Abstract:
An apparatus for permanently securing a grating sheet having parallel and transverse bars that form a pattern of openings to a structural member. The apparatus includes an elongated generally L-shaped connector having an upper plate section generally rectangular in shape for mounting on an upper surface of the grating sheet and a downwardly extending sidewall formed integrally with the plate section and adapted to extend along a longitudinal edge of the grating sheet. The L-shaped connector also can include a plurality of downwardly extending teeth formed integrally with the plate section and spaced apart from each other for insertion in between the grating bars. At least one generally right-angled brace is attached to the outer surface of the sidewall for permanently securing the L-shaped connector to the structural member. The brace has an edge configured to conform to an outer surface of the structural member, wherein the apparatus is formed of corrosion resistant material and is able to withstand the forces of waves in a wave-zone portion of an offshore platform.

Description:
SPECIFICATION 
     1. Field of the invention 
     The present invention relates to a fastening system for securing a grating to a structural support member, and more particularly, to a fastener for permanently securing fiberglass gratings to a walkway or landing in the wave zone area of an offshore platform or other similar platforms located in chemical plants, docks, refineries and elsewhere, where the gratings are subjected to wave pressures exerted by storm wave action or other hydraulic forces. 
     2. Background of the Invention 
     Grating sheets or panels are used in a variety of applications such as in walkways on offshore platforms. Due to its structural strength, a metallic grating has typically been used to form the walking surface of a walkway. Metallic gratings are typically secured to its supporting steel members by tack-welding the grating to the supporting steel members at designated intervals. These “tack-welds,” or the weld affected areas require touch-up painting and it is these ouch-up areas that generally break down first, creating a corrosion cell. However, due to this corrosion caused by deterioration of the paint system, a metallic grating is often not desirable. Although the metallic grating is typically galvanized or painted, the paint eventually wears, chips or fades or otherwise succumbs to corrosion primarily at the weld-affected areas. Fabricating the grating out of a noncorrosive metal, such as stainless steel, is expensive and impractical for a large walkway. 
     For providing support, a typical walkway has longitudinal structural support members, most often pipe members, extending along the edge of the walkway and transverse members extending between and reinforcing the longitudinal structural support members. The grating is placed on top of these structural support members. As previously stated, metallic gratings are typically secured to the structural support members by tack-welding the grating to the transverse supports at every 3rd or 4th support and 6 inch intervals along the longitudinal members. 
     Currently, the solution to the above-discussed corrosion problem typically involves replacing the metallic grating with grating formed from a fiberglass material which is resistant to corrosion and furnishes firm support for the walkway. However, the fiberglass grating introduces additional problems, as the above-described system for mounting the metallic grating does not work when fiberglass grating is used. as the fiberglass grating cannot be welded. Placing the fiberglass grating on top of the structural support pipe members and securing it in place with clips, such as described in U.S. Pat. No. 5,118,147, does not firmly secure the grating in the offshore platform environment subjected to severe wave action. The circular motion of waves that constantly wash through the grating subjects it to multidirectional forces that eventually displaces the grating from the clips and the grating washes out. 
     Other prior art includes the use of flexible bands to secure the fiberglass grating to the underlying crossbar support members. However, the use of flexible bands require a worker to go beneath the grating to secure the grating to the supporting structure. Working beneath the grating can be quite hazardous in an offshore platform environment. Also. this system secures the grating vertically but not laterally and with constant wave action, lateral movement of the grating occurs which produces a “saw cutting” phenomenon that continues until the flexible bands saw through the grating. 
     It would be desirable to have a system for securing the fiberglass gratings to the support members of the platform that would not only be corrosion resistant but would also be able to withstand the forces of the waves in the wave-zone areas of the platform The “wave-zone” is the portion of an offshore structure that, in the event of a hurricane, typhoon or any other violent storm, could be under water as a wave passes through the platform. In a typical platform in the Gulf of Mexico the elevation of this potion of the platform could be as high as 40 to 50 feet above the mean low water level. When large waves pass through the platform, they exert extremely high horizontal and vertical pressures on the platform structure and any appurtenances such as the grating system. 
     It would further be desirable to have a fastening system for permanently securing fiberglass gratings to the support members of the platform that would not only be corrosion resistant but would also be able to withstand the forces of the waves in the wave-zone areas of the platform. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an apparatus for permanently securing a grating sheet having parallel and transverse bars that form a pattern of openings to a structural member. The present apparatus includes an elongated generally L-shaped connector having an upper plate section generally rectangular in shape for mounting on an upper surface of the grating sheet and a downwardly extending sidewall formed integrally with the plate section and adapted to extend along a longitudinal edge of the grating sheet. The L-shaped connector also can optionally include a plurality of downwardly extending teeth formed integrally with the plate section and spaced apart from each other for insertion in between the grating bars. At least one generally right-angled brace is attached to the outer surface of the sidewall for permanently securing the L-shaped connector to the structural member. The brace has an edge configured to conform to an outer surface of the structural member, wherein the improved apparatus is formed of corrosion resistant material and is able to withstand the forces of waves in a wave-zone portion of an offshore platform. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a section of an offshore platform or other walkway illustrating a removable fastening system; 
     FIG. 2 is a partial cross sectional view of an existing embodiment of an edge fastener illustrated in FIG.  1 . 
     FIG. 3 is a perspective view of a section of a permanent edge fastener of the subject invention; and 
     FIG. 4 is a cross sectional side view of the edge fastener of FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF INVENTION 
     This invention is related to the fastening systems described and claimed in U.S. Pat. Nos. 5,732,523 and 5,911,664, which are herein fully incorporated by reference. The fastening systems of these two patents are removable in that the fasteners can be unbolted and removed from the support members of a platform. A portion of a walkway of an offshore platform is shown in FIG.  1 . The walkway has a grating G supported by two underlying parallel. spaced structural support members  100  located and extending along each edge of the walkway. The walkway is reinforced by structural transverse members  102  which are welded to and extend between the structural support members  100 . Typically, these transverse members  102  are framed in to be flush on top with the support members  100 . 
     The grating G forming the walkway is formed from fiberglass in order to inhibit corrosion of the floor of the walkway by salt water. However, as can be appreciated, the grating G could also be made of metal or any other structural material. The grating G has bars  104  extending parallel to the structural support members  100  and crossbars  106  extending perpendicularly to the structural support members  100 . Thus. bars  104  and  106  form a uniform grid pattern having preferably uniform adjacent square or rectangular grid openings of  110 . 
     A removable edge fastener  10  secures the edge of the grating G to one of the structural support members  100  and plate fasteners  20  and  30  secure the grating G to the transverse members  102 . In a preferred embodiment. all of the fasteners  10 ,  10 A,  20 , and  30  are formed of steel such as stainless or carbon steel or any other corrosion resistant material. Depending upon the installment situation, the removable edge fasteners  10  can be used either alone or in combination with the plate fasteners  20  and/or  30 . 
     As illustrated in FIG.  2 . the removable edge fastener  10  is an elongated, generally L-shaped member that attaches to both the edge of the grating G and the support member  100 . The edge fastener  10  includes a rectangular upper plate section  200  with a rectangular sidewall  204  integral with the plate section  200 . The sidewall  204  extends downwardly from the plate section  200  along the edge of the grating G parallel to the support members  100 . In a preferred embodiment the height of the sidewall  204  is approximately equal to or slightly greater than the thickness of the grating G. 
     Plate section  200  laterally extends over the grating G from the edge of the grating G at preferably a distance greater than the spacing of one length of bar  104 . In one embodiment, a plurality of downwardly extending teeth or claws  202  can be located at the inner edge of the plate section  200 . opposite the sidewall  204 . In a preferred embodiment, the teeth or claws  202  are spaced such that each one of the claws  202  extends downwardly inside one grid opening  110  when the plate section  200  extends over the grating G. The edge fastener  10  securely clamps the grating G to the structural member  100  regardless of the direction of the wave forces. The combination of the plate section  200 , the sidewall  204  and the row of extending claws  202  forms a generally U-shaped edge fastener  10 . The claws  202  can be machined or welded or otherwise attached to the longitudinal plate section  200 . 
     Sidewall  204  of the removable edge fastener  10  is secured to the structural support member  100  through one or more rectangular tabs  216  which are welded to the supporting surface of the support member  100 . Each tab  216  is approximately the same height as the thickness of the grating G and includes a hole  218  through which bolts  206  secure the edge fastener  10  to the tab  216 . For each tab  216 , the sidewall  204  has an associated horizontal hole or slot  220  for receiving the bolt  206  therethrough and to facilitate positioning the edge fastener  10  along the support member  100 . 
     To secure the grating G to the support member  100 , each tab  216  is first welded to the upper surface of the structural support member  100  so as to extend upwardly and parallel to the axis of the support member  100  and edge of the grating G. Bolts  206  are then positioned such that each bolt  206  extends through the hole  218  of the tab  216 , and the grating G is set in place. Edge fastener  10  is placed over each corresponding tab  216  and protruding bolts  206  such that the surface of the sidewall  204  closest to the grating G abuts the tab  216 . The bolts  206  thus will extend through the corresponding horizontal slot  220  of the sidewall  204 . 
     The edge fastener  10  is adjusted longitudinally along support member  100  so that each one of the claws  202  extends downwardly inside one grid opening  110 . Bolts  206  are then tightened in place. A disk-shaped washer  212  is located between the nut  214  and the adjacent surface of the sidewall  204 . Utilizing the fastener system  10  of FIGS. 1-2, the edge fasteners  10  extend along each of the support members  100  and grip the edges of the grating G along the length of the generally rectangular edge fastener  10 . As can be appreciated, a worker can install the edge fastener  10  to the grating G without having to work beneath the support members  100  or the grating G. Likewise, to remove the edge fasteners  10 , the bolts  206  are simply removed from tabs  216  and the edge supports  10  and the gratings G are removed without having to work beneath the support members  100  or grating G. 
     There may be situations in which it is desirable to permanently secure the grating to the  30  structural support members of an offshore platform. Thus, the present invention is directed toa permanent edge fastener  10 A for permanently securing the edge of grating G to one of the structural support members  100 . As illustrated in FIGS. 3 and 4, the permanent edge fastener  10 A has generally the same structure as removable edge fastener  10 , including a rectangular upper plate section  200 A with a rectangular sidewall  204 A integral with the plate section  200 A. The sidewall  204 A extends downwardly from the plate section  200 A along the edge of the grating G parallel to the support members  100 . The height of the sidewall  204 A is approximately equal to or slightly greater than the thickness of the grating G in a preferred embodiment. 
     Sidewall  204 A of the edge support  10 A is permanently secured to the structural support member  100  through one or more generally right-angled braces  222  that are welded to an outside surface  224  of sidewall  204 A. Angled brace  222  has a first leg  226  that is attached to sidewall  204 A, preferably by welding, and a second leg  228 , that attaches to the supporting surface of the support member  100 . Edge  230  of second leg  228  has a curved radius that is configured to match the pipe diameter radius of the support member  100 . In a preferred embodiment, the inside portion of the brace  222  is a right-angle corner  231  that produces a gap between the angled brace  222  and support member  100 . However, any shape that produces a gap at the inside corner is contemplated. In a preferred embodiment, a portion of the outside light-angled corner  232  of brace  222  can be removed in order to eliminate the sharp outside corner edge. The width and height of brace  222  is dependent upon the size and/or diameter of the support member  100 . Preferably, the braces  222  are spaced a  12 ″ centers along the length of the sidewall  204 A. 
     In one embodiment, a plurality of downwardly extending teeth or claws  202  can be located at the inner edge of the plate section  200 A, opposite the sidewall  204 A. In a preferred embodiment, the teeth or claws  202  are spaced such that each one of the claws  202  extends downwardly inside one grid opening  110  when the plate section  200 A extends over the grating G. 
     To permanently secure the grating G to the support member  100 , the grating G is set in place and edge fasteners  10 A are positioned over the grating G such that they grip the edges of the grating G along the length of the generally rectangular edge fastener  10 A. Each angled brace  222  is then welded to the upper surface of the structural support member  100 . After welding is completed, the paint repair to the weld affected areas is performed. The curved radius edge  230  of the second leg  228  and the inside light-angled corner  231  allow for continuous seal welds between the braces  222  and support members  100 , which eliminate any corrosion. 
     The permanent edge fasteners  10 A of the present invention are generally used when it is desirable to install a long continuous walkway in which the grating panels or sheets are laid end-to-end, for example in a walkway with dimensions of 4 feet wide by 40 feet long. By example, four grating panels of 4 feet by 10 feet are laid end-to-end on top of the walkway support members and edge fasteners  10 A are installed along both sides of the walkway. In many instances, the plate fasteners  20  and  30  are also used in conjunction with the permanent edge fasteners  10 A. This is a preferred method of securing the fiberglass grating to the underlying support members in the wave zone areas of an offshore platform or other similar platforms where the gratings are subjected to wave pressures exerted by strong wave action of other hydraulic forces. 
     On offshore platforms large areas of grating are used to form a landing or base of a stair in which the grating panels are side-by-side rather than end-to-end. In this situation, the edge fasteners  10 A cannot be used because they extend above the surface of the grating and this would create a hazardous tripping situation. Instead plate fasteners  20  and  30  are used to install the grating panels by placing the plate fasteners  20  and  30  along the longitudinal sides of the grating panels. When properly tightened, plate fasteners  20  and  30  provide the vertical support necessary to resist vertical wave pressures, while providing some lateral support in order to resist horizontal wave pressures. The permanent edge fasteners  10 ,  10 A provide the necessary support in both lateral and horizontal directions. 
     One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. The inventive edge fasteners described herein are presently representative of the preferred embodiments, are exemplary and are not intended as limitations on the scope of the invention. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the claims.