Strapping System and Method to Reinforce Framed Structures
A network of straps is placed over a framed structure and roof decking and secured to the foundation. A tensional force is applied to the straps. The tensioned straps are then secured at strap crossing points, the roof decking, roof structural members and wall structural members. The method also provides special treatment for straps crossing apex ridges or valleys of the structure's roof. Additional framing blocks are included under the roof decking to accommodate fastening the straps to the primary structural members. The runner straps pass through slits cut into roof decking near where the sidewalls attach to the roof joists and rafters. An added framing member or supporting structural device is also installed above the top plate of the stud wall to support the roof decking as tension is applied to the straps. The method calls for determining standard strap spacing based on the design resistance required to counter external forces that could be encountered at the construction location. The straps are placed on all sides at the standard spacing. Special adjustments to the spacing are made to accommodate larger than standard spacing door, garage, and framed openings. The number and configuration of straps is dependent on Building Codes and engineered design guidelines. By securing the strap network to the structure under tension, the strap network provides a distributed resistance force throughout the entire structure greatly enhancing its strength against external winds, internal vacuums, and earthquakes. Suitable straps can be fabricated from range of materials and composites such as metallic and non-metallic banding, a combination of non-metallic banding with wire reinforcement, wire mesh or wire rope.
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STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTN/A
BACKGROUND OF THE INVENTIONThe present invention relates to devices and methods for improving the resistance of a structure to lateral and vertical forces acting upon it. The most common sources of lateral and vertical forces acting on a structure are weather phenomena such as hurricanes, tornados, microbursts, etc. and earthquakes. Without some type of reinforcement means, most structures have relatively poor inherent resistance and are subject to significant damage from such events. For example, strong winds blowing into the sidewall of a structure will exert lateral and oblique forces against the wall and also upward forces on the roof as the forces accumulate and strengthen at building indentions, corners and roof eaves. Exterior framed structure finish veneers such as brick and concrete stucco provide mass and some resistance to lateral wind forces. Other finish veneers such as vinyl siding, EIFS and lap siding provide negligible resistance to lateral wind forces above that resistance provided by the framed structure itself. Interiors and structures are often damaged from the separation of roof decking from framing members. Wood, the most common framed structure building material, has relatively poor tensile strength. Most jurisdictions require compliance with a Building Code. Building Codes define the minimum level of structural reinforcement required to maintain structural integrity when subjected to external forces deemed possible to occur in that local area. Numerous devices and methods have been devised to improve structural resistance for use with framed structures. All of these methods and devices are designed to keep the structure intact during a violent event to maintain integrity of the structure but the devices consistently use the wood structural members for intermediate tensional resistance within the overall reinforcement concept. None of the existing concepts or devices addresses the overall structure and roof decking by connecting all of the structural and decking components with one network system that allows the entire structure and the individual components to act together to counter external forces.
FIELD OF THE INVENTIONIn general, the local Building Code (or “Code”) will dictate which methods of structural reinforcement must be applied. These requirements will vary depending on the most likely event and external forces that could occur to the structure. For example, in the Gulf Coast region of the United States where hurricanes are relatively common, structural reinforcement systems typically consist of bolting or attaching wall reinforcement devices along with rafter straps or cabling, etc. attached at various points onto the framed structure. All of these reinforcements are designed to keep the roof rafters and wall studs tethered to the structure's foundation using the wood structural members as intermediate components of the concept. Codes in other areas subject not to hurricanes but to other potential external forces typically have different reinforcing methods and devices.
Although the devices of the previous examples have generally good individual component yield strength and can protect against separation of the contacting structural members, they provide minimal protection for the overall structure and no protection for the plywood roof decking covering the structure. As a result, when the weakest part of the structure or the roof decking is compromised, significant damage to the structure and contents occurs from rain and wind forces. Secondly, these devices that use wood as the intermediate tensional members are generally not capable of withstanding very strong wind events and many structures are still damaged each year.
What is needed in the art is a cost-effective means for protecting the integrity of the roof decking while at the same time, substantially increasing the resistance of the entire framed structure and decking to separation.
What is also needed in the art is a means for dramatically improving the strength of a framed structure without requiring a substantive change to the method or materials of construction.
What is also needed in the art is a standardized, engineered solution that differentiates varying external forces and prescribes standard components in varying ways to protect an entire framed structure and all components including wall sheathing and roof decking.
BRIEF SUMMARY OF THE INVENTIONThe present invention is a reinforcing system applied to an entire structure that when installed, greatly increases the structure's resistance over prior methods yet can be applied affordably. The principal behind the present invention is that, when interconnected, a series of binding elements is stronger than that of each individual element attached at various points in a framed structure. An additional principal is that the framed structure is being structurally reinforced without using framed members having low tensile strength as part of the reinforcement system. The invention is comprised of plurality of strapping elements placed on top of the roof decking of a structure, extending down the side walls of the structure, and attached to the structure's foundation. Each strapping element is tensioned after being set in place. Once all of the strapping elements are in place and tensioned, the straps are secured to the structure at various locations and at points where the straps intersect. Once fastened together, the straps form an extremely strong web of reinforcement throughout the entire the structure. Resistance to wind loads, for example that may be applied to only one side of the house are actually spread throughout the entire structure due to the network of interconnected straps. Thus, the structure's integrity cannot be lost by the failure of any one element as is typical with devices that are attached at various points in a framed structure.
The present invention is an engineered product, which means that the number of straps, location of the straps, and the fastening points to the structure must be determined by a trained person for each particular structure and the Building Code requirements for the area where the structure is located. In general, the more straps and the more fastening points, the greater the overall network resistive strength will be achieved. To assist in understanding the methodology of applying this system, a four-sided structure is used. However, one skilled in the art can apply the basic principals of the 4-sided structure example to cover other structural layouts.
The basic element of the system is the strap. Each complete strap is comprised of two “foundation” straps and a “runner” strap. Each foundation strap has one end embedded into or otherwise attached to the structure's foundation. The other end of the foundation strap is connected to one end of the runner strap. The runner strap is placed up the outside of the sidewall, through a slit in the roof decking, up over the top of the roof decking, and down the opposite side wall. One end of the runner strap is connected to the foundation strap without tension using various metal strapping means. Using a standard strap-tensioning tool, the end of the opposite foundation strap is set into the device and the opposite end of the runner strap (coming down from above) is set into the device. The device is ratcheted to pull the runner and foundation straps together to a prescribed minimum tension. Once under tension, the pieces are attached together and the tensioning device is removed. Once all of the straps are tensioned, the straps are “networked” by fastening them at various points to the roof structure and at strap crossing points.
It is an object of the invention to provide a structure stabilizing system that includes a plurality of interconnected, pre-tensioned straps.
It is a further object of the invention to provide a structure stabilizing method that presents a simple approach to designing and installing a network of interconnected, tensioned straps to accommodate a wide range of building types, sizes and roofing configurations.
In reference to
The strapping system of this typical structure is designed by first locating the end-wall strap spacing 7 placed within a minimal distance from the outside wall corner. Then, moving toward the opposite wall, the next strap is placed at the standard spacing 1 except when interferences occur. This procedure is repeated for the other two walls resulting in a grid-type layout over the structure. The straps that are placed on standard dimensions that extend down over an opening into the structure's wall, such as a door or window, are then moved according to several standard adjustment formulas. Straps that interfere with openings may be spaced closer than standard as shown by spacing 5. The inventors set forth herein the preferred adjustment means for the most typical of structural openings. The methodology behind these formulas are exemplary and can be applied to other wall openings as well.
The first adjustment formula applies to a window opening 4 that is greater than the standard spacing dimension determined for the structure. In this instance, one end of the strap is placed on the edge of the window opening while the other end of that strap is located at the next forward strap location. A second strap is located on the other edge of the window opening with the other end extending to the preceding adjacent strap location. The strap spacing on the wall opposite the wide window 4 is maintained at standard spacing 1. This design formula results in these two adjacent straps forming an “x” pattern 9 over the structure whereas most other straps between two opposite side walls will be parallel. The “x” pattern 9 allows multiple connections to roof structural members, providing greater overall strength, as the runner strap passes over these structural members on a diagonal.
A second adjustment formula is applied to a garage opening 6 where the opening dimension is more than 2-times the standard spacing dimension. In this instance, a standard spacing dimension 1 is marked on the opposite wall from garage bay opening having a center located directly across from the opening's center. One strap is located on one edge of the garage bay and extends over to the structure's roof to 11. A second strap is located at the other edge of the garage bay and extends over the structure's roof to 12. Additional straps that are located at the garage opening edge run directly across the roof structure and connect to foundation straps on both ends. All four garage bay edge straps are connected with fasteners to the horizontal opening structural member. A third strap is secured to the horizontal structural member at the center of the garage opening and extends directly across the roof structure to the opposite sidewall. This design formula results in these two adjacent straps forming an “x” pattern 8 over the structure with a third strap centered in between.
In continued reference to
As a practical matter, the location and placement of the straps are typically performed graphically by an architect or engineer with strap spacing adjustments made for openings in the side walls. Once the initial structural grid and sidewall opening adjustment formulas have been applied, a drawing is marked and given to field personnel to begin marking the foundation structure at the determined locations and installing the foundation straps.
In reference to
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Once all of the foundation straps are in place at the locations determined by the system design and framed construction is complete to the point of roof decking and outer walls, the matching runner straps are installed over the roof decking of the structure and extended down the sidewall of the structure through the roof decking. In reference to
After the straps are placed over the roof decking and extended down the sides of the stud walls, just prior to joining and tensioning the runner and foundations strap sections, certain runner straps must be anchored. Primarily, these include runner straps crossing roof valleys.
Once the valleys are secured, the straps are ready to be tensioned. From the ground around the structure, the installer joins one end of the runner strap to its related foundation strap by any number of standard metal strapping means. The installer then inserts the opposite loose end of the runner section into a common strap-tensioning tool. The loose end of the foundation strap is also inserted into the strap-tensioning tool. The straps are then pulled together to provide a permanent tension force to the entire runner/foundation strap. The inventors estimate that 50-200 ft-lbs of tension would be adequate for most applications although more or less tension could be applied in special circumstances. A “proper tension-over tension” gauge is used to determine that minimum tension has been reached while also confirming that the strap has not been over tensioned. The uniformity of tension levels through the strap network insures proper performance of each strap. The gauge will be incorporated into each strap at the tensioning location and remain visible for inspection. While under tension, the runner and foundation straps are connected together by any number of standard metal strapping attachment means. When valley points are secured on a roof, the tensioning and joining must take place at both ends of the runner and foundation straps ground locations.
Once the individual straps are tensioned, the system is networked together by fastening the runner sections together at crossing points and fastening the runner sections to the structure. In general, the more fastening points of the tensioned strap network to the structure, the greater reinforcement properties of the system. The critical attachment points to the structure are the roof apex ridge, roof rafters and wall studs. The installer will typically apply structural fasteners into the roof decking at every point where two or more straps overlap.
There are several methods suitable for joining the runner and foundation straps before and after applying tension. The tensioning tool pulls the straps along side each other until the correct tension is established. In
Claims
1. A reinforcing system for increasing a framed building's structural resistance to forces generated by winds, sudden movements, and sudden pressure drops comprising:
- a plurality of parallel runner straps placed at minimum spaced horizontal distances over the roof decking of the structure and extending downward along two opposite side walls of the structure;
- a plurality of matching parallel foundation straps placed at the same spaced distances as the runner straps and secured on both ends to the structure's foundation;
- a means for joining and tensioning each matching runner and foundation straps;
- a means for permanently securing the tensioned straps together; and
- fastening the tensioned straps to the structure.
2. The structural reinforcing system of claim 1 where the fastening of the tensioned straps to the structure occurs where the runner straps intersect with the roof trusses, apex ridge, rafters and wall studs.
3. The structural reinforcing system of claim 1 applied to a 4-sided structure where a second plurality of perpendicular runner straps is placed at minimum spaced horizontal distances over the roof decking of the structure and extending downward along the two other opposite side walls of the structure intersecting the first plurality of runner straps at right angles.
4. The structural reinforcing system of claim 2 where one or more fasteners are placed through the straps and into roof structural members at each point where the perpendicular straps intersect the parallel straps.
5. The structural reinforcing system of claim 1 where the runner and foundation straps are fabricated from steel having a width of from 0.5 inch (12.7 mm) to 4.0 inches (101.6 mm) inclusive and a thickness of 10 standard gauge (0.1382 inch or 3.5 mm) to 32 standard gauge (0.0134 inch or 0.34 mm) standard gauge inclusive.
6. The structural reinforcing system of claim 1 where the runner and foundation straps are fabricated from the non-metallic group consisting of polyethylene, polypropylene, polyvinylchloride, polyethylene nylon, fiberglass, Kevlar, and dynema.
7. The non-metallic straps of claim 6 where the straps have a width of from 0.25 inch (6.35 mm) to 4.0 inches (101.6 mm) inclusive and a thickness 0.250 inch (6.35 mm) to 0.003 inch (0.076 mm) inclusive.
8. The non-metallic straps of claim 6 where the straps further contain one or more metallic wires embedded or woven into the non-metallic material for purposes of reinforcement.
9. The structural reinforcing system of claim 1 where the minimum spaced horizontal distance of the top and bottom straps is between 3 and 12 feet inclusive.
10. The structural reinforcing system of claim 1 where a strap that crosses a roof rafter, a fastener is applied through the strap, through the roof decking and into the structural member.
11. The structural reinforcing strap of claim 1 where a strap that crosses a roof valley is secured to the roof through a plurality of fasteners placed through the strap into a metal plate placed underneath the roof decking and on both sides of the roof valley.
12. The structural reinforcing strap of claim 1 where a strap that crosses a roof valley is secured to the roof through a plurality of fasteners placed through the strap and into blocks placed underneath the roof decking and on both sides of the roof valley.
13. The structural reinforcing system of claim 1 where the structure has an eave, the plurality of parallel top straps extend downward along the side walls through slits cut into the roof decking such that the straps are flush with the outside face of the structural wall.
14. The structural reinforcing system of claim 13 where a support member is placed on top of the wall and under the roof decking to prevent compression of the roof decking when tension is applied to the strap.
15. The structural reinforcing system of claim 1 where the protected structure has 2 or more stories and includes a second roof structure extending below the upper roof and away from the outside wall of the higher structure, the system further comprises a plurality of parallel auxiliary runner straps placed at the same horizontal spacing distances as the top runner straps over the upper roof structure and over the lower roof decking,
- said auxiliary top runner straps connected on one end to the corresponding downwardly extending top runner straps after the top strap is tensioned, and a second end extending downward along outer side wall of the second roof structure, and
- a plurality of matching parallel auxiliary foundation straps placed at the same spaced distances as the auxiliary top runner straps and secured on one end to the structure's foundation; and
- a means for joining and tensioning each matching auxiliary top runner and foundation strap;
- a means for permanently securing the tensioned straps together; and
- fastening the tensioned straps to the roof structural members, through the roof decking, at points where the roof structural members and the strap network intersect;
16. The structural reinforcing system of claim 1 where the structure has an apex roof, further comprising a runner strap that crosses the roof apex, the runner strap is fastened to the roof decking and apex structural roof member at the point of apex.
17. A method of reinforcing a structure to improve resistance to lateral and vertical forces acting upon it from sources such as hurricanes, tornados and earthquakes, comprising the steps of:
- determining a standard strap spacing dimension based on the degree of structural resistance desired,
- marking a grid pattern on a plan view drawing of structure with the grid spacing equal to the standard spacing dimension desired,
- where a grid line intersects a door, window or other opening in the side wall of the structure, move the interfering end of that grid line to the edge of the opening,
- installing a plurality of foundation straps with one end firmly secured to the structure's foundation at each point where the grid lines cross the external face of the structure,
- installing a plurality of runner straps over the top of the structure along the grid lines with each runner having one end extending down along the side wall stud and meeting a matching foundation strap at the structure's bottom and having a second end extending down along the opposite side wall stud and meeting a matching foundation strap at the structure's bottom,
- installing a fastener through each runner strap into the roof decking and structure at each place where the runner crosses a structure's roof valley,
- joining each end of a runner strap to its matching foundation strap applying a standard tension to the joined straps,
- secure the tensioned straps to the roof decking and the roof and wall structural members.
Type: Application
Filed: Aug 19, 2008
Publication Date: Feb 25, 2010
Inventors: David J. Fannon (Daphne, AL), Johnny R. Cahoon (Daphne, AL)
Application Number: 12/193,933
International Classification: E04G 23/00 (20060101); E04H 12/20 (20060101);