I’m writing today’s blog from a motel room at one of the casino’s in Council Bluffs, Iowa where I’m waiting for roads in southwest Minnesota to open.
Another winter storm is raging in the Midwest, meaning another week of disruptions to feed deliveries and deliveries of pigs to slaughter plants. We had several loads of pigs from our research barns delayed until next week. I’m sure many of you reading this blog are having similar problems.
As a result of the Christmas storm, we lost the roofs on at least 5 hog barns and 5 poultry barns in Minnesota. In most cases, snow drifting and unequal weight loads on rafters were the cause. Today’s new snow and more drifting will add to the stress on rafters.
In conversations with 2 structural engineers, there are 2 problems with the snow loads. One is the risk of immediate failure of the rafter due to the unequal loading on the roof, which is what happen on Christmas weekend. The other concern is long term fatigue of the structural members due to the snow loads.
If you live in the upper Midwest, engineers advise that you take a look at the snow loads on your roofs. If it looks ‘deep’, they advise you figure out ways to remove some or all of the snow load relatively soon. In the case of barns in southern Minnesota, producers on may sites have been up on roofs with shovels and other devices to get the snow off the roofs. I heard of one case at a sow unit where they took a snow blower up on the roof.
In all cases, if you are up on the roof, use caution. What some were doing for safety was to push snow from the upper levels off the roof, leaving some along the edge. The reasoning was that some snow along the roof edge would slow/stop a fall from the roof in the case of slippage.
The rafters and supporting bracing of roof members in our facilities were designed by structural engineers to carry a specified snow load. The problem with high winds is that the snow load isn’t uniformly distributed on the roof members, meaning there are points on the roof where the load is more than they were designed to bear. So far the only solution that I’ve been able to identify is to clean the roofs, almost always by hand.
Could be a long winter.