GB2074916A

GB2074916A - Method for Producing I-beam Having Centrally Corrugated Web

Info

Publication number: GB2074916A
Application number: GB8041336A
Authority: GB
Original assignee: Sumitomo Metal Industries Ltd
Current assignee: Nippon Steel Corp
Priority date: 1980-05-09
Filing date: 1980-12-29
Publication date: 1981-11-11
Also published as: IT1174692B; BE886933A; LU83044A1; IT8027005A0; FR2482256A1; DE3049459A1; FR2482256B1; GB2074916B

Abstract

The web portion of an I-beam is transversely corrugated by hot or cold- forming it between two rolls with intermeshing formations. The web is thinned during rolling, but the beam flanges 3 are not reduced. A pair of rolls for corrugating the web has circumferential grooves 21 in each roll for accommodating the flanges. Alternatively, axially adjustable guide rings on the ends of the rolls guide the flanges. <IMAGE>

Description

SPECIFICATION Method for Producing I-beam Having Centrally Currugated Web and Rolls for Producing Such Ibeam The present invention relates to a method for producing an I-beam having a centrally corrugated web and producing rolls for use in said method.

A web of the I-beam has less effect on the section modulus of the I-beam as a bending structural member. In producing the I-beam, accordingly, the web is made as thinner as possible for economy of material. As the demand for lighter steel member becomes stronger in recent years, the web of the Ibeam has become thinner and thinner. However, there is a limit in the thinning of the web from the viewpoint of shearing buckling strength of the web. Theoretically, it is known that the web of the Ibeam can be made thinner than the limit by corrugating the web. As a matter of fact, however, as Ibeam having a corrugated web has not yet been put on the market as an industrial product since the corrugating work of the web of the I-beam is very difficult.

Accordingly, an object of the present invention is to provide a method for prodycing an I-beam having a corrugated web economically and efficiently.

Another object of the present invention is to provide rolls for use in the method for producing the I-beam having the corrugated web economically and efficiently.

A further object of the present invention is to provide a form and dimensions of corrugation having increasing effect both in shearing buckling strength and web lateral compression strength required for the I-beam within the current producing technology.

The producing method according to the present invention is characterized in that corrugating work is performed on the central area of the web of the I-beam by a pair of complementarily intermeshing rolls in such a way that there will be no change in principal dimension of the I-beam except for web thickness.

The producing rolls for use in the method according to the present invention are characterized in that each of which is provided in the roll working surface with a pair of grooves for guiding flanges of an I-beam and a corrugated zone intermediate between said grooves and that a pair of said rolls are complementarily intermeshed in the corrugated zones.

Taking note of the fact that it is not always necessary for the rolls to constrainedly guide both the sides of the flanges of the I-beam and that it is necessary only to guide either one side of each of the flanges for centering of the I-beam, the present invention provides a modification of the producing rolls of the construction obviating the need for forming grooves in each of the rolls with the distance between the grooves adjusted to the flange width.

The invention will be better understood from the following description taken in connection with the accompanying drawings in which: Fig. 1 is a schematic illustration of a production line for working of the method according to the present invention; Fig. 2 is a cross sectional view of an I-beam produced by the method according to the present invention; Fig. 3 is a longitudinal sectional view taken along the line Ill-Ill of Fig. 2; Fig. 4 is an enlarged fragmentary longitudinal sectional view of a corrugated portion in the central area of the web of the I-beam produced by the method according to the present invention; Fig. 5 is a graph showing the relation between the ratio of corrugation amplitude to web thickness and the shearing buckling strength;; Fig. 6 is a schematic illustration of an experiment on mode of buckling due to a laterally concentrated force; Fig. 7 is a graph showing the relation between the ratio of corrugation width to web height and shearing buckling strength; Fig. 8 is a graph showing the relation between the ratio of corrugation width to web height and the laterally concentrated load strength; Fig. 9 is a vertical sectional view of corrugating and producing rolls according to the present invention; Fig. 10 is an enlarged fragmentary sectional view of the body of the roll of Fig. 9; Fig. 1 1 is a sectional front view of the rolls according to the present invention used in the production line of Fig. 1; Fig. 12 is a partial sectional view of an embodiment of the roll according to the present invention;; Fig. 13 is a partial view of another embodiment of the roll according to the present invention; Fig. 14 is a cross sectional view of the flange guide taken along the line XlV-XlV of Fig. 13; Fig. 1 5 is a partial sectional view of a further embodiment of the roll according to the present invention; Fig. 1 6 is a front view of the flange guide seen from the line XVl-XVl of Fig. 1 5; Fig. 1 7 is a partial sectional front view of the rolls according to the present invention showing another mode of use thereof in the production line; Fig. 1 8 is a diagram showing the distribution of residual stress in the corrugated web of the Ibeam; Fig. 19 is a graph showing the load-deflection curve on the lateral compression test; Fig. 20 is a graph showing the load-deflection curve on shearing buckling test.

The method and the producing rolls according to the present invention will now be described with reference to the drawings. In the production line for working of the method according to the present invention as schematically illustrated in Fig. 1, an ordinary I-beam 1 is corrugated by producing rolls 2 according to the present invention into a worked I-beam 3 having a corrugated web.

The ordinary I-beam may be a hot-rolled or welded I-beam. The corrugating working by the producing rolled 2 may be either cold or hot working. The producing rolls 2 will be described in fuller detail with reference to Figs. 9 to 17.

The I-beam 3 worked by the method according to the present invention is corrugated not in the overall width of its web 31 but only in the central portion of the web 31. Since a flat portion 311 is left intact in each of edges of the web, the corrugating working is performed easily without having any adverse effect upon the junction between the web 31 and flanges 32 of the I-beam 3.

While theoretical analysis of various factors such as forces required for the corrugating working in the method according to the present invention is difficult, repeated experiments show that the most approximate is not a theoretical equation of deep drawing but a theoretical equation of cold rolling combined with a theoretical equation of U-bending.The most approximate theoretical equations are as follows: p=P, +P2

where, P: rolling load P,: cold rolling load P2: U-bending load a: tensile strength C: width of corrugation t: thickness of web L: pitch of corrugation At: reduction in web thickness The depth of wave a (see Fig. 4) of the corrugation of the web is, assuming that the elongated length of the web by rolling forms the wave, expressed by the following equation which has been confirmed to be effective by experiments:

where, 0:: reduction rate While a single pass is sufficient for corrugating the web of the beam, two or more passes are preferably for a product free of cambering or torsion because the shape of the corrugation changes by very small extent at the second or later pass to redistribute and reduce the residual stress into a desirable condition.

The dimension for determining the form of corrugation by the method according to the present invention are preferably selected from the following ranges: 9.3t < L < 36t ii. 1 .0t < f < 3.9t iii. 0.5h < C < h-L The characters in these ranges denote dimension of portions of the I-beam shown in Figs. 2 and 4, as follows: t: thickness of web h: height of web f: amplitude of corrugation C: width of corrugation L: pitch of corrugation These ranges were obtained by the reason described below.

(1) Possible Producing Range Corrugation is, as shown in Figs. 2 and 3, formed at right angles to the axis of the beam. While the depressions and the rises must be disposed alternatively to avoid eccentricity, they need not always be continuous but may include flat portions between the depressions and the rises in the corrugation. The corrugation may be of a trapezoidal form instead of a wave form. In production, however, since elongation rate of the web material in the rolling for corrugation is preferably as small as possible and in the case of the same elongation rate the number of the depressions and the rises in the specific length is preferably as many as possible for better effect, the depressions and the rises are preferably continuous.Repeated corrugated production tests show that the elongation rate of corrugation working of 12% or less is a faborable producing range.

(2) Pitch L and Amplitude (f) of Corrugation An effect of the corrugation is to increase flexural rigidity of the web in the direction at right angles to the axis of the beam. The increase in the flexural rigidity is effected most by the amplitude of corrugation f.

Fig. 5 shows the relation between the ratio of corrugation amplitude to web thickness f/t and the shearing buckling strength Tf. The shearing buckling strength T is effected by the corrugation width C, and the web thickness t. The tests were made of I-beams of the shape to which the method according to the present invention is considered to be most generally applied, having the web thickness t=h/1 20, the corrugation width C=0.75h. As seen from the curve of Fig. 5, the strength Tf increases parabolically as the corrugation amplitude f increases.

While the increase in the shearing strength by the corrugation is obtained in spite of thinning the web thickness t, the cost for the corrugating working is not recovered unless there is provided an effect by corrugating sufficiently to reduce the web thickness by at least 25%. Since the shearing buckling strength of the flat web is proportional to (t/h)2, a 25% reduction in the web thickness results in an approximately 50% reduction in strength. In order to compensate for the reduction in strength with the corrugation, accordingly, the corrugation amplitude must be determined so that the strength of the corrugated web is twice or more of the strength zf, of a flat web (f=O). Accordingly, the value off is obtained as f/t > 1 from Fig. 5.

The corrugation pitch L is preferably as small as possible for smaller turbulence of stress and for better stability against a laterally concentrated force F. Experiments on the laterally concentrated force as shown in Fig. 6 showed that a local buckling was caused in the web adjacent the point at which the force was applied and the length of the buckling wave C awa approximately 0.4h. This strength is important in determining the shape of the web. In order to obtain this strength stabilized at any position, it is necessary to determine the corrugation pitch L such that the buckling wave length / includes at least two waves of the corrugation. This requires accordingly that the corrugation pitch L must be 0.2h or less.

On the other hand, the corrugation pitch L and the corrugation amplitude f are related to the elongation upon production, that is, as the value L/f decreases the working elongation due to corrugation forming becomes large In order to limit the working elongation rate to 12% or less as described hereinabove, the value Lif must be greater than 9.3 (L/f > 9.3).

As described above, the corrugation shape is subject to three limitations from performance and workability. Further, assuming that the practical range of the web thickness is

the range of the corrugation pitch L is

or 9.3t < f < 36t, and the range of the corrugation amplitude f is

or 1.0t < f < 3.9t.

(3) Width of Corrugation (C) The corrugation width C is related most strongly to the shearing buckling strength TC and the strength under laterally concentrated load R of the web. Fig. 7 shows the relation between the ratio of the corrugation width to the web height (C/h) and the shearing buckling strength TC of the case, for example, of h/t=1 20 and f/t=1.3. In Fig. 7, black spots represent experimental values and the solid curve represents analytical values. As described hereinabove, the shearing buckling strength TC of the corrugated web is required to be twice or more of the strength TC0 of the flat web (C=O). Accordingly the value of C/h providing the strength in this range is given by Fig. 7 to be C/h > 0.5.

Fig. 8 shows the relation between the ratio of the corrugation width to the web height (C/h) and the strength under the laterally concentrated load R. It will be seen from Fig. 8 that the ratio C/h of 0.5 or greater provides a sufficient corrugation effect. Here,

where

E is elastic modulus and y is Poisson's ratio. In Fig. 8, black spots represent experimental values and the solid curve represents the experimental equation

Accordingly, the practically effective range for corrugating the central portion of the web for the purpose of increasing the shearing buckling strength TC and the strength under the lateral concentrated load R of the web is C/h > 0.5. The upper limit of the value C/h is defined by the working limit and the turbulence of the stress caused in the flange.That is, if the corrugation width C is too great, damages are caused not only because the flange is waved upon corrugation but also because a great stress is caused at the junction between the web and the flange. Trial production tests show that there is no problem if the width of the uncorrugated portion is 6t or greater or 0.5L or greater. The experiments further confirm that turbulence of stress to the flange portion by the corrugation working has no effect if the width of the uncorrugated portion is 0.5L or more.

Accordingly, the effective range of the corrugation width is defined to be 0.5h or greater, (h-L) or less and (h-12t) or less.

The producing rolls 2 for use in the method according to the present invention are of the shape shown in Figs. 9 and 10. As shown in Fig. 9, each of a pair of producing rolls 2 is provided on the working surface thereof with grooves 21 spaced from each other by a distance corresponding to the height of the web h (see Fig. 2) of the I-beam 1 as the blank material, for guiding the flanges of the Ibeam 1, and further with a corrugated zone 22 having the corrugation width C (see Fig. 2j intermediate between said grooves 21.

The corrugated zone 22 is, as shown in Fig. 10, of the shape defined by a pitch radius P, radii of waveform curvature r1 and r2, the corrugation pitch L, the wave depth 8, and the corrugation width C.

The relation among these dimension is determined in accordance with the dimension of the I-beam in such a way that no change is caused in the major sectional dimension thereof except in the corrugating working area of the I-beam.

In the embodiment, each of the producing rolls is provided on the roll surface thereof with pair of grooves 21 for guiding the flanges 32 of the I-beam 1 to be worked. Accordingly, the rolls of this embodiment has a disadvantage that the I-beam to be worked is limited in the width of the web 31 or, in other words, the rolls lack versatility. Particularly in cold forming in which the rolls should be made of high alloy steel having a high hardness, the rolls of this embodiment present a further problem in making that it is extremely difficult to form narrow and deep guiding grooves therein.

These problems are solved by the rolls of various other embodiments of the present invention as will be described hereunder with reference to Figs. 1 1 to 17.

In the embodiment shown in Fig. 1 in a pair of corrugating rolls 2, 2, the roll bodies have the width corresponding to the web height h of the I-beam, that is, somewhat smaller than the web height h so that the flanges 32 of the I-beam are clear of the surface of engagement between the rolls 2, 2.

Further, either one of the upper and the lower rolls is provided with flange guides 4. For example, in the case where the flange guides 4 are provided in the lower roll 2 as shown in Fig. 11, the flange guides 4 are fitted on the journal 23 on both the sides of the body of the lower roll 2, adjusted in the axial positions and then fixed on the journal 23 in correspondence to the positions of the flanges 32 of the I beam 1.

Various type of means are used to fix the flange guides 4. For example, as shown in Fig. 12, the journal 23 of the roll 2 may be threaded, on which a collar 5 is interposed between the body of the roll 2 and the flange guide 4, whereby the flange guide 4 is held in position and securely clamped by a nut 6 from the outside.

As shown in Figs. 13 and 14, the flange guide 4 may be provided partically with a radial split groove 41 and another split groove 42 extending to the central bore on the side opposite to the split groove 41,so that the flange guide 4 is slidably moved along the journal 23 utilizing the expansion and contraction by these split grooves to the selected position at which the split groove 42 is clamped by suitable clamping means 43 such as a bolt to constrict the central bore of the guide 4 to thereby fix it.

As shown in Figs. 1 5 and 16, the flange guide 4 may be provided with the diametrically extending split grooves 41 and 42, and a tapered threadably engaging portion 44 on which a lock nut 45 is threadably engaged so as to constrict the central bore of the flange guide 4 to thereby fix it.

By these various types of fixing means the flange guides 4 are fixed on the journals 23 of the roll 2 to guide the flanges 32 of the I-beam 1 from the outside. Since the flange guides 4 can be positioned as desired on the journal 23 of the roll, the fixing positions of the flange guides are not regulated by the web height h of the I-beam 1. Since it is not necessary that the flange guides 4 are fixed at bisymmetrical positions, it is possible to corrugate the web along an out-of-central line as shown in Fig.

17. Such an eccentric corrugation can be effective under certain circumstances dependent upon, for example, the condition of the load applied upon the use of the I-beam and the joining relation with other members.

The corrugation working rolls of these embodiments according to the present invention have advantages such that they are widely applicable to, for example, working of eccentric corrugation without being regulated by the web height of the I-beam, and that they have excellent guiding effect such as more stabilized centering upon working since they can establish longer effective guide distance than in conventional rolls as well as these embodied rolls are easier to be manufactured.

Specific examples of the practice of the method according to the present invention will now be shown in Table 1.

Table 1

Size of Beam HxBxt'xt" 203.2x68.3x2.0x4.7 256.5x87.4x2.3x4.7 307.3x87.4x2.3x6.0 Working Speed m/min 24 24 24 Corrugating Roll Opening mm 0.8 1.4 1.4 Condition Rolling Load Ton 60-70 130-140 Rolling Torque Ton/M 0.5-0.6 1.0-1.2 Corrugation Width C mm 100 150 200 Corrugation Thickness t " 1.85 2.05 2.05 One- Corrugation pass Pitch L " 30.8 31.0 31.0 Corru- Corrugation gating Depth # " 5 6 6 Torsion - None (Torsion observed when cut short).

Results Corrugation Width C mm 100 150 200 Corrugation Thickness t " 1.80 2.00 2.00 Two- Corrugation pass Pitch L " 30.0 30.0 30.0 Corru- Corrugation gating Depth # " 6 7 7 Torsion - None (Not observed even when cut short).

(t': web thickness of the beam, t": flange thickness of the beam) As seen from Table 1, I-beams having almost desired corrugated webs were obtained by examples of practice of the method according to the present invention. The developed length of the curve of the corrugated zone is longer than the entire rectilinear length of the web material and the increase in the developed length corresponds with the reduction in thickness of the web.

When a short I-beam of the order of 1.5 meters or so in length is corrugated by a single pass, a torsion is caused therein, which is, however, eliminated by a second pass corrugating. In a long l-beam of 6 meters or greater in the overall length, no torsion is caused in appearance by a single pass. When cut into short lengths, however, the internal stress is released and a torsion can appear. In an I-beam worked by two or more passes corrugating, no torsion appears even when cut into short lengths.

Fig. 18 shows the distribution of residual stress in the corrugated I-beam in the central column of Table 1, of the size 256.5x87.4x2.3x4.7, after a single pass corrugating (small white circles) and a second pass corrugating (small solid black circles), respectively.

Figs. 19 and 20 show the results of lateral compression tests and shearing buckling tests, respectively, of an I-beam having a corrugated web and an ordinary I-beam having a flat web. In Figs.

1 9 and 20, solid lines represent the experimental results of the I-beam having the corrugated web and broken lines represent the experimental results of the ordinary I-beam. Size of the materials tested was 212x68.6x2.0x4.6. In the experiments, a 100 ton testing machine was used and the deflection was measured by two dial gauges.

As seen from these experimental results, the strength under the lateral compression of the Ibeam having the corrugated web is approximately three times as great as that of the ordinary I-beam.

The shearing buckling strength of the I-beam having the corrugated web is approximately 1.4 times as great as that of the ordinary I-beam.

Table 2 shows the size of the conventional welded light-weight ordinary I-beams and the size of the I-beams having corrugated web produced by the method according to the present invention. The conventional I-beams shown in Table 2 were chosen from those having the shearing buckling stress greater than the yielding strength. The I-beams having corrugated web were identical to the conventional I-beams in beam height H and in flange size a (see Fig. 2) and smaller only in the web thickness t. If the web thickness is reduced without corrugating it, the shearing buckling strength is reduced to approximately 30% of the yielding strength. In the I-beams with the corrugated web, however, the shearing buckling strength of the web is maintained above the yielding strength by the corrugating effect.

In Table 2, the corrugated zone is excluded in calculation of the bending performance since the corrugated zone is considerably reduced in axial rigidity. As seen from Table 2, the ratio of flexural rigidity per weight can be increased 9% to 13% by corrugating the web.

Table 2

Conventional Method Present Invention Comparison (I) JISG 3353 Material (II) Corrugated Web Material Ratio of Bending Performance (Corrugation width) per Weight (ll/l)* 200x100x3.2x4.5 200x100x1.6x4.5 (150) 1.09 250x125x4.5x6.0 250x125x2.0x6.0(180) 1.13 300x 1 50x2.5x6.0 300x 1 50x2.3x6.0 (220) 1.10 400x200x6.0x12.0 400x150x2.7x12.0 (300) 1.09 Flexural Rigidity of Weight of Conventional I-beam Corrugated I-beam * Ratio of Bending Performance per Weight ----------------- = Weight of Corrugated I-beam Flexural Rigidity of Conventional I-beam While we have shown and described specific embodiments of our invention, it will be understood that these embodiments are merely for the purpose of illustration and description and that various other forms may be devised within the scope of our invention, as defined in the appended claims.

Claims

Claims

1. A method for producing an I-beam having a centrally corrugated web, characterized by corrugating a central portion of the web of a finished ordinary I-beam by means of a pair of complementarily intermeshing rolls.

2. A method for producing an I-beam having a centrally corrugated web as set forth in Claim 1, characterized in that the corrugation is formed under the following conditions:

9.3t < L < 36t 1 .0t < f < 3.9t 0.5h < C < h-L where t: web thickness h: web height f: corrugation amplitude C: corrugation width L: corrugation pitch

3. A method for producing an I-beam having a centrally corrugated web by corrugating a central portion of the web of an ordinary I-beam by means of a pair of complementarily intermeshing rolls as set forth in Claim 1, characterized in that the increase in length of developed length of corrugated web from rectilinear length of flat web before corrugation is brought about by reduction in web thickness under corrugation working and, accordingly, nother change in major dimension of I-beam than web thickness is accompanied with.

4. A method for producing an I-beam having a centrally corrugated web by corrugating a central portion of the web of an ordinary I-beam by means ofa pair of complementarily intermeshing rolls as set forth in Claim 1, characterized by corrugating twice or more to improve residual stress condition and cambering or torsion or corrugation I-beam.

5. Rolls for producing an I-beam having a centrally corrugated web, characterized in that each of said roll is provided in the roll working surface with a pair of grooves for guiding flanges of an I-beam and a wave-shaped corrugated zone intermediate between said grooves and that a pair of said rolls are complementarily intermeshed in the corrugated zones.

6. Rolls for corrugating a web of an I-beam, comprising a pair of forming rolls having each a rolling body corresponding to the width of the web of the I-beam and being provided in the central portion of said bodies with complementarily intermeshing corrugation, and flange guides disposed on both the sides of the body, respectively, of either one of said forming rolls, said flange guides being mounted securely and adjustably in the axial position, said flange guide having a larger diameter than said body of the roll.

7. Rolls for corrugating a web of an I-beam as set forth in Claim 6, characterized in that said flange guides are disposed asymmetrically relative to said body of the roll on the axis thereof.

8. A method for producing an I-beam substantially as hereinbefore described with reference to and as illustrated in, Figures 1 to 8, and 1 or Figures 9 and 10, or Figure 12, or Figures 13 and 14, or Figures 1 5 and 16 or Figure 17 or Figures 18 to 20, of the accompanying drawings.

9. Rolls substantially as hereinbefore described with reference to and as illustrated in, Figures 1 to 8, and 1 or Figures 9 and 10, or Figure 12, or Figures 13 and 14, or Figures 15 and 16 or Figure 1 7 or Figures 1 8 to 20, of the accompanying drawings.