluctuating wind loads are the dominant factor in the elastic stiffness. With the average wind state of conductors as the initial calculation condition, the load-response-correlation (LRC) method can be used to determine the fluctuating windage yaw angle φ d and the corresponding equivalent static wind loads (ESWLs). Then, the improved rigid straight rod model, which uses the actual length of conductors rather than the projected length, was used to determine the average windage yaw angle φ ¯ . Through the linear superposition of the horizontal increments of φ ¯ and φ ^ d (the peak value of φ d ), the formulae to calculate the φ ^ of SISs were derived. Additionally, the formulae for the dynamic wind load factor, β c , which is a key factor in designing wind loads for φ , were derived according to the principle of ESWLs, rather than being empirically determined by the Chinese code. Thus, the calculation model regarding the loads and response for the φ of SISs was established, and an actual TL was used to verify the established calculation model. Afterward, the influence of the different engineering design parameters on φ and its β c were analyzed. The parameter analyses show that the wind speed, span, and ground roughness influence the magnitudes of φ ^ and β c , however, the height difference between the two suspension points of the conductors, the nominal height, and the sag-to-span ratio may be neglected in the approximate calculation. Our method offers a new solution to TL design when there are large deformations and small strains.

The complex aerodynamic shape and structural form affect the wind-induced vibration coefficient β of landscape towers with a twisted column and spiral beam (short for LTs). To clarify the β distribution characteristics, evaluate the applicability of existing load codes, and provide accurate design wind loads, wind tunnel tests and numerical simulations were carried out on a LT. The LT’s aerodynamic coefficients and wind-induced responses were measured using rigid sectional and aeroelastic models. Furthermore, the displacement wind-induced vibration coefficient βd and inertial load wind-induced vibration coefficient βi(z) of the LT were calculated from these measured data. Combined with test data and a finite element model, the impacts of the wind speed spectrum type, the structural damping ratio ξ, and the peak factor g on β of the LT are analyzed. The accuracy of β of the LT calculated by Chinese and American load codes was examined and given the correction method. The results showed that the wind yaw angle had a significant impact on βd of the LT, which cannot be neglected in current load codes. The abrupt mass increase at the platform location makes the distribution characteristics of βi(z) of the LT different from conventional high-rise structures. The values of ξ and g have a significant impact on the calculation results of β, which are the key to the accurate design wind loads of LTs. The existing load codes are not suitable for LTs, and the correction method proposed in this paper can be used to improve them.