Notional horizontal forces

[pba]

Hopefully a quick question:

In the UK steel code, there is a requirement for frames to resist a notional horizontal force, in the absence of greater actual horizontal forces.

This notional horizontal force is defined as 0.5% of the factored vertical load.

Do US codes make a similar provision?

 

[oldrunner]

There is something similar in the Uniform Building Code, but it is an additional rotational force which, if I remember correctly, added to the calculated torsional forces due to a seismic event. This force is an additional 5% and is considered "accidental" torsion. 0.5%, as you noted isn't a very high value.

 

[UcfSE]

Appendix 7 of the new AISC steel code has provisions for using notional loads. It appears the minimum is 0.002 of the gravity load, or 0.2% (A7.3 (2)). I don't know that this new code is yet referenced by any of our model building code but I expect it will be fairly soon.

 

[NewImhotep]

This load not very significant in the steel structures (except u have a heavy loads ) , You should to take this load only if the factored wind load < 1% dead load as Sec 2.4.2.4 in BS5950

notional load become more significant in the concrete structure which equal to 1.5% of dead load as BS8110.