Lateral load structure within building

[isidor_]

Hi,
(Eurocode applies where i work)
Say i have a large building (large industrial building) and within it a smaller structure shall be built. How is the lateral load calculated for a structure within a building?
There is ofcourse the unintended inclination that will affect the new smaller building, but this will not give rise to alot of lateral load.
There is also the section 7.2.9 in EC1991-1-4 for internal wind pressure, but can that be used for load on the smaller structure?

 

[human909]

Live loads and seismic loads also exert lateral forces on your structure. You are an engineer, consider what is reasonable.

For small light structures I use a nominal 10% of dead + live if there is another dominant lateral load. Depending on your structure this could be overly conservative.

 

[isidor_]

There are no seismic loads where i am located. Using a fraction of the dead+live load is an option, but it feels abit arbitrary, but is ofc an option.
Engineering judgement should always be used to judge if something is reasonable or not. But the question is regarding code compliant lateral load on a structure within another structure.

(Using engineering judgement it feels abit wrong to only have the small horizontal load from unintended inclination loading my structure, hence the question)

 

[XR250]

I use 5 psf (interior wind load). Might also add 20% of people load - which is what I use for exterior decks

 

[isidor_]

The 5psf=0.2394013 kPa (according to google) is close to the interior windload (7.2.9 (6) NOTE 2 -> cpi=0.3 multiplied by the exterior wind preasure qp(z)=~1.0kN/m2, 1.0*0.3 = 0.3kN/m^2) which I thought about using on the surfaces, so that seems like a good approximation.

 

[ThomasH]

There is a interior windload in the Eurocode, as you already mentioned. But since you mentioned that it is an industrial building, I would also consider accidental loads. That of course depends on the type of industry but a truck colliding with a wall can happen if they have trucks.

 

[isidor_]

Yes if there is a risk of accidental load (ex. forklift driving into it) that should be accounted for.

Regarding the interior windload, I am somewhat unsure if it only affects the "outer shell" of the main building or if it can be assumed to affect all of the interior surfaces, such as the smaller building inside.

 

[ThomasH]

As far as I know it can affect all internal surfaces. Also, if you have large openings or even permanent openings in the external walls that can have a nasty effect on the internal wind load.

 

[isidor_]

Okay thanks for the input! That is how i was planning to use it since I dont find anything else. It is annoying that EC is not more explicit in some aspects, such as this..

Regarding the openings, I assume you are referring to this section in EC1991-1-4 7.2.9:

(3) Where an external opening, such as a door or a window, would be dominant when open but is
considered to be closed in the ultimate limit state, during severe windstorms, the condition with the
door or window open should be considered as an accidental design situation in accordance with EN
1990.

NOTE Checking of the accidental design situation is important for tall internal walls (with high risk of
hazard) when the wall has to carry the full external wind action because of openings in the building
envelope.

 

[EZBuilding]

ASCE 7-16 1.4.2 has a minimum lateral force of 1% of the dead load of the structure.

Interior wind pressure is 5 psf.

 

[Celt83]

Interior wind minimum Live load pressure is 5 psf. (IBC 2021 1607.16)

 

[EZBuilding]

Thanks Celt - good correction

 

[Celt83]

There was a discussion on here several years ago where that got beat to death, seems for wood wall design industry wide we've all been taking that 5 psf to be wind pressure which ends up allowing you to combine with 0.75*L in the ASD load combos along with a higher Cd factor which can lead to some unconservative wall stack designs.

 

[ThomasH]

Regarding the openings, I assume you are referring to this section in EC1991-1-4 7.2.9:

Correct. But since I don't know your situation, if there are large openings like an airplane hangar, that will be nasty .