03-01-2014, 06:26 AM
Let's apply this to a model. A basic square single story structure with a combined rough design 70psf load at 24'X24' with enormous beams and 4 supporting post at the corners atop footing. 24' square is 576sf times 70psf design load which totals 40320lb divided by the 4 support points is 10,080lb load force per post footing. Using the seismic .4g acceleration load we take 10,080 x .4 = 4032lb applied GFA. Using the average 125psi epoxy bond applied to a 1/2" rebar anchor we take the 4032lb subject GFA divide it by the epoxy bond of 125psi which requires a 32.256si bonding surface. Now we divide the 32.256si by the 1/2" rebar si per inch of 1.57si per inch length = 20.55 anchor depth for one rebar anchor. If we apply 4 rebar anchor we derive 5" depth each and apply the customary 1.25-1.5 CYA factor and we conclude 7.5" depth each of 4ea 1/2" rebar. Now - assume the worst for your rock and be your own judge and jury after mother nature calls up THE bitchin' Earthquake of the century.