Patent Application
20110036051
The present invention relates generally to static structures and, more particularly, to elongated rigid structures such as girders, columns, etc., having composite construction.
Homebuilders are confronted with significant challenges in offering high-quality products at competitive prices. Design trends, fluctuations in lumber costs, and financial unrest often prevent builders from obtaining a reasonable profit for their work. In response to marketplace uncertainties, steel-framed home construction is becoming increasingly popular.
Builders are attracted to the strength, termite resistance, and dimensional stability of steel. Steel materials being used in modern residential construction are also relatively lightweight and easy to handle. Therefore, homes with larger open spaces, longer ceiling spans and higher walls are possible.
Homes constructed with steel frames have proven to be more durable than those framed with wood. In areas vulnerable to hurricanes or earthquakes, they are better able to withstand forces generated by winds and shifting earth. Further, because steel is non-combustible, homes constructed from steel easily comply with local codes and fire regulations. Because it is termite proof, pesticide treatments are unnecessary. Thus, health experts recommend steel framing for chemically sensitive homebuyers seeking the best possible interior air quality.
Most residential steel framing is assembled using the “stick-built” construction method. Stick-built construction utilizing steel components is similar to that involving wood. Layout and assembly are the same except for one crucial difference, steel components are joined together with screws rather than nails. Powered screwdrivers make the turning of screws into steel framing members a snap.
It is my principal object to provide a girder that is stronger and lighter than known structural members, whether made of metal or wood, of similar dimensions. My new, reinforced girder can, therefore, carry greater loads and extend across longer spans than conventional girders and beams. My girder, therefore, can be used in buildings with few, if any, additional supports.
It is a further object of mine to provide a girder of the type described that is made of galvanized steel. Such a material is inherently resistant to corrosion and insect pests. It is also not combustible, making buildings constructed with my girders especially safe.
It is another object of mine to provide a girder that is easily trimmed in the field and installed in a building without resort to special tools or the need for prolonged training. The girder is cut to a desired length with common tools, like reciprocating or circular saws, with metal-cutting blades. Threaded fasteners, like self-tapping screws, are employed to fasten the girder to another structural member. No welding is required.
It is still a further object of mine to provide a girder that is “green,” environmentally friendly, and can be made from recycled materials. There are few uses for recycled wood in new building projects.
I wish to provide improved features and arrangements thereof in a reinforced girder for the purposes described which is lightweight in construction, inexpensive to manufacture, and fully dependable in use.
Briefly, my reinforced girder achieves the intended objects by featuring a pair of C-shaped channel members welded together to form a rectangular box. A pair of stringers is welded in a spaced-apart relationship into each of the C-shaped channel members. The stringers extend the lengths of the C-shaped channel members. A number of transverse connectors are welded in a spaced-apart relationship within each of the C-shaped channel members between the stringers. The transverse connectors are oriented parallel to one another and at right angles to the stringers to form a strong, load-bearing truss.
The foregoing and other objects, features, and advantages of my reinforced girder will become readily apparent upon further review of the following detailed description of the girder as illustrated in the accompanying drawings.
My invention can be more readily described with reference to the accompanying drawings, in which:
Similar reference characters denote corresponding features consistently throughout the accompanying drawings.
Referring now to the FIGS., a reinforced girder is shown at 10. Girder 10 includes a pair of C-shaped, channel members 12 affixed to one another so as to form an elongated, open-ended, rectangular box. Stringers 14, affixed within the corners of the channel members 12, internally reinforce the box. Transverse connectors 16 are affixed within the channel members 12 and join the stringers 14 together, effectively locking stringers 14 in place.
Channel members 12 are cold-formed by bending a thin strip of galvanized steel sheeting into a C-shape. As shown, channel members 12 include a pair of opposed end walls 18 affixed to, and extending at right angles from, an intermediate wall 20. Each channel member 12 also includes a pair of flanges 22 affixed to, and extending inwardly toward one another from, the free ends of end walls 18 in a common plane parallel to intermediate wall 20.
Channel members 12 are reinforced to better resist compressive, tensional, and torsional loads. In this regard, a pair of steel rods or stringers 14 is affixed, as by welding or brazing, within each of the corners where intermediate wall 20 and end walls 18 meet. Stringers 14 extend the length of members 12 which may be any desired length. At set distances from one another, transverse connectors as at 16 are affixed, as by welding or brazing, at their ends to stringers 14 and between their ends to intermediate wall 20. Connectors 16 are oriented at right angles to stringers 14 and, together with stringers 14, form a box truss.
Connectors 16 are formed of the same material as stringers 14. One suitable type of material is rebar commonly used in reinforced concrete structures. Rebar is usually formed from carbon steel and is given ridges for better mechanical anchoring. Since rebar has an expansion coefficient that is similar to that of channel members 12, no additional longitudinal and perpendicular stresses develop within girder 10 at varying temperatures during use.
Most rebar is suitable for welding and is available in different grades that permit a builder to pick rebar with the right strength and chemical composition for a given job. Common rebar is made of unfinished, tempered steel making it susceptible to rusting. Common rebar is available at low cost and is usable where dry conditions are expected throughout the life of girder 10. Galvanized or stainless steel rebars are, thus, employed as stringers 14 and connectors 16 in damp situations where corrosion of girder 10 is more likely to occur. Although galvanized and stainless steel has a greater initial expense, it can greatly increase the service life of girder 10.
After affixing stringers 14 and transverse connectors 16 within channel members 12, channel members 12 are affixed to one another. To do this, channel members 12 are positioned side by side with flanges 22 of one channel member 12 in contact with the flanges 22 of the other channel member 12. Then, channel members 12 are welded or brazed together along the area of contact. The step of affixing the channel members 12 together requires only a few minutes to complete and leaves girder 10 ready to use. Since the steps of affixing the stringers 14 and connectors 16 in the channel members 12 similarly require only a few minutes time, it will be appreciated that girder 10 is rapidly constructed.
The use of girder 10 is straightforward as it withstands loads primarily by resisting bending forces imparted by gravity. The bending force is usually the result of the external loads and its own weight. Girder 10 can also carry horizontal loads, i.e., loads due to an earthquake or wind. The loads carried by girder 10 are transferred to other girders, walls, columns, or beams, which then transfer the loads to adjacent, structural, compression members. In light frame construction, one girder 10 can rest on another girder 10 and can serve as a joist, beam, or column.
Internally, girder 10 experiences compressive, tensile, and shear stresses as a result of applied loads. Typically, under the influence of gravity, the original length of girder 10 is slightly reduced to enclose a smaller radius arc at the top of girder 10, resulting in compression, while the same original length at the bottom of girder 10 is slightly stretched to enclose a larger radius arc, and so is under tension. The original length of the middle of girder 10, halfway between the top and bottom, is the same as the radial arc of bending, and so it is under neither compression nor tension.
The compressive, tensile and shear stresses generated within girder 10 are shared by channel members 12, stringers 14, and connectors 16. Without stringers 14 and connectors 16, channel members 12, joined along abutting flanges 22 to form a box, do not offer great resistance to loads. With the addition of stringers 14 and connectors 16, channel members 12 carry great loads and can be employed to span long distances without support between their ends.
Girder 10, being hollow, is lighter in weight than its conventional, wood counterparts of similar load-bearing capability. Thus, building structures, incorporating airy architectural designs, can be constructed with relative ease and minimal cost. Transporting girder 10 to a construction site is relatively easy because of its lightweight. If girder 10 is too long for a particular application, it can be cut to length with conventional saws. Sheet metal screws (not shown) are employed to secure girders 10 to other building members, such as headers and footers when used in a wall. If the sheet metal used to form channel members 12 is thick, it may be necessary to drill pilot holes in channel members 12 before the screws will penetrate.
While girder 10 has been described with a high degree of particularity, it will be appreciated by those skilled in the art that modifications can be made to it. For example, the dimensions of channel members 12, stringers 14 and connectors 16 can be varied to accommodate expected loads with larger features generally being more appropriate for higher loads. Furthermore, the number of connectors 16 employed between stringers 14 can be increased to boost the stiffness of girder 10. A lightweight girder 10 can be made by placing a single connector 16 between the stringers 14 at the midpoint of each channel member 12. Finally, the diameter of rebar used in stringers 14 can be different from the diameter of rebar employed in connectors 16. The respective diameters can be selected to provide a balance of compressive, tensile, and shear stresses for a particular installation of girder 10. Therefore, it is to be understood that the present invention is not limited to girder 10, but encompasses any and all girders within the scope of the following claims.
