NZ621503B - Hollow section structural member - Google Patents

Abstract

hollow section structural member 10 suitable to form an outer wall of a concrete-filled column in a framework of a multi-storey building, the hollow section structural member comprising two or more steel plates 12, 14 that form different portions of the hollow section structural member, at least one of the steel plates being folded and with the steel plates being welded together and forming the hollow section structural member, and connectors fastened to a surface of one or more of the steel plates, and with at least one of the steel plates having one or more openings for (a) receiving a beam, (b) venting vapour from internally of the hollow section structural member, or (c) enabling drainage of water from internally of the member. one of the steel plates being folded and with the steel plates being welded together and forming the hollow section structural member, and connectors fastened to a surface of one or more of the steel plates, and with at least one of the steel plates having one or more openings for (a) receiving a beam, (b) venting vapour from internally of the hollow section structural member, or (c) enabling drainage of water from internally of the member.

Description

HOLLOW SECTION STRUCTURAL MEMBER FIELD OF THE INVENTION The present invention relates to hollow section structural members made from steel for use in the construction industry, for example in the construction of multistorey buildings, and a method for producing such hollow section structural members.

The invention also relates to concrete filled columns that form part of the framework of a multistorey building and comprise (a) a hollow section structural member made from steel, (b) concrete that fills the hollow section, and (c) reinforcement embedded in the concrete.

BACKGROUND OF THE INVENTION Concrete filled hollow section structural members, such as concrete filled hollow steel tubes, are increasingly widely used to form composite structural columns for buildings. The resistance of the concrete to bending reduces the occurrence of local buckling of the steel tubes, and the steel tubes confine the concrete thereby improving its strength and ductility.

Concrete filled hollow section columns for the building industry are discussed in a Corus Tubes document entitled “Design guide for SHS concrete filled columns” by Dr S J Hicks and Mr G M Newman published in 2012. The following paragraphs in this section of the specification are based in large part on information in this document.

Structural hollow section (SHS) tubes are the most efficient of all structural steel sections in resisting compression. Structural hollow section tubes are readily fabricated from high yield materials to achieve a high strength to weight ratio, allowing columns to be more slender and attractive. Moreover, the width of the steel and the reinforcement, or absence thereof, in the concrete 6833840_1 (GHMatters) P92733.NZ 26/08/15 can be varied whilst maintaining constant external dimensions of the structural hollow section tubes.

Therefore, the structural hollow section tubes can have constant external dimensions over the full height of the building.

Concrete filled hollow section tubes are significantly less susceptible to temperature variations than unfilled hollow section tubes. As such, a concrete filled hollow section tube will maintain its load carrying capacity through fluctuations in temperature. Conversely, for a given load carrying capacity, a smaller composite (i.e. concrete filled) section tube may be used when compared with an unfilled hollow section tube.

Concrete or grout filled hollow section tubes can be divided into those that are externally protected against fire by fire-rated boards, lightweight sprayed protection or intumescent coatings, and those that have no such protection. A further division can be made by differentiating between those hollow section tubes that are filled with plain concrete mixes and those hollow section tubes that contain steel reinforcement within the mix.

In order to facilitate interconnection of the formwork of a building, hollow section structural members, such as hollow section tubes, are roll-formed and connectors such as cleats and flanges are welded to the outside of the roll-formed hollow section structural steel members. The connectors are then bolted or otherwise connected to horizontal floor beams and the like to create the formwork of the building. The attachment of connectors is time-consuming when performed on site since access to a relevant portion of the hollow section structural member is necessary, but that portion may be at a height of multiple storeys from the ground. To avoid this issue, connectors can be attached off-site. However, where connectors are necessary on more than one side of a hollow section structural steel member, which is often the 6833840_1 (GHMatters) P92733.NZ 26/08/15 case, the hollow section structural member may need to be rotated to obtain access to each side. This process is also time-consuming and invariably requires lifting equipment.

The above description should not be taken to be a description of part of the common general knowledge in Australia or elsewhere.

In addition, the reference to the Corus Tubes document mentioned above should not be taken to be an admission that the document and the information in the document is part of the common general knowledge in Australia or elsewhere.

SUMMARY OF THE INVENTION As used herein, the term “longitudinal”, and its derivatives such as “longitudinally”, are intended to mean parallel to a longitudinal axis of the hollow section structural member. Where the terms “longitudinal” and its derivatives are used in relation to features such as welds, folds and steel plates, those terms again indicate reference to the longitudinal axis of the hollow section structural member that will ultimately be formed using the referred to features. The term “longitudinal” and its derivatives may refer to features that extend the full length of the hollow section structural member, or only part of that length.

In broad terms, the present invention provides a hollow section structural member comprising steel plate folded into a hollow section and welded together along longitudinal edges of the plate.

In more specific terms, the present invention provides a hollow section structural member comprising two or more steel plates that form different portions of the member, at least one of the steel plates being folded, and the steel plates being welded together. 6833840_1 (GHMatters) P92733.NZ 26/08/15 In more specific terms, the present invention provides a hollow section structural member comprising two or more steel plates that form respectively different portions of a transverse cross-section of the hollow section structural member, at least one of the steel plates being folded, the steel plates being welded together to form the hollow section structural member.

The or each fold may be a longitudinal fold.

The plates may be welded together by longitudinal welds.

The hollow section structural member may further comprise one or more openings formed in at least one of the steel plates.

The or each opening may be sized and positioned to receive a floor beam.

The or each opening may be sized and positioned to vent vapour from internally of the hollow section structural member.

The or each opening may be sized and positioned to enable drainage of water from internally of the hollow section structural member.

The hollow section structural member may comprise one or more connectors fastened to a surface of one or more of the steel plates.

The or each connector may be selected from the group comprising: a column-beam connector; a moment resisting connector; a fill-connection strengthening lug; a reinforcement locating lug; and a reinforcing member.

The hollow section structural member may comprise two folded steel plates.

The hollow section structural member may comprise one folded steel plate and one flat plate.

The present invention also provides a method for forming a hollow section structural member, comprising: (a) forming two or more steel plates into different portions of a hollow section structural member by folding at least one of the steel plates; and 6833840_1 (GHMatters) P92733.NZ 26/08/15 (b) welding the plates together to form the member.

The step of folding at least one of the steel plates may include forming a longitudinal fold in the or each plate.

The step of welding the plates together may include welding the plates together using longitudinal welds.

The method may further comprise forming one or more openings in one or more of the steel plates, prior to the positioning step.

The forming step may include sizing and positioning the or each opening to receive a beam.

The forming step may include sizing and positioning the or each opening to vent vapour from internally of the hollow section structural member.

The forming step may include sizing and positioning the or each opening to enable drainage of water from internally of the hollow section structural member.

The method may further comprise fastening one or more connectors to a surface of one or more of the steel plates, prior to the positioning step.

The fastening step may include fastening to the surface of one of more of the steel plates one or more connector selected from the group comprising: a column- beam connector; a moment resisting connector; a fill- connection strengthening lug; a reinforcement locating lug; and a reinforcing member.

The present invention also provides a concrete filled column that forms part of a framework of a multistorey building and comprises (a) the hollow section structural member described above, (b) concrete in the hollow section, and (c) reinforcement embedded in the concrete.

Advantageously, in situations where the hollow section structural member is filled with concrete, the steel plate of the structural member substantially prevents construction damage of the concrete filling.

Advantageously, in situations where the hollow section structural member is filled with concrete, the 6833840_1 (GHMatters) P92733.NZ 26/08/15 overall weight of the structural member when compared with a non-composite (e.g. unfilled hollow section member, or exposed concrete column) is lower for a member of the same strength.

Advantageously, the present invention makes it possible for the hollow section structural member to be made to order. Consequently, multiple floors of a multistorey building can be erected concurrently.

Advantageously, floor beam connections may be attached (e.g. by welding) onto the surfaces of the steel plate prior to welding the plates together to form the hollowing section structural member. Consequently, the hollow section structural member may be fabricated to have integral internal and/or external floor beam connections once the steel plates have been welded together. In contrast, roll-forming plate to form a closed section would result in damage and/or distortion of openings of fittings such as connectors that are installed prior to the structural member being rolled into its ‘in use’ form.

Advantageously, the present invention makes it possible for reinforcement, such as reinforcing bars (as individual bars or as cages made from a plurality of bars tied together) or reinforcing I-beams, to be attached to an inner surface of one or more steel plates before the steel plates are welded together. The resulting hollow section structural member will then have integral reinforcement once fabrication is completed.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is now described by way of non- limiting example only, with reference to the accompanying drawings, in which: Figure 1 is a side perspective view of an embodiment of a hollow section structural member according to the present invention; Figure 2 is a transverse cross-section of the hollow 6833840_1 (GHMatters) P92733.NZ 26/08/15 section structural member shown in Figure 1; Figures 3 and 4 show various cross-sections of other embodiments of hollow section structural members according to the present invention; Figure 5 shows connectors and surface features connected to or otherwise formed onto a steel plate that is subsequently used to manufacture a hollow section structural member according to the present invention; Figure 6 shows the steel plate of Figure 5 folded into a form that is suitable to be welded to another steel plate to form a hollow section structural member according to the invention; Figure 7 is a perspective view of another embodiment of a hollow section structural member according to the present invention; and Figures 8 and 9 show the hollow section structural member of Figure 1, filled with concrete and containing various types of reinforcing members.

DETAILED DESCRIPTION A hollow section structural member 10, as shown in Figures 1 and 2, is in the form of a Square Hollow Section (SHS) beam.

The hollow section structural member 10 comprises two steel plates 12, 14 that form respectively different portions of a transverse cross-section of the hollow section structural member 10.

In the embodiment shown in Figures 1 and 2, the steel plates 12, 14 form respectively opposite halves of the transverse cross-section of the hollow section structural member 10.

The steel plates 12, 14 are welded together by welds 16, 18 to form the hollow section structural member 10.

Welds 16, 18 are longitudinal welds that are continuous along the length of the hollow section structural member . It will be appreciated that intermittent or 6833840_1 (GHMatters) P92733.NZ 26/08/15 discontinuous (e.g. spot) welding, or welding at an angle to the longitudinal axis of the hollow section structural member, may be appropriate in some cases, and all such welding techniques and directions are intended to fall within the scope of the present disclosure.

Each of the steel plates 12, 14 in the member 10 shown in Figures 1 and 2 includes a fold 20, 22. The folds 20, 22 are longitudinal, which gives the plates 12, 14 an angle-section. Each angle forms half of the square section of the beam so when the two folded plates 12, 14 are brought together the square section is complete. It will be appreciated that folds in directions other than the longitudinal direction may be appropriate in some cases, and are intended to fall within the scope of the present disclosure.

In a standard, roll-formed structural hollow section beam there will be a single butt weld running longitudinally of the beam. Each longitudinal edge of the beam will constitute a roll-formed angle and thus assume a rounded shape.

In the beam shown in Figures 1 and 2 the two longitudinal seams 16, 18 are positioned at the corners.

Therefore, two of the longitudinal edges of the beam are formed by the longitudinal folds 20, 22 in the steel plates 12, 14 and the other two the longitudinal edges are formed by the seams 16, 18. The two edges formed by the folds 20, 22 will typically have a rounded shape by virtue of the curvature of the fold. The two edges formed by the seams 16, 18 will also typically have a rounded shape as they are formed using butt welds, though another type of weld or connection may be used as desired.

It is desirable that whatever connection is made between the plates 12, 14 is continuous along the length of the plates 12, 14 so that the structural forces are correctly distributed throughout the column and upon filling of the hollow section structural member 10 with concrete there is no unexpected leakage. 6833840_1 (GHMatters) P92733.NZ 26/08/15 As an alternative to connecting the plates 12, 14 by longitudinal seams 16, 18 forming corners of the hollow section structural member 10, the plates 12, 14 may instead be folded to form C-section beams. Welding the two C-section beams together will result in welds along broken lines 24, 26 as shown in Figure 1.

Figure 3 and Figure 4 show transverse cross- sections of other hollow section structural members.

Figure 3 shows a D-section hollow section structural member 28. The hollow section structural member 28 comprises two steel plates 30, 32 that form respectively different portions of the transverse cross- section of the structural member 28. In particular, plate forms a linear backing plate and plate 32 forms a C- section beam welded centrally, with respect to the longitudinal axis of the structural member 28, to plate . Since plate 32 is centrally disposed on plate 30, and the open or long side of the C-section plate 32 is shorter than the width of plate 30, two longitudinal flanges 34, 36 are created, one extending from each side of the C- section plate 32.

Notably, only one of the plates 30, 32 is folded. It will therefore be understood that a hollow section structural member formed in accordance with the present teachings may comprises two or more steel plates and one or more of those plates may be folded, depending on the configuration of the hollow section structural member desired to be fabricated.

The steel plates 30, 32 are welded together by longitudinal fillet welds 38, 40 to form a D-section hollow section structural member 10.

The flanges 34, 36 are useful features in terms of mounting other structural members to the structural member 28. In particular, the flanges 34, 36, enable the hollow section structural member 28 to be attached to concrete or other members of the formwork of a building.

Consequently, the hollow section structural member 28 is 6833840_1 (GHMatters) P92733.NZ 26/08/15 suitable for retrofitting to an existing building structure.

The hollow section structural member 42 as shown in Figure 4 comprises two steel plates 44, 46 that are folded to form different sized angle-section beams. The smaller angle-section beam 46 is positioned centrally on the larger angle section beam 44 and is welded in position by fillet welds 48, 50 to give hollow section structural member 42 is an “E-section”.

The smaller angle-section plate 46 does not extend to the edges of the larger angle-section plate 44 and thus two flanges 52, 54 are formed, one extending laterally outwardly from each fillet weld 48, 50.

The flanges 52, 54 are useful features in terms of mounting other structural members to the structural member 28. In particular, as with the D-section hollow section structural member 28, the E-section hollow section structural member 42 can be readily retrofitted to an existing building structure by flanges 52, 54. The E- section hollow section structural member 42, as with the D-section hollow section structural member 28, can be used to strengthen existing structures and/or to enable extension of existing structures.

Figure 5 shows a steel plate 56 with various elements, including connectors, fastened to an internal surface before the plate 56 is folded. It will be appreciated that the connectors may be fastened at any time up to the point at which two or more plates are welded together to form the hollow section structural member.

A reference to an “internal surface” is intended to mean a surface internal of a hollow section structural member or, with reference to the plate 56, a surface that will ultimately form an internal surface of the hollow section structural member once the plate is folded and/or welded to one or more other plates. Conversely, an “external surface” is a surface that does, or ultimately 6833840_1 (GHMatters) P92733.NZ 26/08/15 will, constitute an external surface of the hollow section structural member.

In use, plate 56 will be folded to form part of a hollow section structural column, and to that end the connectors include a floor beam connector 58 shown extending through an opening, similar to opening 60 and extending (indicated by broken lines) outwardly from an external surface of the plate 56. The floor beam connector 58 is for connecting to a floor beam of the formwork of the building.

Where the hollow section structural member is a beam, the connector 58 will constitute a column connector.

Consequently, connector 58 may be variously referred to as a column-beam connector, a column connector or a beam connector.

The connectors further include, by way of example only: (a) a moment resisting connector 62 for connection to a moment resisting fitting as shown in Figure 6; (b) a fill connection strengthening lug 64, that may or may not be headed, that sets into a concrete in-fill to mechanically bond the hollow section structural member to the concrete, or alternatively may be connected to a reinforcing member internally of the hollow section structural member, thereby constituting a reinforcement locating lug; and (c) a reinforcing member (not shown) that may comprise an I-section beam, reinforcing rod or similar.

In addition to the connectors, the plate 56 can be provided with one or more openings. Presently there are openings 60 and 66. Opening 60 is designed to receive a plate of another connector, such a column-beam connector 58. Opening 66 is designed to receive a beam, such as a floor beam or profiled beam 67, or column where the hollow section structural member is a beam. The opening 66 may have a corresponding opening in another plate to enable a beam or column, as the case may be, to extend right 6833840_1 (GHMatters) P92733.NZ 26/08/15 through the hollow section structural member.

It will be appreciated that an opening of any desired shape such as opening 66 may be cut into the steel plate, for example to suit a particular floor beam profile. A cooperating opening can then be cut in another plate so that when the two plates are welded together a floor beam of the desired profile can extend through the resulting hollow section structural member. The floor beam will be welded to the outside of the hollow section structural member enabling floor beams to be continuous, rather than being segmented with the hollow section structural member between the segments. Such an arrangement is significantly more structurally efficient.

There may be further openings (not shown) at the top and/or bottom of each column, or at the ends of each beam, for the release of water particularly in circumstances where the hollow section structural member is to remain on site during inclement weather without being filled with concrete. The same openings, or additional openings, can be used for venting steam in the event of a fire, to reduce the likelihood of catastrophic failure or rupturing of the hollow section structural member.

Plate 56 is folded into an angle-section as shown in Figure 6. The ends of connectors 58, 62 are available for connection to beams of the formwork of the building in the case of connector 58, and a moment resisting connector member in the case of connector 62.

Although the embodiment shown in Figure 5 and 6 involves the addition of connectors to the plate 56 before folding, it will typically be preferable to add the connectors after folding to reduce the likelihood of damage to connectors during folding.

Figure 7 is a perspective view of another embodiment of a hollow section structural member according to the present invention. The embodiment is similar to the embodiment shown in Figure 3 and shows a D-section hollow section structural member 28. 6833840_1 (GHMatters) P92733.NZ 26/08/15 Specifically, with reference to Figure 7, the hollow section structural member 28 comprises two steel plates , 32 that form respectively different portions of the transverse cross-section of the structural member 28. In particular, plate 30 forms a linear backing plate and plate 32 forms a C-section beam welded centrally, with respect to the longitudinal axis of the structural member 28, to plate 30. Since plate 32 is centrally disposed on plate 30, and the open or long side of the C-section plate 32 is shorter than the width of plate 30, two longitudinal flanges 34, 36 are created, one extending from each side of the C-section plate 32.

In addition, the end of the hollow section structural member 28 shown in Figure 7 includes a connector in the form of a plate 80 positioned to extend through a slot 82 in the C-section plate 32. The end of the plate 8o that extends beyond the member 28 forms a mounting flange. The other end of the plate 80 is welded or otherwise secured to an internal wall of the plate 30.

Figure 8 shows a concrete filled column that can form part of a framework of a multistorey building. The concrete filled column comprises (a) the hollow section structural member 10 described above, (b) concrete 68 that fills the hollow section structural member 10 and, with regard to the embodiment shown in Figure 9, (c) reinforcement 72, 74 embedded in the concrete.

While the embodiment shown in Figure 8 is, in effect, a concrete column sheathed in a metal skin, in order to improve the mechanical connection between the concrete and the hollow section structural member the embodiment includes fill connection strengthening lugs, such as lug 64 in Figure 5, disposed along the length of the hollow section structural member 10.

Hollow section structural member 70 as shown in Figure 9 comprises an SHS hollow section structural member according to Figure 1, filled with concrete. Set within the concrete are reinforcing rods 72 and a rigidifying I- 6833840_1 (GHMatters) P92733.NZ 26/08/15 beam 74. It will be appreciated that any number and type of reinforcing element may be used, the or each member being set within the concrete, or directly connected (e.g. welded) to the hollow section structural member, or connected to the hollow section structural member by being welded to reinforcement locating lugs 64.

The reinforcement can be added prior to the steel plates being welded together to form the hollow section structural member. To that end, the reinforcement can be mechanically connected to the hollow section structural member along its length, rather than simply being set into concrete within the hollow section structural member.

One embodiment of a method for forming a hollow section structural member, such as member 10 described herein, comprises the following steps: (a) forming two or more steel plates 12, 14 into different portions of a transverse cross-section of the hollow section structural member 10, by folding at least one of the steel plates 12, 14; and (b) positioning the steel plates 12, 14 adjacent one another and welding the plates 12, 14 together (e.g. using longitudinal welds 16, 18) to form the hollow section structural member 10.

The fold in the or each steel plate is preferably a longitudinal fold, so as to provide a consistent cross- section along the length of the hollow section structural member.

Similarly, the welds 16, 18 are preferably longitudinal welds that are continuous over the length of the hollow section structural member so as to prevent leaks if the hollow section structural member is filled with concrete.

As mentioned above, one or more openings may be formed in the hollow section structural member. Forming the openings could include sizing and positioning each opening to: (a) receive a beam; and/or 6833840_1 (GHMatters) P92733.NZ 26/08/15 (b) vent vapour from internally of the hollow section structural member, for example steam being vented in the event of a fire; and/or (c) enable drainage of water from internally of the hollow section structural member, particularly where the structural member is on site unfilled during inclement weather.

As also mentioned above, one or more connectors may be fastened to a surface of one or more of the steel plates, prior to positioning the plates adjacent one another.

Fastening the connectors to the surface may include fastening one or more connectors of the following types: a column-beam connector; a moment resisting connector; a fill-connection strengthening lug; a reinforcement locating lug; and a reinforcing member.

Such a method may also include attaching one or more reinforcing elements to an internal surface of one or more of the steel plates prior to welding the steel plates together to form the hollow section structural member.

This may be either by directly connecting the reinforcing elements to the steel plates directly, or by connecting the reinforcing elements to reinforcement locating lugs that are attached to an internal surface of one or more of the steel plates.

The above-described concrete-filled hollow section structural members are suitable for use as columns that form part of a framework of a multistorey building.

Many modifications may be made to the embodiments of the present invention described above without departing from the spirit and scope of the invention.

By way of example, the present invention is not confined to the cross-sectional profiles of the particular embodiments of the hollow section structural member shown in Figures 1 to 5 and 7 and extends to any other suitable profiles. One example of another profile is a circular cross-section profile. 6833840_1 (GHMatters) P92733.NZ 26/08/15 By way of further example, the present invention is not confined to the particular connectors shown in the Figures and extends to any suitable connectors. 6833840_1 (GHMatters) P92733.NZ 26/08/15

Claims (5)

Claims 1.

1. A hollow section structural member suitable to form an outer wall of a concrete-filled column in a framework 5 of a multi-storey building, the hollow section structural member comprising two or more steel plates that form different portions of the hollow section structural member, at least one of the steel plates being folded and with the steel plates being welded together and forming 10 the hollow section structural member, and connectors fastened to a surface of one or more of the steel plates, and with at least one of the steel plates having one or more openings for (a) receiving a beam, (b) venting vapour from internally of the hollow section structural member, 15 or (c) enabling drainage of water from internally of the member.

2. The hollow section structural member according to claim 1 wherein the or each fold is a longitudinal fold.

3. The hollow section structural member according to claim 1 or 2 wherein the steel plates are welded together by longitudinal welds. 25

4. The hollow section structural member according to any one of the preceding claims wherein the or each connector is selected from a group comprising: a column-beam connector; a moment resisting connector; a fill-connection strengthening lug; a reinforcement locating lug; and a 30 reinforcing member.

5. The hollow section structural member according to any one of the preceding claims comprising two folded steel plates. 6833840_1 (GHMatters) P92733.NZ 26/