Pond Boss Forums INTRO Questions & Observations OH NO!

The bolts don't have to be that big if they are the correct grade.

Given that in the above scenario you are trying to support 2500# between 6 posts. Lets say you have to support 2500# on each support for a fudge factor.

If that was the case, then a single 1/4" Grade 8 bolt on each support would be more than strong enough to hold 2500# on each support without failing.

Using a shear strength of 150,000 psi for a grade 8 bolt.
The following sq. in. figures are for the minor thread diameter for each given size. (UNC threads)

1/4" bolt has .0269 sq. in. shear is 4,035 pounds
3/8" bolt has .0678 sq. in. shear is 10,170 pounds
1/2" bolt has .1257 sq. in. shear is 18,855 pounds
3/4" bolt has .302 sq. in. shear is 45,300 pounds

Now if the pier is out of the water when you do this, treated wood weighs around 36.1# per cu. ft.

75 x 36.1 = 2707#
Add the weight of the filled barrels,55x8.35 = 460 say 500# for each filled barrel.
7 barrels x 500# each = 3500# 3500 + 2707 = 6207#

So, my wag is that a 3/8-16 x ? length Grade 8 bolt in each column would be strong enough to hold, even allowing for waterlogged wood. (cu. ft. of water is 62.43#) Now, would the wood stringers (joists) hold that weight without splitting? I dunno. If you can't find bolts that long, McMaster-Carr has grade 8 threaded rods.