Footnote 2 of Table 12J states that tabulated values are based on reduced body diameter. I assume that should also include Fe calculation. For a 1/4" lag, Dr= 0.173", and G=0.5, Fe=16600G^1.84=4637psi, Fyb=70,000psi. I get Z(IV)= 140 lbs. Table 12J lists 150 lbs for ts=1.5". (I must have...
Reference: thread507-436818
I get the same result as OP for 1/4" lag screw capacity. The discrepancy (with NDS) appears to be how Fe is calculated. Since Dr = 0.173 < .25, Fe=16600G^1.84=4637 psi (see footnote 2 of NDS Table 12.3.3), for G=0.50.
It appears that 2018 NDS Table 12J and the...