huangyhg

grade beam supporting roof+concrete block wall
hello everybody:
i think i'm overdesigning these grade beams. it is a one story building. when designing the grade beams that support the concrete block wall and the roof, should i consider that the grade beam only takes the weight of the concrete blocks defined by a isosceles triangle? or should i consider the weight of the total wall height plus roof?
my gut feeling tells me that the loads are going to arch directly to the piles. but i'm not sure if i'm on the right way.
thanks a lot
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i think that except code indicates otherwise both approaches can be taken for the 1 story item you name, with care of point loads (strut and tie care, maybe). if in these simplified modes i normally would choose the safest uniform load, except something insane results.
don't worry as a structural engineer in spending a bit in excess in foundations, with columns is the best place to do so.
today yo can obtain greater understanding of the behaviour by making a simple model of the wall, grade beam, pile support and loads on the wall. do that if only for learning and then you will be able to decide what is more pertinent. let the program determine automatically selfweights and use ecmasonry=500·fcmeanmasonry.
don't forget that if your 1 story of masonry is say 9 feet high and your piles are say 25 feet apart, you will not develop the arching of the masonry.
also..keep in mind that masonry control joints will mess up arching action as well. unless you are specific on the plans, usually maximum spacing of joints is specified and they could end up anywhere.
settlement of ground between piles will determine your decision of designing the grade beam for full load (dead and live).
estimate deflection of your grade beam and compare with immediate and longterm settlement and decide.

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