Systems, Methods and Apparatus for Forming a Wooden Construction Shear Wall

FIELD OF THE DISCLOSURE

The present disclosure relates generally to construction of wooden structures, and more particularly, to methods and systems for forming, testing and utilizing shear wall structures within a wooden structure.

BACKGROUND

Conventional shear walls are one of the most commonly used, lateral force resisting systems used in wooden building construction. Wooden structures, such as typical residential construction and similar scale structures, up to about five stories, typically include one or more conventional shear walls to add lateral stability to the structure.

Conventional shear walls can be built at the construction site, or can be purchased as a premanufactured structural component. There are many, proprietary, commercially available, premanufactured plywood shear walls available in the market. The building code-based design capacities for field constructed plywood shear walls have remained essentially unchanged for nearly a century. The current design capacities of conventional shear walls, as published in the Table 4.3a in the 2021 edition of the Special Design Provisions for Wind and Seismic Published by the American Wood Council (AWC), are based on the structural testing that was conducted on plywood diaphragms conducted in the 1950's Countryman, David R. Lateral Tests on Plywood Sheathed Diaphragms. Report 55, American Plywood Association, Tacoma, Washington, 1952. The current design capacities of conventional shear walls are essentially derived by dividing the ultimate strength obtained from monotonic load testing by a load factor of approximately 3 as described in Adams, Noel R., 1962. “Plywood Shear Walls,” Research Report No. 105, American Plywood Association. There have been many advancements in technology as well as material science since 1962, however, the design capacities of conventional shear walls have remained effectively the same.

FIG. 1 is a schematic diagram of an example of a rectangular-shaped, conventional shear wall 100. The conventional shear wall includes a conventionally framed wall including a single sided structural 1 grade plywood sheet (hereafter referred to as a plywood panel) 114A, 114B. The plywood panels are typically 15/32 inches (12 mm) thick. The plywood panels are nailed with 10d common nails 116, 118 at about 2 inches (5 cm) on-center (o.c.) S1, along the plywood panel edges. A 10d common nail has a diameter of about 0.148 inches (3.76 mm) and a length of about 3 inches (7.6 cm) and a nail head with a diameter of about 0.312 inches (7.9 mm). Nails 116, 118 at the plywood panel edges are staggered. The plywood panels 114A, 114B are also secured to the vertical framing members 102 with 10d common nails 120 at about 12 inches (30 cm) o.c. S2. Middle edges of the plywood panels 114A′, 114B′ meet in the middle 105 of the conventional shear wall, on a center post 104.

Framing members are typically 2 inch by 6 inch (2×6), 4 inch by 6 inch (4×6) and 6 inch by 8 inch (6×8) nominal dimensional lumber. The framing members include 2×6 vertical framing members 102, 4×6 center post 104 and 6×8 end posts 106. The vertical framing members 102, center post 104 and end posts 106 extend between a 4×6 mudsill 108 and a 2×6 doubled top plate 110. The plywood panels 114A, 114B resist lateral shifting and thus improve the ability of the conventional shear wall, and the wooden structures containing the conventional shear wall, to resist lateral forces. The example, conventional shear wall 100 is nominally 8 feet (2.4 meters) wide and nominally 9 feet (2.7 meters) tall and having only two plywood panels 114A, 114B, however, it should be understood that the conventional shear wall can be taller than 9 feet (2.7 meters) and wider than 8 feet (2.4 meters) and include more than two plywood panels.

Conventional shear walls add lateral strength to the wooden structure. However, conventional shear walls do still fail when sufficient lateral force is applied to the conventional shear wall. Typical failure mechanisms include nail slip, edge tear out and nail head pull through. Each of the typical failure mechanisms contribute significantly to the deflection and ductility of the conventional shear wall 100. The nail slip failure mechanism occurs when the forces subjected to the nail cause the nails to bend and slip or decrease penetration from the connecting stud wall member. Edge tear out failure mechanism occurs when nails, that are placed near plywood panel edges, tear out of the edge of the plywood panel when the plywood panel displaces due to the lateral forces imparted on the conventional shear wall. The nail head pull-through failure mechanism occurs when the plywood panel displaces, causing the nails to bend and the nail heads pull through the thickness of the plywood panel. One or more of these failure mechanisms can occur when the conventional plywood shear wall is subjected to lateral loads exceeding the design capabilities and the individual plywood panels begin to deform from a flat, rectangular form and into a flexed, rippled, twisted, non-flat panel. The plywood panel deformation is also referred to as racking. Another important aspect of racking is that adjacent plywood panel edges 114A′, 114B′ move in opposite directions when the conventional shear wall 100 racks due to excess lateral loads.

It is in this context that the following embodiments arise.

SUMMARY

Broadly speaking, the present disclosure fills these needs by describing an improved wooden shear wall system. It should be appreciated that the present disclosure can be implemented in numerous ways, including as a process, an apparatus, a system, computer readable media, or a device. Several inventive embodiments of the present disclosure are described below.

At least one implementation, includes forming a wooden shear wall including a framed wall section having multiple framing members including a first and second end posts, a center post framing member, a mudsill bottom plate coupled to a bottom end of the framing members and a top plate coupled to a top end of the framing members. Two plywood panels are fastened to a first side of the framed wall section with a ductile metal gauge strap, ductile metal gauge strap securing adjacent edges of the plywood panels to the center post and multiple metal gauge straps, disposed along the edges of the plywood panels secure the edges of the plywood panels to the framed wall section.

The ductile metal gauge strap includes multiple cutouts. The cutouts can have a substantially triangular shape. The cutouts can be disposed to alternate in orientation to form diagonal web sections. The diagonal web sections can have a width of between 0.2 inches and 0.6 inches. The cutouts are disposed offset and alternating across a width of the ductile metal gauge strap. The cutouts have a width equal to about 50 percent of a width of the ductile metal gauge strap.

Another implementation can include a method of constructing a shear wall including, building a framed wall section including multiple vertical framing members and a center post disposed between and secured to a top plate and a bottom plate, securing a first plywood panel to a first side of the framed wall section, securing a second plywood panel to a first side of the framed wall section. The first plywood panel has a first middle edge and the second plywood panel has a second middle edge disposed adjacent to the first middle edge. A ductile metal gauge strap disposed along a length of the first middle edge and spanning across the first middle edge and the second middle edge, wherein a first selection of nails secures the ductile metal gauge strap through the first plywood panel and the second plywood panel and into the center post.

Other aspects and advantages of the disclosure will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings.

FIG. 1 is a schematic diagram of an example of a rectangular-shaped, conventional shear wall.

FIG. 2 is a schematic diagram of a first embodiment of a MeGa wall, for implementing embodiments of the present disclosure.

FIG. 3 is a schematic diagram detailed view, of a first embodiment of metal gauge straps, for implementing embodiments of the present disclosure.

FIG. 4 is a detailed view, schematic diagram of a first embodiment of metal gauge straps, for implementing embodiments of the present disclosure.

FIG. 5 is a detailed view, schematic diagram of a second embodiment of a single, wider, metal gauge strap, for implementing embodiments of the present disclosure.

FIG. 6 is a schematic diagram of a second embodiment of a MeGa wall, for implementing embodiments of the present disclosure.

FIG. 7 is a detailed view of a second embodiment of a single, metal gauge strap, for implementing embodiments of the present disclosure.

FIG. 8 is a detailed view, schematic diagram of a third embodiment of a single, metal gauge strap, for implementing embodiments of the present disclosure.

FIG. 9 is a schematic diagram of a rectangular-shaped, conventional shear wall, configured for testing purposes, for implementing embodiments of the present disclosure.

FIG. 9A is a schematic diagram of a third embodiment of a MeGa wall, for implementing embodiments of the present disclosure.

FIG. 10A is a top view schematic diagram of a test fixture, for testing shear walls, for implementing embodiments of the present disclosure.

FIG. 10B is a front view schematic diagram of a test fixture, for testing shear walls, for implementing embodiments of the present disclosure.

FIG. 11 show placement of strain gauges, for implementing embodiments of the present disclosure.

FIG. 12 illustrates a MeGa Wall that has failed in in-plane shear as well as buckled out-of-plane, for implementing embodiments of the present disclosure.

FIG. 13 is a graphical representation of a Loading and Unloading Cycle of the MeGa Wall, for implementing embodiments of the present disclosure.

FIG. 14 illustrates the force-displacement backbone curves of the conventional shear wall and MeGa Walls, for implementing embodiments of the present disclosure.

FIG. 15 is a graphical representation of the energy dissipation versus drift curves comparing the shear walls can absorb before failure, for implementing embodiments of the present disclosure.

FIG. 16 is a graphical representation of the values detected by the strain gauges during testing a shear wall, for implementing embodiments of the present disclosure.

FIG. 17 is a graphical representation of an energy elastic curve and the corresponding load displacement curve, for implementing embodiments of the present disclosure.

FIG. 18 illustrates backbone curves obtained from testing Mega Walls, for implementing embodiments of the present disclosure.

FIG. 19 illustrates hysteresis curve obtained from testing Mega Walls, for implementing embodiments of the present disclosure.

FIG. 20A is an illustration of the shear failure of Mega Wall, for implementing embodiments of the present disclosure.

FIG. 20B is an illustration of the shear failure of Mega Wall, for implementing embodiments of the present disclosure.

FIG. 21 is a graphical representation of the force measured by strain gauges on the metal gauge strap, for implementing embodiments of the present disclosure.

FIGS. 22-25 provide experimental calculations and modeling of the MeGa walls, for implementing embodiments of the present disclosure.

DETAILED DESCRIPTION

Several exemplary embodiments for building, testing and utilizing an improved shear wall structure will now be described. It will be apparent to those skilled in the art that the present disclosure may be practiced without some or all of the specific details set forth herein.

Various iterations of a design build test program resulted in strengthening conventional plywood shear walls with the use of metal gauge straps to produce improved plywood shear wall designs which are referred to as Metal Gauge reinforced plywood shear wall and MeGa wall, for short reference herein.

The MeGa walls eliminate or reduce the typical failure mechanisms of conventional plywood shear walls including nail slip, edge tear out and nail head pull. Eliminating the nailed connection as a controlling failure mode provides significantly higher, lateral load capacities for the MeGa wall. The MeGa wall includes metal gauge straps that allow the MeGa wall to achieve higher lateral load capacities while also retaining the ductility similar to that of conventional plywood shear walls. The metal gauge straps are disposed along the nailed edges of the plywood panels 114A, 114B to eliminate the conventional failure modes and allow the plywood panels to reach their ultimate capacity. The metal gauge strap includes a more ductile configuration to avoid a brittle shear failure.

FIG. 2 is a schematic diagram of a first embodiment of a MeGa wall 200, for implementing embodiments of the present disclosure. The MeGa wall includes plywood panels 114A, 114B and vertical framing members 102, the center post 104 and the end posts 106 extending between a 4×6 mudsill 108 and a 2×6, doubled, top plate 110, substantially similar to the conventional shear wall described in FIG. 1 above. The MeGa wall 200 also includes metal gauge straps 202, 204A, 204B, 206, 208 and 210 extend along the entire length of each vertical edge of the plywood panels 114A, 114B and across the entire length of the MeGa wall.

The plywood panels 114A, 114B are attached to the framing members with a metal gauge straps 202, 204A, 204B, 206, 208, 210 secured with 10d common nails at the plywood panel edges and along the center post 104, with a nail installed in every hole of the metal gauge straps. Additionally, the field nail spacing S2′ on the vertical framing members 102 of the MeGa wall was reduced from 12 inches (30 cm) o.c., as used on the conventional shear wall 100, to 6 inches (15 cm) o.c.

A hold down unit 212 is also shown, the hold down unit is included for securing the MeGa wall 200 to a test fixture, for testing purposes, as will be described in more detail below. The hold down unit would also be included in an actual MeGa wall in use in a wooden structure for securing the MeGa Wall to the foundation of the wooden structure. It should be understood that the dimensional lumber sizes described herein are nominal measurements which can be about 0.5 inches (12 mm) smaller. By way of example a 2 inch (5 cm) by 6 inch (15 cm) (i.e., 2×6) can be nominally about 1.5 inches (3.8 cm) by 5.5 inches (14 cm). Similarly, the plywood panels 114A, 114B are described as having a height of about 9 feet (2.7 meters), a width of about 4 feet (1.2 meters) and a thickness of about 0.5 inches (12 mm), however each of the height, width and thickness of the plywood panels may vary as required for the design for the specific application.

FIG. 3 is a schematic diagram detailed view 230, of a first embodiment of metal gauge straps 202, 204A, 204B, 206, 208 and 210, for implementing embodiments of the present disclosure. The metal gauge straps can have a thickness of 14 gauge (1.8 mm), 16 gauge (1.5 mm) and 18 gauge (1.2 mm) or other thicknesses, and a width S3 of about 1.5 inches (3.8 cm) to about 3 inches (7.6 cm) or other widths, as may be called for in the specific design specification. The metal gauge straps include multiple holes 302. The holes have a diameter of about 0.17 inches (4.3 mm), sufficiently large enough for 10 d common nails. The holes 302 are spaced S5 about 1.5 inches (3.8 cm) lengthwise and spaced S4 about 1.5 inches (3.8 cm), laterally across the width of the metal gauge strap. The holes 302 are staggered, about 0.75 inches (19 mm), along the length of the strap, as shown.

FIG. 4 is a detailed view 240, schematic diagram of a first embodiment of metal gauge straps 204A, 204B, for implementing embodiments of the present disclosure. The metal gauge straps 204A, 204B are disposed along the middle edges 114A′, 114B′ of the plywood panels 114A, 114B and are secured through the plywood panels and into the center post 104. Metal gauge strap 204A is disposed immediately adjacent to metal gauge strap 204B.

FIG. 5 is a detailed view 240′, schematic diagram of a second embodiment of a single, wider, metal gauge strap 204AB, for implementing embodiments of the present disclosure. The metal gauge strap 204AB is a single, wider metal gauge strap disposed across the adjacent edges 114A′, 114B′ of the plywood panels 114A, 114B, in place of the two separate, narrower, metal gauge straps 204A, 204B. The metal gauge strap 204AB has a width S6 approximately twice the width S3 of the metal gauge straps 204A, 204B. In at least one implementation, S6 is about 3.0 inches (7.6 cm), although it should be understood that S6 could be greater than about 3.0 inches. Holes 302 are distributed across the metal gauge strap substantially similar to the holes in the metal gauge straps 204A, 204B.

FIG. 6 is a schematic diagram of a second embodiment of a MeGa wall 250, 250′, for implementing embodiments of the present disclosure. The MeGa wall 250, 250′ includes plywood panels 114A, 114B, vertical framing members 102, center post 104 and end posts 106 extending between a 4×6 mudsill 108 and a 2×6 doubled top plate 110, substantially similar to the conventional shear wall 100 described in FIG. 1 above.

Metal gauge straps 202, 206 extend along the entire height of each outer, vertical edge of the plywood panels 114A, 114B and across the entire length of the MeGa wall 250, 250′. Metal gauge straps 208, 210 extend across the entire width of the MeGa wall. The MeGa wall 250 also includes a metal gauge strip 640 along the center post 104 and spanning across the adjacent, middle edges 114A′, 114B′ of the plywood panels 114A, 114B. Similarly, the MeGa wall 250′ includes a metal gauge strip 640′ along the center post 104 and spanning across the adjacent, middle edges 114A′, 114B′ of the plywood panels 114A, 114B.

FIG. 7 is a detailed view of a second embodiment of a single, ductile, metal gauge strap 640, for implementing embodiments of the present disclosure. The metal gauge strap 640 is a single, wider metal gauge strap disposed across the adjacent edges 114A′, 114B′ of the plywood panels 114A, 114B, similar to metal gauge strap 240′, described in FIG. 5 above. The ductile metal gauge strap 640 has a width S6. Holes 702 are distributed across the metal gauge strap substantially similar to the holes 302 in the metal gauge strap 240′. The metal gauge strap 640 includes multiple, substantially triangular-shaped cutouts 710. The cutouts 710 alternate left and right, as shown, to form diagonal web sections 712. The web sections have a dimension S11 of about 0.6 inches (15 mm). The cutouts 710 have a length S12 of about 1.6 inches (4 cm) and a width S14 of about 50% of the width S6 of the ductile, metal gauge strap. The number, length, width and spacing of the cutouts 710 and the web sections 712 allow the metal gauge strap 640 to be tuned to a desired failure load. In this exemplary implementation, the holes 302 are separated along the length of the metal gauge strap 640 by S7 of about 1.5 inches (3.8 cm). The holes 302 are separated across the width of the metal gauge strap 640 by S8 of about 1.5 inches (3.8 cm). The holes 302 are arranged in offset pairs across the width of the metal gauge strap 640. The holes pairs are offset by about 0.375 inches (9 mm). the holes 302 are spaced away from the edges of the strap 640 by about 0.5 inches (12 mm).

FIG. 8 is a detailed view 640′, schematic diagram of a third embodiment of a single, metal gauge strap 640′, for implementing embodiments of the present disclosure. The metal gauge strap 640′. The metal gauge strap 640′ includes multiple, substantially triangular-shaped cutouts 810. The cutouts 810 alternate left and right, as shown, to form web sections 812. The web sections have a dimension S13 of about 0.2 inches (5 mm). The number, length, width and spacing of the cutouts 810 and web sections 812 allow the metal gauge strap 640′ to be tuned to a desired failure load. The metal gauge straps 640, 640′ can be cut with a band saw, a plasma cutter or a water jet or equivalent manufacturing tools.

FIG. 9 is a schematic diagram of a rectangular-shaped, conventional shear wall 100′, configured for testing purposes, for implementing embodiments of the present disclosure. The conventional shear wall 100′ includes a hold down unit 212 for securing the shear wall for testing purposes. FIG. 9A is a schematic diagram of an adjusted MeGa wall 250″, configured for testing purposes, for implementing embodiments of the present disclosure. MeGa wall 250″, was the same height as MeGa wall 200, 250, however the length was reduced to 4.5 feet (1.37 m) so the effects of in-plane bending of a slender wall could be evaluated.

FIG. 10A is a top view schematic diagram of a test fixture 1000, for testing shear walls 1030, for implementing embodiments of the present disclosure. FIG. 10B is a front view schematic diagram of a test fixture 1000, for testing shear walls, for implementing embodiments of the present disclosure. The test fixture includes a computer controlled hydraulic actuator 1002 capable of approximately 84 kips push and 52 kips of pulling force. The actuator is bolted to a spreader beam 1004 that is attached to a structural steel reaction frame 1006. The reaction frame 1006 is post-tensioned to a strong floor and has capacity to resist the full force of the actuator 1002. The actuator is connected to a W12×22 loading beam 1010 at its centroid. The loading beam is connected to a test shear wall's 1030 double top plates with multiple screws through pre-drilled holes in a bottom flange of the loading beam.

The test shear wall's 1030 mudsill is connected to a W12×53 foundation beam 1014 with threaded rods that are welded to the top flange of the foundation beam. The foundation beam provides a continuous member to secure the test shear wall 1030, at various points, to resist the shear and overturning forces. The foundation beam is bolted to concrete footings 1016 with bolts from the bottom flange of the foundation beam to threaded inserts in the concrete footings. The concrete footings are post-tensioned to the concrete strong floor 1018 with anchor bolts 1020 to secure the foundations to the floor and resist the shear force through friction between the concrete foundation and the strong floor. Two “W” beams 1012 on each side of the test shear wall 1030 are attached to several free-standing frames 1024 that provide out-of-plane lateral support for the wall during testing.

A conventional shear wall 100′, as shown in FIG. 1 above, was selected as a baseline test candidate to determine the lateral force required to cause the conventional shear wall to fail. For testing purposes, the height and length of the conventional shear wall has a height of 9′-0½″ (2.76 meters) and a width of 8′-0″ (2.44 meters) respectively. Two hold downs 112 were installed on the tension post 106 with screws to resist the overturning forces. For testing purposes, MeGa walls 250 and 250′ have the same height and width as the conventional shear wall 100′.

The testing protocols for each of the test shear walls 1030 are based on the procedure described in APA 154 (Tissell, John R., 1993. “Wood Structural Panels Shear Walls,” American Plywood Association, Report NO. 154, May 1993 revision), which has three test cycles. A first test cycle loads the test shear wall to the design value established by the SDPWS code (Special Design Provisions for Wind and Seismic with Commentary, 2021 edition, American Wood Council, Leesburg, Virginia). A second test cycle loads the test shear wall to twice the design value. Lastly, a third test cycle loads the test shear wall until failure. Following each of the test cycles, the test shear walls are fully unloaded before proceeding to the next test cycle.

The design value for the conventional shear wall 100′ was determined using the SDPWS code to be 6960 lbs. of lateral force given the framing configuration described herein. The corresponding test shear wall and force level were used for comparison to each of the test shear walls. The test cycles conducted for each of the test shear walls and the corresponding target values are referenced in Table #2.

TABLE 2

Conventional

Test

shear wall
MeGa
MeGa
Mega

Number
Loading
100
Wall 200
Wall 250
Wall 250′

1
Design
100%
25%
25%
25%

Stop (lb)
6960
1740
1740
980

2
Design
200%
100%
100%
100%

Stop (lb)
13920
6960
6960
3915

3
Design
300%
200%
200%
200%

Stop (lb)
20880
13920
13920
7930

4
Design
350%
Failure
Failure
300%

Stop (lb)
24360
7 inches
10 inches
11750

5
Design
Failure

450%

Stop (lb)
7 inches

17600

6
Design

Failure

Stop (lb)

8 inches

As mentioned above the test shear walls generally followed the loading protocol described in APA 154, for this shear wall test, there were two additional loadings added prior to the final load to failure: 300% and 350% of the design load for each test shear wall. These additional test shear wall loadings were added to slowly approach a corresponding maximum shear wall capacity.

An additional first cycle, to only 25% of design load, was added to the testing protocol to confirm the test shear wall was assembled and mounted correctly to the test fixture. The second test cycle, to 100% of the design load, assesses the test shear walls' elastic response under stress conditions allowed by code. The third test cycle, to 200% of the design load, further challenged the test shear walls and examine the respective ability to withstand significantly increased forces. The first three cycles were tested until the actuator reached the predetermined force. The final test cycle to failure was performed by transitioning the actuator to a deflection control cycle.

For MeGa wall 250, the final test cycle was set to a displacement of 7 inches (17.8 cm). The displacement level provided valuable insights into the MeGa wall's 250 behavior and performance at near maximum displacement capacity. For the MeGa wall 250, the modified strap design configuration allowed for greater ductility for the MeGa wall, therefore, a higher target displacement of 10″ was set for the final test cycle, allowing for a more extensive examination of the MeGa wall's 250 overall performance.

MeGa wall 250″, has a shorter length of 4.5 feet (1.37 m) compared to the MeGa walls 200, 250 measuring 8′-0″, the design shear value was adjusted to 3915 pounds.

The testing protocol for MeGa wall 250′, has two additional test cycles: 300% and 450% of the design load. Both additional test cycles were conservatively added to assess the ductile strap buckling. The strain gauge values recorded at 300% of the design load were used to calculate a rough estimate of when the center strap 640′ would buckle. The center strap 640′ buckled at slightly less than 450% of the design load. Like the MeGa walls 200, 250, MeGa wall 250′, was fully unloaded before proceeding to the next test cycle load. The test to failure was set to 10″ of displacement to accommodate for the increased deflection allowed by the improved ductile strap 640′.

The design philosophy of the ductile straps 640, 640′ was to make the strap strong enough for the shear wall to resist higher lateral loads, near its ultimate capacity, but weak enough to yield prior to a sudden, abrupt shear failure of the plywood panels 114A, 114B. Small scale testing was performed on various prototypes to narrow in on a viable design that could be easily fabricated and installed. Once the small-scale testing was completed, the ductile strap was installed on a full-scale shear wall with strain gauges attached to the strap, as shown in FIG. 11, above, to measure the corresponding strain so that the forces in the strap could be calculated and compared with calculations. This provided a method of calculating the force in the ductile strap, given the expected design capacity of the shear wall, so that the strap can be fabricated to provide the added strength required for increased shear capacity of the shear walls, but also act as a fuse to protect the shear wall from sudden, abrupt shear failure.

The small-scale tests give insight on how the strap will behave on a shear wall. As adjacent panels rack, the adjacent edges 114A′, 114B′ of the plywood panels will attempt to slip past one another. As described above, this slip between adjacent edges is typically held limited panel edge nailing to a common stud. In the embodiments described herein, the slip between adjacent edges is limited by the common center strap 240′, 640, 640′ spanning across the adjacent edges and secured to the center post with nails through the strap and the plywood panels. This shear transfer from one plywood panel to an adjacent plywood panel, through the strap causes longitudinal shear in the strap. The use of web sections 712, 812 within the strap can be fine-tuned to permit ductile deformation prior to abrupt rupture in the plywood panels 114A, 114B. This internal deformation will result in some compressed web sections that may experience a buckling limit state.

FIG. 12 illustrates the MeGa wall 250′ that has failed in in-plane shear as well as buckled out-of-plane, for implementing embodiments of the present disclosure. FIG. 13 is a graphical representation of a Loading and Unloading Cycle of the MeGa wall 250′, for implementing embodiments of the present disclosure. MeGa wall 250′, behaved mostly linear until the buckling of the compression sections in the strap during the fourth test loading cycle. Some residual displacement in the linear region was also present, which did not occur during testing the MeGa wall 250. The buckling began at a lateral force of 17,500 lbs. at the end of the fourth test cycle. The buckled test shear wall is shown in FIG. 12, where the force vs displacement curve flattens out and then returns to a significand residual displacement. The actuator force peaked at 24400 lbs. with a drift of 6.75 inches. The test shear wall was forced to a displacement of 8 inches and then unloaded to conclude the test.

FIG. 14 illustrates the force-displacement backbone curves of the conventional shear wall 100, MeGa wall 250, MeGa wall 250′, and an adjusted MeGa wall 250″, for implementing embodiments of the present disclosure. The dotted curves result from linear regressions of the elastic regions of each curve that visualize the walls' modulus of elasticity. The adjusted MeGa wall 250″, curve is determined by analyzing the force travelling vertically through the center strap at the panel joint. A higher lateral force will be needed for an 8 foot shear wall to apply a specific vertical force along the strap in comparison to the 4.5 foot wall. In a comparison of moments applied at the bottom of the compression post, the adjusted MeGa wall 250″, lateral force is multiplied by a factor of 8/4.5 in order to produce the adjusted curve. This is an approximation, because other factors, such as the bending contribution to wall deflection, may begin to play a larger role in the displacement and strength.

Comparing the elastic regions of the curves, adjusted MeGa wall 250″ has the mildest slope. The milder slop indicates a lowest modulus of elasticity compared to the other shear walls. Since adjusted MeGa Wall 250″, is only 4.5 feet long compared to the 8-foot wide MegA walls 200, 250, these properties make sense. As the length of the shear wall increases, more force is needed to put the shear wall into bending.

Adjusted MeGa wall 250″, is adjusted to estimate behavior as an 8-foot shear wall, with the slope similar to the conventional shear wall 100. MeGa Wall 250 has the steepest slope and modulus of elasticity due to the stiffness of the non-buckling, central strap. It is inferred that the buckling strap in MeGa Wall 250″ allows the adjacent plywood panel edges to displace similarly to the conventional shear wall 100, lowering the stiffness, whereas the non-buckling, central strap prevents this from happening.

Adjusted MeGa wall 250″, proved to be the most effective shear wall in terms of capacity and ductility according to the adjusted curve. At the maximum force of 43,372 lbs., the adjusted MeGa wall 250″, drifts 6.77 inches. MeGa wall 250, has a similar maximum force of 42,860 lbs., but the displacement is only 3.45 inches. Shear walls 250, 250′, 250″ are significantly stronger than the conventional shear wall 100, which records a capacity of 24,540 lbs. with a 3.48 inch drift. Overall, MeGa wall 250′ produces capacity and displacement that is roughly twice as much as a conventional shear wall 100.

FIG. 15 is a graphical representation of the energy dissipation versus drift curves comparing the shear walls 100, 250, 250′, 250″ can absorb before failure, for implementing embodiments of the present disclosure. A Reimann Sum, an approximation technique to determine the area under the curve, was used to numerically integrate the force-displacement curves from zero to where the shear wall loses more than 20% of its capacity. The energy absorbed by each of the shear walls is a reliable indicator of the shear walls' resiliency. A shear wall that can dissipate more energy will be able to withstand a greater number of lateral forces, which is a critical design point in high seismic and high wind locales. The ductile strap 640′ used in MeGa wall 250′ is shown to increase the resiliency over conventional shear walls 100 and wooden structures that include conventional shear walls.

Table 3 shows the energy dissipation of the shear walls 100, 250, 250′, 250″. Energy dissipation is also a reliable indicator of ductility. Greater energy dissipation provides an increase in the shear walls' ductility. These values are used in the process of calculating the shear walls' ductility. In comparison to the conventional shear wall 100, the less ductile metal strap 640 of MeGa wall 250 has a substantially greater ability to absorb energy. The ductile strap 640′ of MeGa wall 250′ has an even greater increase in energy dissipation.

TABLE 3

Energy dissipation compared to conventional shear wall

Percentage of

Energy
Conventional

Wall
Dissipated (lb-in)
Shear Wall 100

Conventional shear wall 100
62900
100

MeGa Wall 250
95850
152.4

Adjusted MeGa Wall 250″ *
110900
176.3

MeGa Wall 250″ **
197200
313.5

* 4.5 feet (1.37 m) wall length

** Adjusted to 8 feet′ (2.44 m) wall length

The forces in each of the sections were calculated from the strain gauge measurements using the following equation #1:

$\begin{matrix} P = ε EA & Equation #1 \end{matrix}$

The strain gauge measurements can be inaccurate for the compression sections after they start buckling. FIG. 16 is a graphical representation of the values detected by the strain gauges during testing a shear wall, for implementing embodiments of the present disclosure. The strain gauges measure a change in displacement, so the displacement caused by buckling cannot be used to measure force. For this reason, the compression curve in FIG. 16 stops just before the strap 640, 640′ buckles.

Before the buckling occurs, the compression strain gauge measures more force than the tension strain gauge. During buckling, the compression sections offer reduced capacity, so a greater percentage of the load flows through the tension section. This is visualized by the flattening of the tension curve around 17,500 lbs. of lateral force in FIG. 16. After the buckling occurs, the tension section goes into strain hardening at around 1800 lbs. in the strain gauges.

FIG. 17 is a graphical representation of an energy elastic curve and the corresponding load displacement curve, for implementing embodiments of the present disclosure. Increasing unit shear wall strength is most directly accomplished by increasing the number of panel edge fasteners (nails). By increasing the edge fasteners, there is a risk of moving the failure mode from the more ductile fastener deformation to the less ductile through-thickness panel shear rupture or out-of-plane panel buckling. One objective of the experimental research was to observe and attempt to manage the ductility while at the same time increasing shear wall strength. Without clear linear elastic-plastic behavior, evaluating ductility of wood panel shear walls has in the past utilized the creation of an equivalent energy elastic-plastic curve (Dolan, J. D., 1994. “Proposed Test Method For Dynamic Properties of Connections Assembled with Mechanical Fasteners,” Journal of Testing and Evaluation, ASTM, Vol. 26, November 1994, pp. 542-547). For each shear wall's load-displacement curves, an artificial curve is generated depicting how an ideal perfectly elastic—plastic wall would perform and dissipate an equivalent amount of energy. The displacement at yield, is defined as the displacement where the elastic and plastic lines of this curve intersect. The elastic portion has a slope equal to the elastic stiffness, which is taken as the secant stiffness at 40% of capacity. The horizontal plastic line is located so that the area under the equivalent elastic-plastic curve and load-displacement curve are equal. With these two energy equivalent curves, the ductility ratio can be found as follows equation #2:

$\begin{matrix} μ = \frac{Δ_{fail}}{Δ_{yield}} & Equation #2 \end{matrix}$

Despite the shorter wall length of adjusted MeGa wall 250″ compared to MeGa walls 250, 250′, the ductility ratio can still capture the inherent nature of the shear walls' assembly for comparison because the unitless parameter is evaluating ultimate displacement compared with yield displacement. Using the backbone curves of the tested wall data, there is a clear increase in ductility from MeGa wall 250, 250′ ductility ratio of 1.90 to MeGa wall 250″ ductility ratio of 2.55.

Static calculations were performed on the shear walls to determine the force in-between plywood panels at 90% of the ultimate applied load to force yielding prior to ultimate failure of the wall. This yielding force is divided by the number of nails at the joint of the plywood panels so the load through each nail at the desired yield can be determined. With this information, a free body diagram (FBD) of the strap would reveal the amount of tensile force through the diagonal at the desired load. The required width of the diagonal was then determined by Equation 3:

$\begin{matrix} \begin{matrix} F = σ_{y} A & \overset{‵}{a} & b = \frac{F}{σ_{y} * t} \end{matrix} & Equation 3 \end{matrix}$

The metal gauge strap 204A, 204B had a yield strength of 50 ksi and rupture strength of 65 ksi. The average thickness of the straps are about 0.06 inches (1.5 mm) with minimal variation. The calculated required width was slightly over 0.5 inches (12 mm).

FIG. 18 illustrates backbone curves obtained from testing Mega walls 200, 250, 250′ and 250″, for implementing embodiments of the present disclosure. The backbone curves consistently demonstrated high capacities, showcasing robust structural performance. These curves exhibited excellent stiffness and minimal deformation under applied loads, as indicated by the steep initial segments. As the load increased, the curves continued to rise, demonstrating the walls' ability to withstand substantial forces while maintaining their structural integrity. Importantly, the consistent high capacities observed in the backbone curves of both variants indicate that Mega wall 200, 250, 250′ are comparable in strength to a double-sided plywood shear wall with the same components, except for the metal gauge strap and field nail spacing adjustment. These findings highlight the effectiveness of including the metal gauge straps in enhancing the load-carrying capabilities of the shear walls. Such improvements have the potential to enhance overall structural efficiency and resilience in plywood shear wall applications.

FIG. 19 illustrates hysteresis curve obtained from testing Mega walls 250, for implementing embodiments of the present disclosure. Mega walls 200, 250, 250′ demonstrated increased hysteresis behavior during force-controlled test cycles, indicating increased structural performance. The hysteresis loops obtained from the testing showed that the shear walls remained almost completely elastic for force-controlled test cycles up to 200% of the allowable strength design (ASD) capacity. This means that the wall exhibited minimal energy dissipation and inelastic deformation during the loading and unloading cycles. The near-elastic behavior indicates that Mega wall 200 effectively distributed and redistributed the applied forces, maintaining its stiffness and resisting significant deformation. This characteristic highlights the wall's ability to withstand substantial loads while minimizing permanent deformation or damage.

Mega wall 250 performed consistently with Mega wall 200 as the shear wall maintained elastic up through 200% design load. The Mega wall 250 was able to reach a capacity of 42860 lbs. compared to 42755 lbs. for Mega wall 200. One difference was a more abrupt and brittle failure of Mega Wall 200 due to shear in the plywood panel.

Understanding the mode of failure of lateral force resisting systems is important for design. From previous testing, failure modes of the shear walls included nail head pull through, stud splitting, and plywood buckling resulting in sudden shear failure. Nail head pull through came as a result of the plywood sheets rotating and drifting. The nails were inserted firmly into the stud behind the plywood resulting in pull through instead of pullout. Each iteration of the shear walls sought to overcome the previous failure mode, resulting in shear walls with greater capacities each time. In Mega Wall 200 and 250 the failure mode was plywood buckling resulting in panel shearing. The buckling was slight but caught on camera happening the moment before the panel sheared. FIG. 20A is an illustration of the shear failure of Mega Wall 200, for implementing embodiments of the present disclosure. FIG. 20B is an illustration of the shear failure of Mega wall 250, for implementing embodiments of the present disclosure. Mega wall 200 sheared horizontally in several locations, but Mega wall 250 sheared vertically along a weak section of plywood.

Strain gauges were installed onto the center strap during the testing of Mega wall 200 to measure the maximum principal strain and stress as the metal gauge strap 204 underwent throughout the loading process. Rosette strain gauges measured strain in the x, y, and 45-degree directions. Two strain gauges can be used to verify results. FIG. 21 is a graphical representation of the force measured by strain gauges on the metal gauge strap 204, for implementing embodiments of the present disclosure. The data from the Rosette strain gauges were inputted into Excel and the maximum principal stress at every point was calculated and graphed using the mechanics of materials equation shown in FIG. 22. At the maximum applied force, the peak principal stress reached approximately 6 ksi. By multiplying this stress value by the thickness of the strap (0.06 inches) and the vertical length of the shear wall (9 ft), the total force between plywood panels exerted on the metal gauge strap amounted to 38.9 kips. 38.9 kips represents only 80% of the theoretical force of 48.2 kips calculated using statics. The observed difference between the measured force and the theoretical force highlights the need for further investigation into the load transfer mechanisms within the strap and potential factors influencing its performance.

Mega walls 200, 250 both exhibited much greater elastic regions than the conventional shear wall 100. Both Mega walls 200, 250 retained elasticity until 23 kips and had greater stiffness than the conventional shear wall due to the metal gauge strap which prevented nail slippage from occurring. FIG. 18 illustrate the difference in magnitude of the elastic regions as well as the stiffness shown by the slope of the line. The stiffness of each shear wall was calculated using linear trendlines in a spreadsheet. For Mega wall 200, the elastic stiffness was determined to be 20.18 k/in, while Mega wall 250 exhibited a stiffness of 20.02 k/in. These stiffness values were approximately 38% higher than that of the conventional shear wall 100, which displayed a stiffness of 14.52 k/in. This larger elastic region prevents the MeGa walls 200, 250 from going plastic during dynamic loading, making them more resilient to external forces such as seismic events or high winds. As a result, Mega wall 200 and Mega wall 250 offer increased safety and structural integrity, reducing the risk of permanent damage to the wall during unexpected loading conditions.

To evaluate the energy absorbed by the shear walls, a line of best fit was determined for each force versus displacement graph. Integrating these equations provided a measure of the energy absorbed by each wall, expressed in pound-inches (lbs-in). Mega wall 200 absorbed a total of 101,843 lbs-in of energy, while Mega wall 250 absorbed 94,674 lbs-in. For comparison, it is worth noting that the conventional shear wall 100 exhibited significantly lower energy absorption. The conventional shear wall absorbed only 48,764 lbs-in of energy, which is approximately half of the energy absorbed by Mega walls 200, 250, 250′. The calculated energy absorbed emphasizes the robustness of Mega walls 200. 250 and 250′. These shear walls 200, 250, 250′ exhibited significant capacity to absorb and dissipate energy, indicating the respective ability to effectively withstand dynamic loads and resist excessive deformation.

The ductility of the shear walls was evaluated using ASTM E2126's ductility ratio (D), which compares the ultimate displacement (Au) to the yield displacement (Δyield) from the test data. Mega Wall 200 exhibited a ductility ratio of 3.236, while Mega wall 250 had a ratio of 2.974. Both ratios of the Mega walls 200, 250, 250′ are very similar to the ductility ratio of the conventional shear wall 100, which measured at 3.051. The close resemblance in ductility ratios among Mega walls 200, 250, 250′, and the conventional shear wall 100 indicates that all three variants displayed comparable levels of ductility during testing. Mega walls 200, 250, 250′ demonstrated similar ductility to the conventional shear wall 100 despite the design modifications reinforcing their respective structural performance and reliability.

Mega wall 200 exhibited a load-carrying capacity of a double-sided plywood shear wall despite having only a single side. This demonstrates the effectiveness of the design modifications implemented in Mega wall 200, including the change in field nail spacing and the use of specific metal gauge straps 202-210.

During the small-scale tests conducted after Mega wall 200, several interesting observations were made. The vertical slot strap failed in a brittle manner under shear forces, suggesting potential limitations in its design and performance. The horizontal slot strap did not exhibit the anticipated double curvature or achieve flexural yielding. On the other hand, the alternating diagonal tension strap yielded as expected and displayed significant ductility. However, the X diagonal strap, despite being very stiff, experienced buckling near the nail head, leading to additional stress on the nails and the fracturing of one of the nail heads. These findings provide valuable insights into the behavior and performance of the metal strap for Mega wall 250. After testing Mega wall 200 the strain gage results from the center strap 204 were analyzed. As mentioned in the strain gage results section, 80% of the total lateral load was transferred into the center strap. Design of the center strap 640 for Mega wall 250 was based upon the assumption that the strap would experience 80% of the lateral load and yield when reaching 90% of that load. The strap did not experience the forces as predicted. The center strap 640 was then redesigned to the center strap 640′ to narrow down potential strap sections towards a desirable outcome. Mega wall 250′ provided more ideal and predictable yielding.

FIGS. 22-25 provide experimental calculations and modeling of the MeGa walls, for implementing embodiments of the present disclosure. These calculations and modeling illustrate the projected, theoretical load capacities of the MeGa walls 200, 250, 250′ and 250″ for comparison to the conventional shear wall and the actual test results provide herein.

Terms such as about, on the order of, and approximately, can include+/−10-20% of the stated value as applicable to the disclosed embodiments. Although the foregoing disclosure has been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the disclosure is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.

	Number	Date	Country
	63530993	Aug 2023	US
	63531305	Aug 2023	US

Systems, Methods and Apparatus for Forming a Wooden Construction Shear Wall

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