Out-of-Plane Wall Anchorage Design

While the Simpson Strong-Tie Tye Gilb R&D lab in Stockton is a large testing facility, the world’s largest R&D lab is Mother Nature herself. Natural disasters such as earthquakes or storms put our engineering designs to the test. In this week’s blog post, I’ll be turning attention to wall anchorage for out-of-plane forces and the lessons we have learned from Mother Nature so far.

The 1979 building code incorporated many of the lessons learned from the 1971 San Fernando earthquake. In 1994, Mother Nature put the 1979 building code to the test with the January 17 Northridge earthquake. The Northridge earthquake showed that some of the increased design and detailing requirements in the 1979 building code worked well to improve performance over what was observed in 1971. However, it also revealed to researchers that acceleration at the roof level of single story warehouse buildings were three to four times the ground acceleration. The combination of higher than expected acceleration and excessive deformation of the wall anchorage assembly caused many wall anchorage failures.

Figure 1 Out-of-Plane Wall Anchorage Assembly

Several changes in the design forces used for wall anchorage and additional detailing requirements were incorporated in the 1997 Uniform Building Code. The requirements have been refined with each new building code, but overall the requirements and design forces have remained about the same under the current International Building Code. Wall anchorage design is governed by ASCE 7-05 and ASCE 7-10 Section 12.11. These provisions aim to mitigate the brittle wall anchorage failures observed in past earthquakes by increasing the design force and in Seismic Design Categories C through F, requiring:Continue Reading

Who's Thinking About Deck Safety? I Am!

A few months ago, the Today Show asked Simpson Strong-Tie to demonstrate a deck collapse to educate the public about deck safety. Often through the Fall and Winter months, decks go unused yet see a lot of activity from rain, sleet and snow. When the sun comes out in the Spring, people get out on their decks again without much thought about how the elements may have affected the important connections on their deck.
In addition to the weather, there are other factors to consider about deck safety:

  • Experts agree that the average life expectancy of a wood deck is 10 to 15 years.
  • It’s estimated that there are millions of decks in the U.S. that are beyond their useful life and may be unsafe.
  • The number of deck collapses has increased in recent years.
  • Within the past five years, 651 injuries and four deaths have occurred due to deck collapse.

So, I’m thinking about deck safety. I thought I’d share with you the “5 Warning Signs of an Unsafe Deck” we discussed on the Today Show:
Continue Reading

Who’s Thinking About Deck Safety? I Am!

A few months ago, the Today Show asked Simpson Strong-Tie to demonstrate a deck collapse to educate the public about deck safety. Often through the Fall and Winter months, decks go unused yet see a lot of activity from rain, sleet and snow. When the sun comes out in the Spring, people get out on their decks again without much thought about how the elements may have affected the important connections on their deck.

In addition to the weather, there are other factors to consider about deck safety:

  • Experts agree that the average life expectancy of a wood deck is 10 to 15 years.
  • It’s estimated that there are millions of decks in the U.S. that are beyond their useful life and may be unsafe.
  • The number of deck collapses has increased in recent years.
  • Within the past five years, 651 injuries and four deaths have occurred due to deck collapse.

So, I’m thinking about deck safety. I thought I’d share with you the “5 Warning Signs of an Unsafe Deck” we discussed on the Today Show:

Continue Reading

So, What's Behind A Structural Connector's Allowable Load?

This is Part 1 of a four-part series I’ll be doing on how connectors, fasteners, anchors and cold-formed steel systems are load rated.
Today I did my presentation for the WoodWorks webinar on Testing and Product Evaluation of Products for Wood-framed Construction. We covered a lot of material regarding code requirements for using alternate materials or construction methods, how testing and evaluation criteria are developed, and some specifics on several Acceptance Criteria (AC’s) that are commonly used for connector evaluations. We also discussed some specific testing requirements, so I thought it would be timely to discuss some of those issues in this week’s blog post.
So, how are structural connectors for light frame wood construction load rated? What’s behind the allowable loads information published in Simpson Strong-Tie literature or wood connector evaluation reports? These are things that you might find yourself wondering while driving to the office or jobsite, or on a Sunday afternoon while enjoying your favorite iced tea or barley-based beverage.
The short answer is: testing, calculations, and of course, sound engineering judgment.
Continue Reading

So, What’s Behind A Structural Connector’s Allowable Load?

This is Part 1 of a four-part series I’ll be doing on how connectors, fasteners, anchors and cold-formed steel systems are load rated.

Today I did my presentation for the WoodWorks webinar on Testing and Product Evaluation of Products for Wood-framed Construction. We covered a lot of material regarding code requirements for using alternate materials or construction methods, how testing and evaluation criteria are developed, and some specifics on several Acceptance Criteria (AC’s) that are commonly used for connector evaluations. We also discussed some specific testing requirements, so I thought it would be timely to discuss some of those issues in this week’s blog post.

So, how are structural connectors for light frame wood construction load rated? What’s behind the allowable loads information published in Simpson Strong-Tie literature or wood connector evaluation reports? These are things that you might find yourself wondering while driving to the office or jobsite, or on a Sunday afternoon while enjoying your favorite iced tea or barley-based beverage.

The short answer is: testing, calculations, and of course, sound engineering judgment.

Continue Reading

Why a Structural Boundary Member Between a Truss/Rafter is Not Optional

Blocking or boundary member?

In my experience traveling across the country observing wood-framed construction, it was apparent that east of the Rocky Mountains, structural wood members in-line with supporting walls between roof framing cease to be installed. Some may call these wood members blocking and deem them as optional. And often in a humid environment, installation of these members may be ardently resisted in order to provide ample attic ventilation and prevent mold growth. It is important, however, to understand that this blocking creates the structural boundary members for the roof diaphragm and it is not optional.

Continue Reading

How Do You Use Technology To Make Your Job Easier?

I confess to being a bit of a technology junkie. I think it was around 1995 when I first overcame my fears and cracked open my computer case, installed a new hard drive and upgraded to an enormous 8 megabytes of RAM. While I still enjoy building my own home computer every now and then, it seems like keeping up with technology is a full-time job. For every new website or app, you can expect two or three more just like it to follow. Trying to filter through all of that information to find what’s useful to your specific job, process or project can be impossible.

I’ve found it’s usually best to let the need dictate the technology, versus the other way around. When I was designing buildings, contractor sketches or descriptions of field issues were often not clear (especially the ones that had been faxed 5 times!). Sometimes we could figure it out with several phone calls, but other situations would require a field visit. A photograph would work, but developing film and sending the photos would take too long. The development of inexpensive digital cameras so field questions could be e-mailed with photos really streamlined my process for responding to field issues.

Continue Reading

Join Me for a WoodWorks Webinar on Acceptance Criteria and Testing Methods for Connectors

I have the privilege of presenting a free WoodWorks webinar, “Testing and Product Evaluation of Products for Wood-framed Construction” on Thursday, October 25 at 10 am PST. Here is the webinar description:

Products that are not covered by the code are used in many if not all buildings. While the code permits a single engineer to review and submit to a building official and a single building official to review and approve a product not covered by the code, many feel a more robust process is needed to ensure that these products meet the code intent. Also, many code or evaluation reports are used not just for one project, but for multitudes of projects in numerous locations. Test setups can affect the performance and load rating of products.

Several private entities have been created over the years to assist the industry by developing public and transparent processes to develop test requirements, load rating requirements, design and detailing requirements, and ongoing quality compliance as well as product evaluation methodologies. This webinar will discuss various acceptance criteria and testing methods used for products used in wood construction, such as ASTM D7147 and ICC-ES AC155 to further advance the knowledge of these test methods and processes for those in the wood construction industry.

This will be a great opportunity for those of us who work in wood frame construction to discuss code and test requirements for connectors and other products for wood. I hope you’ll consider joining us! To register for the webinar, click here.

– Paul

Designing Steel Roof Deck Attachment for Combined Tension and Shear

In last week’s post I made a reference to California’s golden sunshine. Californians may have to deal with wildfires, earthquakes, and wearing sunscreen year round, but we generally don’t have high wind to worry about. In a previous blog post, Roof Deck Design Considerations for High Wind Events, I discussed some of the general challenges in designing for wind uplift. This week, I wanted to get a little more specific and discuss the standards applicable to steel roof deck attachments.

Historically, procedures for design of structural connections that utilize fasteners recognize the importance of combined loading effects on structural performance. Whether bolts or screws are the connector choice, the metallic structure of steel alloys includes transverse slip planes of relatively low resistance. This results in yield criteria (function that defines the onset of yielding or fracture) that are often limited by load-deformation performance along transverse planes.

Continue Reading

October 11 – Buildings At Risk: Earthquake Loss Reduction Summit

I don’t travel too much for work, so the last three weeks has been a bit different from my normal routine. On August 30, I attended an unreinforced masonry retrofit workshop in Memphis, had a sales meeting the following week in St. Louis, and the annual SEAOC convention last week in Santa Fe, New Mexico.

I have been remiss in not talking about an important summit taking place in California next month. SEAOSC is hosting the 2nd annual Buildings at Risk Earthquake Loss Reduction Summit on October 11 in downtown Los Angeles, California. The summit is a precursor to the “Great California ShakeOut” event that will be held on October 18.The summit will serve as a forum to not only increase awareness of seismic risk, but spur action. This will be an important conference not only for structural engineers working in seismic areas, but for building officials, architects, building owners, insurance companies, and first responders. The sessions will stress the benefits of mitigation and encourage the different stakeholders to work together on solutions.

Early registration for a discounted rate and a chance to win an iPad ends today, but there is still time to register.

– Paul