Patent Publication Number: US-2003230042-A1

Title: Shearwall structure and method of making the same

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Art  
       [0002] The present invention relates generally to shearwall structures and methods of making a shearwall structure and more specifically to a shearwall enhancement product and method of using the same to construct a shearwall structure.  
       [0003] 2. The Prior Art  
       [0004] Shearwalls or shearwall structures are essentially walls that have been reinforced and tied down to a foundation or other base structure for the purpose of resisting lateral forces. Shearwall structures are prevalent in high risk seismic and wind zones such as those in California and the southeastern coastal areas and in other geographical areas where there is a probability of earthquakes and/or high winds. Shearwalls are intended to absorb or resist lateral forces applied to a wall panel or section of the wall structure. The ability of a wall panel or section to resist a lateral force is directly related to the dimensions of such wall panel or section. Specifically, increasing the height and decreasing the width of a wall panel or section will reduce the lateral force resistance. Likewise, reducing the height and increasing the width of the wall panel or section will increase the lateral force resistance. In evaluating the ability of a wall panel or section to resist lateral forces, the ratio of its height to its width is determined. This ratio is referred to as the “aspect” ratio. Thus, the “aspect” ratio for a wall section which is 4 feet wide and 8 feet high would be 2:1, while the aspect ratios for wall sections which are 2 feet wide and 8 feet high or 3 feet wide and 8 feet high would be ratios of 4:1 and 8:3, respectively. The lower the aspect ratio for a given wall section, the greater its ability to resist lateral forces.  
       [0005] Two basic types of shearwalls currently exist to resist lateral forces in wall sections. One is a “site built” shearwall in which a wood based sheathing panel is connected to a stud wall section via nails or screws with all of the work done at the building site. The ability of this sheathing panel and its associated stud wall construction to resist lateral forces is a function of the thickness and grade of the sheathing panel, the nail size, pattern and density connecting the wood based panel to the stud structure and the aspect ratio of the wall section. Sheathing panels commonly comprise sheets of plywood, oriented strand board, chipboard and the like.  
       [0006] A second type of shearwall is a prefabricated or factory built shearwall in which the entire wall section is prebuilt at the factory to meet certain lateral force resistance specifications. It is estimated that a prefabricated or factory built shearwall can run as much as ten times or more the cost per lineal foot of construction as a “site built” shearwall. Examples of prefabricated shearwall structures disclosed in the prior art are the shearwall structures shown in U.S. Pat. Nos. 5,706,626; 5,729,950 and 6,067,769 in which the structures are formed of metal. Another prefabricated shearwall structure comprises a conventional wood structure in which the edges of a wooden sheathing panel are reinforced by metal strips or channels.  
       [0007] Regulations and building codes currently exist for certain seismic zones which prohibit the building of “site built” shearwalls with an aspect ratio greater than a certain value (such as 2:1). Thus, to comply with these regulations and codes, the builder is required to install prefabricated, factory built shearwall panels for wall sections greater than such aspect ratio. While some effort has been made to enhance factory built shearwalls to meet the requirements of the various building codes and regulations which exist, little if anything has been done to enhance “site built” shearwalls other than increasing the sheathing panel thickness, increasing or altering the nail pattern and/or density, etc.  
       [0008] Accordingly, there is a need in the art for a shearwall enhancement product for “on site” shearwalls and for a shearwall enhancement product by which the lateral force resistance of a wall section or panel can be improved at the construction site, by the builder, without increasing the thickness of the sheathing panel.  
       SUMMARY OF THE INVENTION  
       [0009] In contrast to the prior art, the present invention provides a shearwall enhancement product by which the lateral force resistance of a wall section or panel can be significantly increased “on site” by the builder without changing or increasing the thickness of the sheathing panel.  
       [0010] Specifically, the shearwall enhancement product of the present invention includes a plurality of edge sections designed for connection to the peripheral edges of a conventional sheathing panel and a plurality of corner brackets which are designed for connection to the corners of a conventional sheathing panel.  
       [0011] More specifically, each of the edge sections comprises a generally channel shaped configuration defined by inner and outer legs. The outer leg of the channel includes a plurality of nailing holes for receiving fasteners such as nails, screws or the like, with such fasteners extending through both channel legs, through the sheathing panel and into the wooden stud of the wall structure. Each of the corner brackets includes a pair of channel shaped edge sections and a web portion extending between and interconnecting such edge sections. Each corner edge section is provided with a plurality of fastener holes to receive corresponding fasteners which are designed to extend through both legs of such edge sections, through the sheathing panel and into the stud of the wall section.  
       [0012] The method of constructing a shearwall in accordance with the present invention includes providing a stud wall structure having a sole plate, a top plate and a plurality of studs extending between the sole plate and the top plate. The method further includes providing a sheathing panel having a plurality of peripheral edge sections and corners at the intersections of adjacent peripheral edge sections and applying a corner bracket to one or more of the corners and a peripheral edge bracket section to one or more of the peripheral edges. Finally, such method includes attaching the sheathing panel, with the corner brackets and edge brackets applied, to the stud wall structure with nails, screws or other fasteners or connecting means.  
       [0013] In a preferred embodiment of the shearwall enhancement product of the present invention, the edge brackets and/or the corner brackets are provided with means for retaining the edge and/or corner brackets on the sheathing panel before it is connected with the stud wall structure. In the preferred embodiment, this means may include any means that is capable of performing this retaining function such as, but not limited to, inwardly extending protrusions such as dimples or tabs along at least one of the channel legs.  
       [0014] Accordingly, it is an object of the present invention to provide a shearwall enhancement product.  
       [0015] A further object of the present invention is to provide a shearwall enhancement product which can be installed “on site” by the builder.  
       [0016] A further object of the present invention is to provide a shearwall enhancement product by which the lateral force resistance and stiffness of a wall section can be significantly increased without increasing the thickness of the sheathing panel.  
       [0017] A still further object of the present invention is to provide a shearwall structure including such shearwall enhancement product.  
       [0018] Another object of the present invention is to provide a method for constructing a shearwall on the building site.  
       [0019] These and other objects of the present invention will become apparent with reference to the drawings, the description of the preferred embodiment and the appended claims. 
     
    
    
     DESCRIPTION OF THE DRAWINGS  
     [0020]FIG. 1 is an isometric view of a shearwall structure comprising a pair of enhanced shearwall panels connected with a stud wall structure in accordance with the present invention.  
     [0021]FIG. 2 is an elevational front view of the stud wall structure of the shearwall structure of FIG. 1 with the sheathing panels removed.  
     [0022]FIG. 3 is a view, partially in section as viewed along the section line  3 - 3  of FIG. 1.  
     [0023]FIG. 4 is an isometric view of a further shearwall structure embodying the shearwall enhancement product of the present invention.  
     [0024]FIG. 5 is an elevational view from the inside of the shearwall structure shown in FIG. 4, but without holdown hardware.  
     [0025]FIG. 6 is an isometric view of an enhanced sheathing panel in accordance with the present invention prior to installation on the stud wall structure of FIG. 4.  
     [0026]FIG. 7 is an isometric view of a corner bracket.  
     [0027]FIG. 8 is an elevational plan view of the material blank from which the corner bracket of FIG. 7 is made.  
     [0028]FIG. 9 is a view, partially in section, of an edge portion of the corner bracket as viewed along the section line  9 - 9  of FIG. 7.  
     [0029]FIG. 10 is a view, partially in section, of a portion of the web section of the corner bracket as viewed along the section line  10 - 10  of FIG. 7.  
     [0030]FIG. 11 is an isometric, fragmentary view of the edge bracket in accordance with the present invention.  
     [0031]FIG. 12 is an elevational plan view of the metal blank from which the edge bracket of FIG. 1I is constructed.  
     [0032]FIG. 13 is a view, partially in section, of the edge bracket as viewed along the section line  13 , 13  of FIG. 11.  
     [0033]FIG. 14 is an enlarged sectional view showing one embodiment of a retaining means in the form of a dimple.  
     [0034]FIG. 15 is an isometric view of a further embodiment of a retaining means.  
     [0035]FIG. 16 is a sectional view showing the retaining means of FIG. 15.  
     [0036]FIG. 17 is a sectional view showing a further retaining means. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0037] Reference is first made to FIG. 1 showing an assembled shearwall or shearwall structure  10  and to FIG. 2 showing the stud wall structure of the shearwall  10  prior to application of the sheathing panel. In the structure shown in FIGS. 1 and 2, the stud wall structure includes an outer face and comprises a sole plate  11 , a top plate  12 , a pair of end posts  14 , 14 , a center stud  15  and a plurality of intermediate studs  16 . The end posts  14  and the studs  15  and  16  are parallel to one another and extend between the sole plate  11  and top plate  12  and are interconnected with such plates in a conventional manner. In the specific embodiment of FIGS. 1 and 2, the end posts  14 , 14  are nominally 4 inches thick (actual 3½ inches), the center stud  15  is nominally 3 inches thick (actual 2½ inches) and the studs  16  are nominally 2 inches thick (actual 1½ inches). The sole plate  11  is nominally 3 inches thick (actual 2½ inches), while the top plate is a 2 ply of nominally 2 inch thick lumber (actual 1½ inches). It is understood that the various posts, studs and plates can be of various dimensions and what are shown and referred to as posts or end posts, could be referred to and considered as studs. As shown in FIG. 2, the end posts  14  are provided with holdown anchor assemblies  18  to tie the posts  14  into the concrete foundation or other substrate  20 , while the sole plate  11  is provided with a plurality of anchor bolts  19  which extend through the sole plate  11  in conventional manner and are anchored into the concrete foundation or other substrate  20 .  
     [0038] The shearwall structure of FIG. 1 includes the stud wall structure of FIG. 2 and the shearwall enhanced sheathing panels in accordance with the present invention. Specifically, the shearwall structure of FIG. 1 includes a pair of generally rectangular-shaped sheathing panels  21  and  22 . Each of the sheathing panels includes a pair of parallel vertical side edges, parallel top and bottom edges and inner and outer parallel faces. Each of the inner side edges of the panels  21  and  22  is provided with an edge bracket section  24 , and each of the outer side edges of the panels  21  and  22  is provided with a further edge bracket section  25 . Each of the top and bottom edges of the panels  21  and  22  is provided with an edge bracket section  26  and each of the peripheral or outside corners of the panels  21  and  22  is provided with a corner bracket  28 . As will be discussed below, the edge bracket sections  24 ,  25  and  26  and the corner brackets  28  and the sheathing panels  21  and  22  are connected with the stud wall structure of FIG. 2 via nails or screws.  
     [0039]FIGS. 4, 5 and  6  illustrate a further embodiment of a shearwall structure. As shown best in FIG. 5, the stud wall structure of this further embodiment includes a sole plate  29 , a top plate  30 , a pair of end posts or studs  31 , 31  and a pair of intermediate studs  32 , 32 . The enhanced sheathing panel is shown best in FIG. 4 and FIG. 6. FIG. 4 shows the enhanced sheathing panel connected to the stud wall structure, while FIG. 6 shows the inside of the sheathing panel with the edge and corner brackets attached. The enhanced sheathing panel of this further embodiment includes a conventional sheathing panel  34  with a pair of parallel side edges, parallel top and bottom edges and inner and outer parallel faces. A pair of edge bracket sections  35 , 35  are connected with the side edges of the panel  34  and a pair of edge bracket sections  36 , 36  are applied to the top and bottom edges of the panel  34 . Each corner of the panel  34  is provided with a corner bracket  28 . Like the enhanced sheathing panels of FIG. 1, the enhanced sheathing panel of FIG. 4 is connected with the stud wall section by a plurality of nails, screws or other similar connecting means.  
     [0040] Reference is next made to FIGS. 7, 8,  9  illustrating the details of the corner bracket  28 . Each corner bracket  28  includes a pair of corner edge sections  39  and  40  and a web section  41 . The web  41  is integrally formed with each of the edge sections  39  and  40  and spans the area between such edge sections  39  an  40 . Thus, the web  41  interconnects the edge sections  39  and  40 . An open corner area  42  is provided at the extended intersection of the edge sections  39  and  40 . In the preferred embodiment, the edge sections  39  and  40  lie in a common plane and are positioned at 90° relative to one another. It is contemplated that the edge sections  39  and  40  could be interconnected by a structure other than the web  41 .  
     [0041] As shown best in FIGS. 7 and 9, each of the peripheral edge sections  39  and  40  comprises a channel or U-shaped configuration having an open channel area or panel receiving cavity  44  defined by first and second or outer and inner generally parallel legs  45  and  48  and a base or base leg  46  extending between the legs  45  and  48 . The leg  45  is integrally joined along its base edge with the base leg  46  and includes a free edge  47  which extends outwardly at right angles from the base leg  46 . The leg  48  is also integrally connected along its base edge with the base  46  and extends outwardly at right angles from the base  46  and is integrally formed with the web  41 . Although FIG. 9 is a cross-section of a portion of the corner edge section  39 , the edge section  40  is preferably of the same cross-sectional configuration and structure.  
     [0042] The corner edge sections  39  and  40  each include an outer end  49  and  50  and an inner end  51  and  52 , respectively. As shown, the inner ends  51  and  52  are adjacent to the open corner area  42 . Each of the legs  45  of the edge sections  39  and  40  is provided with a plurality of nailing openings  54 . The nailing openings  54  in the preferred embodiment are longitudinally spaced along the length of the sections  39  and  40 . Alternate nailing patterns can, however, be provided. The leg section  48  is free of nailing holes, although such holes could be provided if desired.  
     [0043] The web  41  is generally planar and is integrally joined along each of its sides with the legs  48  of the edge sections  39  and  40 . Thus, the web  41  is essentially an extension of the legs  48 , 48  and spans the area between them. The web  41  includes an inner or corner edge  43  defining a portion of the open area  42  and a free edge  55  extending between the ends  48  and  50  of the edge sections  39  and  40 . As shown best in FIGS. 7, 8 and  10 , the web  41  is provided with a plurality of embossed stiffening ribs  56  to provide structural rigidity and strength to the web  41 . The ribs  56  are of various lengths depending on their position on the web and extend at a right angle to the free edge  55  and at approximately a 45 degree angle relative to the edge sections  39  and  40 . The web  41  is provided with a plurality of nail holes  58  to retain the corner bracket  28  relative to the sheathing panel. If desired, other retaining means such as those shown in FIGS.  11 - 17  may also be provided to one of the corner edge sections.  
     [0044]FIG. 8 illustrates the material blank from which the corner bracket  28  is constructed. Preferably, the corner bracket is constructed of galvanized steel such as 20 gauge Galv ASTM A365. However, it can be made from other materials and from other thicknesses and types of steel provided those other materials provide the desired strength to the corner bracket when formed. The corner bracket can be of various sizes and configurations although the preferred embodiment provides a bracket in which each of the edge sections  39  and  40  are about the same length. Advantages of the present invention could, however, be achieved with a structure in which the sections  39  and  40  are of different lengths. The common use of a corner bracket to enhance a shearwall in accordance with the present invention will usually be a structure in which the sections  39  and  40  are positioned at right angles to one another. However, advantages of the present invention will still be achieved with a structure in which the sections  39  and  40  are at other angles relative to one another.  
     [0045] Preferably, the length of the edge sections  39  and  40  should be from about 5 to 20 inches, more preferably from about 10 to 20 inches and most preferably from about 12 to 16 inches. The distance between the legs  45  and  48 , and thus the width of the base leg  46 , should approximate the thickness of the sheathing panel being used. This permits the corners of the sheathing panel to be received by the panel receiving cavity  44  when assembled. To assist in retaining the bracket in the panel corners, the cavity width may be slightly smaller than the panel thickness. The height of the leg  45  may vary, but preferably is at least about one-half inch and more preferably from one-half to 1½ inches or more.  
     [0046] Reference is next made to FIGS. 11, 12 and  13  showing various views of the edge bracket  33  from which the various edge bracket sections are cut. As illustrated best in FIGS. 11 and 13, the edge bracket  33  is a generally elongated U-shaped or channel member having a pair of laterally spaced legs  60  and  61  and a base leg  62 . The leg  60  is the outer leg of the edge bracket  33  and includes a base edge  64  and a free edge  65 . The leg  60  is joined to the base leg  62  along the base edge  64  and extends outwardly from the base leg  62  at substantially right angles and terminates at the free edge  65 . The leg  60  is provided with a plurality of nailing holes  66  which are spaced longitudinally along the leg  60 . A variety of nailing patterns may be utilized.  
     [0047] In a preferred embodiment, the leg  60  is also provided with an edge bracket retaining means in the form of a plurality of edge bracket retaining members such as the protrusions  68 . As shown in FIGS.  11 - 14 , the leg  60  is provided with a plurality of inwardly extending protrusions or dimples  66 . As will be described in greater detail below, these protrusions  68  function to assist in retaining the edge bracket  33  to the edge of the sheathing panel prior to connection of the reinforced sheathing panel to the stud wall section. A variety of other retaining means can also be utilized. One alternate structure is shown in FIGS. 15 and 16. This includes an inwardly extending tab  69  which is cut from the leg  60  and is bent inwardly as shown. A further structural embodiment is illustrated in FIG. 17. This embodiment is similar to that of FIGS. 15 and 16 except that the cutout member  70  is bent outwardly at the point  73  and then inwardly at its distal end to provide an inwardly extending prong  71 . The prong  71  may be driven into the sheathing panel after positioning of the bracket  33 .  
     [0048] The leg  61  is parallel to and spaced from the leg  60  to form the panel receiving cavity  37 . The leg  61  is integrally connected with the base leg  62  along its base edge  72  and extends outwardly from the base leg  62  at right angles and terminates at the free edge  74 .  
     [0049]FIG. 12 illustrates the material blank from which the edge bracket  33  is constructed. Like the corner bracket  28 , the edge bracket  33  is preferably constructed of a galvanized steel material such as 20 gauge Galv ASTM A653. Other materials and other thicknesses and types of steel, however, can be used if desired. In the preferred embodiment, the legs  60  and  61  are at least about one-half inch in height and preferably at least one-half to 2½ inches or more in height. Most preferably, the height of the legs  60  and  61  is about 1¼ to 2-1½ inches. The width of the panel receiving cavity preferably approximates the thickness of the sheathing panel to be used.  
     [0050] Having described the details of the shear wall enhancement product and the resulting shear wall structure, the method of making or constructing a shearwall structure in accordance with the present invention is as follows. First, a stud wall structure is constructed. This can take any desired form, but is typically a stud wall structure such as that shown in FIGS. 1, 2,  4  and  5 . Next, a sheathing panel is cut to the proper size so that it will cover the outer face of the stud wall structure and its associated elements when installed. A corner bracket  28  is then applied to each of the corners of the sheathing panel by inserting its adjacent edges into the channels or panel receiving cavities  44  formed by the leg sections  45  and  48  of each edge section  39  and  40 . In this application, the web  41  is positioned adjacent to the inner surface of the panel. If desired or needed, the corner brackets  28  can be retained to the sheathing panel by fasteners through the holes  58  of the web  41 .  
     [0051] Edge bracket sections are then applied or cut and applied to each exposed edge of the sheathing panel by inserting the sheathing panel edge into the channel or panel receiving cavity  37  formed by the legs  60  and  61 . When inserted, the inwardly protruding dimples  66  or other retaining means engage the outer surface of the panel and assist in retaining the edge bracket section to the panel. Because of the varying lengths of edge bracket sections that may be required, a length of edge bracket stock  33  may need to be cut to the correct length before application to the sheathing panel. Preferably the edge bracket sections should be applied to the entirety of the exposed panel edge between adjacent corner brackets  28 .  
     [0052] Although certain benefits will be achieved in accordance with the present invention without having corner brackets at each corner and without having an edge bracket section applied to each exposed edge, it is preferable for at least one corner and at least one edge of the sheathing panel to be provided with a respective corner bracket and edge bracket section. More preferably, at least two corners and at least two of the exposed edges should be provided with corner brackets and edge bracket sections and most preferably all four corners and all four exposed edges of the sheathing panel should be provided with corner brackets and edge bracket sections. This is the preferred structure shown in the drawings.  
     [0053] Certain shear wall enhancement properties can also be obtained by applying a corner bracket to each corner of a sheathing panel, without using the edge bracket sections or by applying edge bracket sections to less than all of the exposed sheathing panel edges. This is particularly true as the length of the corner bracket edge sections  39  and  40  increases or as the width of the sheathing panel decreases. For example, a sheathing panel which is 32 inches wide and 8 feet high would preferably have a corner bracket  28  at each corner, but an edge bracket section only on its two long exposed edges.  
     [0054] After the corner brackets and edge bracket sections have been applied to the sheathing panel, the enhanced sheathing panel is positioned onto the outer face of the stud wall structure and connected to such structure by nails or screws or other fasteners through the holes  54  in the corner brackets and the holes  66  in the edge bracket sections. These fasteners extend through the outer legs or leg sections of the corner or edge brackets, through the sheathing panel, through the other legs or leg sections of the corner or edge brackets and then into the corresponding stud wall structure element. For the top edge of the sheathing panel this would be the top plate of the stud wall structure, for the bottom edge of the sheathing panel this would be the sole plate and for the side edges of the sheathing panel, this would be the end posts or other studs. To the extent there are intermediate studs between the side edges of the sheathing panel, nails or screws are driven through the panel and into such intermediate studs.  
     [0055] Although the preferred application of the present invention is to apply a sheathing panel with the shearwall enhanced hardware (the edge and/or corner brackets) to only one side of the stud wall structure, the present invention also contemplates applying a sheathing panel with such shearwall enhancement hardware to both sides of the stud and framing.  
     [0056] Further, although some regulations may restrict certain types of shearwall structures with certain “aspect” ratios in certain locations, nothing precludes the application of the present invention to all shearwall structures, regardless of their “aspect” ratio.  
     [0057] Although the description of the preferred embodiment has been quite specific, it is contemplated that various modifications could be made without deviating from the spirit of the present invention. Accordingly, it is intended that the scope of the present invention be dictated by the appended claims rather than by the description of the preferred embodiment.