GB2272714A

GB2272714A - Beam for e.g.mine support arches

Info

Publication number: GB2272714A
Application number: GB9323175A
Authority: GB
Inventors: Robert Thackray; Douglas Herbert Grainger
Original assignee: LOADMASTER Ltd
Current assignee: LOADMASTER Ltd
Priority date: 1992-11-18
Filing date: 1993-11-10
Publication date: 1994-05-25
Anticipated expiration: 2013-11-10
Also published as: GB2272714B; GB9323175D0; PL300928A1; HUT69498A; GB9224130D0; HU9303272D0

Abstract

The invention relates to beams, particularly of I- or H-section such as are used in deep mining applications. The beam has a construction in which respective flanges 2 of the beam have a root radius connecting the respective sidewall of the web to the respective innermost face of a respective flange and an outer radius connecting the innermost face to a respective outermost toe of the flanges, each said innermost face from the point of commencement of the outermost radius being parallel to the outermost face of the flange over a first section 5 and followed by an inclined section leading to the commencement of the root radius. <IMAGE>

Description

BEAMS This invention relates to beams and in particular to metal beams of I- or H-section such as are used particularly but by no means exclusively in deep mining applications for example in roadway arches and square work supports for the roof.

Historically, failure of roadway arches and square work supports has occurred as a consequence of the failure of a joint between adjacent I- or H-section members, but as a result of the evolvement of higher performance joint plates, failure of the support now more usually occurs remote from the joints and as a result of deformation of the I- or H-section steelwork itself.

Examination of failed I- or H-section steelwork has shown that the subjecting of the steelwork to mine roadway strata forces results in an initial yielding and plastic deformation at the extremities of the flanges, causing a rippling effect, which as the load on the support increases extends across the flanges to the root radii between the flanges and the web, with the direct effect of buckling and collapse of the I- or H-section steelwork.

It is the object of the invention to eliminate to a considerable degree the above-mentioned disadvantage.

According to the present invention, an I- or H-section member comprises respective flanges to either end of a connecting web, each flange to both sides of the web having a root radius connecting the respective sidewall of the web to the respective innermost face of a respective flange and an outer radius connecting the innermost face to a respective outermost toe on the flanges, each said innermost face from the point of commencement of the outermost radius being parallel to the outermost face of the flange over a first section and followed by an inclined section leading to the commencement of the root radius.

Preferably, the length of each parallel first section is approximately 25% of the distance from the commencement of the root radius to the commencement of the radius at the toe of each flange.

The redisposition of material of the flanges of the Ior H-section member of the invention, in comparison with conventional I- or H-section members, generates optimum additional strength characteristics over the length of that part of the flange where the innermost face is parallel to the outermost face, and as a consequence is of constant thickness.

As a result of the provision of greater strength at this sector of the construction, a considerably greater resistance to yielding and plastic deformation at the extremitites of the flanges, is provided with a consequential delay in the onset of any rippling effect and reduction in rippling effect, together with a major depression in the progress of any such rippling effect towards the root radii between the flanges and the web.

Most desirably the I- or H-section member of the invention is formed from a high strength micro-alloyed steel specifically developed to provide optimum strength and yielding characteristics to enhance the improvement provided by the invented section itself.

In comparison with conventional I- or H-section steelwork members of comparable size, the member of the invention provides a most significant and unpredictable improvement in resistance to buckling and hence failure of a mine roadway arch or squarework support. An additional advantage of the invention, and perhaps for employment in less arduous conditions, IS the ability to produce an I- or Hsection member of a size approximately 708 of that of a conventional I- or H-section member and approximately 30% lighter in weight per linear metre without any sacrifice of strength characteristics or resistance to buckling. The cost of, and the physical advantages in the transportation of, lighter support components in deep mining applications generates significant savings in respect of all facets of such as roadway construction.

One embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view of a conventional I-section member; Figure 2 corresponds to Figure 1 but shows an Isection member in accordance with the invention; and Figure 3 is an enlarged view of one flange of the member of Figure 2.

In Figure 1, an I-section member 1 has flanges 2 to each side of a web 3. Each flange 2 has a root radius 4 connecting the innermost faces 5 of the flanges to the respective face of the web 2, and an outer radius 6 connecting the innermost faces 5 to the outer toes 7 of the flanges.

Over the full width of each flange, its depth progressively decreases from the commencement of the root radius 4 to the commencement of the outer radius 6.

In contrast to this, and as is shown in Figure 2 where the same reference numerals as in Figure 1 are employed, the I- or H-section beam of the invention has a redisposition of the material of the flanges 2. Thus, each flange 2 has an innermost face 5 that -from the commencement of the outer radius 6, has a first length Li extending over 25% of the distance between the commencements of the outer radius 6 and the root radius 4, formed -parallel with the top face 8 of the flange. Each innermost face 5 has a following length L2 inclined to provide a progressively increasing flange depth from the end of the parallel section to the commencement of the root radius 6.

In addition to the redistribution of material over the width of the flanges 2, the I- or H-section member of the invention is formed. from a high strength micro-alloyed steel to provide optimum strength and-yielding characteristics to enhance the improved- performance characteristics provided by the redistribution of the material of the flange discussed above.

Claims

1. An I- or H-section member comprising respective flanges to either end of a connecting web, each flange to both sides of the web having a root radius connecting the respective sidewall of the web to the respective innermost face of a respective flange and an outer radius connecting the innermost face to a respective outermost toe on the flanges, each said innermost face from the point of commencement of the outermost radius being parallel to the outermost face of the flange over a first- section and followed by an inclined section leading to the commencement of the root radius.

2. An I- or H-section member as in Claim 1, wherein the length of each parallel first section of the flanges is approximately 25% of the distance from the commencement of the root radius to the commencement of the radius at the toe of each flange.

3. An I- or H-section-member as in Claim 1 or Claim 2, wherein the member is formed from a high strength microalloyed steel to provide optimum strength and yielding characteristics.

4. An I- or H-section member substantially as hereinbefore described with reference to Figures 2 and 3 of the accompanying drawings.