- Page 50 of 50 - News, Notes and Discussion from the Simpson Strong-Tie Engineering Department

The Anchorage to Concrete Challenge – How Do You Meet It?

We structural engineers here at Simpson Strong-Tie have a love/hate relationship with anchorage to concrete. Ever since the introduction of the strength design provisions in the 2000 IBC and ACI 318 Appendix D, anchorage to concrete has been a challenge for designers, building officials and manufacturers. SEAONC’s recent testing and the resulting code changes offer some relief to wood-frame designers for sill-plate anchor design at the edge of concrete, but many challenges remain.

With the increasing demand for high-density housing and urban infill projects, designers are now faced with anchoring multi-story wood-framed shear walls to relatively thin elevated concrete slabs (typically referred to as podium slabs). Overturning tension anchorage forces at the ends of shear walls in these projects can routinely be in the 40 kip range and even get as high as 60 kips or more.

Testing – Then & Now

“One test result is worth one thousand expert opinions.”

– Wernher von Braun

While reviewing some of our first catalogs, I was curious about the testing we did on those iconic products that launched our company. I found a test report from December 20, 1957 on crinkled yellow paper with a short description: U-29 Download Test. The signature from the independent testing agency was a little faded, and the data was typed by hand in a table. But I was thrilled to discover that our 1957 customers received exactly the same thing as our modern-day customers – the confidence in knowing that our allowable loads are supported by physical testing.

There simply is no substitute for a physical test.

Welcome to the Structural Engineering Blog

Welcome to our Structural Engineering Blog! I’m Paul McEntee, Engineering R&D Manager at Simpson Strong-Tie. We’ll cover a variety of structural engineering topics here that I hope interest you and help with your projects and work. Social media is “uncharted territory” for a lot of us (me included!), but we here at Simpson Strong-Tie think this is a good way to connect and even start useful discussions among our peers in a way that’s easy to use and doesn’t take up too much of your time.
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Contest Winners Announced Soon!

Thank you to everyone who subscribed to our new SE Blog! If you subscribed by June 1, you were automatically entered to win one of five Simpson Strong-Tie prize packs. Those of you who also posted a comment to the blog received a bonus entry. We will announce our winners on the blog soon. Good luck!

Official rules for the sweepstakes can be found here.

Code Development: The ASTM Process

I spent a few days last week traveling to attend the Spring ASTM International meetings held in Phoenix, AZ. When I was working as a building designer, I always used ASTM standards in my project specifications or testing and special inspection requirements on a job. But I did not know how these ASTM standards were developed, nor did I know that I could participate in the process.

ASTM standards are voluntary in the sense that ASTM does not require their use. However, since ASTM standards are referenced in building codes and design standards that are adopted by states and local jurisdictions, compliance with those standards is required. So it might be useful for structural engineers to know a little bit about how these standards are created.

Designing Light-Frame Wood Structures for Tornadoes. It Can Be Done!

Being from California, I had always bought into the common misperception that wood light-frame construction can’t be designed to resist tornadoes. While it is true that debris impact can’t be cost-effectively designed into residential structures, there is a lot that can be done to strengthen the structure and protect the occupants inside. Using the same technology common in hurricane-prone regions, these buildings can protect people for more than 95% of reported tornadoes.

The effect of tornadoes on wood light-frame structures has been extensively researched over the last few years, and researchers agree: A strong, continuous load path is essential to minimize destruction.

Do You Design with Wood (Shrinkage) in Mind?

Wood is a unique building material because its characteristics are dependent on the environment and its moisture properties, which can vary over time. Often, sawn lumber is delivered to the jobsite with relatively high moisture content. Over the life of the building, moisture content will decrease until equilibrium has been achieved. As moisture content drops, the wood members shrink. Most wood shrinkage occurs during the first six months of the building life and it’s an important design consideration.

But I Don’t Design Cold-Formed Steel…

For the first half-dozen years of my professional career, my experience with cold-formed steel (CFS) consisted of sizing studs for non-structural walls and red-marking the bracing details on architectural plans. When the dotcom bubble burst, my firm needed to shift its focus from high-tech commercial and industrial to more multifamily design work. Several developers we worked with built with CFS, so in addition to designing condominiums instead of cleanrooms, I was designing CFS.

Less than 10% of engineers have any exposure to CFS design as part of their undergraduate education. OK – so this is based on an informal survey of about 50 colleagues, but I suspect if I were to hire a market research firm for lots of money, I’d pretty much get the same response.