Tag Archives: wind speed

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.

Self-Designed Pole Buildings

Spring, When a Young Man’s Heart Turns to Self-Designing Pole Buildings

For some obscure reason a plethora of otherwise intelligent people have an idea. This idea being they can structurally design a building to be adequate to resist applied climactic loads, without any actually engineering background. Given an under designed building can lead to failure, injury and even death of occupants and/or bystanders, one might think it would be best left to professionals.

Reader NORM in SILVERTON writes:

“I’m considering building an open pavilion style pole building, with outside (the posts) dimensions of 20’ x 16’ x no more than 9’ to 10’ high posts, secured to cement pad with Simpson CC66 caps.  There would be 3 posts on both the left and right sides, that would be 8’ from middle, of middle post, to outside edge of front and back post.  The alignment of 3 posts on each side, would be 20’ apart with 6/12 gable roof, supported with roof trusses (50 PSI Snow Load).  On each side, the roof overhang would be 3’, which I don’t think matters when considering my question.  The posts are more than sufficient size and strength for the gabled metal roof …..  I’ve been told.  

Question: What “wind gust” strength would I need to be concerned about from side to side, for the “sway” factor ?  Would that “wind strength” be less if directly behind this “pavilion”, was a slightly larger and taller building, AND directly behind that building, was standing forest with trees that were 60’ to 100’ tall ?  We obviously are NOT in tornado country like the Midwest and South.

Thank You.”

About Hansen BuildingsThank you for your interest in a new Hansen Pole Building. We should be able to take care of all of your needs with a third-party engineer sealed set of blueprints specifically for your building. Face it – this eliminates any guesswork, as anything you do without a Registered Design Professional involved is nothing but a W.A.G. (Wild Ass Guess), probably an errant one. Given height of your roof (it takes full brunt of wind coming from a side) it is unlikely a 6×6 column will work in bending (it is plenty strong enough to support downward forces from building weight and roof snow load acting alone).

Even without being an engineer I can tell you a proposed Simpson CB66 is totally inadequate. Frankly your ideal design solution is to embed your six columns into the ground and concrete them in to avoid uplift and overturning challenges. If you feel you must have columns above ground, then we can design using a proper wet set anchor capable of carrying imposed loads.

If your building is wind unprotected on even one side or end chances are it is Exposure C for wind design. You do not get credit for a building being protected on one side (or even two or three) by a larger taller building or a forest – only if it were to be entirely surrounded. (read more here about Wind Exposure: https://www.hansenpolebuildings.com/2012/03/wind-exposure-confusion/).

A Hansen Pole Buildings’ Designer will be reaching out to you to further discuss your proposed project, or dial 1 (866) 200-9657 and talk with one now!

A Tornado and a Pole Barn

Pole Barns and Tornados

(Excerpts from a July 21, 2018 Jeffersonville, Indiana News and Tribune article by Jenna Esarey are incorporated in this article)

“NEW MIDDLETOWN — With Bobcats, ATVs and chainsaws, many residents of New Middletown spent their Saturday cleaning up after an EF-1 tornado cut a swath through homes, barns and cornfields Friday afternoon.

The National Weather Service on Saturday confirmed that an EF-1 tornado, with winds of 105 miles per hour, hit the small community just southwest of Corydon in Harrison County around 2:16 Friday afternoon.

The worst of the damage was near New Middletown, though. Homes along Simler Road were buffeted by the tornado, however, most structural damage was to out buildings.

Just down the road, Danny Perry’s farm was severely damaged.

“I lost my barn, back side of my pole barn, the back of my roof and all of my fruit trees,” Danny Perry said.”

2018 International Building Code (IBC) shows for Indiana in Section 1609.3 a basic wind speed (Vult) of 107 mph (miles per hour) for Risk Category I buildings – these would be buildings unlikely to pose a risk to human life in event of a failure, or 114 mph for most other buildings (Risk Category II).

Given EF-1 tornado speed of 105 mph, there should have been minimal damage to any pole barn (post frame) buildings designed by a RDP (Registered Design Professional – architect or engineer) and built according to sealed plans.

In order for this to occur, all jurisdictions should be conforming – requiring Building Permits for structures, RDP sealed plans in order to obtain a structural permit to build, and jobsite inspections to insure conformity to building plans.

Not only do many jurisdictions allow construction without RDP designed plans, but some do not even require building permits!

In this or other areas where buildings may be subject to higher wind speed tornados, building owners can opt for greater wind speeds than Code minimum (keep in mind minimum is LEAST). In many cases designing to withstand higher winds is a nominal investment, so why not?

 

Fire Resistance, Condensation, and Wind Speed

Fire Resistance, Condensation, and Wind Speed

DEAR POLE BARN GURU: Do you know if WMP-10 metal building insulation facing is ok to have exposed in a commercial building in regards to its fire resistance rating? JON

DEAR JON: WMP-10 facings are flame resistant, however you should consult with your local building code enforcing agency to determine if they will allow it to remain exposed given your use of the structure. An alternative might be Johns Manville FSK-25 faced batts which are laminated with an FSK (foil-scrim-kraft) facing, which enables the insulation to carry a fire hazard classification rating of 25/50 or less per ASTM E 84. The FSK-25 facing also serves as an excellent vapor retarder and may be left exposed where codes permit. The FSK-25 batts are a lightweight fire-resistant thermal and acoustical fiberglass insulation made of long, resilient glass fibers bonded with a bio-based binder.

Personally, I’d look at using unfaced fiberglass or rock wool batt insulation then covering the interior surface with 5/8″ Type X gypsum wallboard. Probably less expensive and would afford greater R-values with less of an investment.

 

DEAR POLE BARN GURU: I recently had a small pole barn constructed in Northern NJ which I’m about to insulate. Needless to say, the information regarding this is very confusing. The end goal here is to not have a condensation problem. With no insulation on the walls currently the metal walls sweat. The roof consists of metal roofing on top of “double bubble” on top of purlins with ridge vent and soffit vents.  The walls will be filled with 6″ fiberglass and a poly vapor barrier applied. The ceiling will either be OSB or gypsum attached to the bottom of the trusses with blown insulation on top with no vapor barrier. With that said, my question is with this configuration, will the gable ends above ceiling height sweat or do they need to be insulated? If so what would be the recommended insulation?

Thanks, CONFUSED in NEW JERSEY

DEAR CONFUSED: With proper ventilation in your attic I won’t say it will be impossible to have condensation on the inside of the attic gable endwalls, however the probability should be small. If you want to make certain, an inch of closed cell foam can be sprayed on the inside of the endwall steel and it will eliminate any chance.

DEAR POLE BARN GURU: Are your plans for stick built frames or CBS frames or both? If only for frame built what is the wind ratio? SUNSHINE in JUPITER

DEAR SUNSHINE: Our buildings are neither stick built or concrete block – they are post frame buildings.

Since January 1973 anemograph stations within the United Kingdom have tabulated for each clock hour the mean hourly speed and the maximum gust (of approximately three second duration). The ratio of maximum gust speed to the mean speed for individual hours as an effective height of 10 meters is referred to as the gust ratio. The mean wind ration is the ratio of the extreme gust speed to the extreme hourly mean speed, both having a return period of 50 years. This ratio turns out to be 1.60.

Here in the colonies, we design using Vult (Ultimate Wind Speed). Until the 2012 IBC (International Building Code) we designed for Vasd (Allowable Stress Design) which is 60% of Vult.

One of the beauties of post frame construction is the buildings can be designed to support any wind load situation needed.

PVC Pipe for Post Sleeves

Reader TOM in PURVIS shares a concept I had neither seen before nor had I even contemplated – using PVC pipe to protect post frame (pole building) columns from decay.

TOM writes: “ I know your posts are treated, but I live in the damp state of MS. In recent years 3 of my friends have pole barns, all of them very nice. But one in particular, the contractor added 8″ PCV pipe around the outside of the pole inserted into the ground – then concreted the pole. The claim is that this is an additional protection against termites and rot. It does appear to have given more protection from Mother Nature. Do you have an opinion about use of PVC when setting posts?”

Mike the Pole Barn Responds:
Virtually anything can be made out to be a benefit with a convincing argument. In my humble opinion, this builder is truly not adding any value to the buildings, and is potentially setting them up for failure from another act of Mother Nature – wind.
A properly pressure preservative treated column should out live not only us, but probably everyone else who is alive on the planet today (for more on the lifespan of pressure preservative treated wood please read: https://www.hansenpolebuildings.com/2017/12/will-poles-rot-off/).
The eight inch diameter PVC pipe probably just allows a 6×6 column to fit inside. Filling the balance of the pipe with concrete ads no real value as the concrete would never be over an inch and a quarter thick and work fracture under a load – either bending or withdrawl. This leaves whatever material is filled on the outside of the slick PVC surface to resist uplift forces. There is also an issue of connecting the PVC to the column, if unsealed holes are placed through the pipe by screws, bolts, nails, rebar, etc., water is going to get inside the pipe and the entire premise is defeated.
My opinion, if this was such a wonderful idea (and it actually added value) everyone would be doing it – just say no to the PVC pipe column sleeve.