Calculating lift of a tarp carport

[4WD]

Indeed … I'm about 35 miles from the saltwater …

But 30-40 mph winds can occur most anywhere and while folks play with the math … I'll place my bet that's all it takes to lift that much sail area on a light frame …

 

[ABN_CBT_ENGR]

Originally Posted by 4WD
Indeed … I'm about 35 miles from the saltwater …

But 30-40 mph winds can occur most anywhere and while folks play with the math … I'll place my bet that's all it takes to lift that much sail area on a light frame …



On occasion I have had a "gentle breeze" from a cross wind literally jerk me off my feet before I could collapse a chute.

It doesn't take a Dorothy level wind depending on the surface area and collective to generate significant lift even if for a second or two.

 

[JHZR2]

Originally Posted by ABN_CBT_ENGR
FWIW

Went with the crew yesterday to set up the food truck and briefly talked with the awning guys setting up. ( figure they are the experts on this as they do it for a living)

They don't like bags because they don't last and wires because they get in the way.

They make anchors with steel rims with a bit of cement with a pipe in the middle and paint them.

Gives them a footprint area for tipping as well as weight- easy to roll and move, store and works in all kinds of storms according to them.


Originally Posted by 4WD
+1 on subterranean anchors … you do the cinder blocks and the wind flips and buckles one side … then those cinder blocks and frame will destroy what you tried to protect …



Yes, agree. This all makes sense.

 

[JHZR2]

Originally Posted by 4WD
Indeed … I'm about 35 miles from the saltwater …

But 30-40 mph winds can occur most anywhere and while folks play with the math … I'll place my bet that's all it takes to lift that much sail area on a light frame …



Me too. Hard not to be as the crow flies, living in NJ.

Originally Posted by ABN_CBT_ENGR
Originally Posted by 4WD
Indeed … I'm about 35 miles from the saltwater …

But 30-40 mph winds can occur most anywhere and while folks play with the math … I'll place my bet that's all it takes to lift that much sail area on a light frame …



On occasion I have had a "gentle breeze" from a cross wind literally jerk me off my feet before I could collapse a chute.

It doesn't take a Dorothy level wind depending on the surface area and collective to generate significant lift even if for a second or two.


Right. A short lived gust at 30-40 can happen readily anywhere during a storm. That's why I tried to set my analysis at 45.

Frankly, if a tarp rips at that point, I don't care. It's the cost of doing business.

It's a matter of letting the tarp and bungees be the weak point, and not having the frame, cinderblocks, or whatever else lift up.

At some point even subterranean anchors will rip out, but I suspect the depth is a major factor there... and if that happens, I'm sure there are bigger issues due to the local weather!

Given the pull out strengths of tapcons, and the fact that the design of the feet of this thing provide the ability to mount it with 24 such screws, I'd say there is sufficient safety factor if I only had the right substrate!

 

[ABN_CBT_ENGR]

Originally Posted by JHZR2


Right. A short lived gust at 30-40 can happen readily anywhere during a storm. That's why I tried to set my analysis at 45.

Frankly, if a tarp rips at that point, I don't care. It's the cost of doing business.

It's a matter of letting the tarp and bungees be the weak point, and not having the frame, cinderblocks, or whatever else lift up.

At some point even subterranean anchors will rip out, but I suspect the depth is a major factor there... and if that happens, I'm sure there are bigger issues due to the local weather!

Given the pull out strengths of tapcons, and the fact that the design of the feet of this thing provide the ability to mount it with 24 such screws, I'd say there is sufficient safety factor if I only had the right substrate!



Maybe but most likely not and I'll explain why- I have a career in setting machines with precision foundations holding critical tolerances where all these things matter and no movement over decades can be tolerated without adverse effect.

The problem with a tapcon method is the hardness will continuously cut and shave concrete ( from normal flexing and lateral shear loading) which eventually wear the threads down or wallow the hole. Then add a little rain leading to corrosion and they yield. They work fine for temporary applications but should not be considered for anything semi permanent.

The other problem is the substrate in terms of size/geometry, moisture, compaction and density. That's why anchors tend to fail because these things are not considered and why we have to bed and tamp before many installations. This directly determines the outcome of a vertical pull test.

"asphalt" has all the structural strength of a brownie so it doesn't even rate.

There are several options and most will give you satisfaction but if your goal is semi to permanent ( replaceable tarp) then do the pipe/hole- you wont have to ever redo it.

Less than that, a heavy solid wide footed anchor per leg- that should work very well too.

 

[supton]

Originally Posted by eljefino
I love the bucket and sand idea!

Ditto. I have a cheapo HF 10x10 "shed" that is held down by 4 buckets of sand and some tie straps. Not the same as the OP as it has sides, and it's somewhat sheltered in the woods (was next to the house too, so some shelter) and it managed a winter. Maybe the OP's carport would do better with sides?

Buckets of sand could be the ones used for holding winter sand for the driveway, so, it's not like they have to be one-time use things.

 

[JHZR2]

Maybe it would do better with sides, but not really interested in that. Since it is so close up to the garage (see HD stock image in OP), I have to wonder if that changes the pressure behaviors to allow flipover.

Because I have kids running around, and generally want a slightly better aesthetics, Im really not into buckets, dual use or not.

Whether I cut the asphalt and do that, or just build a legitimate carport is my decision process now...