I think this one's a losing battle. There aren't any building codes that require a building to be designed to resist tornado loads, except ICC-500 which is for storm shelters.
Faith is taking the first step even when you can't see the whole staircase. -MLK
Tilt-up can be made safer, but we typically do not design the roof deck for both maximum uplift and maximum lateral force simultaneously, as is the usual condition for severe wind events.
I will again be teaching part of the engineering seminar at the Tilt-up Concrete Association annual meeting (in San Jose, CA, on October 1st) and plan to address this specifically. Connections are the weak link on all designs (except cast-in-place, reinforced concrete - you all knew I had to say that.)
As far as litigation, this could help turn the tide toward improved building codes. Also owners need to recognize that while building codes are minimum requirements, they should do additional risk assessment to decide if they want to do more than minimum. There is no law saying that you must design to minimums and threat of future litigation is often a motivating factor to build better buildings. As for the merits of the case, the employee directed them to the training room, and all those sheltering there were safe. We probably do not want to set precedent that every place in every building must be tornado-safe. Or if we do, we should expect the cost of the things we purchase there to increase.
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<rant on>
We require buildings in earthquake regions to be designed to stand up long enough for safe egress, similar to what we require for fires. We know that these events strike suddenly over large areas (Probability is moderate, severity is catastrophic) and structural collapse is likely unless the design considers this. We require buildings to withstand hurricanes because they are frequent events - although arguably, people usually have sufficient warning that they should already be well out of harm's way before the storm arrives. (probability is near 100% in coastal zones; severity is low to high)
Tornadoes are very unlikely to ever hit a particular building during the life of the building, and the impact is highly variable (probability is very low, near 0%; severity is moderate to catastrophic, depending on construction type and storm strength). A rudimentary risk assessment says that we should require all buildings in seismic zones to be designed for those loads. Structures in Gulf and Atlantic coastal zones which are high value or must remain occupied/intact should be designed for hurricanes. The complicating factors for this are 1) when one structure is torn apart in a hurricane, it increases the risk to other structures and infrastructure, and 2) the insured and uninsured costs in a single hurricane landfall can be overwhelming. These are a strong reason for increased minimums, as the code requires.
In contrast, tornadoes present such a very low risk on the scale of most communities that there is very little incentive to increase requirements. Personal risk perception and tolerance aside, there is no compelling case to require tornado-resistant construction in most cases.
Consider the case of Moore, where although tragic and catastrophic on an individual level, the number of houses destroyed was approximately equal to the number of vacant houses in the city of Moore the year before the 2013 tornado. (Not including the city of Oklahoma City or other OKC suburbs.) This is really not catastrophic to the community, from a purely numerical perspective. Contrast this to the significant increase in cost to acquire conventionally-constructed housing which has been designed and built to resist tornadoes. If they use something like ICFs for the house shell, the incremental cost to make a house tornado-safe is low. But builders resist change and often overstate the cost of ICF construction because of a perception that doing so risks their profitability. Contractors are all about pricing based on risk.
</end rant>
How many tilt-wall buildings fail each year due to loss of roof framing in an extreme storm event? This is the first one I've heard of, though surely not the first ever.
We had an earlier discussion about this. However, the article which JedClampett referenced at that time has disappeared, probably due to the litigation.
"How many tilt-wall buildings fail each year due to loss of roof framing in an extreme storm event? This is the first one I've heard of, though surely not the first ever."
My point exactly. The probability is very near zero. With the data available, an owner would not be able to justify the costs of strengthening an entire building for these never-to-be-seen events, absent some other motivation (like one or more lawsuits.)
But I have seen failure of roof decking or framing to stay attached, occasionally leading to leaned or crooked panels, but it takes a truly huge storm and a direct hit to do what happened in Joplin.
New PostHelpful Member! jike (Structural) 6 Aug 14 10:25
There are NO WINNERS IN LAWSUITS (except the lawyers).
How about this one; Recently a fellow killed his wife and then himself.
A month later a newspaper article stated that the estate of the wife was suing the estate of the husband.
