Notional load Changes in ASCE 7-10

[PicoStruc]

It's me or the concept of notional load is a lot simpler in ASCE 7-10

The way I understand it from the page 4 :

1) A Specific combination (similar to other lateral combination) is now assigned to notional load. The notional load is independant load and not combined with other lateral loads.

2) Notional Load is now 5% of the weight instead of 2%

This means that if the seismic or wind load are greather that 5% of the weight.... no notional load to consider at all ???

AM I Right ?

 

[DST148]

I don't know what is given in ASCE 7-10, but I have AISC 360-10 which is based on ASCE 7-10.
Table 2-2 provides summary comparison of methods for stability analysis and design. Based on that table it seems....
The notional loads are additive to other lateral loads depending on the ratio of the second order drift to first order drift. However, there are exceptions when it is not additive. The notional loads are 0.2% of story gravity loads in case of direct analysis method and effective length method but 0.42% of story gravity load for first-order analysis method.

 

[PicoStruc]

i don't understand why there is Notional Load Combination in ASCE 7-10 Then !

 

[WillisV]

The updated structural integrity requirements of ASCE 7-10 (including the notional loads and tie force requirements etc) have nothing to do with the direct analysis design procedure and its accompanying notional loads as defined by AISC 360-10. The ASCE 7-10 requirements are totally separate from the AISC steel design method and represent one of the code changes resulting from the code review bought about by 9/11.

 

[DST148]

@WillisV: As I mentioned in my post I do not have ASCE 7-10. The OP by PicoStruc gives notional loads as 2% and 5%. I was using AISC 360-10 as a back-up to suggest that the magnitude of the notional loads are in the range of 0.2% to 0.5% of gravity loads.

 

[PicoStruc]

Sorry for that, not used to US codes, Still learning !

So if I understand correctly, there is "two" notional loads to consider !

1) 0.2% or 0.5% of weight as defined by steel codes for all loads combinations

2) 5% of weight as defined by ASCE 7-10 only for the notional load combination (similar to other lateral load combination).

Then, if the seismic or wind load are greather then 5%W, the notional load don't govern lateral behivour and only usual #1 notional load case is to be considered in analysis.