AU643015B2 - Traffic grating - Google Patents

Description

1 This invention is concerned with improvements in grating construction and, in particular, to traffic grates.

In order to withstand the rigours of increasingly heavier vehicular traffic, both from the point of view of vehicle mass and traffic density, gratings for roadway drains have tended to become heavier in construction and thus more expensive to produce and more difficult to handle.

Furthermore, the competing requirements of improved drainage capacity, greater load capacity and durability, and 0 safety considerations have tended to lead to compromise in design and construction of such grates to the extent that 6 there are serious deficiencies in design from the point of e view of utility, cost and performance.

On the one hand, over-engineered grates comprising very heavy components are robust but very expensive in terms of materials cost, cost of galvanizing and the cost of transportation and handling. In addition, the use of heavy section components can restrict the drainage capacity of such grates.

On the other hand, less expensive grates utilising a lighter construction, while being less expensive to construct and handle, are frequently much less robust and are subject to damage thereby requiring frequent repairs or replacement to maintain adequate safety standards.

While many of the heavier grate constructions, notwithstanding their higher cost, are effective to handle increased vehicular traffic loads and frequency, nevertheless do not meet local government requirements relating to bicycle and pedestrian safety standards. Of more recent times, bicycle safety standards have required that in addition to spaced members extending in one direction, there should also be additional members extending transversely thereto at predetermined minimum distances to prevent damage to bicycle wheels or accidents arising as a result of bicycle wheels extending too far into the spaces between adjacent grating members. Furthermore, such transverse members are required to be adjacent the top surface of the grate structure.

The problems associated with prior art grating structures are now being exacerbated by a requirement for gratings of increased span to provide a greater drainage

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ooo capacity.

Hitherto, lightweight grating structures having a span of up to say 300 mm have been adequate with spaced parallel bars of 3 to 6 mm in thickness and from 30 to 40 mm in depth, spaced at about 15 to 20 mm intervals.

For greater spans up to about 600 mm it is usual to employ much heavier sections comprising spaced parallel bars of from about 10 mm to 20 mm in thickness and from 53 mm to Ocoe: about 75 mm in depth with spacings from about 40 mm to about 65 mm. To prevent intrusion of bicycle wheels and also to provide some lateral stability to the spaced bars, it is common to employ transverse rods of from 15 mm to 25 mm in diameter at about 100 mm spacings. These rods are usually located in the central region of the spaced load bearing bars.

Although lightweight section gratings have been used for spans up to about 600 mm, this has necessitated the use of closer spacings between adjacent bars to provide lcad capacity and the use of transverse bars or rods at or near the upper surface of the load bearing bars to provide bicycle safety.

More importantly however, the location of the transverse bars or rods must be near the upper surface of the load bearing bars to prevent deformation or twisting of the lightweight baxis under the influence of vehicular trcffic in order to maintain structural integrity.

With current requirements for a grating span of up *s 0" to 1 metre, the cost problems of scaling up a typical heavy

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grate construction or a typical light weight construction are greatly amplified.

Heavyweight gratings are readily engineered to cope with vehicular load requirements, safety stand rds, corrosion resistance and the like, the resultant costs attendant with significantly increased materials usage and corrosion resistant measures such as galvarizing are almost prohibitive.

Significantly however, the greatly increased mass of such gratings would require greatly increased physical labour and/or the use of heavy lifting equipment to install the grates and subsequently to remove the grate for maintenance of drainage channels thereunder.

It is considered that typical lightweight grating structures could not simply be scaled up to accommodate increased spans of up to 1 metre. By increasing the width and depth of the load bearing bars and decreasing the spacing therebetween load capacity may be increased. However to maintain safety standards and structural integrity, transverse 4 transverse bars of greater strength and decreased spacing must be provide near the upper surface of the load bearing bars. In turn this decreases the size of the grate openings and effective drainage efficiency of the grating.

It is an aim of the present invention to overcome or ameliorate the problems with prior art drainage grates for vehicular roadways and to provide an inexpensive yet effective grating structure.

In accordance with one aspect of the present invention there is provided a drainage grate for vehicular roadways, said grate comprising:a rectangular peripheral frame of steel bar stock; 15 a plurality fo spaced parallel load bearing members of steel bar stock extending between a pair of opposed sides of said frame; Sa plurality of parallel stabilising bars extending transversely to said load bearing members, 20 said stabilising bars being separately spaced adjacent :an upper lorngitudinal edge of said load bearing members to form a first array and separately spaced adjacent a lower longitudinal edge of said load bearing members to form a second array.

S o• Preferably said stabilising members of said first and second arrays are aligned in upright planes.

Alternatively said stabilising members of said first and second array are spaced in staggered relationship to each other.

Preferably said upper and lower stabilising members are located in apertures in said load bearing members.

Alternatively said upper and lower stabilising members are secured to respective upper and lower edges of said load bearing members.

Suitably, at least some of said load bearing members are attached at opposing ends thereof to said peripheral frame by fusion welding.

Prefeirbly at least some of said stabilising members are attached to said load bearing members by fusion welding.

Preferably said grate is coated with a corrosion 15 resistant coating.

Suitably said grate is coated by a corrosion resistant coating by a galvanising process after e fabrication.

gIn order that the invention may be more fully 20 understood, reference is now made to various preferred 0 *o embodiments illustrated in the accompanying drawings in which:- FIG 1 illustrates a partial perspective view of one aspect of the invention FIG 2 illustrates a side elevation of the embodiment of FIG 1 FIG 3 illustrates a plan view of the embodiment of FIGS 1 and 2.

FIG 4 illustrates a perspective view of one form of

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S S 6 a grate made in accordance with the invention.

FIG 5 illustrates an alternative form of the invention.

FIG 6 illustrates a partial view of an alternative form of the invention.

In FIG 1 the drainage grate for vehicular roadways comprises peripheral frame members 1, 2 with spaced load bearing members 3 comprised of steel bar stock similar to frame members 1, 2. Suitably, load bearirg members 3 are 0o secured by welding at opposed ends to frame member 1 and an "e opposite member (not shown).

Extending transversely of load bearing members 3 are

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e. upper and lower stabilising members 4 in the form of steel rods aligned one above the other in spaced pairs, each of the rods being located adjacent respective opposed longitudinal edges of members 3. Stabilising members 4 are located in apertures formed in load bearing members 3 and may be secured at each intersection or at least some of the intersections by Gee 0 fusion welding. The free ends 4a of stabilising members 4 are all preferably secured to respective frame member 2 and an opposing frame member (not shown) by fusion welding.

FIGS 2 and 3 respectively show a side elevation and a plan view of the grating structure of FIG 1.

FIGS 4 and 5 respectively show a square and rectangular configuration of a grate made in accordance with the invention.

Roadway gratings generally extend across a roadway with a minor axis extending in the direction of vehicular traffic. While conventional wisdom might dictate that the load bearing members extend in a direction parallel to the direction of vehicular traffic flow, FIG 4 shows the load bearing members 3 extending transversely to the direction of traffic flow. In this manner the question of bicycle safety is accommodated by the close spacing of the load bearing members 3 transverse to the normal direction of traffic flow.

In the event that a bicycle does travel across the grating in a direction parallel to load bearing members 3, safety requirements are met by the spacing of stabilising

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members 4 and the location of these members relatively close 64189 to the upper surface of the load bearing members 3.

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Immense load bearing capacity is conferred on the grating of FIGS 1 and 2 by the provision of dual stabilising members 4 located adjacent upper and lower surfaces of the load bearing members 3. In use, the normally upper stabilising member 4 acts as a safety device in preventing penetration of a bicycle wheel and simultaneously stabilises the load bearing members 3 against distortion and twisting which might act to seriously reduce the load bearing capacity see* of members 3. At the same time, the lower stabilising members 4 act in tension under load to confer a resistance to deflection under load in the same manner as a reinforcing tendon in a load bearing concrete beam.

While FIGS 2, 3, and 5 show a norma3ly preferred configuration for roadway drainage gratings in accordance with the invention, FIG 4 shows that the invention is equally applicable to the opposite configuration wherein the load bearing members 3 extend perpendicular to the direction of traffic flow and the stabilising members 4 extend transversely thereto for use where traffic direction is not constrained.

FIG 6 shows an alternative embodiment of the invention wherein the grating comprises peripheral frame members 5, 6 and load bearing members 7 secured in spaced parallel relationship at their respective ends to the frame member 5 and a frame member (not shown) opposite thereto.

Stabilising members 8 are secured to the upper and lower edges of load bearing members and opposite ends of peripheral frame by fusion welding. in the embodiment shown, the stabilising members 8 are twisted steel rods of rectangular cross section which are secured to load bearing members 7 by forge welding in a welding press (not shown).

The embodiment of FIG 6 is constructed in a similar manner to fabricated catwalks or suspended walkways except that an additional stabilising member is added to the lower 0* edges of normally longitudinally extending load bearing age members, thus substantially increasing the load bearing capacity of the structure whilst providing a structure capable of withstanding heavy vehicular traffic.

Suitably, gratings in accordance with the present invention are constructed from mild steel bar and rod stock and, after fabrication, are coated with a corrosion resistant coating by a hot dip galvanising process. Alternatively, the gratings are fabricated from pre-galvanised steel bar and/or rod stock.

Typically, a steel roadway drainage grating manufactured in accordance with the invention may be manufactured in any convenient length of up to about 6 metres and may have a width of, say, 750 to 1250 mm.

The peripheral frame members and the load bearing members may comprise steel strip having a rectangular cross section measuring from about 5 to 8 m'a i thickness and about to 75 mm in width. The load bearii: members may be spaced at intervals of from 20 to 40 mm.

The stabilising members typically may comprise steel 0* rod of circular cross-section of from between 8 to 14 mm in diameter and may be spaced at intervals of from 100 to 150 mm.

A particular advantage of the present invention it its reversible nature. Unlike prior art lightweight gratings which may be inadvertently installed upsi-de down with potentially disastrous consequences, the symmetrical nature of the structure avoids such a possibility.

0 It will be readily apparent to a skilled addressee 0 that many modifications and variations may be made to the invention without departing from the spirit and scope of the invention.

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Claims (9)

1. A drainage grate for vehicular roadways, said grate comprising:- a rectangular peripheral frame of steel bar stock; a plurality of spaced parallel load bearing members of steel bar stock extending between a pair of opposed sides of said frame; a plurality of parallel stabilising bars e> ing transversely to said load bearing members, said stabilising bars being separately spaced adjacent an upper longitudinal edge of said load bearing members to form a first array and separately spaced adjacent a lower longitudinal edge of said load bearing members to form a second array.

2. A drainage grate as claimed in claim 1 whtrein said stabilising bars comprising said first array and said stabilising bars comprising said second array are respectively aligned in upright planes.

3. A drainage grate as claimed in claim 1 or claim 2 wherein So. respective stabilising bars of said first and second arrays are spaced in staggered relationship relative to each other.

4. A drainage grate as claimed in any preceding claim

5. wherein said stabilising bars are located in apertures in said S load bearing members. A drainage grate as claimed in any one of claims 1-4 S wherein said stabilising bars are secured to opposing edges of said load bearing members.

6. A drainage grate as claimed in any preceding claim wherein at least some of said stabilising bars are attached at 11 respective opposing ends thereof to said peripheral frame.

7. A drainage grate as claimed in one of claims 1-4 or 6 wherein at least some of said stabilising bars are attached to said load bearing members at respective intersections by fusion welding.

8. A drainage grate as claimed in any preceding claim wherein a corrosion resistant coating is applied after fabrication of the grate.

9. A drainage crate substantially as hereinbefore described with reference to FIGS 1-5 or FIG 6 of the accompanying drawings. DATED this Twenty-sixth day of August 1993 MICHAEL GRAHAM RICHARDS By his Patent Attorneys FISHER KELLY S S.. 0 o ABSTRACT A lightweight roadway drainage grating comprises a rectangular peripheral frame of thin steel bar with spaced parallel load bearing members of thin steel bars extending between opposed sides of the peripheral frame. Spaced parallel stabilising members in the form of thin steel rods extend transversely to the load bearing members adjacent to upper and lower edges thereof to stabilise the load bearing members against distortion and to confer reinforcement against deflection under load. The structure is reversible. 0* e Be