US20020162284A1

US20020162284A1 - Wood frame wall construction

Info

Publication number: US20020162284A1
Application number: US10/115,281
Authority: US
Inventors: Meho Karalic
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-04-06
Filing date: 2002-04-04
Publication date: 2002-11-07

Abstract

A wall panel has elongate members connected together to form a rectangular frame having a top, a bottom and opposite sides, a sheathing extending over the rectangular frame; and connectors providing a connection between the sheathing and the rectangular frame. The connectors are varied so that the strength of the connection increases from the top and bottom towards the middles of the opposite sides of the frame.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the construction of wood frame walls for buildings.

2. Description of the Related Art

It is known in the art to construct a building diaphragm consisting of a skin and a frame that are attached to each other by means of connectors (nails, screws, staples, etc.). A building diaphragm is subject to lateral forces as in roofs and floors, where wind and seismic forces are transferred to side walls and by the side walls to the ground. Walls that transfer horizontal loads in the plane of the walls are called shear walls. Shear walls resist horizontal loads imposed by shear and moment forces, i.e. the wall is subject to shear forces and rotated by an overturning moment. Shear forces and overturning moments are resisted at the wall-to-ground interface by tie-downs and anchors driven through bottom members of the frame walls into foundations.

Shear walls and roof and floor diaphragms are subject to two design considerations, namely ultimate load and allowable deformation.

In a shear wall, the frame is usually made from 2×4 or 2×6 lumber framing members at 16″ or 20″ spacings, and provided with a skin is made from 4′×8′ particle board or plywood sheathing. In floor or roof diaphragms, frame members are usually joists made conventionally of 2×8 to 2×12 lumber or of engineered I-joists. The prevailing failure mode in prior art shear walls is shearing at connectors (nails) in frame corners due to rotation of the skin panels that are very stiff in that phase compared to the relatively pliant frames. Hitherto, this has been counteracted by driving more nails into the frames or by reinforcing connection zones by attaching steel strips and driving nails through the strips. While the corner nails (connectors) are sheared, all other nails are less stressed and do not contribute to the overall resistance to their full capacity.

BRIEF SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to strengthen wood frame wall constructions

According to one aspect to the present invention, a sheathing is attached to a wood frame by connectors (nails, screws, staples, etc.) so as to transfer shear force uniformly to all panel areas. This is achieved by strategically placed and/or selected connectors.

This may be achieved by:-

A. Driving stiffer nails into a control zone of the sheathing close to the centre of rotation or by driving more nails in the same zone; or

B. Installing diagonal members flush to the frame and skin and driving nails (connectors) into the frame and driving nails into diagonal members provided within the frame; or

C. Providing the frame with corner connectors that counteract movement of sheathing relative to the studs.

According to another aspect of the present invention, there is provided a wood frame wall construction which comprises rectangular frames of e.g. lumber provided with sheathing, e.g. in the form of panels, with corner connectors connecting the corners of the rectangular frames, the corner connectors being fastened directly to the sheathing.

According to a further aspect of the present invention, the corner connectors at lower ends of the rectangular frames are secured to a foundation or other support by resilient tie-down devices which allow limited resilient displacement of the corner connectors and thus of the rectangular frames relative to the foundation or support. Resiliency in the corner connectors may be achieved by two principal methods, i.e. by a combination of resilient neoprene rubber-like materials and steel inserts or by spiral, conical, flat or washer-type steel springs, or by a combination of both of these methods.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more readily understood from the following description thereof taken with reference to the accompanying drawings, in which: [0015]
FIG. 1 shows a diagrammatic view in elevation of a pair of wall panels in shear; [0016]
FIGS. 2 and 3 show views in front elevation of a pair of wall panels embodying the present invention; [0017]
FIGS. 4 through 6 show views in front elevation of three different frame constructions for use in the panels of FIGS. 2 and 3; [0018]
FIGS. 7 and 8 show, respectively, a broken-away view in front elevation and a horizontal cross-section of a further wall panel construction; [0019]
FIG. 9 shows a broken away view in front elevation of a corner of a wall panel frame provided with a metal corner connector; [0020]
FIGS. 10 and 11 show, respectively, a front elevational view and a plan view of a further corner connector; [0021]
FIGS. 12 and 13 show a broken-away front elevational view and a broken-away plan view, respectively, of a frame corner employing the connector of FIGS. 10 and 11; [0022]
FIGS. 14 and 15 show views corresponding to those of FIGS. 13 and 14 but illustrating a still further frame corner; [0023]
FIGS. 16 through 21 show broken-away views in vertical cross-section of corner connectors provided with resilient tie-downs; [0024]
FIGS. 22 through 26 show plan views of the corner connectors of FIGS. 17 through 21, respectively; [0025]
FIGS. [0026] 27 to 29 illustrate panel under deflection:
FIG. 30 shows a pair of panels subject to a shear force; [0027]
FIGS. 31 through 33 each show a pair of panels connected to one another; [0028]
FIGS. 34 and 35 show views in horizontal cross-section through a pair of panel connectors and wall components connected thereby; [0029]
FIG. 36 shows a view in front elevation of a wall structure according to a further embodiment of the present invention; and [0030]
FIGS. [0031] 37 to 41 show broken-away views, taken in front elevation, of connections between adjacent panels in further embodiments of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a pair of [0032] wall panels 10 of the type comprising a rectangular wooden frame provided on one side with a sheathing of plywood or other suitable material. Assume that, due to the rigid body of sheathing, the deformed shape of adjacent panels 10 of a shear wall subject to a shear load is linear as shown in broken lines in FIG. 1 and indicated by reference numeral 12.
The nail stress and shear forces in [0033] nails 14 used as connectors between sheathing and lumber frames of the panels 11 are proportional to deformation, and are maximum at the top and minimum at the centre of rotation RC.
If a stiff nail has to be deformed to the same extent as a weaker one, a proportionally larger force must be used. If A=deformation, F=force and K=nail stiffness, the deformation relationship is described as A=F/K. [0034]
For full utilization of the nails, with proportionally lesser deflection as one approaches the centre of rotation RC, the nail stiffness should be increased, as in Fconstant=A (reduced)×K (increased). [0035]
This can be achieved by using progressively stronger nails from the top and bottom of the panel to the middle, as shown in the left-hand half of FIG. 2, which shows the use of 8[0036] d nails at the top and bottom sections of the panel, 10d nails at intermediate sections thereof and 12d nails at middle sections. As shown in the right-hand half of FIG. 2, this arrangement is reversed.
Alternatively, as shown in the left-hand half of FIG. 3, uniform nails can be used but with spacings varying from 12″ at the top and bottom sections, through 9″ spacings at the intermediate sections to 6″ spacings at the middle sections. As shown in the right-hand half of FIG. 3, this arrangement is reversed. [0037]
Another alternative is for different stiffnesses of nails to be achieved by using nails made of different quality materials and/or alloys. [0038]
FIGS. [0039] 4 to 6 illustrate wall panel frames 20, 21 and 22 of three wall units embodying the present invention, with the sheathings of these wall units omitted. The frames 20 through 22 can be installed between conventional wall studs (not shown) or can be used as frame members in lieu of standard vertical and horizontal frame members.
The [0040] frames 20 through 22 each have a top member 24, a bottom member 26 and opposite side members 28.
The [0041] frame 20 has inclined brace members 30, the frame 21 has brace members 32 forming triangles and the frame 22 has horizontal braces 34 and inclined braces 36 between the top and bottom members 24 and 26 and the horizontal braces 34.
In each of the wall units in which the [0042] frames 20 through 22 are provided, the sheathing, indicated by reference numeral 38 in FIGS. 7 and 8, is in face-to-face contact with one side of each of the frame members, which are all flush with one another and which are indicated by reference numerals 40 in FIGS. 7 and 8. This facilitates full contact of all frame members with the sheathing 38. The brace members and any other members of the frames between the side members are attached along their entire lengths to the sheathing 38 by connectors, which as shown comprise nails 42 but which may alternatively comprise screws, staples, etc.
The [0043] frames 20 through 32 may be replaced by the frames disclosed in my co-pending patent application Ser. No. 08/955,805, filed Oct. 22, 1997, the disclosure of which is incorporated herein by reference. Also, the present frames may have their frame members flush with wall studs and other components of wall framing so that the latter likewise contact face-to-face with the sheathing 38.
Prior art diaphragm walls (shear-walls) are built with non-direct connections between the most stressed parts. Tie-downs in such walls are usually connected to studs, which are usually connected to the sheathing. The sheathing panels are normally connected separately to the weak frames. The entire systems lack simple straightforward load-paths. [0044]
Embodiments of the present invention include metal corner connectors which directly connect anchor bolts to the sheathing, by-passing the weak frames, which allows for maximum transfer of vertical force in the studs while not resisting stud rotation that is detrimental to the connections, and allows for resisting horizontal forces at the wall-foundation interfaces while allowing for sheathing rotation. [0045]
In addition to this, the new corner connectors described below may be designed and utilized as energy absorption components that will act as isolators and will reduce ground motion (earthquake) effects on buildings, since most of the energy will be spent in deformation of these isolators. [0046]
FIG. 9 shows a first one of such corner connectors, which is indicated generally by [0047] reference numeral 50 and which comprises an abutment portion in the form of a tube 52 of square cross-section, against which abut the ends of wood frame members 54 and 56 connected by the connector 50.
The [0048] connector 50 has flanges 58 and 60 in face-to-face contact with sides of the frame members 54 and 56, and co-planar side flanges 62 and 64 which extend from and at right angles to the flanges 58 and 60. The flanges 62 and 64 are formed with nail openings through which nails 66 are driven through the flanges 62 and 64 into the frame members 54 and 56 to connect the latter at the corner of a wall unit frame which may, for example, be similar to any of the above-described frames. A sheathing 68 of plywood or other suitable sheathing material, shown in chain-dot lines, is secured directly to the co-planar side flanges 62 and 64 at the outer sides of the flanges 62 and 64, i.e. at the sides of the flanges 62 and 64 opposite from the frame members 54 and 56, by rivets 70, without being otherwise connected to the frame members 54 and 56. This ensures a direct transference of shear loads from the sheathing 60 to the flanges 62 and 64 of the connector 50, by-passing the frame members 54 and 56. Instead of nails and rivets, other means, e.g. prongs punched out from the flanges 62 and 64, may be provided for connecting the latter to the frame members 54 and 56 and to the sheathing 68
When the frame is subjected to shear stress, the [0049] metal corner connector 50 will be deformed, as illustrated in broken lines, to allow deformation of the frame.
FIGS. 10, 11, [0050] 12 and 13 show another embodiment of the corner connector, which in this case is indicated generally by reference numeral 70, and which includes a square-sectioned abutment portion 72 in one piece with a pair of flanges 74 and 76, which each extends from the middle of a respective side of the abutment portion 72, at right angles thereto, between a pair of wood frame members 78, 80 and 81, 82, respectively, (FIGS. 12 and 13), to which the flanges 74 and 76 are connected by prongs 84 punched from the flanges 74 and 76. Co-planar side flanges 83 and 85 extend at right angles to the flanges 74 and 76 from the abutment portion 72.
A [0051] sheet 86 of plywood or other suitable sheathing material, which is shown broken-away ion FIGS. 10 and 11, is connected to the flanges 83 and 85 and the frame members 78, 80 and 81, 82 by nails 88. which extend through the nail holes 89 in the flanges 83 and 85.
In FIGS. 14 and 15 there is shown a corner connector comprising a square-sectioned [0052] abutment portion 90 with side flanges 92 and 94 but no flanges corresponding to the flanges 74 and 76 of FIGS. 10-13. The flanges 92 and 94 are secured by nails 96 to wood frame members 98, and a sheathing panel 100 secured by nails 102 to the frame members 98.
FIGS. 16 through 26 show various tie-down devices for securing the square-sectioned abutment portions of the above-described corner connectors to a foundation (not shown). Each of these anchor devices has an energy absorbent insert which acts as a linear or non-linear spring. [0053]
More particularly, FIG. 16 shows a square-sectioned abutment portion, indicated generally by [0054] reference numeral 102, of a corner connector, which may e.g. be one of the above-described corner connectors or a modification thereof, and which is formed with an internal horizontal web 103. An anchor bolt 104, the lower end of which is embedded in a foundation 106, extends through the web 103, a washer 106 and a retaining nut 108, with rubber blocks 110 and 112 interposed between the foundation 106 and the web 103 and between the web 103 and the washer 106. The anchor bolt 104 extends through a circular hole 111 in the web 103 and has a diameter less than that of the hole 111 to allow the anchor bolt 104 to deflect laterally relative to the web 103.
FIGS. 17 through 26 show various modifications of the tie-down device of FIG. 16. [0055]
In FIGS. 17 and 22, an [0056] anchor bolt 114 has a head embedded in a rubber ball 116; in FIGS. 18 and 23 rubber discs 118 are interposed between washers 120 on an anchor bolt 122 and a transverse web 124; in FIGS. 19 and 24 a disc 126 fixed to an anchor bolt is embedded in a rubber block 128; in FIGS. 20 and 25 a disc 130 on an anchor bolt is located on a rubber block 132 and in FIGS. 21 and 26 a vertical plate 132 is sandwiched between two rubber blocks 134.
By the above-described means, the ultimate load capacities and deformation under load of the frames are controlled by connectors attached directly to the sheathing or diaphragm panel and to the frame. [0057]
The stiffness of the frames may be controlled by any combination of the above-described embodiments. [0058]
When a frame wall comprising rectangular frames provided with sheathing in the form of sheathing panels is subject to shear stress, and if there is no relative movement between adjacent sheathing panels, the wall will have the same strength and stiffness as a single sheathing panel having the same dimensions as the entire wall. It is possible to provide sheathing panels which are larger than standard sized sheathing panels, and which may for example be 8 feet by 16 feet, 8 feet by 24 feet, 16 feet by 16 feet, et cetera. Although such large size sheathing panels would have increased strength and stiffness compared with standard sheathing panels, they are nevertheless too rigid, heavy, expensive and difficult to handle. The present invention allows for the building of a large size continuous skin from a plurality of standard sized sheathing panels. Also, the present invention provides for the flexibility in design, e.g. by varying the size and number of connectors employed to connect adjacent sheathing panels, thus retaining the benefits of small, conventionally sized sheathing panels while also achieving the benefits of large size sheathing panels. [0059]
Standard shear wall design can sustain an allowable force which is limited to that producing one half inch horizontal deflection, provided that the force is less than one third of the ultimate strength of the wall unit. [0060]
The allowable shear force is in the range of 275-550 pounds per linear foot. For an 8-foot sheathing panel, this translates to 2200 to 1400 pounds, approximately. If a single sheathing panel of 8 feet by 8 feet dimensions is loaded by 4400 pounds, the deflection will be given by the equation:[0061]
A=A panel rotation+A panel shear
FIG. 27 diagrammatically illustrates, in broken lines, the deflection under shear of a wall unit, while FIG. 28 shows the deflection under rotation. The panel rotation illustrated in FIG. 28 is caused by yielding of connections at the corners A and B of the wall unit due to yielding of the nails between the sheathing panel and the studs. [0062]
FIG. 29, in broken lines, the combined effects of the rotation and the deflection under shear of the wall unit. [0063]
When the sheathing panel is connected directly to a corner connector as described above, the upward and downward deflections of the panel are greatly reduced due to the direct transfer of force from the sheathing panel to the corner connectors, and the remaining shear deformation is negligible, as indicated for example by the following equation:- [0064] $Ashear = \frac{6}{5} \times \frac{4400}{0.5 \times 96 \times 100000} = {0.001}^{''} << < {0.5}^{''}$
Consequently, most of the deformations of present shear walls are caused by yielding of the connectors, i.e. nails or staples, and the consequential relative movement of the sheathing panels relative to one another and to the corner connectors. [0065]
The present invention proposes to counteract relative movement of adjacent sheathing panels by connecting the adjacent sheathing panels directly to one another through [0066] connectors 140, such as those shown in FIGS. 9 to 15, as shown in FIG. 31.
In this way, it is possible to counteract relative movement of the sheathing panels within an 8-foot by 8-foot wall, between the corners of the sheathing panels and anchor bolts securing the wall to a foundation or other anchorage and between the shear wall units in order to form, for example, an 8-foot by 24-foot continuous shear wall. [0067]
By increasing the number of the [0068] connectors 140, as shown in FIG. 32, and by increasing the sizes of the connectors 140, as shown in FIG. 33, the shear wall stiffness can be correspondingly increased.
FIGS. 34 and 35 show two types of connectors which may be employed for interconnecting adjacent wall units and their sheathing panels [0069]
In FIG. 34, a metal connector indicated generally by [0070] reference numeral 150 has parallel flanges 152 secured by nails 154 to a stud 156. The flanges 152 extend from a plate 158, to which a pair of sheathing panels 160 are secured by fasteners which, in the present embodiment, comprise rivets 162. If required, an additional backing plate (not shown) may be provided at the sides of the sheathing panels 160 opposite from the connector 150.
In FIG. 35, there is shown a metal connector, indicated generally by [0071] reference numeral 164 which is of generally H-shaped cross section and which is secured by nails 166 to studs 168, with sheathing panel edges 170 sandwiched between the studs 166 and the metal connector 164.
FIG. 36 shows a reinforcement structure indicated generally by [0072] reference numeral 180 provided with corner connectors such as those of FIGS. 9 through 15, indicated by reference numeral 181 installed between two studs 182. More particularly, the modified reinforcement structure 180 comprises rectangular frames, having side members 184 and 186 and top and bottom members 188 and 190, with sheet material diaphragms or panels 192A-F secured to the side members 184 and 186 and the top and bottom members 188 and 190. A window opening 194 interrupts the four central rectangular frames, and has a sill 196 and an upper board 198.
FIG. 37 shows broken-away portions of two [0073] sheathing panels 200 and 201, which are secured to a vertical elongate wood member 202 by means of a cross-shaped metal fastener 204, which is pressed into embedded engagement with the elongate wood member 202 and the panels 200 and 201.
In FIGS. 38 and 39, there are shown modified cruciform connectors, indicated by [0074] reference numerals 206 and 208, respectively, which are embedded in plywood panels 200 and 201 and in the elongate wood member 202 for the same purpose.
FIGS. 40 and 41 illustrate the use of generally S-shaped [0075] fasteners 210 and 212 for the same purpose. These fasteners 210 and 212 may also be used to interconnect elongate members.

Claims

1. A wall panel, comprising:

a plurality of elongate members connected together to form a rectangular frame having a top, a bottom and opposite sides;

a sheathing extending over the rectangular frame; and

a plurality of connectors providing a connection between the sheathing and the rectangular frame;

wherein

the connectors are varied so that the strength of the connection increases from the top and bottom towards the middles of the opposite sides of the frame.

2. A wall panel as claimed in claim 1, wherein the strengths of the connectors increase along the opposite sides of the rectangular frame from the top and bottom to the middles of the opposite sides of the rectangular frame.

3. A wall panel as claimed in claim 2, wherein the connectors are nails.

4. A wall panel as claimed in claim 1, wherein the connectors are spaced apart from one another along the opposite sides of the rectangular frame by distances which decrease from the tops and bottoms to the middles of the opposite sides of the rectangular frame.

5. A wall panel as claimed in claim 4, wherein the connectors are nails.

6. A wall panel, comprising:

elongate frame members;

the frame members comprising top and bottom members and side members and having ends connected to one another to form a rectangular frame;

metal corner connectors connecting the ends of the frame members to one another at corners of the frame;

the metal corner connectors each comprising a hollow intermediate portion abutting the ends of a pair of the frame members, and flanges extending from the abutment portion along the pair of frame members;

the flanges comprising a pair of co-planar flanges extending at right angles to one another;

a sheathing covering the frame, the sheathing extending in surface-to-surface contact with the coplanar flanges; and

connectors securing the coplanar flanges directly to the sheathing.

7. A wall panel as claimed in claim 6, wherein the intermediate portion is in the form of the tube of square cross-section.

8. A wall panel as claimed in claim 6, wherein the intermediate portion is in the form of a tube of square cross-section.

9. A wall panel as claimed in claim 6, wherein the corner connectors each have further flanges extending to along and at right angles to the co-planar panels.

10. A wall panel as claimed in claim 9, wherein the frame members comprising pairs of frame members at opposite sides of the further flanges.

11. In combination, a corner connector and a tie down device,

the corner connector comprising a hollow intermediate portion and a pair of flanges extending from the intermediate portion at right angles to one another; and

the tie down device comprising an anchor bolt having an upper end within the hollow intermediate portion of the corner connector and a resilient retainer resiliently retaining the upper end of the anchor bolt in the intermediate portion of the corner connector.