hand tight nuts in small residential construction allowed? 1

[beautifulhills]

We're necessarily importing some components (all tested, QAed, reports) from outside the country for a project (necessarily per client).

There is a specification for bolts - "all bolts to be hand tight. no preloading is prescribed". Is this currently permitted per ASCE and others, for USA?

Bolts are M20 L50mm and M20 L225mm. The entire system has extensive posts and beams, is modular in nature, and thus leans to over specified already, given the strong nature of multiple frames with multiple posts and joists, there is due to the nature of the system a lot of spare, redundancy and one failure will be protected by other frames in place.

They're small residential structures 2 storeys. (Not public use etc etc)

Any insight appreciated, the core question being 'are hand tight bolts/nuts' allowed per codes?

Designer, Specifier (I don't regulate anything despite what my profile says)

 

[gtaw]

What were the assumptions in the design?

Hand tightened; most of the connections would be in shear, not subject to preload as is necessary for slip critical connections. The engineer should be specifying the grade of the bolts used. That would determine the allowable shear per bolt. There is no vibration to speak of in a residence, so the issue of the nut backing off should be a non-issue, especially if the bolts are exposed to the weather for a few weeks before being enclosed, i.e., the threads will rust enough that loosening shouldn't be a concern.

Best regards - Al