help with wind loading 1

[COEngineeer]

Lets say you have a gable roof supported with only 1 wall and the rest with columns(and knee brace for fixity). The roof is supported by trusses that sit on a shoulder beam on the single wall and on beam on the other side. What is the "proper way" to get the wind loading? I just feel that the asce is impossible to understand. Can someone maybe guide this dumb me? Theoratically I cant use 1st (simplified) method since there is only one wall, right? My boss told me to just use simplified method but I am totally disagree with him. But then again I tried to read the analytical method (and the appendix) and I am still confused. Can someone enlighten me?

Never, but never question engineer's judgement

 

[Lion06]

We always use the analytical method (so I am not sure of the restrictions on the simplified method). All of the paramaters in ASCE 7 are pretty straightforward for the analytical method. Do you have any specific questions?

 

[fasboater]

You can’t use the simplified method because section 6.4.1.1 number 3 states that the building must be enclosed per section 6.2.

don’t think you meet that requirement.

I think you’re stuck with the analytical method. I have been attempting to use this as well and it doesn’t seem too bad providing you follow 6.5.3. ASCE also puts out a handy design guide called "guide to the Use of the Wind Load Provisions" which I found to be very useful.

Hope this helps..

 

[COEngineeer]

EIT, I guess I am not very good when it comes to reading codes (English is not my 1st language but I think that isnt the case). I didnt find it very straight forward. I will look for that book fast boater. At the mean time, can you maybe do a dummy version of analytical method for me? Lets say my wind speed is 100 mph category C.

Never, but never question engineer's judgement

 

[Lion06]

how tall is the building?
You will need to calc the windward pressure and the leeward pressure and add the two.
Is this the the "building" with one wall that you mentioned above?

 

[COEngineeer]

Yes. It is 30 ft by 17 foot platform. The roof is a bit larger (3.5' overhang). Mean roof height about 15 ft.

Never, but never question engineer's judgement

 

[fasboater]

What version of ASCE are you using 02/05?

 

[COEngineeer]

05


Never, but never question engineer's judgement

 

[fasboater]

I hope this helps. I am sure its not perfect.

 

[COEngineeer]

Wow, I appreciate your time fastboater. I will go through it. I tend to follow examples better than the codes.

Never, but never question engineer's judgement

 

[COEngineeer]

The windspeed is 3 second gust already so I dont have to do Gf? Right? Just make it = 1?

Never, but never question engineer's judgement

 

[ron9876]

I also recommend getting the "Guide to the use of ASCE7". Often there are conditions that don't meet the code. You have to try to find a boundary condition that you know meets or exceeds the "real" values. For instance when you calculate the uplift on your roof structure you won't find this condition in the code. If you use uplift for an open building it may be low because of the wall. If you use the value for overhangs it may be too much but it is, to my knowledge, the only way to get an uplift that meets or exceeds the code requirements.

 

[fasboater]

The Gf should be calced because (unless I am missing something) this factor is for turbulence and structure interaction.

 

[ron9876]

Values in Figure 6-11A for instance are for GCp

 

[fasboater]

ron9876 is correct some of the terms and design limitations can be some what tricky.

Be sure you familiarize yourself not only with the wind load section but also the commentary in the back of ASCE, the wind section starts on pg 281.

 

[fasboater]

ron9876

The values for figure 6-11A are for enclosed or partially inclosed buildings. I dont think COEngineer meets the criteria for this type of building.

 

[COEngineeer]

ok, here is the 3D. Fasboater, I am still confused. OK pretty much there is no wall at the gable end. So I need to look at the lateral on the other side. So what is the most critical scenario? Can you help me a little more? I need to design the knee brace for the column, also I want to know how much lateral the bottom of the hut takes because it is on stilt (see my other post floating around).



Never, but never question engineer's judgement

 

[ron9876]

I was using that as an example where the G is included. Will have to use the worst case for the loads.