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Load combo's on footing subjected to large wind loads

  1. Jul 8, 2010 #1
    I am working on a spreadsheet for designing a small footing to support 1-4 Radiation Portal Monitors (RPMs). These are vehicle scanners weighing in around 2-2.5 kips a piece and roughly 7.5'Hx3'Wx1.5'D. they are arranged on the footing in a few different configurations. aside from the self weight, they are to be designed for wind loads around 100-140 mph. they also have input for ice and snow loads.

    in my spreadsheet, its assumed that the RPM/footing connection is fixed and i do not need to supply a design for it. so in the spreadsheet i have checks for overturning, moment capacity, shear (1-way and 2-way), and sliding of the footing. also, i have a check for soil bearing capacity.

    before i go any further...i am an intern, and this is the previous interns work that im... basically redoing completely lol

    back on topic, i feel as though i pretty much have all the theory set right with a few assumptions here and there. im still working on formatting (the previous interns spreadsheet was horrendous!), but i think its still easy enough to follow so far. one major issue with the spreadsheet though is that it references old code/standards. a lot of it was ASD with random interjections of LRFD and other methodologies (dont ask me why, it wasnt my doing). also, it references TIA standard...i dont see the previous intern's logic here. so im trying to update the whole thing in conjunction with AASHTO spec for signs/supports (2009), AASHTO spec for highway bridges (if i have access to it), ASCE-7 08, and ACI 318-08.

    my major issue comes in load factoring. it seems as though in AASHTO sign/support it says to factor the lateral wind load. however, the moment arm for the wind is different than that of the self weight and other loads. id think i should factor the loads at a common level (i.e. M for moment capacity, q for soil bearing, etc.). However, if i were to do that, it'd literally have thousands of iterations of the load combo equations to do...to account for wind in all directions, stress induced in +/- directions on both x & y axes. i just dont have time to do that kind of data entry, i have other spread sheets to work on.

    am i missing something here? or what are my options, rather? thanks in advance.

    (i tried attaching the spreadsheet, but it exceeds forum size limits. i cant access sites like megaupload.com here at work, so ill get it up when i get home)
     
  2. jcsd
  3. Jul 9, 2010 #2
    i got home waaaay later than i had planned last night, so i didnt get it up. but perhaps someone can help me with the load factoring without having the spreadsheet?
     
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