This invention relates to a method of manufacturing a beam, in particular for structural metal beams.
Universal beams also known as I-beams or H-beams are regularly used in building structures. However, the type of beam that is commonly used is not as efficient or optimised as it could be. Typically, the beams are of constant cross section along their length. The size of cross section is selected from a list of catalogue sizes and chosen based on the maximum bending moments and shear forces expected in use. There may be additional criteria such as buckling limits and allowances for holes. The size of the cross section is therefore based on the worst case condition along the length of the beam. However, in practice these sizing criteria do not apply to all points along the length of the beam, so at points along the beam the beam is over specified; it has excess material and excess weight that is not required.
One reason why the majority of universal beams have a constant cross section along their length is that most of these beams are rolled in universal beam rolling mills and the standard technology in this type of mill does not allow the beam cross section to be varied along the length of the beam.
Recently there have been various attempts to overcome this restriction. WO2012032301 describes apparatus and methods for rolling beams with variable depth, variable flange thickness, variable flange width etc. EP0756905 describes a related technology whose main purpose is to achieve consistent overall beam depth for different flange thicknesses. JP2000343102 describes another method of producing beams with variable web depth and flange thickness. These methods have several significant disadvantages. The main problem is that the material flow patterns involved in rolling a one piece beam with variable cross section along its length are very complex and it is difficult to achieve the correct material properties and to avoid undesirable curvature of the beam. Another issue is that new equipment is required.
To avoid the difficulties involved in rolling a beam with varying cross section along its length an alternative manufacturing method is to fabricate the beam, that is to construct the beam by welding or joining plates or sections together. The construction of fabricated beams is well known, for example as described in U.S. Pat. No. 1,843,318, where arched beams are provided, or truss beams as illustrated in U.S. Pat. No. 620,561 where the depth is modified by cutting material from the web and then joining the cut edges together. A characteristic of these beams is that the thickness of the material in the web and the flange is constant along the length of the beam. The only thing which changes along the length of the beam is its depth. Another well known type of fabricated beam is the castellated or cellular beam although in general this construction is used to increase the beam depth relative to its parent section along the full length of the beam and not specifically to vary the section along the length of the beam. A significant disadvantage of these prior art fabricated beam designs is that because the web thickness and flange thickness are constant along the length of the beam the change in section can only be achieved by modifying the web depth or the flange width. Whilst changing the web depth or flange width is acceptable for some applications, in building applications it is preferable to have beams of constant depth and constant flange width to make the fitting of floor slabs, ceiling parts and walls simple.
In
Another method of producing a beam with the ideal variation in cross section along its length is to machine the beam out of either a solid bar or out of a beam which starts with a constant cross section along its length, equal to, or greater than the maximum cross section required. A related method is to fabricate the beam from plates or sections which have been machined to give variations in thickness along their length. However, these methods of manufacture are extremely wasteful of material and expensive and are typically only used for beams in things like aircraft. They are not practical or cost effective solutions for beams in building construction.
Another method of producing a beam with a variation in cross section along its length is to fabricate the beam using longitudinally profiled (LP) plates. The rolling of LP plates in which the thickness of the plate varies along the length of the plate is well known and such plates are commonly used in shipbuilding and bridge building. Large I-beams have been fabricated using longitudinally profiled plates as described by Schroter in “Heavy steel plates for efficient constructional steelwork” and Richter and Schmackpfeffer in “Longitudinally profiled plates cut costs”. However, the application of LP plates in the fabrication of I-beams has so far been limited to very large structures such as bridges, power stations and very tall buildings. I-beams for general constructional use in buildings still mostly use constant cross-sections. One of the reasons for this is that the production of LP plates in which the thickness varies smoothly over the relatively short length of a standard building I-beam has not been practical.
U.S. Pat. No. 3,335,596 describes manufacturing an H section beam, then applying projections to the surface of its flanges by a rolling pass in a finishing mill using rollers having grooves or notches.
In accordance with a first aspect of the present invention a method of manufacturing a beam comprises rolling, in a longitudinally profiled rolling process, two flange pieces, such that one surface of each rolled flange piece is profiled according to a predetermined thickness profile; and joining the rolled flange pieces together via the profiled surfaces.
Preferably, the method further comprises rolling the flange pieces such that another surface of each rolled flange piece is substantially flat.
The rolling process imparts a profile to one face of the flange piece, whilst keeping the opposite surface flat, so that the beam has the required strength at various points along its length without extra material and weight being used unnecessarily, as well as having the convenience for the end user of a flat surface.
Preferably, the method further comprises rolling the two flange pieces together and back to back.
Preferably, the rolled flange pieces comprise T shaped flange pieces.
Preferably, the flange surfaces of the manufactured beam remote from the web are substantially flat and parallel.
In accordance with a second aspect of the present invention, a method of manufacturing a beam comprises rolling, in a longitudinally profiled rolling process, a flange piece, such that a plurality of surfaces of the rolled flange piece are profiled according to a predetermined thickness profile; wherein the longitudinally profiled rolling process comprises rolling Y-shaped sections; and finishing the Y-shaped sections to form T-shaped sections; and wherein the method further comprises joining two of the rolled flange pieces together via a profiled surface of each flange piece.
Preferably, the method further comprises providing a corresponding rolled web piece and joining the rolled flange pieces via the rolled web piece.
A profiled surface of each flange piece is joined to a correspondingly profiled surface of the web piece to join the two flange pieces together.
Preferably, the method further comprises manipulating one or more rolls during the rolling operation in order to vary individual beam dimensions along the beam length.
Preferably, the method further comprises casting raw material with at least part of the required thickness variation already present in the cast material and rolling the cast material.
The present invention provides a fabricated beam which is constructed from one or more LP plates with one flat side and one profiled side or from one or more T-sections in which the thickness of the flange part varies along the length of the beam, so that those parts at which higher forces are applied have additional material for strength and areas of relatively low loading have a reduced cross sectional area. It also provides for an apparatus to produce T-sections with varying thickness along their length. The invention is able to produce a beam with constant or almost constant depth and flange width, but with varying flange and web thickness along its length to satisfy the requirement of the building industry for beams of constant depth and constant flange width to make the fitting of floor slabs, ceiling parts and walls simple.
An example of a beam and a method of manufacturing a beam according to the present invention will now be described with reference to the accompanying drawings in which:
a and 1b respectively illustrate a side view (1a) and a cross section (1b) of a typical rolled universal beam;
a to 3c respectively illustrate an exploded side view of a beam (3a), a cross-section of an assembled beam (3b) and a side view of the assembled beam (3c) of a first example of a fabricated beam using LP profiled plate for the flanges;
a to 4e respectively illustrate prior art of a top view of a web of varying thickness for a beam (4a), a side view of the web (4b), an end view of the web (4c), an end view of a beam comprised of a web with flanges (4d) and a side view of the beam comprised of a web and flanges (4e) of a second example of a fabricated beam using an LP profiled plate for the web;
a to 5g respectively illustrate a top view of a web (5a), an end view of the web (5b) and a side view of the web and of one flange (5c) and an end view thereof (5d), a cross sectional view (5e), and a side view (5f) of a web and two flanges assembled into a fabricated beam and a method of rolling the flanges of the beam using LP profiled plate with one flat side according to the present invention (5g);
a to 6d respectively illustrate the rolling of a T-section part with a variable flange thickness (6a), side view of the T-section part (6b) and side views (6c) and (6d) of two variations of a beam assembled, and construction of a fabricated beam according to the present invention;
a illustrates a roll gap view of an alternative mill configuration for rolling T-section parts according to the present invention and
In a conventional universal beam as illustrated in
The present invention provides a beam and methods of manufacturing a beam which enable the profile to be tailored to the loading requirements at each point along the beam, rather than using the maximum load requirement throughout. By continuously matching the section properties to the stress of the beam along its length, a mass reduction of the beam is possible. This is achieved by continuously determining the most efficient cross section possible whilst satisfying all standards, codes and regulations throughout the length of the beam.
Recent developments such as those described in GB1213011.8 make it possible to produce plates with multiple changes in thickness in the short length of a standard building I-beam and to efficiently produce these LP plates by shearing the as-rolled length into several shorter lengths each with a longitudinal profile. This makes it possible to construct fabricated beams for general building use in which the flange thickness or the web thickness or both vary along the length of the beam. However beams for general constructional use in buildings fabricated from LP plates still suffer from certain problems. One problem is that it is difficult to achieve a flat top and bottom face and constant beam depth with conventional LP plates. Another problem with fabricated beams constructed from LP plates is that the welds are situated at the interface or corner between the flanges and the web in areas of high stress and thus they potentially weaken the beam.
a, 3b and 3c illustrates a fabricated beam constructed from LP (longitudinally profiled) plates for the flanges. The thickness variation along the length of the plates of the flanges and of the web includes multiple points of inflection as described in GB 1213011.8. In typical applications, the maximum loads in the beam are not at the ends of the beam, but in the center and the minimum loads are not at the ends, but part way along the beam. Profiles such as those illustrated in
a to 4e illustrate views of components of and an assembled alternative fabricated beam construction according to the known prior art. In
Combining the LP flanges illustrated in the embodiment in
a to 5g illustrate a beam and a method of rolling the flanges of a beam according to one aspect of the present invention. In order to produce a beam with constant overall depth along its length, each flange 6, 7 is produced with one flat surface 10 as in
a to 6d illustrate the final stage of rolling of a T-shaped (T-section) part 61 according to a second embodiment of the present invention. The upper roll 60 has a groove 54 which accommodates the stem 62 of the T. The lower roll 52 does not have a groove. By moving rolls 60, 52 closer to each other, or further apart from each other, the thickness of the flange part 63 of the T section may be varied along the length of the T section as illustrated in
An even simpler construction may be achieved if the T-sections are rolled with sufficiently long stems that the required beam depth is achieved by simply welding the two stems 55, 56 together with a single weld 501 as illustrated in
a to 8c illustrate an alternative method of rolling the T-section parts for a beam according to the invention. The mill has three rolls 71, 72, 73 which can be moved closer to each other or further away from each other in order to vary the thickness of both the flange and the stem parts of the T-section. By analogy with the conventional beam rolling process, the step which is illustrated in
The sectional properties of a beam may be influenced by varying a number of geometrical parameters. The parameters addressed according to the present invention are the flange thickness and the web thickness. This avoids complication of the design and construction process by maintaining the outer envelope dimensions of the beam, so that it can fit into any construction where a universal beam would have been used previously. The T-sections with varying flange thickness may also be used to fabricate beams with variations in beam depth along their length.
All aforementioned embodiments of the invention can be produced using standard raw material geometry i.e. billets and plates as the feedstock. The stages required and forces required by the invention can be reduced if variable cast materials are used at the start of the process. For example a T-section which has large variations in thickness along its length could be rolled from a cast product which already has some thickness variation along its length.
The examples of the present invention described above allow for implementation of a set of beam profiles tailored to particular applications, such as a specific office grid structure, which can be designed according to standard building codes and loading conditions. This means a final product can be manufactured as specified by the designer, rather than having to use standard products. For example, the beams can be tailored to a specific structure, or a specific position within that structure and a product specification for the beams can specify the working limits of the mill or workshop allowing more flexibility for the designer.
The invention has the benefit of maintaining parallel or almost parallel flange outer surfaces which are convenient for construction purposes, as well as reducing the total amount of metal used in the construction. In the case of the beams constructed from T-sections the invention has the additional benefit of moving the welds between the components away from the highly stressed areas of the beam. In each example, use of a longitudinally profiled rolling process results in a web or flange having a profile which varies in thickness along its length.
Number | Date | Country | Kind |
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1302281.9 | Feb 2013 | GB | national |
The present application is a 35 U.S.C. §§371 national phase conversion of PCT/EP2014/050365, filed Jan. 10, 2014, which claims priority of Great Britain Patent Application No. 1302281.9, filed Feb. 8, 2013, the contents of which are incorporated by reference herein. The PCT International Application was published in the English language.
Filing Document | Filing Date | Country | Kind |
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PCT/EP2014/050365 | 1/10/2014 | WO | 00 |