Snow Pg
Snow Pg
(OP)
Lots of roof collapses in the area lately.
So, I had a little time during lunch and decided to run outside and measure Pg. I used a 5 gallon bucket and a fish scale to measure the snow (I pushed the bucket into the snow and then collected the snow within the circle created by the bucket).
Weight of empty bucket = 1 lb 12oz
Weight of snow bucket 1 = 16 lb 6 oz
Weight of snow bucket 2 = 7 lb 0 oz
Total Weight = 23lb 6oz
Total Weight of snow (less 2 buckets) 19 lb 14 oz
Area of bucket = 84.5 in2
Pg = 33.9 psf
Density = 18.9pcf
Comparison:
Jurisdiction Required Pg = 50
Density = 20.5pcf
ASCE 7-10 Pg = 40 (however really close to 50)
Density = 19.2 pcf
I only took the measurements at one location.
So, I had a little time during lunch and decided to run outside and measure Pg. I used a 5 gallon bucket and a fish scale to measure the snow (I pushed the bucket into the snow and then collected the snow within the circle created by the bucket).
Weight of empty bucket = 1 lb 12oz
Weight of snow bucket 1 = 16 lb 6 oz
Weight of snow bucket 2 = 7 lb 0 oz
Total Weight = 23lb 6oz
Total Weight of snow (less 2 buckets) 19 lb 14 oz
Area of bucket = 84.5 in2
Pg = 33.9 psf
Density = 18.9pcf
Comparison:
Jurisdiction Required Pg = 50
Density = 20.5pcf
ASCE 7-10 Pg = 40 (however really close to 50)
Density = 19.2 pcf
I only took the measurements at one location.






RE: Snow Pg
So roofs designed to ASCE 7-10, even without your local increase, should be OK.
DaveAtkins
RE: Snow Pg
I would say the roof of my house should be OK.
RE: Snow Pg
RE: Snow Pg
RE: Snow Pg
RE: Snow Pg
The estimated weight of the snow was about 13 psf (pretty wet). So that theoretically meant that all the Roof Live Load capacities in that area should have been 20 psf....all OK.
The problem seemed to be clogged roof drainage and ponding of water as the snow began to melt. Resulted in a warehouse collapse that we were hired to look at. Only problem with this one was that the owner had hired out some workers to start torching up the steel and moving it off the building pad to allow trucks to haul it off. The torches caught the paper products stored underneath on fire - which resulted in even more damage.
I recall seeing all the building columns (12" square concrete columns) still standing as the wide flange steel roof beams had no stiffeners and simply twisted off the columns and dropped - with the columns poking through the metal roof deck.
So many San Antonians were shocked by the snowfall that they ran out and bought all the camera film (and all the toilet paper for some reason) from the stores. Lots of photos of the Alamo with snow on it.
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RE: Snow Pg