School Roof Failure from Snow - Shoring?
School Roof Failure from Snow - Shoring?
(OP)
In the attached picture is a local school that has a massive drift on it's low roof. The school was built in the 50's. The roof beams are deflecting approx. 4-6", the wall is bowing outwards...assuming the columns are buckling as well.
Question, is there any "safe" way to shore this sucker up? We have discussed bringing in a track hoe and pulling snow off the roof, but are concerned that it will add additional weight and maybe cause the entire thing to collapse. We talked about a boom lift and a guy with a shovel, but if he gets close to the gym roof, and the low roof fails, then there is potential that the gym wall could collapse onto him.
I don't know how you would begin to design a shoring system to keep this post and beam building from caving in. I haven't seen it done, I'm sure it has been done, but I just have no experience with it. Is it possible? Trying to keep the low roof from collapsing and then pulling the gym wall with it.
Question, is there any "safe" way to shore this sucker up? We have discussed bringing in a track hoe and pulling snow off the roof, but are concerned that it will add additional weight and maybe cause the entire thing to collapse. We talked about a boom lift and a guy with a shovel, but if he gets close to the gym roof, and the low roof fails, then there is potential that the gym wall could collapse onto him.
I don't know how you would begin to design a shoring system to keep this post and beam building from caving in. I haven't seen it done, I'm sure it has been done, but I just have no experience with it. Is it possible? Trying to keep the low roof from collapsing and then pulling the gym wall with it.






RE: School Roof Failure from Snow - Shoring?
RE: School Roof Failure from Snow - Shoring?
First job is getting that snow load off of there without overload or injury. Definitely wouldn't put any equipment or people on or in the structure while doing this. I'd say snow removal from the ground would be safe enough, though. I'd get some of those long roof rakes and pull it off of the worst areas. Then you can see about a manlift getting in close or getting someone up there with shovels safely.
Once you get into the repair that's where I'd really worry. My job I only had one snapped joist and the rest were fine. Sistered on a new joist and we were good to go. For yours that might be the end of that roof.
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com
RE: School Roof Failure from Snow - Shoring?
RE: School Roof Failure from Snow - Shoring?
After that storm blows through you'll probably be looking at demoing the finishes around the structure and performing a detailed inspection. I'd suspect you can do this safely without shoring but I'd not let the structure be re-occupied by non-essential personnel until you've come up with a shoring or repair plan.
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com
RE: School Roof Failure from Snow - Shoring?
RE: School Roof Failure from Snow - Shoring?
RE: School Roof Failure from Snow - Shoring?
RE: School Roof Failure from Snow - Shoring?
Dik
RE: School Roof Failure from Snow - Shoring?
RE: School Roof Failure from Snow - Shoring?
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: School Roof Failure from Snow - Shoring?
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: School Roof Failure from Snow - Shoring?
Is the snow wet or dry? If dry, you might be able to vacuum from roof. Sewer vacuum boom truck could handle that.
RE: School Roof Failure from Snow - Shoring?
-the photos don't look like 4"-6" deflection, so I'm interested if that's a number you measured yourself.
- if the wall is bowing outward, it may be an indication that there's a moment connection creating a frame over these classrooms.
- with about a 40' span (my guess), you might expect a 2" deflection and this deflection would probably be what limited the design. meaning that there could be additional capacity beyond the deflection limit.
-wind will keep depositing snow from the upper roof onto the lower one, but it will also blow snow off the lower roof. It looks like the roof has its max drift and therefore the wind is your friend.
-posts in the classroom will keep it until spring if you determine that it was really overstressed.
-rain in the forecast, and/or a couple slightly above freezing days, are/is a bigger problem than another snow storm.
RE: School Roof Failure from Snow - Shoring?