Load-bearing Capacity Of The Key Conversion Nodes Of Single-and Dual-angle Steel For Ultra-high-voltage Power Transmission Tower

With the advantages like convenient transportation as well as easy construction and installation, angle-steel tower has been widely applied to the structure of overhead power transmission tower. As transmission voltage is upgraded, the external load of the power transmission tower becomes increasingly larger, thus making higher demands on the load-bearing capacity of the connection nodes. As a result of this, varieties of new problems arise in the calculation about the strength, rigidity and stability of tower structure. Particularly, technical engineers are not clear about the load-bearing mechanism while designing and computing the key nodes of angle-steel tower, and there is also a lack of corresponding referential theories in relevant specifications. Given the safety in actual projects, the thickness of node plate is improperly increased according to relevant computing results, thereby leading to the blindness in the computation of strength and stability.This paper is aimed at studying the load-bearing capacity of a new key node(namely, the key conversion node of single-and dual-angle steel) in the ultra-high-voltage power transmission tower design. For this sake, the mechanical model is built to conduct a theoretical analysis on the key conversion nodes of single-and dual-angle steel in accordance with approximate plane assumption theory, as well as present a method to calculate the thickness of horizontal connection plate for the key conversion nodes of single-and dual-angle steel. Given the uneven stress distribution of horizontal connection plate as well as the ratio of the horizontal plate's bending moment to that of shoe plank, the coefficient of load transmission for the conversion nodes of single-and dual-angle steel is proposed. Then, based on the summarization of existing research achievements, the computing method for shoe plank is brought forward. For the key conversion nodes of single-and dual-angle steel, lots of numerical simulating calculations have been performed, and the correctness of theoretical calculations has also been verified by means of full-scale experiment.According the needs of full-scale experiment, this paper carries out numerical simulating calculations about the experimental mode of the key conversion nodes of single-and dual-angle steel, and compares the stress distribution of the dangerous areas in the nodes on the condition of different parameters. Apart from these, this paper figures out the structural form and dimension of a full-scale model and maps out a loading scheme for the purpose of making preparations for experimental study.In the experimental measurement and study about the load-bearing capacity of the conversion nodes of single-and dual-angle steel, the full-scale test pieces for the conversion nodes of single-and dual-angle steel are produced to study the strain distribution in the dangerous cross-sections of the horizontal plates and shoe planks with different thicknesses on different operating conditions. Meanwhile, a comparative analysis on the experimental and finite results is implemented to figure out the source of errors and verify the load transmission mechanism in the key conversion nodes of single-and dual-angle steel. In addition, the feasibility of the method for the design and computation of horizontal connection plate is verified.Relying on theoretical analysis, numerical simulation and experimental verification, this paper ascertains the load-bearing mechanism of the key conversion nodes of single-and dual-angle steel for ultra-high-voltage power transmission tower, as well as proposes a simplified mechanical mode and a load-bearing computing means. This has provided theoretical guidance for the design of new key nodes of single-and dual-angle steel.