Title of Invention

"A HOT ROLLED Z-SHAPED SHEET PILE"

Abstract

A hot-rolled Z-shaped sheet pile comprising two flanges having parallel outer faces, and an oblique web connected to the two flanges so as to make an acute angle α≤75° with a plane parallel to the outer faces of the flanges, the said web being delimited between the connections with the flanges by the two parallel faces, characterized in that each of the two flanges has an extension which protrudes with respect to a fictitious plane extending the plane face of the web located on the same side as the outer face of the respective flange.

Full Text

The present invention relates to a Z-shaped sheet pile with a high section modulus. Z-shaped sheet piles have been known for a long time. They have an inclined web connected to two substantially parallel flanges. Each flange is fitted with a gripping element, in order to form a joint in a supporting wall by interlocking with a gripping element of an adjacent sheet pile. In such a wall, the Z-shaped sheet piles are most frequently arranged so that their flanges are substantially parallel and equidistant from the neutral bending plane of the wall. The product obtained by multiplying the section modulus of the wall with respect to this neutral plane by the maximum admissible elastic stress determines the maximum elastic moment that the wall can withstand. What is called the "section modulus per unit length" of the sheet-pile wall is the section modulus with respect to the neutral plane of the wall per running metre of the wall. What is called the "specific section modulus" or the "performance criterion" of the sheet-pile wall is the section modulus per unit length divided by the mass of the wall per square metre of wall. It is specified that a "sheet-pile wall" in the present context is understood to be a wall consisting of Z-shaped sheet piles which are connected so that their flanges are substantially parallel and equidistant from the neutral bending plane of the wall. ProfilARBED S.A. (Luxembourg) currently market a Z-shaped sheet pile called "AZ36", which has a section modulus of 3600 cm3 per running metre of wall. This AZ36 sheet pile has a mass of 194kg/m2 and hence a specific section modulus of 18.6 (cm3/m) (kg/m2). This is a sheet pile with gripping elements of the LARSSEN type and with a web making an acute angle of about 63° with a plane parallel to the flanges. ProfilARBED S.A. (Luxembourg) also market a Z-shaped sheet pile called "BZ42", which has a section modulus of 4200 cm3 per running metre of wall, but a mass of 271 kg/m2 and hence a less favourable specific section modulus of 15.5 (cm3/m) (kg/m2). This is a sheet pile with gripping elements of the BELVAL type and with a web making an acute angle of about 83.5° with a plane parallel to the flanges. Other types of Z-shaped sheet piles also to be found on the market can have section moduli up to 4550 cm3 per running metre of wall. However, these types of sheet pile with a higher section modulus are very heavy sections, with a very great weight per square metre of wall and therefore quite a low specific section modulus. Now, the lower the specific section modulus the higher the cost price of the wall. The main reasons why Z-shaped sheet piles with a section modulus greater than 4550 cm3 are not found on the market are as follows: a) most frequently, there is a limit to the maximum thickness of the flanges. This is because the rolling of the gripping elements, particularly the LARSSEN type gripping elements, requires the flanges to be folded during the last pass of the rolling mill. Now, this folding becomes very difficult when the thickness of the flanges becomes too large. Thus, there is no present industrial method of rolling flanges with a thickness greater than 20 mm when they have gripping elements of the LARSSEN type. b) there is also a limit on the maximum width of the flanges and the maximum distance between the outer faces of the flanges (height of the section). This is because, for a given angle of inclination of the web, the width of the flanges and the height of the section determine the development of the sheet pile and consequently the width of the roll stand rollers. Now the width of these rollers is limited by the width of the roll stands of the sheet pile rolling train. If it is required to roll sheet piles with a high section modulus on current rolling trains, the development of these sheet piles between the axes of the gripping elements must be less than a value predetermined by the width of the roll stands of the sheet pile rolling train. c) a saving in the rolling width could be achieved by increasing the acute angle that the web makes with a plane parallel to the flanges (angle of inclination of the web). However, the nearer this angle of inclination of the web is to 90° the greater the resistance experienced when driving in the sheet pile. For reasons related to the use of the sheet pile, it is therefore recommended that the angle of inclination of the web should be chosen to be less than 75°. Using an optimisation program and a computer, the above-mentioned parameters have been optimised for a type AZ sheet pile, and a sheet pile has been obtained with a maximum section modulus of 4400 cm3 per running metre of wall. This type AZ sheet pile has, for a web thickness of 15 mm, a mass of 229 kg/m2 and thus a specific section modulus of 19.21 (cm3/m) (kg/m2). A section modulus of 4400 cm3 therefore seems to be a limiting value for a Z-shaped sheet pile when compliance with the above-mentioned constraints is required. It would of course be possible to increase the web thickness still further, but such a step, while slightly increasing the section modulus, would mainly cause an appreciable reduction in the specific section modulus of the sheet pile. The problem on which the present invention is based is to find a solution in order to increase still further the section modulus of a hot-rolled Z-shaped sheet pile, without at the same time reducing the specific section modulus of the sheet pile and without requiring an increase in the width of the roll stands. This problem finds a solution in a Z-shaped sheet pile according to the first claim. As regards the present state of the art, it should also be noted that protruding extensions at the points connecting the flanges and webs of the sheet piles have already been described in the documents US-A-1,831,427 and FR-A-686816, but in a context completely different from the present invention. The document US-A-1,831,427 describes special Z-shaped sheet piles which make it possible to produce, in cooperation with intermediate flat sheets, a sheet-pile wall with a continuous plane surface. The special sheet piles described in this document are more than likely sheet piles made of cast iron. Their web makes an angle close to 90° with a plane parallel to the outer faces of the flanges. At the joins between the web and the flanges, they have ribs, ridges, shoulders or projections incorporated in the sheet pile or attached by any means whatsoever to it. The only purpose of these ribs, ridges, shoulders or projections is to become engaged in recesses of complementary shape made in the said intermediate sheets. In this way, they make it possible to insert and hold in place these intermediate sheets between two Z-shaped sheet piles, in order to create the sheet-pile wall with a continuous plane surface. U-shaped sheet piles of small height are known from the document FR-A-686816, such sheet piles having a reinforced part at the position of the connections between the web and the flanges. In an assembly consisting of two of these sheet piles, the said reinforced part, located immediately before the opening in a clutch in the first sheet pile, acts in combination with the inner part of this clutch to create a shape capable of cooperating with the outer part of a clutch on the second sheet pile. The hot-rolled Z-shaped sheet pile according to the invention comprises, like all hot-rolled Z-shaped sheet piles, two flanges having substantially parallel outer faces, and an oblique web connected to the two flanges. This web makes an acute angle less than or equal to 75° with a plane parallel to the outer faces of the flanges and is delimited between the connections to the flanges by two substantially plane faces. The hot-rolled sheet pile according to the invention is distinguished from a conventional hot-rolled sheet pile mainly in that each of the two flanges has an extension which protrudes with respect to a fictional plane extending the plane face of the web located on the same side as the outer face of the respective flange. It is to be appreciated that a hot-rolled sheet pile according to the invention has the advantage of being produced with a small surplus of material, and therefore with a small increase in the mass per square metre of wall, a distinct improvement in the section modulus and consequently also an improvement in the specific section modulus. It is to be particularly appreciated that this improvement in the section modulus may be obtained without increasing the width of the roll stands, without increasing the thickness of the flanges, and that it even makes it possible to increase the useful width of the flanges. The proposed solution also leads to a strengthening of the corners of the flange/web connection on the outer side, and hence a lower risk of these critical places being damaged when the sheet piles are used. This strengthening is also favourable to a better resistance to accelerated corrosion at low water levels since Z-shaped sheet piles, unlike U-shaped sheet piles, have above all a tendency to become corroded at the web/flange connections. It remains to point out that the flanges have greater supporting surfaces (= outer faces of the flanges) for walings or anchoring plates, and that the transmission of the anchoring forces from the flanges to the web and vice versa is improved. It is to be particularly appreciated that it has been possible to obtain sheet piles according to the invention with the following characteristics: thickness of flanges approximately 19 to 20 mm; width of flanges > 200 mm; height of sheet pile section modulus per unit length of wall > 4800 cm3/m; specific section modulus approximately 20 (cm3/m) (kg/m2). A preferred embodiment of a sheet pile according to the invention is described with the help of the appended drawings, in which: Figure 1 shows a transverse cross-section of the sheet pile; Figure 2 shows an enlargement of a flange/web connection of the sheet pile of Figure 1. Accordingly, there is provided hot-rolled Z-shaped sheet pile comprising two flanges having parallel outer faces, and an oblique web connected to the two flanges so as to make an acute angle a characterized in that each of the two flanges has an extension which protrudes with respect to a fictitious plane extending the plane face of the web located on the same side as the outer face of the respective flange. A preferred embodiment of a sheet pile according to the invention is described with the help of the appended drawings, in which: Figure 1 shows a transverse cross-section of the sheet pile; Figure 2 shows an enlargement of a flange/web connection of the sheet pile of Figure 1. The Z-shaped sheet pile according to Figure 1 comprises, like all Z-shaped sheet piles, two flanges 12', 12" having substantially parallel outer faces 14', 14", and an oblique web 10 connected to the two flanges 12', 12". This web 10 makes an acute angle a with a plane 16 which is parallel to the outer faces 14', 14" of the flanges 12', 12". It is thinner than the flanges 12', 12" and is delimited between the connections to the flanges 12', 12" by two substantially plane and parallel faces 18', 18". Each of these flanges 12', 12" is fitted with a gripping element 20', 20". More precisely, these are gripping elements of the LARSSEN type, which make it possible to form LARSSEN type joints by becoming interlocked, in a sheet-pile wall, with the gripping elements of adjacent sheet piles. The dimensions of the sheet pile represented have been optimised using an optimisation program and a computer in order to obtain a high section modulus given the various constraints mentioned in the introductory part of the present description. This optimisation has led to the following dimensions being adopted: height of the sheet pile section (distance between the outer faces of the flanges): h = 482 mm width of each flange 12', 12": a * 208 mm thickness of the web 10: ti = 15mm thickness of each flange 12', 12": t2 = 19 mm angle of inclination of the web 10: a = 71 ° Thanks to the optimisation of the above-mentioned dimensions, a section modulus was obtained of 4400 cm3 per unit length of a wall in which these sheet piles are connected so that the outer faces 14', 14" of their flanges 12', 12" are substantially parallel and equidistant from the neutral bending plane of the wall. The specific section modulus of such a sheet-pile wall is slightly less than 20 (cm3/m) (kg/m2). The aim was now to increase still further the section modulus of the sheet pile thus optimised. This aim was achieved by fitting each of the two flanges 12', 12" with an extension 22', 22" which protrudes with respect to a fictitious plane 24', 24" extending the plane face of the web 18', 18" located on the same side as the outer face 14', 14" of the respective flange. A connecting surface 25 which would terminate the flange 12' in a conventional Z-shaped sheet pile has been shown by a broken line in Figure 2. This connecting surface 25 would be tangential to the outer face 14' of the flange 12' and would be connected tangentially to the face 18' of the web 10. Referring to Figure 2, it will be noted that the web 10 is connected to the flange extension 22' by a local extra thickness 26' of the web 10 so as to avoid the formation of a concave corner between the flange extension 22' and the web 10. This extra thickness 26' of the web 10 slightly reduces the specific section modulus of the sheet pile, but it makes rolling easier and avoids deformations of the flange extension 22' during pile driving. In addition, a better transmission is obtained of the anchoring forces from the flanges 12', 12" to the web 10 and vice versa. It can also be seen in Figure 2 that the flange extension 22' is delimited by a first plane surface 30 which extends the plane face 14' of the flange 12', a second plane surface 34 which is substantially perpendicular to the said first plane surface 30, and a convex cylindrical connecting surface 32 which connects the said first plane surface 30 to the said second plane surface 34. The said extra thickness 26' of the web 10 then defines a concave cylindrical connecting surface 36 which connects the face 18' of the web 10 to the said second plane surface 34 of the flange extension 22'. This is a configuration of the flange extensions 22' and 22" which is optimised from the point of view of rolling. In the example of Figure 1, the convex cylindrical connecting surface 32 has a radius of 15 mm, and the concave cylindrical connecting surface 36 has a radius of 125 mm. The section modulus per unit length of the optimised sheet pile with flange extensions 22', 22" is 4800 cm3/m, which represents an increase of about 9% compared with the optimised sheet pile without the flange extensions 22', 22". The specific section modulus of the optimised sheet pile with flange extensions 22', 22" is about 20 (cm3/m) (kg/m2). It is to be appreciated that the rolling of the flange extensions 22', 22" causes no major problems and in particular requires no increase in the width of the roll stands of the rolling train, which makes the invention particularly attractive for sheet piles of large section. It remains to point out that the invention is, of course, not limited to the sheet pile described in detail, but that it can also be advantageously applied to Z-shaped sheet piles having a section modulus per unit length smaller or greater than 4800 cm3/cm of substantially different dimensions, and to sheet piles having gripping elements other than LARSSEN type gripping elements. WE CLAIM:- 1. Hot-rolled Z-shaped sheet pile comprising two flanges (12', 12") having parallel outer faces (14', 14"), and an oblique web (10) connected to the two flanges (12', 12") so as to make an acute angle a the flanges (12', 12"), the said web being delimited between the connections with the flanges (12', 12") by the two parallel faces (18', 18"), characterized in that each of the two flanges (12', 12") has an extension (22', 22") which protrudes with respect to a fictitious plane (24', 24") extending the plane face (18', 18") of the web located on the same side as the outer face (14', 14") of the respective flange. 2. Sheet pile as claimed in claim 1, wherein the web (10) is connected to each flange extension (22', 22") through the intermediary of an extra thickness (26', 26") of the web (10) so as to avoid a concave corner between the respective flange extension (22', 22") and the web (10). 3. Sheet pile as claimed in claim 2, wherein the said flange extension (22', 22") is delimited by a first plane surface (30), which extends the plane face (14', 14") of the respective flange, a second plane surface (34), which is perpendicular to the said first plane surface (30), and a convex cylindrical connecting surface (32) which connects the said first plane surface (30) to the said second plane surface (34). 4. Sheet pile as claimed in claim 3, wherein the said second plane surface (34) is connected to the respective plane face of the web (18', 18") by a concave cylindrical connecting surface (36). 5. Sheet pile as claimed in any one of claims 1 to 4, comprising the following parameters: a) ' section modules per unit length of the wall>4800 cm3/m; b) specific section modulus 20 (cm3/cm)(kg/m2). 6. Sheet pile as claimed in any one of claims 1 to 5, comprising the following parameters: a) thickness of the flanges 19 to 20 mm; b) width of flanges >200 mm; c) height of the sheet pile 7. Sheet pile as claimed in any one of claims 1 to 6, wherein the web makes an acute angle a equal to 71° with a plane (16) parallel to the outer faces (14', 14") of the flanges. 8. Sheet pile as claimed in any one of claims 1 to 7, wherein each of the flanges is fitted with a gripping element. 9. Sheet pile as claimed in any one of claims 1 to 9, wherein each of the flanges is fitted with a LARSSEN TYPE gripping element. 10. Sheet pile substantially as hereinbefore described with reference to any one or more of the figures.

Documents:

295-DEL-1997-Abstract.pdf

295-DEL-1997-Claims.pdf

295-DEL-1997-Correspondence-Others-(20-01-2009).pdf

295-del-1997-correspondence-others.pdf

295-del-1997-correspondence-po.pdf

295-DEL-1997-Description (Complete).pdf

295-del-1997-drawings.pdf

295-del-1997-form-1.pdf

295-del-1997-form-13-(20-01-2009).pdf

295-del-1997-form-13.pdf

295-del-1997-form-19.pdf

295-DEL-1997-Form-2.pdf

295-del-1997-form-3.pdf

295-del-1997-form-4.pdf

295-del-1997-form-6.pdf

295-del-1997-gpa.pdf

295-DEL-1997-Others-Document-(20-01-2009).pdf

295-del-1997-petition-137.pdf