US20100163506A1

US20100163506A1 - Storage rack beam

Info

Publication number: US20100163506A1
Application number: US12/063,193
Authority: US
Inventors: Murray Clarke; Paul Berry; Stephen Celati
Original assignee: Dematic Pty Ltd
Current assignee: Dematic Pty Ltd
Priority date: 2005-08-08
Filing date: 2006-08-08
Publication date: 2010-07-01
Also published as: CA2617931A1; MY141833A; WO2007016735A1; NZ565873A

Abstract

A storage rack beam includes top and bottom flanges and at least one web that interconnects the flanges. The web includes at least one stiffening formation arranged to stiffen an intermediate region of the web along at least a substantial portion of its length so as to resist lateral loading applied to the beam. The racking beam may take various forms, including first and second U-shaped sections in opposed abutting relationship, or formed as a closed S-shaped profile. Also disclosed is a storage rack beam that has a vertical loading capacity and a horizontal loading capacity, wherein at least part of the horizontal loading capacity is independent of the vertical loading capacity applied to the beam.

Description

FIELD OF THE INVENTION

The present invention relates generally to storage racking systems and more particularly to racking beams used in such systems.

BACKGROUND OF THE INVENTION

Storage racking systems are widely used in warehousing and other industrial facilities. These systems typically include multiple levels of metal racking beams arranged to support cartons or pallets and which are supported by vertical load bearing members commonly referred to as uprights. These uprights are typically made from a profiled steel section and metal bracing is provided which extends between adjacent uprights.
The racks are usually arranged in straight rows with aisles formed between those rows that allow access to the stock. To make the most efficient use of the available space, these aisles are made as narrow as possible. As such, there is an ongoing risk of damage to the racking system from handling equipment such as forklifts or the like in view of the confined spaces in which the handling equipment operate.

SUMMARY OF THE INVENTION

In a first aspect, the present invention provides a racking beam comprising top and bottom flanges, at least one web interconnecting the flanges, and at least one stiffening formation arranged to stiffen an intermediate region of the at least one web along at least a substantial portion of its length so as to resist lateral loading applied to the racking beam.
In accordance with this aspect of the invention, a racking beam is provided which has enhanced lateral loading capacity. This capacity is ideally suited to resist frontal impact on the racking beams which would otherwise cause beam damage. Whilst such frontal impact may not compromise the safety of a beam, a damaged appearance to the beam looks both unsightly and often causes concern amongst operators and managers.
Racking beams are susceptible to lateral impact typically by damage from forklifts or the like operating in the confined spaces provided in the aisles or by stocking procedures where operators use the racking beam to assist in locating the stock in place, typically by lowering a pallet onto the beam prematurely and then pushing the load until the bottom front board of the pallet hits the beam.
The at least one stiffening formation is located in an intermediate region of the web. This has particular advantages as it not only stiffens a region of the racking beam which is most susceptible to failure under lateral load, but moreover it provides a condition where part of the capacity of the beam to resist lateral loading is independent of the vertical loading applied to the beam.
In a further aspect, the invention relates to a racking beam that has a vertical loading capacity and a horizontal loading capacity, wherein at least part of the horizontal loading capacity is independent of the vertical loading capacity applied to the beam.
In one form, at least 20% of the horizontal loading capacity is independent of the vertical loading capacity.
In one form, the racking beam is formed as a hollow section, having two spaced apart webs interconnecting the flanges. In this form, the at least one stiffening formation is arranged to stiffen at least one of the webs. In use, these webs typically form the front and back faces of the racking beam. In an arrangement where only one of the webs include a stiffening formation, typically the stiffening formation is formed on the front web.
In a particular form, one or more stiffening formations is arranged to stiffen both the webs.
In one form, the racking beam is formed from first and second members that are disposed one on top of the other and are joined together. In a particular form, the at least one web of the racking beam comprises a first part formed from the first member and a second part formed from the second member and wherein the at least one stiffening formation is formed at the joint between the first and second members.
In a particular form, the two members are joined by one or more conventional stitch welds or a continuous laser weld.
In one form, the racking beam is formed from first and second U shaped sections, each section having a flange, first and second webs projecting from the flange, inwardly extending lips at the distal end of the respective webs, and a lip return disposed at a distal end of the lips. With this configuration, the two U shaped sections are in opposed abutting relationship with the flanges of the sections forming respectively the top and bottom flanges of the racking beam and respective ones of the webs of the sections being aligned so as to form the first and second webs of the beam.
With this arrangement, the lips of the webs of the respective sections form respective stiffening formations of the racking beam which are disposed intermediate the top and bottom flanges.
In another form, the at least one stiffening formation is in the form of a diaphragm which connects the spaced apart webs.
In one form, the racking beam is formed from a rectangular or square hollow section and a U section as described above. In this form the respective lips of the U section are disposed in abutment with one side of the hollow section, which side forms the diaphragm of the racking beam.
In another form, the racking beam is formed from sheet material which is configured generally as a closed S shape which thereby forms two generally square or rectangular hollow sections that share a common wall that in turn forms the diaphragm of the racking beam.
In yet a further form, the at least one stiffening formation is in the form of a dimple or rib of sufficient depth in the web to provide adequate stiffening.
In general, the at least one stiffening formation may be continuous along at least a substantial portion of the length of the beam, or may be formed from a plurality of shorter lengths that function in a similar manner as a continuous stiffening formation.
In general, the racking beam according to embodiments of the invention allows for stiffening of one or more webs in the beam. Typically this stiffening may be positioned anywhere in an intermediate region of the web, from 20% of the depth down to 80% to the depth, but is preferably located just above the neutral axis at approximately 40-45% of the depth.
In a particular form, the stiffness is sufficient so that the web does not suffer from local buckling, but instead is able to realise the full yield capacity of the material. At a particular level of stiffness depending on the dimensions of the web, the web will change from behaving as a single plate element supported by the top and bottom flanges, to behaving as two separate plate elements both supported by the stiffening formation and one of the flanges. In this latter case, since the buckling half wave length decreases in direct proportion to the reduced width of each plate element, namely by a factor of two, the buckling strength of the total plate assembly will increase by a factor of approximately four, and generally yielding rather than buckling will become the determining factor. Rather than an abrupt change in behaviour, this transition may occur more gradually, as the effectiveness of the stiffening formation increases, and produce an intermediate partially stiffened buckling response.
A further advantage of adding the stiffening formation near the neutral axis of the beam, is that the stiffener is relatively unstressed due to vertical load and is thus able to fully contribute to the horizontal resistance of the beam, irrespective of the level of vertical loading.
The beam is typically made from metal such as aluminium, titanium, stainless steel or normal steel. Stainless steel may find niche applications in clean room or pharmaceutical environments but the most common commercial use is typically normal steel. Whilst titanium could be used it is anticipated to have limited application because of the expense of the metal. The beam is ideally suited for thinner materials and typically the gauge of the metal is from between 1.2 mm to 2.5 mm. In addition to using metals, the beam could be applied to a range of other materials such as plastics or composites.
In one form the beam is formed from sheet metal which may be roll formed into its final shape. If the beam is formed from metal such as aluminium or plastic, the beam may be formed using an extrusion process instead of a roll forming process.
As will be appreciated, frontal impact as indicated above, often occurs when the beams are already heavily loaded with pallets and that the applied horizontal loading may have a dynamic opponent. The racking beam according to embodiments of the invention is able to cater for the combined vertical and horizontal load conditions as well as the potential for localised damage from dynamic point loading.

BRIEF DESCRIPTION OF THE DRAWINGS

It is convenient to hereinafter describe embodiments of the present invention with reference to the accompanying drawings. It is to be appreciated however that the particularity of the drawings and the related description is to be understood as not limiting the preceding broad description of the invention.

In the drawings:

FIG. 1 is a front schematic view of a storage racking system;

FIG. 2 is an isometric view of a first embodiment of a racking beam for use in the racking system of FIG. 1;

FIG. 3 is an elevation view of the racking beam of FIG. 2;

FIG. 4 is a plan view of the racking beam of FIG. 2;

FIG. 5 is a sectional view of along the section line A of FIG. 3;

FIG. 6 is an isometric view of a second embodiment of racking beam for the racking system of FIG. 1;

FIG. 7 is a cross sectional view of the racking beam of FIG. 6;

FIG. 8 is an isometric view of the third embodiment of a racking beam for the racking system of FIG. 1;

FIG. 9 is a cross sectional view of the racking beam of FIG. 8.

FIG. 10 is an interaction graph illustrating horizontal and vertical loading capacity for 1.6 mm thickness beams;

FIG. 11 is an interaction graph illustrating horizontal and vertical loading for 2.0 mm thickness beams; and

FIG. 12 is a graph of horizontal deformation and the reciprocal of available moment capacity for various beams.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 illustrates a storage racking system 100 that includes multiple levels 101, 102 of metal racking beams 10 which support cartons or pallets 103 that are supported by vertical members 104 that are commonly referred to as uprights. These uprights are typically made from a profiled steel section and metal bracing (not shown) is provided which extends between adjacent uprights 104. The metal racking beams 10 include connectors 11 at opposite ends which connect the beams to the adjacent uprights 104.
A first embodiment of the racking beam 10 is disclosed with reference to FIGS. 2 to 5. The beam comprises top and bottom flanges (12 and 13) which are interconnected by webs 14, 15. The racking beam is generally rectangular in cross section and further incorporates stiffening formations 16 which are disposed in an intermediate region of respective ones of the webs 14, 15. These stiffening formations are designed to stiffen the intermediate region of the webs 14, 15 along its length so as to improve the beam's resistance to lateral loading applied to the racking beam 10. Such lateral loading may be caused by frontal impact of the racking beams from forklifts or the like operating in the confined spaces provided in the aisles of the storage racks 100.
In the illustrated form, the beam is made from steel strip having a gauge of between 1.2 mm to 2.5 mm. However, it is to be appreciated that beam 10 may be made from other metal such as aluminium, titanium or stainless steel which may be formed from strip which is roll formed or could be formed using an extrusion process. The beam also could be made from other non-metallic materials such as plastic or composite structures.
As best illustrated in FIG. 5, the racking beam 10 is formed from first and second U shaped members 20, 21. These members 20, 21 are disposed one on top of the other in opposing relationship with the bottom member 21 being equal to or slightly larger than the top member 20.
Each member 20, 21 includes a flange 22, 23 and webs 24, 25, 26 and 27 which project from the respective flanges 22, 23. The members 20, 21 also include inwardly directed lips 28, 29, 30 and 31 disposed at the distal end of the respective webs and lip returns 32, 33, 34 and 35 which extend from the respective lips.
The members 20, 21 are joined so that respective ones of the lips 28, 29, 30 and 31 are in abutting relationship. The members are typically welded together along this joint by either conventional stitch welding or a continuous laser welding process.
Through this construction, the stiffening formations 16 are formed by the interconnecting lips and lip returns. Furthermore, in the embodiment shown the respective webs 14 and 15 of the racking beam are formed by the respective webs 24, 25, 26 and 27 of the members 20, 21.
FIGS. 6 and 7 illustrate a second embodiment 40 of the racking beam. The racking beam 40 includes many of the features of the first racking beam and like features have been given like reference numerals.
In a construction which is similar to the earlier embodiment the racking beam 40 is formed from first and second members 41 and 42 which are disposed one on top of the other. Further, the bottom member is a U shaped member as in the racking beam 10. However, in contrast to the earlier embodiment, the top member is in the form of a square or rectangular hollow section and the stiffening formation 16 is in the form of a diaphragm 43 which extends across an intermediate region of the racking beam 40 thereby interconnecting the opposite beam webs 14, 15.
FIGS. 8 and 9 illustrate yet a further form of racking beam 50. The racking beam 50 incorporates many of the features of the earlier embodiments and like reference numerals have been given to like features.
In the embodiment shown in FIGS. 8 and 9 the configuration of the racking beam 50 is similar to that shown in FIGS. 6 and 7 with the stiffening formation 16 incorporating a diaphragm 51 that extends between the opposite webs 14 and 15 at an intermediate portion of those webs. However in the racking beam 50, the beam is not constructed from two sections but rather is formed from a single metal sheet which is folded into a closed S shape. As best illustrated in FIG. 9, the sheet from which the racking beam 50 is formed incorporates opposite longitudinal edge margins 52 and 53 which are folded over so as to abut an intermediate region of the sheet which forms the diaphragm 51. Typically these edge margins 52 and 53 are joined to the intermediate region 51 by means of a continuous laser or a conventional stitch welding process.
An advantage of the racking beams 10, 40 or 50 is that they have improved capacity to resist the lateral impact which may occur from forklifts or the like operating in the confined spaces. Further, the stiffening formations 16, in their various forms, are located in an intermediate region in the web. This has particular advantage as it not only stiffens a region of the racking beam which is most susceptible to failure under lateral load, but moreover it provides a condition where a significant part of the capacity of the beam to resist lateral loading is largely independent of the vertical loading applied to the beam.
Typically under static loading behaviour, the bending due to vertical load on the racking beam causes a linear stress gradient from compression in the top flange 12 through zero stress at the neutral axis to tension in the bottom flange 13. If the beam is heavily loaded, both the top and bottom flanges may be fully stressed due to the vertical load and may not have any excess capacity to contribute to the beam's resistance of horizontal loads.
Under horizontal loading, such as by lateral impact, the bending due to horizontal load causes a linear stress gradient from compression in say the front face i.e. web 14 through zero stress at the neutral axis to tension in the rear face 15. If the beam is already carrying heavy vertical loads, the horizontal resistance may need to derive primarily from the webs 14 and 15. In prior art arrangements, these webs were not stiffened and as such these webs behave as a long plate element under axial compression supported by its edges, for which the typical failure mode is local buckling with a half wave length similar to the width of the plate element.
By incorporating the stiffening formations 16 in the webs, the webs may change from behaving as a single plate element supported by the top and bottom flanges of the beam, to behaving as two separate plate elements, both supported by the central stiffener and one of the flanges. In this latter case, since the buckling half wave length decreases in direct proportion to the reduced width of each plate element, namely by a factor of two, the buckling strength of the total plate assembly will increase by a factor of approximately four, and yielding rather than buckling will become the determining factor. A further benefit of adding the stiffener near the neutral axis of the beam is that the material is relatively unstressed due to vertical load and is thus able to fully contribute to the horizontal resistance of the beam, irrespective of the level of vertical loading.
FIGS. 10 and 11 are interaction graphs illustrating the relationship between the vertical loading capacity and horizontal loading capacity of beams according to the above embodiment (the “S” and “UU” type beams as compared to a RHS).
FIG. 10 illustrates loading capacity for beams having 1.6 mm thickness whereas the graph in FIG. 11 is for a 2 mm case.
In these graphs the vertical axis represents the vertical loading whereas the horizontal axis illustrates lateral or horizontal loading. In the case of the vertical axis, 100% of the vertical loading capacity is represented by 1.0. As will be appreciated from these graphs the incorporation of the stiffening formations effectively increases the total horizontal loading capacity by 50% for the 1.6 mm case, and 30% for the 2.0 mm case. This is represented by a horizontal shift of the graph line along the horizontal axis.
As a result of this shift, for the case where the vertical beam is under 90% of loading, the “RHS” has only approximately 10% horizontal capacity whereas the “S” and “UU” beams have approximately 40% capacity in the 2.0 mm case, and 60% capacity in the 1.6 mm case. Furthermore, as can be appreciated from these graphs there is a minimum horizontal loading capacity created in the “S” and “UU” beams which is independent of the vertical loading capacity.

Example

Background

In order to validate the biaxial bending behaviour presented in the interaction diagrams of FIGS. 10 and 11, frontal impact tests were conducted for two RHS beams and one UU beam.
Each beam of standard length 2590 mm was loaded with the equivalent of 1000 kg pallets, which equates to an applied vertical moment M_xat mid-span of 3.29 kN·m. A pendulum weight was used to simulate the impact of a 3000 kg forklift at 2 km/h and the permanent horizontal deformation δ_ywas measured.

Results

The horizontal and vertical bending capacities, M_sxand M_sy, of each beam were calculated using recognised methods of cold-formed steel design. These values, together with the applied vertical moment, were then applied to the appropriate interaction line from the biaxial bending diagram shown in FIG. 11, in order to determine the horizontal bending moment capacity M_yavailable to resist frontal impact. The results are summarised in the following table.


	M_sx	M_sy	M_x	M_y	δ_y
Beam type	(kN · m)	(kN · m)	(kN · m)	(kN · m)	(mm)

100 × 50 × 2.0 RHS	5.24	3.00	3.29	1.12	18
100 × 50 × 3.0 RHS	7.31	4.98	3.29	2.74	8
110 × 50 × 2.0 UU	6.73	4.87	3.29	3.04	6

It is to be expected that there would be an inverse relationship between the available horizontal bending moment capacity M_yand the permanent horizontal deformation δ_y, namely that the greater the moment resistance the lower the expected permanent deformation. FIG. 12 shows a graph of the permanent deformation plotted against the reciprocal of the available moment capacity, which indicates that there is an inverse relationship and therefore provides supporting evidence for the general concepts and theory presented.
In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.
Finally, it is to be appreciated that various alterations or additions may be made to the parts previously described without departing from the spirit or ambit of the present invention.

Claims

1. A racking beam having vertical loading as its primary loading condition and comprising top and bottom flanges, at least one web interconnecting the flanges, and at least one stiffening formation arranged to stiffen an intermediate region of the at least one web along at least a substantial portion of its length such that the at least one stiffening formation enables the racking beam to provide resistance to lateral impact loading at any level of primary loading up to the full vertical loading capacity of the beam.

2. A racking beam that has a vertical loading capacity as its primary loading condition and a horizontal loading capacity, wherein at least part of the horizontal loading capacity is independent of the level of vertical loading applied to the beam so that the racking beam can still provide resistance to horizontal impact loading whilst the beam is supporting its full vertical load.

3. The racking beam according to claim 2, wherein at least 20% of the horizontal loading capacity is independent of the vertical loading capacity loading applied to the beam.

4. The racking beam according to claim, wherein the racking beam comprises top and bottom flanges, at least one web interconnecting the flanges, and at least one stiffening formation operative to stiffen an intermediate region of the at least one web along at least a substantial portion of its length.

5. The racking beam according to claim 4, wherein the racking beam is formed as a hollow section having two spaced apart webs interconnecting the flanges, the at least one stiffening formation being arranged to stiffen at least one of the webs.

6. The racking beam according to claim 4, wherein the one or more stiffening formations is arranged to stiffen both the webs.

7. The racking beam according to claim 4, wherein the racking beam is formed from first and second members that are disposed one on top of the other and are joined together, the at least one web of the racking beam comprising a first part formed from the first member and a second part formed from the second member, and wherein the at least one stiffening formation is formed at the joint between the first and second members.

8. The racking beam according to claim 7, wherein the two members are joined by one or more stitch welds or a continuous laser weld.

9. The racking beam according to claim, wherein the first and second members are U sections, each section having a flange, first and second webs projecting from the flange, inwardly extending lips at the distal end of the respective webs, and a lip return disposed at a distal end of the lips, and wherein the two U sections are in opposed abutting relationship with the flanges of the sections forming respectively the top and bottom flanges of the racking beam, and respective ones of the webs of the sections being aligned so as to form the first and second webs of the beam.

10. The racking beam according to claim 9, wherein the lips of the webs of the respective sections form respective stiffening formations of the racking beam which are disposed intermediate the top and bottom flanges.

11. The racking beam according to claim 5, wherein the at least one stiffening formation is in the form of a diaphragm which interconnects the spaced apart webs.

12. The racking beam according to claim 11, wherein the racking beam is formed from first and second members that are disposed one on top of the other and are joined together, the at least one web of the racking beam comprising a first part formed from the first member and a second part formed from the second member, and wherein the at least one stiffening formation is formed at the joint between the first and second members and wherein the first member is in the form of a rectangular or square hollow section, and the second member is in the form of a U section having a flange, including first and second webs projecting from the flange, inwardly extending lips at the distal ends of the respective webs, and a lip return disposed at a distal end of the lips, and wherein the respective lips of the U section being disposed in abutment with one side of the hollow section, which side forms the diaphragm of the racking beam.

13. The racking beam according to claim 11, wherein the racking beam is configured generally as a closed S shape having two generally square or rectangular hollow sections that share a common wall, with the common wall in turn forming the diaphragm of the racking beam.

14. The racking beam according to claim 4, wherein the at least one stiffening formation is in the form of a dimple or rib of sufficient depth in the web to provide adequate stiffening.

15. The racking beam according to claim 4, wherein the at least one stiffening formation is continuous along at least a substantial portion of the length of the beam.

16. The racking beam according to claim 4, wherein the stiffening formation is formed from a plurality of sections that function in a similar manner as a continuous stiffening formation.

17. The racking beam according to claim 4, wherein the at least one stiffening formation is positioned from 20% of the beam depth down to 80% of the depth of the web.

18. The racking beam according to claim 17, wherein the at least one stiffening formation is positioned approximately 40% to 45% of the beam depth.

19. The racking beam according to claim 4, when made from metal.

20. The racking beam according to claim 19, wherein the metal is steel.

21. The racking beam according to claim 20, wherein the gauge of the steel is between 1.2 mm to 2.5 mm.