I have been a Structural Steel Welding and Bolting inspector for 34 years and in Commyfornia with all of the Earth Quake crap they frown very heavily of the use of a Grade 8 bolt for Structural use.
I have seen Engineers spec out Grade 8 bolts but not very often.
They do not like brittle bots for Structural use due to the Shock values.
Just my opinion but pulling a trailer with the bumps and humps in the road.
That may create Shock on the Hitch pins
Structural bolts are almost exclusively used in shear. The shear strength of a grade 8 is higher than grade 5, and provides a higher shear strength value for the connection. Period. That being said, the bolt may not be the weak link - so using a stronger bolt might not gain any overall connection strength. There is no "bending" of a bolt in structural shear connection. Failure modes in steel are almost all catastrophic. The bolt shears, or the steel tears out in chunks (block shear). Seismic design requires the steel members not the connections, to yield and absorb the seismic energy. When a contractor complains about grade 8 bolts, it's because of the expense and availability, or lack there of.
