- #1
Fat Ryan
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I am an civil engineering intern for SAIC in MD. The PE I work under asked me to create a spread sheet for designing the foundations for our projects which are 30-50' steel speaker poles subjected to 100-140 mph winds. there are 4 foundation/pole types, standard anchor bolt, direct embed, stub up, and slip fit. all types that use bolts have circular bolt patterns. I am working on the standard anchor bolt design.
we (SAIC) apparently send out the pole dimensions and loading to a third party to calculate the forces at the base and design the specific amount of bolts, their diameters, and the loading on each one. I am assuming they use finite element analysis, which I am unfamiliar with at the moment. Is there a way I can calculate this stuff myself to save them some money? I've heard FEA is rather expensive, and this is taking quite a while to get the results as well.
Or perhaps, if I could approximate the pole calc by assuming its a cantilever beam, I could get the N, V, and M at the base. But from there Id need a method to determine the correct amount of bolts to use and their respective diameters. Assuming I desiged for a worst case M scenario, then the most heavily loaded bolt would be the furthest from the NA, correct? Also, I can assume it has an eccentric axial load. by the way, the lateral (wind) load controls by a long shot in these cases. in older hand calcs i have access to, its assumed that the shear force at the base is divided evenly amongst the bolts. given all this, it seems as though i have a method for doing this by hand. the problem comes in deciding a bolt pattern. if I could make it decide on an amount and diameter of bolts, that'd be convenient, however I am not quite sure if I can do that. furthermore, i don't know if its common practice to only have an even number of bolts. it seems that an odd number makes things a bit more complicated.
perhaps I've just overthought this so much that my brain has given up on trying to find a solution lol. that said, if you have any advice, let me know...and don't laugh at me if this is way simpler than I am making it out to be :D
we (SAIC) apparently send out the pole dimensions and loading to a third party to calculate the forces at the base and design the specific amount of bolts, their diameters, and the loading on each one. I am assuming they use finite element analysis, which I am unfamiliar with at the moment. Is there a way I can calculate this stuff myself to save them some money? I've heard FEA is rather expensive, and this is taking quite a while to get the results as well.
Or perhaps, if I could approximate the pole calc by assuming its a cantilever beam, I could get the N, V, and M at the base. But from there Id need a method to determine the correct amount of bolts to use and their respective diameters. Assuming I desiged for a worst case M scenario, then the most heavily loaded bolt would be the furthest from the NA, correct? Also, I can assume it has an eccentric axial load. by the way, the lateral (wind) load controls by a long shot in these cases. in older hand calcs i have access to, its assumed that the shear force at the base is divided evenly amongst the bolts. given all this, it seems as though i have a method for doing this by hand. the problem comes in deciding a bolt pattern. if I could make it decide on an amount and diameter of bolts, that'd be convenient, however I am not quite sure if I can do that. furthermore, i don't know if its common practice to only have an even number of bolts. it seems that an odd number makes things a bit more complicated.
perhaps I've just overthought this so much that my brain has given up on trying to find a solution lol. that said, if you have any advice, let me know...and don't laugh at me if this is way simpler than I am making it out to be :D