Design of Building for both wind and sesimic

[faromic]

I recieved a project a couple days ago to do. It's s one story wood structure about 100'x50'. It's not rectangular, but skewed about 30 degrees maybe a bit more. Anyways, I have do design for the governing load out of wind and seismic. It's in Michigan so I think wind will govern. There are 18' wide common trusses that bear on an exterior bearing wall and interior beams (supported by intermediate columns) The rest of the roof (at the interior portion of the building) is made of flat roof trusses. I've been reading IBC 2003 and 2006 and am confused about the process of how design for seismic. There are so many figures I don't know which one to use, the 1 second or .2 second figures. Overall, I'm just not sure of the procedure to find the g value to multiply by the self weight of the structure. I calculated the wind load (MWFRS) to be 20 psf, so I'm assuming this will govern but I still need to do the check.
THanks

 

[JKStruct]

Do you have a supervisor to guide you through this process? The 1 second and short term spectral response accelerations to which you refer are a starting point. You don't multiply those by the building weight to yield a seismic force. Get each of those accelerations for the location of your building, and go through the equations in the code to arrive at the story shear to determine if wind or seismic governs. The controlling forces of wind or seismic need to be verified for each building component. With the structure you describe, it appears there are also irregularites to consider, and you should walk through the process with your supervisor.

 

[DaveAtkins]

I seriously doubt seismic will control for a one story wood structure, even if you are in lower Michigan. Rather than waste time calculating seismic forces, see if you automatically qualify for Category A.

DaveAtkins

 

[faromic]

Should I take the worst case of the short term and one second response spectra g values? I'm going to really get into reading it today, I would like to be knowledgeable before I begin working on it at work.

 

[JAE]

faromic,

Based on these questions of yours, I would second what JKStruct says and get someone who knows how to do seismic design to help you on this.

There is really no such thing as wind, or seismic, "governing a building". Each case (wind or seismic) should be included in the various load combinations listed in chapter 16 of the IBC and each element of the building should be checked for all those combinations. It may very well be (and usually is) the case where a combination with wind will govern one design element (say a brace, stud or connection) and seismic control other elements.

DaveAtkins may have a helpful point though - if it is an SDC A then the seismic loads throughout may be low enough where wind cases would control most designs. But not understanding the basics of seismic design would tell me you need to at least get some good direction on this.