A Better Shear Wall with the TJ®-Shear Panel

The TJ®-Shear Panel is a prefabricated wood shear panel that offers a solution for structures needing a high-aspect-ratio shear wall. Designed for applications in wind and seismic regions, the TJ®-Shear Panel delivers better performance than highly variable site-built alternatives. It is an easy-to-install, highly predictable panel that provides the benefits of wood construction and the reliability of a Trus Joist engineered wood product.

The panel was developed as an alternative for builders and engineers to comply with the changes in the 1997 Uniform Building Code, which placed restrictions on aspect ratio for site-built shear walls. These code changes were precipitated by observations of the performance of narrow site-built walls during the 1994 Northridge earthquake in California. Specifically, high-aspect ratio walls were overly flexible and unreliable, resulting in increased structural damage. Prefabricated shear panels were developed to address these concerns.

Some of the specific critical factors to be aware of in narrower site-built walls include the following:

• Construction variables - How well is the wall put together? Are there nails missing? Are nails hitting the studs correctly? Are nails overdriven? Are there gaps in the sheathing? Are construction tolerances adequate, such as plumb-cut studs and sheathing seams centered on framing members? A wall with these issues may fall far short of a designer's expectations of lateral performance.
  The TJ®-Shear Panel is prefabricated under tight quality control requirements, thus eliminating site-built performance variability.
• Material variables - What is the moisture content of the lumber and will it shrink with time? Is there wane and twist in the lumber? Is it the correct species for the design? Are your sheathing products certified? Are you using the correct fasteners? Nails? Staples? Screws?
  The TJ®-Shear Panel is manufactured using engineered lumber which by its nature is straight, consistent, dimensionally stable, and dry. The sheathing material (or web) uses TJ®-Performance Plus oriented strand board, the same high performance material used as the web of the Silent Floor® joist.
• Hold down forces - As the wall gets narrower, the uplift forces increase; this makes conditions at the hold down very critical. Is the hold down attached tightly to the foundation? Is the connection to the stud (or rail) solid with little "slop"? Will there be crushing of the bottom plate, allowing undesirable movement? Does the hold down induce bending forces on the stud or rail? A small vertical movement at the base of a high-aspect ratio wall translates to a big horizontal movement at the top -resulting in a wall with greater flexibility than anticipated.
  Because Trus Joist's TimberStrand® LSL, the engineered wood used in the rails of the panel, is dimensionally stable, we are able to hold extremely tight tolerances in the attachment of the specially designed hold down. This eliminates slop. The hold down is concentric so it does not induce bending moments in the rail and the fit is very tight, resulting in very little movement under high loading.
• Bending vs. shear - As a wall gets narrower, a larger percentage of the movement comes from bending forces as opposed to shear forces. A long wall will rack in the shape of a parallelogram, a short wall will bend more like a column. Plastic racking absorbs a great deal more energy than elastic bending and therefore it is desirable in a shear wall to have more racking and less bending.

The TJ®-Shear Panel uses a pin-connected frame to force the deflected shape into a parallelogram. This shape causes most load resistance and energy dissipation to be resisted by the web/rail interface, where it can be dealt with predictably. The result is a better performing shear wall even at high-aspect ratios.

Trus Joist introduced the TJ®-Shear Panel in 2002 to the California, Nevada, and Arizona markets. Today the TJ®-Shear Panel is available throughout the country. The TJ®-Shear Panel is gaining wide-spread acceptance as an effective alternative to code-prescribed braced panels.

In addition to meeting the needs of today's home designs, some of the benefits experienced by current users of the TJ®-Shear Panel include:

• Quick and simple installation.
• Trus Joist's engineered wood in every panel provides consistent, predictable performance that resists bowing, twisting, and shrinking
• Compatible with traditional wood frame construction.
• Pre-drilled access holes allow for placement of utilities without field modification.
• Concentric design. The TJ®-Shear Panel was specifically designed and optimized for high-aspect-ratio shear wall applications.Trus Joist now offers an installation-ready, raised floor kit as a companion to the TJ®-Shear Panel. The raised floor kit includes preassembled components, simple instructions, and all the hardware needed for installation. The kit allows builders to use the standard TJ®-Shear Panel in a raised wood floor application for homes built with crawl spaces.
• Trus Joist also offers a new anchor installation system which acts as a template for properly placing the holdown anchors. It also works as supplemental reinforcement to transfer the shear forces to the foundation without the need for site-fabricated alternatives.
• This system provides simplicity and confidence for engineers, and quick and simple installation for the field crews.
• Ready acceptance by building and code officials.

Designers and builders throughout the country are finding the TJ®-Shear Panel to be the right solution for their lateral design needs.

Trus Joist, A Weyerhaeuser Business is recognized as the world's leading manufacturer and marketer of engineered lumber products, which provide greater value for the consumer, the builder and the environment. Trus Joist operates 19 manufacturing plants in North America and Australia, and has sales offices worldwide.