Abstract
A new type of weld-necked flange (WF) joint is presented in this paper. The flange neck of the new WF joint adopts an inner-slope section with a taper angle ranged from 20° to 25°, with the flange plate being thicker than the traditional WF joint. Compared to the traditional WF joint, the bolt cluster circle of the new WF joint is reduced relative to the steel tube wall. As a result, the effect of tensile load eccentricity on the steel bolts is significantly reduced. A series of dynamic tensile tests is conducted on the new WF joint. The stiffness of the flange plate is of importance to reduce the prying force for the new WF joint. The thickness of the flange plate, which is an important parameter for the new WF joint, is investigated to study the effects on the new WF joint’s dynamic behavior. Meanwhile, the finite element model of the new WF joint is developed to study their dynamic tensile behavior. The finite element model is verified by experimental results and proved to be precise and reliable. Base on the finite element analysis, the dynamic stress distribution and contact pressure at typical locations of the new WF joints are better revealed. Afterwards, a simplified design model for the new WF joints under tensile force is proposed, which can meet the safety and economic requirements in practical engineering projects. Furthermore, the design model can provide valuable reference for the design of the new WF joints.
Highlights
With the development of ultra-high voltage (UHV) transmission lines, as well as the applications of multi-loop lines and large-capacity conductors, the steel transmission tower tends to be increasingly larger, and external loads increase significantly
With the increase of dynamic tensile load, the dynamic strains at typical positions bifurcated gradually, and relatively obvious tensile deformations occurred in steel tubes
The design procedure is based on the assumptions listed below: a) The flange should be designed with higher capacity and rigidity than the steel tube which it splices; b) In order to mitigate the effects of bending moment, the weld-necked flange (WF) joint adopts inner-slope section, and the bolt cluster circle reduces relative to the steel tube wall
Summary
With the development of ultra-high voltage (UHV) transmission lines, as well as the applications of multi-loop lines and large-capacity conductors, the steel transmission tower tends to be increasingly larger, and external loads increase significantly. The traditional angle-steel tower is no longer applicable to UHV transmission lines. Due to the excellent integral rigidity, the large load bearing capacity and the small wind drag coefficient, the steel tubular tower (STT) has been widely used in UHV transmission lines and long-span transmission lines [1, 2]. Among various connection joints available for steel tubular structures, bolted flange (BF) joint is always preferred due to many advantages, such as: reliable force transmission, simple configuration, ease of on-site installation, and low maintenance requirement.
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