This invention relates generally to beam assemblies for use in structural support applications.
Structural beams are typically made of steel or wood. Each has its advantages and disadvantages. Composite plastics material has been used for railroad beam applications but likewise has its limitations.
While wood is readily available and relatively inexpensive, it has attributes which make it less than an ideal material for use in exterior beam applications. Woods beams are known to have inconsistent performance over their life span even when used under the best conditions. The wood in a new beam will continue to season and shrink over time. The environment also has a tremendous impact on the performance and integrity of the wood. When exposed to wet conditions, the wood absorbs water and becomes water-logged and heavy. Soaked wood can lose as much as 2/3 of its beam strength which has a direct impact on the load-carrying capacity of the beam. Wood is further prone to fungus and insect attack, rotting and deterioration, especially in extremely harsh, wet applications, greatly limiting the useful service life and safe utilization of wooden beams. Even extreme dry conditions present a problem of embrittlement and dry rot for wood. Wood can be quickly eroded under the load and abuse of heavy equipment, especially tracked vehicles, the caterpillar tracks of which are prone to digging into wood beams and gouging and shredding the wood fiber if exposed. Such wear and tear on exposed wood beams is greatly magnified in wet operating conditions and serves to thin the beams and create crack-initiation risers at the surface which further compromise the integrity load-carrying capacity of wood beams under heavy load.
Wood used in beam applications is sometimes treated with chemicals to help preserve the wood in wet conditions. Wood will also soak up any oil and other chemicals that it may come into contact with at a construction site. Some of these chemicals are toxic to the environment and can be leached back into the soil.
A composite beam assembly constructed according to one preferred embodiment of the invention comprises at least one beam member fabricated of plastics-based composite material and at least one flitch plate which may be fabricated of steel or other similarly performing material such as glass fiber reinforced resin. The at least one beam member and flitch plate are secured tightly together and the combination enhances the overall structural rigidity and beam strength of the beam assembly beyond what the at least one composite beam and flitch plate alone or in combination would provide in a disassembled state. The flitch plate has a longitudinal length and has top and bottom surfaces defining a height therebetween and first and second side surfaces defining a width therebetween. The composite beam assembly further comprises a rod extending laterally through holes formed in the flitch plate and beam. The rod compresses the flitch plate and beam against each other in a lateral direction. The width of the beam is greater than the width of the flitch plate. The flitch plate is secured to the beam to provide additional stiffness to the beam. The hole in the flitch plate is in the form of a slot extending in the longitudinal direction to allow relative longitudinal movement between the flitch plate and the beam in response to longitudinal expansion and contraction of the beam.
The structural reinforced composite beam assembly constructed according to a preferred embodiment of the invention has the advantage of being lighter, stronger, longer lasting and consistent in performance during its extended lifecycle than timber beams for outdoor applications in particular and its plastics-based beam members do not shrink overtime. The beam assembly does not lose strength in prolonged wet conditions, nor does it absorb water, rot or otherwise deteriorate during use or exposure. The beam assembly can be pre-engineered to the strength and load requirements of a particular job and will maintain its properties throughout its service life, unlike a wood beam.
These and other features and advantages of the invention will be better understood when considered in connection with embodiments of the invention illustrated in the following figures and described in greater detail below:
A structural reinforced composite beam assembly constructed according to an embodiment of the invention is generally shown in perspective view in
The assembly 10 has a top surface 12, a bottom surface 14, longitudinally opposite ends 16 and laterally opposite sides 18. The beam assembly 10 has an overall length dimension Lbeam extending between the two ends 16, an overall width dimension Wbeam extending between the two sides 18, and an overall thickness Tbeam dimension extending between the top 12 and bottom 14 surfaces.
The assembly 10 illustrated in
The beam members 20 each have a thickness dimension Tb, a width dimension Wb, and a length dimension Lb.
The beam members are of a plastics (polymer) material, preferably a structural thermoplastic composite polymer. One such material suitable for the beams 20 is an HDPE-based proprietary structural composite plastic beam material available from Axion Structural Innovations, of Zanesville, Ohio. Such plastics material comprises a blend of polypropylene and polyethylene (PP:PE) , but predominately polyethylene with 5-50% glass fiber reinforcement, and more preferably 5-25% glass fiber reinforcement. Other HDPE-based plastics materials may also be suitable depending upon the structural load requirements of a particular application, as well as plastics materials in general provided they are able to meet the load and strength and environmental requirements that a particular application may call for. It is thus to be understood that the invention contemplates the usage of a variety of plastics materials and plastic based composite material systems as the beam 20 material, particularly when coupled with the structural, load-enhancing flitch plate 22 to be explained in more detail below. The idea is that the composite plastics beams 20 and metallic flitch plate(s) 22 work in synergy to collectively provide a lightweight, strong and water/chemical resistant beam assembly suitably reinforced by the flitch plate(s) 22 to yield the strength and rigidity required of a particular job application for which the assembly 10 is to be used. The flitch plate(s) 22 thus open up the possibilities for the types of candidate plastics materials beyond what may be otherwise suitable for beam application on their own without the flitch plates. For example, plastics materials that on their own may not possess the strength or rigidity required for use on their own as beams 20 may well become suitable when paired with one or more flitch plates 22, such that the overall structure is able to meet the requirements of an application.
The dimensions of the individual beams 20 may vary depending upon the requirements of a particular application and the material used for the beams. For example, the beam 20 may have a thickness Tb x width Wb x length Lb of, respectively, 22.86 cm x 17.78 cm x 7.34 m (9 inches x 7 inches x 24 feet). As will be explained below, the beam 20 may be turned on edge such that the TxWxL dimensions are now 17.78 cm x 22.86 cm x 6.10 m (7" x 9" x 20') as in the embodiment of
The flitch plate(s) 22 is preferably fabricated of metal and preferably steel. The grade of steel may be ASTM A36. The flitch plate(s) 22 each have a thickness dimension Tflitch, a width dimension Wflitch, and a length dimension Lflitch. For the 7.34 m (24 foot) beam 20 above with a 22.86 cm (9") thickness, the T, W and L dimensions of the flitch plates 22 are, for example, 21.59 cm x 1.27 cm x 7.32 m (8.5 inches x 0.5 inches x 288 inches). For the 17.78cm (7") beam thickness embodiment of
As illustrated in
It will be seen by a comparison of the dimensions that the flitch plates 22 are considerably narrower in width than that of the beams 20, and are slightly smaller in thickness (vertical height) and length than that of the beams 20. Preferably, at least the top edge of the flitch plates 22 is recessed below the top surface 12 of the beams 20. The invention does contemplate having one or more portions of the flitch plate projecting outwardly beyond a surface of the beams and such projecting feature (such as an ear) may function as an anchor point, a tie or strapping point for lifting or moving the mat, for example or securing the mat to something or something to the mat. The ear could also serve as a interconnection feature that may cooperate with a similar feature on an adjacent mat for linking the mats together with, for example, a rod extended through aligned openings on the ears. Recessing the flitch plates 22 below the surface of the beams 20 serves to keep the flitch plates 22 out of direct contact with equipment that may be moved against 10, or out of direct contact with additional structure to which the assembly 10 is mounted. For example, if the beam assembly 10 is used in a construction environment, for instance as support structure for building, adjacent structure may be kept out of contact with the flitch plate 22, protecting each from unnecessary wear or damage. The recessing of the flitch plate(s) 22 may also serve as a wear indicator of the beams 20, such that when the flitch plates 22 become exposed the users know it is time to replace the worn beams 20. And even if the flitch plates 22 do become exposed to the surface, the structural integrity of the assembly 10 remains intact. It may be desirable to recess the flitch plate(s) 22 from both the top 12 and bottom 14, especially if the assembly 10 is to be reversible in nature such that both surfaces may be at times facing upward and directly engaged by other structure, vehicles, or the like.
Another reason to recess the flitch plate(s) 22 from the bottom 14 as well is to keep the plates 22 from engaging the surface of adjacent structure on which the beam assemblies 10 are supported, especially if there is concern of damage that may be caused by direct exposure to metal edges of the flitch plate(s) 22. The length and width of the flitch plates 22 is at least 90% that of the length and width of beams 10 and with the edge surfaces of the flitch plates 22 preferably being recessed below the exposed top, bottom and end surfaces of the beams 20. Beams 20 may also display surprising surface durability and toughness, exhibiting a lack of chipping when exposed to other metal structure. These properties of the beams 20 may extend the useful life of protecting the flitch plates 22 in the assembly 10.
As illustrated in farther detail in
With reference to
While in accordance with the invention the flitch plate 22 and the beam 20 are described above as being fixed to each other via the use of the rods 24 to create a frictional engagement therebetween, the flitch plate 22 and beam 20 may be secured to each other in other ways which are not part of the invention. For example, the flitch plate 22 may be secured to the beam via the use of adhesives, bonding, welding, or brazing. In another approach, a screw may be threaded into one or more beams 20 to secure the beams 20 and the flitch plate 22. In yet another approach, a nut/bolt mechanism may be used, in which at least one nut is threaded over the end of a bolt extending through the beams 20 and flitch plate 22.
In yet another approach which is not part of the invention, shown in
The flitch plate(s) 22 may be fabricated from steel plate stock or other similarly performing material, such as fiberglass, of suitable dimensions, examples which are provided above.
The flitch plate(s) 22 may have smooth sides or may, alternatively, have grip-enhancing features, such as knurling or other textured features 30, along some or all of the side surfaces, as shown in
Additionally, or alternatively, the flitch plates 22 may include other grip enhancing features. For example, the flitch plates may include projections 40 that extend outward from the surfaces of the flitch plates 22, as shown in
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In each of the above described alternatives, the previously described features of the flitch plates 22 will also apply to the alternatives, such as the slots 28 and the surface feature 30.
The compressive strength of the composite beams greatly exceeds that of it wood counterparts. A surprising synergistic effect is realized when the high compression composite beams are paired with the flitch plates in the form of a beam assembly, wherein the bending load of the assembled assembly exceeds that of the collective load capacity of the beams and flitch plates alone. The high compression beams act to laterally support the flitch plates under bending load against beyond what would normally cause the flitch plate material to become wavy and buckle. Surprising levels of loading without failure are realized by the composite beam assembly described above Rather than buckling under extreme loads, the metallic flitch plate(s) will undergo a slight plastic deformation (stretching/thickening) of the opposing compressed and tensed edges of the flitch plates.
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It will be appreciated that further arrangements and quantities of beams 20 and flitch plates 22 may be used, including instances in which the lateral stackup of parts alternates between flitch plate and beam, or arrangements in which the lateral stackup has multiple flitch plates and/or beams adjacent each other and without the disposition of the other type of part therebetween.
Sometimes preservatives such as creosote, chromated copper arsenate (CCA), ammoniacal copper zinc arsenate (ACZA) and ammoniacal copper arsenate (ACA) are used to treat wood timbers to protect against rot, and these materials may leach out of the lumber and into the environment. This does not happen with the assembly 10 made in accordance with the invention since its composite beams are not prone to moisture attack, do not require any chemical treatment, and do not absorb water or chemicals. The assembly 10 according to the invention remains inert and unchanged by the environment they occupy.
The beam assembly 10 may have further plating applied to the surface and/or ends and may further have coating applied to its surface(s) such as polymer coatings.
It is to be understood that the above drawings and description is exemplary of the construction and practice of embodiments of the invention and is not limiting of the invention. Rather, the invention is defined in the appended claims which follow.
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.