WO2010109267A1

WO2010109267A1 - Device for coaxial adjustment in lattice bars

Info

Publication number: WO2010109267A1
Application number: PCT/IB2009/051194
Authority: WO
Inventors: Paulo Emmanuel De Abreu
Original assignee: Paulo Emmanuel De Abreu
Priority date: 2009-03-21
Filing date: 2009-03-21
Publication date: 2010-09-30
Also published as: BRPI0924520A2

Abstract

Device for coaxial adjustment in lattice bare of metallic structures, such as, metallic towers or the like utilized for electric power transmission lines, telecommunications, wind energy generators and other applications. In the prior art structures, there is a lack of concentricity between the mechanical loads vector and the axis of the section centers of gravity. One basic aspect of the present invention is directed to a device for coaxial adjustment in lattice bars of metallic structures characterized by comprising an aligner (207) to a end region of the lattice bar (4). The aligner (207) is adapted to provide a connection between the lattice bar (4) and another component of the metallic structure, and is fixed to a region of the lattice bar (4) in order to coaxially concentrate the mechanical loads vector of the connection in the axis of the center of gravity of the lattice member (4).

Description

Title of Invention: DEVICE FOR COAXIAL ADJUSTMENT IN

LATTICE BARS

Technical Field Technical Field

[1] This invention relates to metallic structures, more particularly, metallic towers or the like utilized for electric power transmission lines, telecommunications, wind energy generators and other applications. Background Art Background Art

[2] Metallic structures such as towers or the like utilized for electric power transmission lines, telecommunications, wind energy generators and other applications are well know in the prior art. The structural designs, components and materials of such towers vary depending upon the application. Nevertheless, due to structural design and cost constraints, it is very common the use of metallic lattice towers in high voltage electric power transmission and telecommunication applications.

[3] In such lattice towers, the skilled in the art usually adopt the standard sections such as the ones described in the European Standard prEN 1993-3-1:2004 - Eurocode 3: Design of steel structures, Part 3.1.: Towers, masts and chimneys - Towers and masts.

Disclosure of Invention Technical Problem

[4] The standard plane sections usually have different values for the gyration radius depending on the symmetry axis of each section. The critical load for dimensioning the lattice bars is the buckling load under axial compressive stress. As truss bars are structurally slender, the critical load is proportional to the square of the gyration radius; therefore the utilization of the strength in the other axes is hindered. In addition, the standard sections with plane faces, besides having different gyration radius in each axis, have sharp edges and were not conceived for reducing the aerodynamic forces on the towers.

[5] Furthermore, the non-alignment of the mechanical loads in relation to the axis of the center of gravity (CG), or more precisely, of the center of mass, of the plane sections of the prior art limit the best use of the properties of metals. As can be verified from the Figure 9.33 'Column Formulas Around the World' from the book 'Structural steel design' (Lynn S. Beedle et al, Fritz Engineering Laboratory, New York: Ronald Press Co, 1964, p. 319), the standards of many countries adopt high safety factors, which vary among each other, for the buckling curves. This safety factor serves exactly for compensating the imperfections in the connections created by the lack of symmetry of the sections, and particularly, due to the lack of concentricity of the loads vector with the axis of the sections' centers of gravity. Technical Solution

[6] To overcome the drawbacks and problems described above and other disadvantages not mentioned herein, in accordance with the purposes of the invention, as described herein, one basic aspect of the present invention is directed to a device for coaxial adjustment in lattice bars of metallic structures characterized by comprising an aligner fixed to a end region of the lattice bar. The aligner is adapted to provide a connection between the lattice bar and another component of the metallic structure, and is fixed to a region of the lattice bar in order to coaxially concentrate the mechanical loads vector of the connection in the axis of the center of gravity of the lattice member. Advantageous Effects

[7] The present invention has several advantages over the prior art. By adopting the device for coaxial adjustment according to the present invention, the problem of lack of concentricity of the loads vector in relation to the axis of the center of gravity of the sections is therefore eliminated. Hence, there is a better utilization of the sections properties, particularly those with equal gyration radius in all axes. Therefore, due to the improvement of the structural performance and the aerodynamic behavior, it is obtained a surprising reduction in the total weight of the structure. Description of Drawings

[8] The accompanying drawings are not necessarily drawn on scale. In the drawings, some identical or nearly identical components that are illustrated in various figures may be represented by a corresponding numeral. For purposes of clarity, not every component may be labelled in every drawing.

[9] Fig. 1 illustrates one exemplary embodiment of a channel section with equal gyration radius in all axes.

[10] Fig. 2 illustrates a perspective view of a first exemplary embodiment of the device for coaxial adjustment according to the present invention.

[11] Fig. 3 illustrates another perspective view of a first exemplary embodiment of the device for coaxial adjustment according to the present invention.

[12] Fig. 4 illustrates a perspective view of a second exemplary embodiment of the device for coaxial adjustment according to the present invention.

[13] Fig. 5 illustrates another perspective view of a second exemplary embodiment of the device for coaxial adjustment according to the present invention. Mode for Invention

[14] This invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of 'including', 'comprising', 'having', 'containing' or 'involving', and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

[15] Fig. 1 illustrates one exemplary embodiment of a channel section (also know as 'U-

Section') with equal gyration radius in all axes, with a web (2) and legs (3).

[16] Figs. 2 and 3 illustrate a first exemplary embodiment of the device for coaxial adjustment according to the present invention, which in this case is adapted for a lattice bar (4) with channel section (U-Section). In this embodiment, the device for coaxial adjustment in lattice bars of metallic structures comprises an aligner (104) formed with a plate (106) welded to one end region of the lattice bar (4), more specifically, to the legs (3) of the bar, in the region of the center of gravity. The plate (106) is adapted to provide a connection between the lattice bar (4) and another component of the metallic structure, for example, a column or a beam, and wherein the aligner (104) is fixed to the bar in order to coaxially concentrate the vector of the mechanical loads of said connection in the axis of the center of gravity of the lattice bar (4).

[17] In the example illustrated in Fig. 2 and 3, the plate (106) has at least one hole for the passage of at least one connection fastener that provides the connection between the lattice bar (4) and another component of the metallic tower. This configuration is more practical when the dimensions of the section of the lattice bar and the aligner allow adequate access for the welding.

[18] Figs. 04 and 05 illustrate a second exemplary embodiment of the device for coaxial adjustment according to the present invention, which in this case is adapted for a lattice bar (4) with channel section (U-Section). In this embodiment, the device for coaxial adjustment in lattice bars comprises an aligner (204) formed with a structural section (207) that is fixed to an end region of the lattice bar (4) through at least one structural fastener, which in this embodiment is composed by a bolt (210), a washer (211) and a nut (212).

[19] The structural section (207) is adapted to provide a connection between the lattice bar and another component of the metallic tower.

[20] As shown, the fastening of the aligner (204) in the lattice bar (4) is made in such a way to coaxially concentrate the mechanical loads vector of the connection in the axis of the center of gravity of the lattice bar.

[21] More specifically, in the example illustrated in Figs. 4 and 5, the structural section

(207) is composed of: two parallel leg-plates (208), which when positioned into the channel section of the lattice bar (4) lie adjacent to the legs (3) of the channel section; and of at least one web-plate (206) welded between the two leg-plates (208), which when positioned into the channel section, in a parallel level in relation to the web (1) of the channel section, the plane of the web-plate (206) lies along the axis of the center of gravity of the channel section, wherein the web-plate (206) is adapted to provide the connection between the lattice bar (4) and another component of the metallic structure.

[22] Other modifications to the details of construction may be possible. For instance, the bolt and nut connection shown in Figs. 4 and Fig. 5 may be substituted by welded joints, groove coupling or any other suitable connection means. Other variations in the components and project may also be possible according to the application.

[23] For illustrative but non-limiting purposes, in Table I there are shown the characteristics of a channel section with a device for coaxial adjustment ('U/Aligner') according to one exemplificative embodiment of the invention, compared to a channel section (¹U') without the device for coaxial adjustment.

[24] TABLE I [Table 1] [Table ]

[25] In this example, with distance between rotulas of L= 1.5m and a device for coaxial adjustment was used in each both ends of the lattice bar. For the sake o simplicity, it was adopted buckling stress given by the equation T= 10.4xl0⁶/ Y² for F>86 where Y= L/i and L = distance between rotulas and i = gyration radius.

[26] As can be seen from Table I, a channel section with the device for coaxial adjustment according to the present invention is capable of supporting approximately 40% more load under axial compression.

[27] This surprising increase on the capacity of supporting loads allows many other enhancements, such as improvement in the aerodynamic behavior and structural, performance, and specially a significant reduction in the total weight of the structure. [28] While the invention has been disclosed by this specification, including its accompanying drawings and examples, various equivalents, modifications and improvements will be apparent to the person skilled in the art. Such equivalents, modifications and improvements are also intended to be encompassed by the following claims.

Claims

[Claim 1] 01. Device for coaxial adjustment in lattice bars of metallic structures characterized by comprising an aligner which is fixed to an end region of a lattice bar, the aligner being adapted to provide a connection between the lattice bar and another component of the metallic structure, and wherein the aligner is fixed to the lattice bar in order to coaxially concentrate the mechanical loads vector of said connection in the axis of the center of gravity of the lattice bar.

[Claim 2] 02. Device for coaxial adjustment in lattice bars of metallic structures according to claim 01, wherein the aligner comprises a plate welded to the lattice bar, the plate being adapted to provide a connection between the lattice bar and another component of the metallic tower.

[Claim 3] 03. Device for coaxial adjustment in lattice bars of metallic structures according to claim 02, wherein the welded plate has at least one hole for the passage of at least one connection fastener that provides the connection between the lattice bar and another component of the metallic tower.

[Claim 4] 04. Device for coaxial adjustment in lattice bars of metallic structures according to claim 01, wherein the aligner comprises a structural section.

[Claim 5] 05. Device for coaxial adjustment in lattice bars of metallic structures according to claim 04, wherein the structural section is welded to the lattice bar.

[Claim 6] 06. Device for coaxial adjustment in lattice bars of metallic structures according to claim 04, wherein the structural section is fixed to the lattice bar by at least one structural fastener.

[Claim 7] 07. Device for coaxial adjustment in lattice bars of metallic structures according to claim 04, 05 or 06, wherein the structural section has at least one hole for the passage of at least one connection fastener that provides the connection between the lattice bar and another component of the metallic tower.

[Claim 8] 08. Device for coaxial adjustment in lattice bars of metallic structures according to claim 04, 05 or 06, wherein the lattice bar is a channel section; and wherein the structural section is composed of: two parallel leg-plates, which when positioned into the channel section lie adjacent to the legs of the channel section; and at least one web-plate welded between the two leg-plates, which when positioned into the channel section, in a parallel level in relation to the web of the channel section, the plane of the web-plate lies along the axis of the center of gravity of the channel section, wherein the web- plate is adapted to provide the connection between the lattice member and another component of the metallic structure.