US20150322671A1

US20150322671A1 - System and Method for Structural Restraint Against Seismic and Storm Damage

Info

Publication number: US20150322671A1
Application number: US14/691,018
Authority: US
Inventors: Gerry Edward LICHTENFELD
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-06-21
Filing date: 2015-04-20
Publication date: 2015-11-12

Abstract

A system for structural restraint of wood framed structures against seismic and storm damage comprises a plurality of structural wood framing components; a plurality of structural wood sheathing components; a plurality of structural wood fasteners; one or more structural foundations; and a structural bonding agent applied to the interior and exterior over top of and in direct contact with structural fasteners to prevent failure of structural wood fasteners.

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to wood framed construction systems. In particular, the present invention relates to a restraint system for reinforcement of wood framed buildings against seismic and storm damage by reinforcing the structural wood fastener locations.

BACKGROUND OF THE INVENTION

Much of the world's population is located along seismic fault lines or in the paths of powerful storms such as hurricanes, monsoons, floods and tornadoes. The buildings in such areas are at risk of structural damage from seismic and storm events. As these population centers grow, the risk of loss of life and damage to structures will only increase.
During powerful seismic and storm events, prior art wood framed construction techniques do not adequately hold the structural building components together. Although such wood framed structures are among the safest currently available, powerful seismic and storm events may result in the failure of their structural integrity through the failure of the structural wood fasteners. The primary reason for structural failure is the inability of the structural fasteners to keep the structural wood sheathing firmly attached to the structural wood framing. As structural fasteners primarily are designed to be static devices, they are likely to fail when subjected to dynamic forces.
Many jurisdictions are seeking ways to mitigate the effects of these powerful seismic and storm events through the upgrading of building codes. To date, nothing has been available to solve the problems associated with these events. Governments, as well as construction, insurance and forest industries and the general population, all have a great deal to benefit from a solution to these damaging effects.
As powerful seismic and storm events act on a structure, the three dimensional dynamic forces compromise the structural wood fasteners, causing them to work their way loose or out of the members in which they are embedded or, if they remain in place, they may tear their way through the structural wood sheathing or simply break off. The result is the weakening or complete loss of structural integrity of the wood framed building as the structural forces no longer are able to be transferred safely down to the structural foundations.
During powerful seismic and storm events failure points occur primarily along structural wood fastener strips of structural wood sheathing. These failure points may be at corners, at intersections, around door, window and other openings, at vertical joints, and along horizontal joints at floor and ceiling edges.
Presently there are no systems or structural wood fasteners which can prevent these failures. Existing prior art solutions use a form of building restraint consisting of a complex engineered system of steel rods, anchors, plates and straps requiring extensive notching, drilling and additional structural reinforcement. Installation of such a system may interfere significantly with construction schedules in that electrical, plumbing and other sub-trades will have their work suspended while the required building modifications are carried out. This form of restraint system fails to provide a solution to the problem of structural wood fasteners breaking off or pulling loose, out or through the structural wood sheathing, putting at risk the structural integrity of the wood framed structure.
The restraint system of the present invention provides a solution which maintains the integrity of the structural wood fasteners. This results in the structural wood sheathing remaining firmly attached to the structural wood framing and the structural foundations. The integrity of the entire wood framed structure is maintained and the structural loads are able to be transferred safely down to the structural foundation.

SUMMARY OF THE INVENTION

There is provided a system for structural restraint of wood framed structures against seismic and storm damage, the system comprising a plurality of structural wood framing components; a plurality of structural wood sheathing components; a plurality of structural wood fasteners; one or more structural foundations; and a structural bonding agent.
The structural bonding agent may be a thermoset polyurea elastomer having a tensile strength of at least 15 MPa (2000 psi) and may have an elastomeric flexural strength of at least 300%. The structural bonding agent may remain flexible to temperatures as low as −40° C. (−40° F.).
There is further provided the use of a structural bonding agent to reinforce wood framed building structures against seismic and storm damage by preventing egress of structural wood fasteners from structural wood framed building components. The structural bonding agent used may be a thermoset polyurea elastomer.
The invention further comprises a method of reinforcing a wood framed structure against seismic or storm damage comprising the steps of wood framing a desired structure; applying a structural flexible bonding agent to completely cover over structural wood fasteners and be in direct contact with the external end of each fastener at selected locations of the wood framed structure to achieve a desired thickness.
The bonding agent may be applied by spraying. The flexible bonding agent may be applied to an area of between 100 mm (4″) and 255 mm (10″) wide centered over the structural wood fastener components.

BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of the preferred embodiments is provided by way of example only and with reference to the following drawings, in which:

FIGS. 1A and 1B are cross-sectional views of two exterior walls of a building extending between structural foundation wall and roof truss, one (1B) of which depicts door and window openings, according to one embodiment of the present invention;

FIG. 2 is a cross-sectional view of the assembly of a wall stud, floor joist and structural foundation wall, according to one embodiment of the present invention;

FIG. 3 is a cross-sectional view of an assembly of a wall stud, floor joist and structural foundation wall including a door opening, according to one embodiment of the present invention;

FIG. 4 is a cross-sectional view of an assembly of a lower level wall stud, floor joist, and upper level wall stud above a door opening, according to one embodiment of the present invention;

FIG. 5 is a cross-sectional view of an assembly of a lower level wall stud, floor joist, and upper level wall stud, according to one embodiment of the present invention;

FIG. 6 is a cross-sectional view of a wall stud adjacent a window opening, according to one embodiment of the present invention;

FIG. 7 is a cross-sectional view of a wall stud and roof truss, according to one embodiment of the present invention;

FIG. 8 is a cross-sectional view of a wall stud and roof truss above a window opening, according to one embodiment of the present invention;

FIG. 9 is a front plan view of sections A, B and C of a structural wall, according to one embodiment of the present invention;

FIGS. 10A, 10B, and 10C are cross sectional views of corresponding wall sections A, B, and C of FIG. 9, according to one embodiment of the present invention;

FIG. 11A depicts a top view cross section of a wall configuration consisting of a 90 degree framed exterior corner;

FIG. 11B depicts a top view cross section of a wall configuration consisting of a 90 degree framed exterior corner, two 45 degree framed exterior corners and a 90 degree framed interior corner; and

FIG. 11C depicts a top view cross section of a wall configuration consisting of two typical 45 degree framed interior corners; according to one embodiment of the present invention.

In the drawings, one embodiment of the invention is illustrated by way of example. It is to be expressly understood that the description and drawings are only for the purpose of illustration and as an aid to understanding, and are not intended as a definition of the limits of the invention.
For the purposes of clarity the structural wood fasteners have not been shown as specific locations may be different from what would be shown. It is understood through description that the structural bonding agent may be applied to an area of between 100 mm (4″) and 255 mm (10″) wide centered over top of the structural wood fastener components.

DETAILED DESCRIPTION OF THE INVENTION

There is provided a structural restraint system to maintain wood framed building structural integrity during powerful seismic and storm events. The restraint system of the present invention reduces or eliminates structural wood fastener failure, whether through breakage, loosening, detachment, or rupture through the structural wood framed components they are meant to secure. This result is achieved by providing a layer of a structural bonding agent over top of the structural fasteners so as to sandwich the external ends of the fasteners between the structural frame and the structural bonding agent. The presence of the structural bonding agent over top of the ends of the fasteners prevents egress of the fasteners from the structural framing components.
The restraint system of the present invention comprises five wood framed structural building components. These five structural building components are wood framing, wood sheathing, structural wood fasteners, a structural foundation, and a flexible bonding agent.
The structural wood framing may be manufactured of wood or composite wood materials and combinations thereof structural Framing components may include studs, posts, plates, joists, rafters, beams, lintels, built up assemblies and trusses.
The structural wood sheathing may be manufactured of wood, plank, plywood, oriented strand board (OSB), wafer board, composite boards and other structural membranes for walls, roofs and floors;
Each structural wood fastener (25) may be a hardware device that mechanically joins two or more structural components together, for example, nails, staples, screws. In the drawings, nails are depicted.
The foundation may be constructed of concrete, masonry, treated wood, or other approved material
A suitable flexible bonding agent may be a spray-applied structural flexible elastomer, for example polyurea or equivalent. The flexible bonding agent is applied to corresponding interior and exterior portions of the structure as noted on the diagrams and as previously described. The flexible bonding agent ideally should be rapid thermosetting, have fast reactivity, be relatively insensitive to moisture, and be fully curable in high humidity, cold or moist substrate conditions. The flexible bonding agent should have a tensile strength of 2200 to 2500 psi for thermoset elastomer. The flexible bonding agent should have an elongation range of 300% to 600% elongation flexural strength for sprayed elastomer, and should adhere tenaciously to multiple substrates including wood, composites and concrete. It should remain flexible at temperatures as low as −40° C. (−40° F.), and should permit application of multiple coats over one another. According to one embodiment, the sprayed elastomer may have Shore D hardness rating of between 54.5 and 55.5. Other hardness ratings are also possible within the scope of the invention.
Existing prior art wood framed building restraint systems are designed to lessen the effects of powerful seismic and storm events only to the extent necessary to maintain structural integrity long enough to permit evacuation or rescue to save lives. The structure itself may suffer extensive damage and require extensive repairs to reattach the structural wood sheathing, or the building may be condemned to demolition. In contrast, the restraint system of the present invention not only maintains structural integrity to the extent necessary for the structure to survive one powerful seismic or storm event, but to survive multiple such events. The restraint system of the present invention achieves this improved outcome by holding the structural wood fasteners in place during the seismic or storm event so they can effectively perform their function of maintaining the structural integrity of the wood framed building. The fasteners are held in place by the application of a flexible bonding agent completely over the structural fasteners and in direct contact with the external end of each fastener, after it has been used to fasten together structural components.
The restraint system of the present invention is easy to apply to existing or new wood framed structures, greatly reduces the costs of seismic upgrades to wood framed buildings, does not interfere with construction schedules, and is highly effective in preventing structural wood fasteners from working their way loose, out or through the structural wood sheathing, or breaking off entirely.
The system is able to compensate for natural settling and shrinkage of wood framed structures, and is applicable to all site and factory assembled, platform or balloon framed, wood construction for single and multi-family residential, commercial, industrial and institutional structures, whether single or multi story structures.
The restraint system of the present invention is compatible with building codes around the world. The degree of protection may be adjusted to meet the design parameters for a particular structure. Increased protection may be achieved by increasing the width of spray application as previously described, or by applying multiple coats to increase the thickness of the bonding agent.
According to the present invention, the sprayed polyurea elastomer is applied to the interior as well as the exterior of a wood framed building structure.
In operation, at wood framing completion or at the completion of a phased portion of the wood framed construction, the structural flexible bonding agent is applied in a generally linear spray pattern at a plurality of locations specified in the figures. These locations include along the length of framing components and over top of fasteners where applied through external sheathing. The flexible bonding agent is applied generally in a linear spray pattern approximately 100 mm (4″) to 255 mm (10″) wide and centered over the structural wood fastener components that are being covered and restrained. The structural flexible bonding agent should be applied approximately 5 mm-7 mm ( 3/16″-¼″) thick. Special care should be taken to ensure the structural wood fastener strips are covered.
Wherever structural wood fasteners are used to connect together two or more structural wood components, the flexible bonding agent may be applied over the fasteners to prevent the fasteners from losing their function during a seismic or storm event. The structural flexible bonding agent will ensure the structural fasteners are prevented from working loose, out or through the structural wood sheathing, or breaking off, thus maintaining the connection of the fastener to the structural wood framing. The restraint system of the present invention acts to completely integrate the structural wood framed components and binds them together as a single unit.
Referring now to FIGS. 2 and 3, these drawings depict a wall stud (1) vertically disposed above a subfloor (3), which is over a floor joist (4). Adjacent the exterior wall surface, a floor rim joist (5) abuts the floor joist. Wall sheathing (6) is applied to the exterior of the wall stud. An anchor bolt assembly (8) passes through a sill plate (9) and sill plate gasket (10) or equivalent into a structural foundation wall (11). In FIG. 2, a top or bottom wall plate (2) is shown below the wall stud. As previously noted the structural wood fasteners have not been shown in the diagrams for sake of clarity as specific locations of the structural wood fasteners may vary. In general the location of the flexible bonding agent is centered over the structural wood fasteners. This is applicable to all the diagrams.
According to the present invention, a structural flexible bonding agent (7) is spray applied adjacent selected wood framed connection points between structural wood framed components. As shown in FIG. 2, the flexible bonding agent is applied at the interior lower end of the structural wall sheathing along the area at which it is adjacent the structural wall plate, as well as along the exterior of the area at which the structural wall sheathing is in proximity to the structural subfloor and the structural floor rim joist, and along the area at which the structural floor rim joist, structural sill plate, sill plate gasket and structural foundation wall are adjacent. FIG. 3 depicts application of the flexible bonding agent along the exterior of the area at which the structural wall sheathing is in proximity to the structural subfloor, and the structural floor joist, and along the area at which the structural floor rim joist, structural sill plate, sill plate gasket and structural foundation wall are adjacent.
Referring now to FIG. 4, the flexible bonding agent of the restraint system is depicted applied along the connection area between the structural wall sheathing and the structural wall plate; exterior to the structural wall sheathing, structural subfloor and structural floor rim joist; exterior to the structural floor rim joist, structural wall plate and structural wall sheathing, and along the connection between the structural wall sheathing, a structural lintel sill opening (14) and a structural jack stud opening (15). FIG. 4 depicts a structural lintel opening (12) and a lintel space opening (13) above the lintel sill opening.
Referring now to FIG. 5, the flexible bonding agent of the restraint system is depicted applied along the connection area between the structural wall sheathing and the structural wall plate for an upper level; exterior to the structural wall sheathing, structural subfloor and structural floor rim joist; exterior to the structural floor rim joist, structural wall plate and structural wall sheathing, and along the connection between the structural wall sheathing and a structural wall plate for a lower level.
Referring now to FIG. 6, a jack stud opening is shown above a sill opening (17) disposed above a trimmer stud opening (18). The flexible bonding agent is applied into the jack stud opening, along the connection area between the structural wall sheathing and the top of the sill opening, and along the connection area between the interior of the structural wall sheathing and the bottom of the sill opening.
Referring now to FIG. 7, the top of a structural wall stud is shown where it is adjacent a structural roof truss (20). Structural roof sheathing (21) is disposed above the structural roof truss. Flexible bonding agent may be applied between the interior of the structural wall sheathing and bottom of a structural wall plate, along the exterior of the structural wall sheathing where it is adjacent the structural roof truss, and between the structural roof truss and structural roof sheathing.
Referring now to FIG. 8, flexible bonding agent may be applied between the structural roof truss and structural roof sheathing, along the exterior of the structural wall sheathing where it meets the structural roof truss, along the exterior of the structural wall sheathing where it meets the lintel sill opening, and into a jack stud opening.
Referring now to FIG. 9, an interior view of a framed wall with a window and a door is depicted, showing the interior component of the sprayed elastomer as viewed from the interior. The section marked “A” depicts a portion of wall which contains a framed window opening. The section marked “B” depicts a portion of wall which contains an exterior vertical joint of the structural sheathing, and the section marked “C” depicts a section of wall which contains a framed door opening. FIG. 10A, 10B, and 10C show top view cross sections, below the top plates of the wall, of section “A”, section “B” and section “C”, respectively, of FIG. 9, including openings for jack studs (15), king studs (16), and trimmer studs (18).
FIGS. 11A, 11B, and 11C show the application of the interior and exterior bonding agent components at typical vertical structural sheathing joints and at a framed exterior corner.
It will be appreciated by those skilled in the art that other variations of the preferred embodiment may also be practiced without departing from the scope of the invention.

Claims

1. A system for structural restraint of wood framed structures against seismic and storm damage, the system comprising a structure built from a plurality of structural wood framing components, a plurality of structural wood sheathing components, and one or more structural foundations;

a plurality of structural wood fasteners, each structural wood fastener connecting together two or more of the structural wood framing components, structural wood sheathing components, or structural foundations; and a structural bonding agent, wherein the structural bonding agent is applied to the structural wood framing components, structural wood sheathing components, and structural foundations completely covering over the structural wood fasteners and in direct contact with the external end of each structural wood fastener to prevent egress of the structural wood fasteners.

2. The system of claim 1, wherein the structural bonding agent is a polyurea thermoset elastomer having a tensile strength of at least 2200 psi.

3. The system of claim 1 wherein the structural bonding agent has an elastomeric flexural strength of at least 300%.

4. The system of claim 1, wherein the structural bonding agent remains flexible to temperatures as low as −40° C. (−40° F.).

5. Use of a structural bonding agent to reinforce wood-framed building structures against seismic and storm damage by applying the structural bonding agent in direct contact with, and to completely cover over structural wood fasteners to prevent egress of the structural wood fasteners from structural wood framed building components.

6. The use of the structural bonding agent as in claim 5, wherein the structural bonding agent is a polyurea thermoset elastomer.

7. A method of reinforcing a wood framed structure against seismic or storm damage comprising the steps of:

wood framing a desired structure; and

applying a structural flexible bonding agent to completely cover over structural wood fasteners at selected locations of the wood framed structure to achieve a desired thickness, wherein the structural flexible bonding agent is in direct contact with and completely covers over the external end of each structural wood fastener.

8. The method of claim 7, wherein the flexible structural bonding agent is applied by spraying.

9. The method of claim 7, wherein the flexible bonding agent is applied to an area of between 100 mm (4″) and 255 mm (10″) wide centered over top of the structural wood fasteners, and in direct contact with the external end of each structural wood fastener.

10. The method of claim 7, wherein the flexible structural bonding agent is applied to selected locations on the interior of the framed structure, and corresponding selected locations on the exterior of the framed structure.

11. The method of claim 10, wherein the flexible structural bonding agent applied to selected locations on the interior of the framed structure is a polyurea thermoset elastomer, and the flexible bonding agent applied to corresponding selected locations on the exterior of the framed structure is a spray foam insulation polyurea thermoset elastomer.