Tag Archives: building code requirements

Tornadoes Reek Havoc

Tornadoes Reek Havoc, Don’t Let Them Wreck You
Excerpts in italics below are from an article first appearing in SBC Magazine June 3, 2019:
“In the past few weeks, weather systems throughout Texas, Oklahoma, Missouri, Indiana and Ohio have had a significant impact on the built environment. As is well known, tornadoes cause severe stress on buildings where the high localized wind loading conditions find the weak point of the structure quickly. This usually is at the location of a wood nail, wood connector or anchor bolt connection, or in our testing experience, a knot or slope of grain deviation in a lumber tension member. An interesting point is that most studs in wall systems are meant to see compression forces not tension, where studs in tension may also be a structural weak point.

As the pictures herein attest, finding the key building material weak point that caused the structural performance to be a debris field is challenging, if not impossible, to do.

Tornado damage in Jefferson City, Mo. as seen on Thursday, May 23, 2019. Photo by David Carson, St. Louis Post-Dispatch.

Questions that need to be sincerely addressed follow, which include but are certainly not limited to:
What were the as-built conditions?
Was the building built to code?
Which aspects of the structure were built to code?
Which aspects of the structure were not built to code?
What is the cause/effect analysis for each code compliant and each non-code compliant condition?

It is obvious that proper construction implementation is key to satisfactory building material performance. Paying close attention to all connecting systems that make up the load path is essential.

The most important outcomes of poor building performance in a high wind or seismic event are that no one gets hurt; the construction industry continues to learn and evolve; and design and installation best practices improve.

The entire construction industry can greatly benefit by staying focused on providing framer-friendly details that are easy to understand and implement. It’s critical that we come together with the goal of fostering innovation, using accepted engineering practice, creating installation best practices, working closely with professional framers and assisting building departments to focus inspections on key load path elements. We all are educators. By working together, we will significantly improve the built environment.”

 

Mike the Pole Barn Guru adds:
Readers will note, these failures are in stick frame construction. Certainly there were also pole barns failing in tornado areas as well, however it is my opinion post frame buildings, engineered to withstand appropriate wind speeds, and assembled according to engineering documents would survive these storms – preventing both loss of property and life.

Code requirements are merely minimum design standards and often do not address severity of real life events. My recommendation is when in doubt, design to higher loads than minimum, in most cases these higher design loads involve a nominal investment and your family and expensive possessions deserve this type of protection.

Talk with your Hansen Pole Buildings’ Designer today at 1(866)200-9657 to find out what a lifetime of protection will involve.

Wood Construction in High Wind Areas

New Guides to Wood Construction in High Wind Areas

My long time readers will probably recognize the name Dr. Frank Woeste, as he has appeared in a plethora of my articles. When it comes to wood design, and especially post frame buildings, Frank is at the top of the game. For the curious, here is his background: https://cmec.wsu.edu/facultypages/WoesteResume.pdf

When I first met Frank in 1985, he made me a deal – come to Virginia Tech in Blacksburg, speak to his AgEngineering class and he would share his post frame design programs with me. One of his students was a young John “Buddy” Showalter. As much as I would like to take credit for Buddy’s engineering career successes (he is now a vice president at the American Wood Council https://www.awc.org), I’m thinking Buddy is far more self-made than influenced by me.

Buddy recently authored an article, “New Guides to Wood Construction in High Wind Areas”, from which I have excerpted the following:

“According to the Insurance Institute for Business and Home Safety, high winds cause millions of dollars in property damage each year. The good news is that much of this damage can be avoided through quality design and new construction methods that are available to strengthen wood structures.

Pole Barn FramingTo help address the design challenges associated with high wind, this week the American Wood Council (AWC) published a series of updated Guides to Wood Construction in High Wind Areas. The guides are based on provisions contained in AWC’s 2012 Wood Frame Construction Manual (WFCM), and establish a specific set of prescriptive, wind-resistive structural requirements for wood-frame buildings in compliance with the 2012 International Building Code (IBC) and International Residential Code (IRC).

Design wind loads are provided in a national standard, Minimum Design Loads for Buildings and Other Structures, ASCE 7, and may vary between jurisdictions located in different wind zones. Accordingly, architects and engineers are encouraged to work with their local code officials to ensure an understanding of what is required for designs in their jurisdiction.

AWC is also a resource for designers, translating what are often complex building code requirements for wood buildings into an easily understandable format. Wood buildings can meet the challenges of providing robust wind-resistive designs due to redundant load paths and multiple fasteners creating very ductile (flexible) assemblies. This makes wood a logical choice for design in high wind areas.”

Previous articles speak to the ability of post frame (pole) building design: https://www.hansenpolebuildings.com/blog/2011/06/tornado-proof-pole-buildings-can-limit-damage/

Not only is wood a logical choice – but utilizing it in post frame affords even more advantages, when it comes to resisting high winds!

Mean Roof Height

Don’t be Mean, be Average

At Hansen Pole Buildings, every building plans is originally drafted to meet the client’s specific needs and what they ordered. Every once in a while they receive some interesting feedback. Like this:

“Project #15-05xx has declined plan approval for the following reason: page S-0 under code data mean roof height should be 22.67”

 Let’s begin with a refresher course on what “mean” is mathematically:

mean

(mēn) an average; a numerical value that in some sense represents the central value of a set of numbers

In the case of this particular building, it has a 32’ width gabled roof, 12 foot eave height and an 8/12 roof slope. Taking ½ of the building width (16 feet) x the slope 8/12 gives us a rise in the center of 128 inches (or 10’8”). Adding the 10’8” to the eave height of 12’ makes the overall building height 22’8” (or 22.67’).

pole barnThe mean roof height would be the average of 12’ plus 22.67’ or 17.33’ as shown on the building plans. It appears there may have been some confusion, on the client’s part, as to the definition of “mean roof height”.

So why is mean roof height even important and why is it even listed on the plans? Wouldn’t the Planning Department care more about the overall building height, to make sure I don’t have a building which is too tall for my zoning?

Building plans deal with the structure of your building, how it is put together. The design wind speeds are based upon the mean (or average) height of the building roof, with a minimum of 15 feet. This mean roof height is stated on the building plans as well as the design wind loads for each sector of the building which corresponds to this mean roof height, as well as wind speed and exposure.

And yes, overall height can be important to a local jurisdiction with specific height restrictions. But not to be mean…this is not what mean roof height is all about.