We Need You! Share Your Marketplace Challenges
We Need You! Share Your Marketplace Challenges
perspective on the test plans developed for upcoming testing in SBCRI and to generate future testing concepts.
When the SBC Research Institute (SBCRI) was built in 2007, I remember our discussions on the Board about the ways in which this state-of-the-art structural testing facility would give our industry significantly greater understanding about the three-dimensional performance of buildings. More than anyone else could! We’d have the ability to finally look at the “systems effects” that exist in real buildings, begin to quantify this information, and eventually gain the benefit of that knowledge by incorporating it into how we design our products.
Everything we do as component manufacturers (CMs) focuses on designing and building products that will do their part to withstand all of the loads they intended to bear and to create the load path intended by the building designer, from the point they originate down into the foundation. As we gain a deeper understanding of how loads actually flow through an entire building’s structural system, we can figure out how to take advantage of it and create value for ourselves and our customers. Every test conducted at SBCRI helps us learn more about structural performance.
There’s a lot of opportunity out there, so the big questions are: where should SBCRI focus its efforts, and what questions do we try to solve? The answers to those questions rely mostly on you. Up until recently, most of the industry testing conducted at SBCRI was limited by external factors. When the housing industry crashed starting in 2007, funding for industry testing dried up very quickly. SBCRI remained financially viable and operational by becoming a proprietary research and development (R&D) facility, conducting private testing for companies seeking to create new structural framing products, materials and construction methods.
Through proprietary testing, SBCRI acquired a deeper understanding of testing techniques and approaches, and further refined how to more accurately apply loads and measure load path. None of the actual information collected from the proprietary testing was ever used or shared with anyone but the client. However, as we all have learned, practice and experience make us all better at what we do.
While proprietary testing made up a majority of SBCRI’s testing calendar, it’s important to point out that industry-specific testing continued to occur. (SBC Magazine has already covered many of these tests: top chord bearing, lumber design values, wood structural panel shear walls, seismic design coefficients, etc.). Over the coming months, we will share the results of other tests, including those described in the sidebar below.
By 2014, the housing industry had recovered enough making it possible to resume funding on the important activity of industry testing. Since 2007, SBCA and the Truss Plate Institute (TPI) have kept a prioritized list of industry tests to perform. The intent of putting together that list is to define and explore challenges CMs regularly experience in the marketplace and devise testing plans to gather empirical data to address those challenges.
So where do you come in?
All SBCA CM members are encouraged to think about the framing challenges in their markets and share them with SBCA staff. Testing concepts can then be developed around those challenges to try to either address a problem or create an opportunity for CMs to reduce their costs or sell more products. To more fully understand how the test concept process works, SBCA has developed a flowchart (see graphic). A good explanation of how the flowchart really works can be found here.
In 2015, there are multiple opportunities within SBCRI for industry testing. The great part is that each of these tests will yield real data that should benefit CMs through better understanding of load capacities and load paths, more efficient design procedures, or easier installation methods. The sidebar below lists summaries of three testing concepts currently under review. On March 19, SBCA’s Board reviewed these test concepts during its meeting in Denver, CO. However, SBCA continues to seek testing input from all its membership.
SBCRI was built to benefit all TPI and SBCA members, as well as those who supply goods and services to our industry. As SBCRI helps our manufacturing businesses grow, our entire supply chain will benefit. SBCRI is an extremely valuable tool our industry can use to help us create even more efficient component framing solutions for our customers. In the end, the testing at SBCRI makes the products you produce better than all the alternatives, leading to greater market share for you.
In the eight years since SBCRI opened its doors, most of us have been testing our survival skills in the market rather than testing structures in the lab. Those survival skills prompted our industry to change even more rapidly, with technology, ingenuity and just plain desperation, leading us to make advancements we probably wouldn’t have otherwise made. Those changes created additional opportunities for components to gain market advantage. So I encourage you to think about this for a few minutes, and if you ever had one of those, “I wonder if this would work” ideas, send them to us and we will submit it to the committee.
Let’s get back to the fun stuff we built this association on and brush off the dust of gridlock brought on by difficult times. I personally have never been more excited about this industry and SBCA than when I think about the opportunities we have coming up this year for gathering important information to grow our markets.
Top Chord Bearing Reaction Testing
The current ANSI/TPI 1-2007 standard limits the allowable reaction for top chord bearing trusses. The purpose of this testing is to determine if the tabulated end reactions can be increased based on test data. All tests will conform to the requirements in ANSI/TPI 1-2007 Figure 7.4-1(a) and (d). The trusses will be designed to isolate the failure mode to the end condition, in order to ensure the best value for our testing.
Toe-Nail Connection Testing
The National Design Specification for Wood Construction (NDS) provides a method for calculating the strength of a toe-nailed connection for withdrawal and lateral loads. The method in the NDS was used to develop the uplift and lateral resistance capacities in Table B8-1 in the Building Component Safety Information (BCSI) book.
The NDS applies a toe-nail factor (Ctn) of 0.67 and 0.83 to withdrawal and lateral design values, respectively. These factors reduce the strength of a toe-nailed connection compared to a face-nailed connection. However, the International Residential Code (IRC) “assumes that the toe-nail factor does not need to be applied to roof-to-wall connections” (NAHB Research Center, 2008). Eliminating or increasing this adjustment factor would allow for much higher connection capacities than currently published in BCSI.
Truss Ply-to-Ply Connection Testing
Multi-ply trusses typically support a side load attached to one ply and must be connected together to transfer the load from ply-to-ply. No guidance is given in TPI 1 on what type of load distribution is appropriate, how to design the connections between plies, or how frequently the connections need to be placed. Some of the factors that may influence the failure of a multi-ply truss connection are:
- Deflection of the truss
- Bending of chord members between panel points
- Spacing of concentrated loads
- Friction between truss plies
- Connection slip
A connection design process that accounts for these factors needs to be developed to optimize ply-to-ply connections.