AU744148B2

AU744148B2 - Reinforcing steel

Info

Publication number: AU744148B2
Application number: AU38308/97A
Authority: AU
Inventors: Maxwell Thomas Renwick
Original assignee: Broken Hill Pty Co Ltd
Current assignee: Broken Hill Pty Co Ltd
Priority date: 1996-09-23
Filing date: 1997-09-18
Publication date: 2002-02-14
Anticipated expiration: 2017-09-18
Also published as: AU3830897A

Description

I~ a

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant: THE BROKEN HILL PROPRIETARY COMPANY LIMITED A.C.N. 004 028 077 Invention Title: REINFORCING STEEL The following statement is a full description of this invention, including the best method of performing it known to me/us: 1- 2 REINFORCING STEEL The present invention relates to reinforcing steel.

In particular, the present invention relates to reinforcing steel for reinforcing concrete.

It is well known to manufacture structural elements for the building industry (and for the civil engineering industry generally) from concrete that is 15 reinforced with reinforcing steel.

The term "reinforcing steel" is understood to *cover elongate members, such as bar or wire, manufactured from steel.

Structural elements may be manufactured from reinforcing steel in the form of separate elongate members or in the form of two or more elongate members which are connected together to form products, such as, but not limited to, fabric/mesh, stirrups, and cages.

The surface of reinforcing steel may be plain or may be profiled, for example, by means of ribs or indentations.

In use, reinforcing steel may be tensioned or untensioned. Typically, the nominal strength of elongate members for untensioned applications is 400-500 MPa and for tensioned applications is 800-1100 MPa.

The principal purpose of reinforcing steel in structural elements is to strengthen them by developing \\MELB01\homeS\Maria\Keep\BHP P02515 REINFORCING STEEL.doc 18/09/97 3 tension or compression. For example, it is important that reinforcing steel develop compression in vertical columns and in the compressive regions of horizontal beams and develop tension in the tensile regions of horizontal beams.

When reinforcing steel is used in structural elements it is important to anchor reinforcing steel in concrete to allow load to be transferred from the concrete 10 to reinforcing steel. One purpose of a profiled, eg ribbed or indented, surface on elongate members is to optimise anchoring of the untensioned reinforcing steel in concrete thereby to optimise the efficiency of transferring load from the concrete to reinforcing steel.

SAn object of the present invention is to provide reinforcing steel for reinforced concrete which has improved performance when compared with known reinforcing steel.

According to the present invention there is provide reinforcing steel for concrete in a reinforced concrete product, such as a structural element, the reinforcing steel comprising an elongate member having'a core and a profile formed on the core, the profile comprising opposed sides, with one or both sides comprising at least two sections, with a first section being steeper than a second section, and with the second section describing an angle of 10 to 40" with a longitudinal axis of the elongate member.

In use, when reinforcing steel is embedded in concrete in a reinforced concrete product, the purpose of the sections of the profile is to optimise load transfer from the concrete to the reinforcing steel. The efficiency of load transfer is dependent on the follow parameters.

S\\mel_fileB\homes\kraOt\ee\aBp2ci\HF\3B -7 amended paes.doc 28/13/61 28/12 '01 FRI 12:00 [TX/RX NO 6686] -3a i.The maximum shear stresg that can be sustained by the concrete/reinforcing steel interface (the "load transfer- property).

see 0000 :0000 *00* 00*0 ee 00 :.04.

0. 0.: \\melb.-fileobomrs\BLDK rot\KeO\10tc\ X\3838-9 mndrd page5.doc 26f12101~ 28/12 '01 FRI 12:00 [TX/RX NO 66861 4 2. The rate of generating shear stress (the "stiffness" property).

The present invention is based on the realisation that the structural requirements of reinforcing steel that have a bearing on the load transfer and stiffness properties are different. The present invention is also based on the realisation that the performance of a reinforced concrete product in terms of these properties can be optimised by providing a profile on reinforcing steel that has at least two sections on at least one side of the profile, with one section (the "first section") being formed to optimise the stiffness property and another section (the "second section") being formed to optimise the load transfer property.

It is preferred that the core be generally cylindrical.

•The term "generally cylindrical" as used herein in connection with the core of the elongate member is understood to cover, but is not limited to, (i) arrangements in which the core is cylindrical; and (ii) e eo 25 arrangements in which the core is cylindrical except for lengthwise extending flats or channels.

It is preferred that the elongate member comprise a solid core.

It is preferred, although by no means essential, that the opposed sides of the profile converge to a ridge or apex.

The term "ridge or apex" as used herein in connection with the profile is understood to mean the juncture of the converging sides of the profile.

\\MELB01\home$\Maria\Keep\BHP P02515 REINFORCING STEEL.doc 18/09/97 It is noted that, whilst in theory the juncture of converging sides is a sharp line, in practice (particularly in situations where the profiles are formed by rolling) the juncture as formed may be rounded or flattened to a certain extent.

It is preferred that both sides of the profile comprise the first and the second sections.

0: 0: 10 In an alternative arrangement it is preferred 0000 that only one side of the profile comprise the first and the second sections, 0 It is preferred that one or more of the sections 15 of the profile tobe plana.

is preferred that one oirstr o h sections profile extend from the core to a junction of the first and the second sections.

With this arrangement, in situations where both sides of the profile comprise the first and second 0.000sections and the second sections are curved, the second :sections and ridge or apex may define a continuous arcuate surface.

It is preferred that the first section describes an angle of 40 to 800 with a longitudinal axis of the elongate member.

It is preferred particularly that the angle be 3S to 650.

RA(It is preferred particularly that the angle be amendeil pagee.doe 28/12/01 28/12 '01 FRI 12:00 [TX/RX NO 6686] 6to 300.

comprise that the that the angle 40 angle be included In a situation where both sides of the profile the first and the second sections it is preferred first and the second sections it is preferred first sections be planar and describe an included to 1000.

It is preferred particularly that the included 50 to It is preferred more particularly that the angle be 55 to 750

S

9 9 9 9.

9 0 *0900@ s e 9069 6*94 0 0 0@ 000 9

S.

.9 *0 00

OS

Furthermore, with such an arrangement, it is preferred that the second sections be planar and describe an included angel of 100 to 160°.

It is preferred particularly that the included angle be 120 to 1600.

It is preferred that the total width of the profile, as measured between the junctions of the first sections and the core, be 2 to It is preferred that the width of the second section(s) of the profile be 40 to 85% of the total width of the profile.

It is preferred particularly that the width of the second section(s) of the profile be 50 to 80% of the total width of the profile.

It is preferred that the height of the profile, \\mclBD_ilee\h eS\Bkrat\Kep\peci\BP\3 306-97 amended pages.doc 21/13/01 28/12 '01 FRI 12:00 [TX/RX NO 6686] 7 as measured between the ridge or apex of the profile and the core, be 0.04 to 0.20 the diameter of the core.

It is preferred particularly that the height of the profile be 0.05 to 0.15 the diameter of the core.

In one preferred arrangement, it is preferred that the profile be a series of ribs spaced apart along the length of the elongate member.

In a situation where only one side of the profile comprises the first and the second sections, it is preferred that the profile be repeated along the length of the elongate member such that the first and the second 15 sections are on the same side of each rib.

In an alternative arrangement, it is preferred that adjacent ribs be mirror images with the first and the second sections of one rib being on the opposite side to the first and the second sections of adjacent ribs.

It is preferred that the pitch of the ribs be 0.3 to 1.2 times the diameter of the core.

25 It is preferred particularly that the pitch be to 1.0 times the diameter of the core.

The ribs may or may not form a thread.

In this connection, the thread may be: continuous or discontinuous; left or right handed; and single or multi-start.

\\MELBO1\homeS\Maria\Keep\BHP P02515 REINFORCINr STEELdoc 18/09/97 -;LL~L~LL; r IL~I~ i 8 In another preferred arrangement, it is preferred that the profile be a hoop.

It is preferred particularly that there be a plurality of the hoops spaced apart along the length of the elongate member.

According to the present invention there is also provided a reinforced concrete product comprising reinforcing steel described above embedded in concrete.

The present invention is described further by way of example with reference to the accompanying drawings in S* which: Figure 1 is a plan view of a section of a length of a preferred embodiment of a reinforcing bar in accordance with the present invention; Figure 2 is an end view in the direction of the arrow A in Figure 1; Figure 3 is an enlarged view of the circled region in Figure 1 which illustrates the profile of the 25 reinforcing bar; Figure 4 is a plan view of the section of the reinforcing bar shown in Figure 1 rotated through 900 about the longitudinal axis of the reinforcing bar; Figure 5 is a plan view of a section of a length of another preferred embodiment of a reinforcing bar in accordance with the present invention; Figure 6 is an end view in the direction of the arrow A in Figure \\MELB01\home$\Maria\Keep\BHP P02515 REINFORCING STEEL.doc 18/09/97 9 Figure 7 is an enlarged view of the circled region in Figure 5 which illustrates the profile of the reinforcing bar; Figure 8 is a plan view of the section of the reinforcing bar shown in Figure 5 rotated through 900 about the longitudinal axis of the reinforcing bar; Figure 9 is a plan view of a section of a length of another preferred embodiment of a reinforcing bar in accordance with the present invention; *Figure 10 is an end view in the direction of the arrow A in Figure 11; Figure 11 is an enlarged view of the circled region in Figure 9 which illustrates the profile of the reinforcing bar; Figure 12 is a plan view of the section of the reinforcing bar shown in Figure 9 rotated through 900 about the longitudinal axis of the reinforcing bar; Figure 13 is a plan view of a section of a length 25 of another preferred embodiment of a reinforcing bar in accordance with the present invention; Figure 14 is an end view in the direction of the arrow A in Figure 13; Figure 15 is an enlarged view of the circled region in Figure 13 which illustrates the profile of the reinforcing bar; Figure 16 is a plan view of the section of the reinforcing bar shown in Figure 13 rotated through 900 about the longitudinal axis of the reinforcing bar; \\MELBOl\home$\Maria\Keep\BHP P02515 REINFORCING STEEL.doc 18/09/97 I li I 10 Figure 17 is an enlarged view, similar to that of Figures 3, 7, 11 and 15 of a section of a length of another preferred embodiment of a reinforcing bar in accordance with the present invention which illustrates in detail the profile of the reinforcing bar; Figure 18 is an enlarged view, similar to that of Figures 3, 7, 11, 15 and 17 of a section of a length of another preferred embodiment of a reinforcing bar in accordance with the present invention with illustrates in o*o. detail the profile of the reinforcing bar; and Figure 19 is an enlarged view of the profile of 15 another preferred embodiment of a reinforcing bar in accordance with the present invention.

The preferred embodiments of reinforcing steel in accordance with the present invention shown in the figures are in the form of reinforcing bars. It is noted that the present invention is not limited to reinforcing bars and extends to any other suitable form of reinforcing steel.

It is also noted that the reinforcing bars shown in the figures are intended for use in the manufacture of 25 reinforced concrete products, such as structural elements, which comprise the reinforcing bars embedded in concrete.

With reference to the Figures 1 to 4, the reinforcing bar 1 shown in the drawings comprises: a generally cylindrical core 5 having opposed flats 17; and a profile on the core 5, the profile comprising a single start right-hand thread 3 extending from the core 5 and inclined at an angle of 50 to the transverse axis of the \\MELBO1 \home$ \Mari \Keep\BH P P02515 REINFORCING STEEL.doc 12/09/97 11 reinforcing bar 1.

The reinforcing bar 1 may be formed by any suitable means and of any suitable material. It is preferred that the reinforcing bar 1 be formed from steel and that the thread 3 be formed on the reinforcing bar 1 by hot rolling or any suitable cold forming process.

The thread 3 in the preferred embodiment of the reinforcing bar 1 shown in Figures 1 to 4 comprises opposed sides, generally identified by the numerals 6, which converge to a ridge or apex 7. It is noted that, in practice, in a hot rolling operation or cold forming process, the ridge or apex 7 may not be as sharply defined 15 as shown in the figures and could be rounded to a certain extent.

Furthermore, each side 6 of the thread 3 comprises a planar first section 9 to optimise the stiffness property of a reinforced concrete product based on the reinforcing bar 1 and a planar second section 11 to optimise the load transfer property of the reinforced concrete product.

.o° 25 The first sections 9 are steeper than the second sections 11. In this connection, in the preferred embodiment shown in Figures 1 to 4, the first sections 9 are formed with an included angle of 600 and the second sections 11 are formed with an included angle of 140°.

The dimensions of the first and the second sections 9, 11 may be selected as required, provided that the dimensions are effective in terms of the functional objectives, namely to optimise stiffness and load transfer properties.

The thread 3 has a multi-step profile which is \\MELB01\home$\Maria\Keep\BHP P02515 REINFORCING STEEL.doc 18/09/97 12 formed to control the stress distribution between the reinforcing bar 1 and concrete in a reinforced concrete product based on the reinforcing bar 1 thereby to control the transfer of load from the concrete to the reinforcing bar 1. More particularly, the multi-step profile is formed to enhance load development in the reinforcing bar 1 by improving load transfer between the interface between the concrete and the reinforcing bar 1.

The reinforcing bar 1 may be of any suitable dimensions.

The preferred embodiment of the reinforcing bar 1 shown in Figures 5 to 8 is identical to that shown in 15 Figures 1 to 4 save for several minor differences. The differences between the two preferred embodiments are summarised below.

The reinforcing bar 1 shown in Figures 5 to 8 comprises a two-start right handed thread •3 (as opposed to the single start thread of the reinforcing bar 1 shown in Figures 1 to 4).

I. 25 The first sections 9 of each thread 3 form an included angle of 800 in the reinforcing bar 1 shown in Figures 5 to 8 (as opposed to 600) The threads 3 are inclined at an angle of to the transverse axis in the reinforcing bar 1 shown in Figures 5 to 8 (as opposed to With particular reference to Figure 11, the profile of the threads 3 in the preferred embodiment of the reinforcing bar 1 shown in Figures 9 to 12 is identical to \\MELBOI\home$\Maria\KeeP\BHP P02515 REINFORCING STEEL.doc 18/09/97 13 that shown in Figures 5 to 8, with the exception that the width of the threads 3 is narrower than that in the preferred embodiment shown in Figures 5 to 8.

The preferred embodiment of the reinforcing bar 1 shown in Figures 13 to 16 is identical to that shown in Figures 1 to 4 except for the several minor differences.

The differences between the two preferred embodiments are summarised below.

The threads 3 are inclined at an angle of S.to the transverse axis in the reinforcing bar 1 shown in Figures 13 to 16 (as opposed to 50 in the reinforcing bar 1 shown in Figures 1 to 4).

The core 5 is cylindrical (as opposed to the i :'...cylindrical core 5 with flats 17 in the reinforcing bar 1 shown in Figures 1 to 4).

the preferred embodiments of the reinforcing bar shown in Figures 17 and 18 only one side 6 of the thread 3 comprises the first and the second sections 9, 11 too*°" and the other side 6 comprises a relatively steep face 31.

In the case of the Figure 17 embodiment the thread profile is repeated along the length of the reinforcing bar 1. In the case of the Figure 18 embodiment the adjacent ribs of the thread 3 are mirror images.

The preferred embodiment of the reinforcing bar 1 shown in Figure 19 is similar to embodiments shown in Figures 1 to 18. The major difference is that the second sections 11 are not planar and do not converge to a welldefined ridge or apex 7. Rather, the second sections 11 and the ridge or apex are formed as a continuous arcuate surface which extends between the junctions 41 of the first \\MELB01\home$\Maria\Keep\BHP P02515 REINFORCING STEEL.doc 18/09/97 1 :j 11 14 sections 9 and the second sections 11.

It has been found experimentally by the applicant that reinforced concrete products which include the multistep profile reinforcing bars 1 shown in Figures 1 to 18 have significantly better performance than reinforced concrete products which are based on conventional reinforcing steel.

As is discussed above, the performance of a reinforced concrete product is dependent on the efficiency of transferring load to a reinforcing steel from the concrete which in turn is dependent on the load transfer and stiffness properties of the reinforced concrete i. 15 product.

'go The optimum theoretical performance of a reinforced concrete product can be defined as when reinforcing steel develops load rapidly to the desired level and then maintains the load for as long as possible.

S: It has been found experimentally by the applicant that by

L

forming a multi-step profile on reinforcing steel, such as that shown in the reinforcing bars of Figures 1 to 18, it is possible to approach the optimum theoretical performance 25 of a reinforced concrete product based on the reinforcing steel. In this connection, whilst the load transfer and stiffness properties of a reinforcing concrete product act in association along the profile of the reinforcing steel, the experimental work of the applicant has shown that by dividing the profile into discrete sections, i.e. the first and second sections 9, 11, it is possible to approach optimum performance.

Many modifications may be made to the preferred embodiments described with reference to the drawings without departing from the spirit and scope of the present invention.

\\MELBO\home$\Maria\Keep\BHP P02515 REINFORCING STEEL.doc 18/09/97 _7 15 In this regard, whilst each preferred embodiments of the reinforcing bar 1 of the present invention comprises a two-step profile having a first section 9 which is steeper than a second section 11, it can readily be appreciated that the present invention is not so limited and extends to reinforcing bars having profiles with more than two sections.

In addition, whilst each preferred embodiment of the reinforcing bar 1 of the present invention comprises planar first and second sections 9, 11, it can readily be appreciated that the present invention is not so limited and the first and second sections 9, 11 may be any suitable 15 shape, such as curved, provided the shape and dimensions are effective to optimise the stiffness or load properties.

r In addition, whilst each preferred embodiment of the reinforcing bar 1 of the present invention shown in Figures 1 to 12 comprises a cylindrical core 5 having opposed flats 17 and in Figures 13 to 16 comprises a cylindrical core 5 without flats 17, it can readily be appreciated that the present invention is not so limited 4* and extends to any suitable shaped core 5, such as oval or 25 elliptical shaped cores \\MELB01\homeS\Maria\Keep\BHP P02515 REINFORCING STEEL.doc 18/09/97

Claims

1. Reinforcing steel for concrete in a reinforced concrete product, such as a structural element, the reinforcing steel comprising an elongate memiber having a core and a profile formed an the core, the profile comprising opposed sides, with one or both sides comprising at least two sections, with a first section being steeper than a second section, and with the second 10 section describing an angle of 1-0 to 40' with a longitudinal axis of the elongate member. 00 Reinforcing steel defined in claim I. wherein the core is generally cylindrical. e. Reinforcing steel defined in claim 1 or claim 2 wherein the elongate member comprises a solid core.

4. Reinforcing steel def ined in any one of the 20 preceding claims wherein the opposed sides of the profile converge to a ridge or apex. Reinforcing steel defined in any one of the preceding claims wherein both sides of the profile comprise the first and the second sections. *0 0 *0. to 4 wherein only one side of the profile comprises the first and the second sections.

7. Reinforcing steel defined in any one of the preceding claims wherein one or more of the sections of the profile are planar.

8. Reinforcing steel defined in any one of the preceding claims wherein one or more of the sections of the profile is curved. .ZC ,\\Thmbfiea\h\ r\ erp\pci\HP\R383n-97 amended pagea.doc 2B112/D1 28/12 '01 FRI 12:00 [TX/RX NO 6686] 17

9. Reinforcing steel defined in any one of the preceding claims wherein the first section of the profile extends from the core to a junction of the first and the second sections. Reinforcing steel defined in any one of the preceding claims wherein the first section describes an angle of 40 to 80* with a longitudinal axis of the elongate 10 member. 0 0 0

011. Reinforcing steel defined in any one of the preceding claims wherein the total width of the profile, as measured between the junctions of the first sections arnd the core, is 2 to lomm.

12. Reinforcing steel defined in any one of the preceding claims wherein the width of the second section(s) of the profile is 40 to 85% of the total width 20 of the profile,

13. Reinforcing steel defined in any one of the *0 preceding claims where the height of the profile, as measured between the ridge or apex of the profile and the core, is 0.04 to 0.20 the diameter of the core. :14. Reinforcing steel defined in any one of the preceding claims wherein the profile is a series of ribs spaced apart along the length of the elongate member. Reinforcing steel defined in claim 14 wherein the pitch of the ribs is 0.3 to 1.2 times the diameter of the core.

16. A reinforced concrete product comprising reinforcing Steel defined in any one of the preceding claims. ~~amndc pagee .0oc 28/121911 28/12 '01 FRI 12:00 [TX/RX NO 66861 18

17. Reinforcing steel substantially as hereinbefore described with reference to the accompanying drawings. Dated this 28th day of December 2001 THE BROKEN HILL PROPRIETARY COMPANY LIMITED By their Patent Attorneys GRIFFITH RA~CK Fellows Institute of Patent and 10 Trade Mark Attorneys of Australia *00 0 550 0 0 0 00 0 0 *0 00 0 0 0 0 =R K- 4za \\m1 ri~a~iam; rr.\rap \pgj \ilp\ 9 0 9- 97 aIndad page;l. oe 26/12/01. 28/12 '01 FRI 12:00 [TX/RX NO 6686]