huangyhg

connection design at top of basement wall
i have a 9' basement wall, 6' retained soil. zone 3, vertical condition (two story), wind governs with a base shear of 291 plf. i have a 2x6 sill plate connected with 1/2" anchor bolts at 3' o.c. i have floor joist at 12" o.c connected to the rim joist with simpson lpt5 clips at 2' o.c. and simpson a34 clips at each joist to resist the shear. i have design my wall with quikwall for basement wall condition "at rest". the dimension of the stem are 8"x9', the heel is 1'x2', the toe is 2'x10' because i have a soil bearing pressure of 1000psf. the plan checker says i need to add the 60 pcf of soil to the base shear, but the five other engineers in my office say that this is wrong.
what am i missing?
when you say "add the 60 pcf of soil to the base shear" do you mean taking into account seismic force on the retaining wall? or do you mean to design the connections for both the lateral wind shear plus the force along the top of the wall from the retained soil?
it seems that you have developed an independent retaininag wall for your basement. if that is so, then you would not need any base sher at the connection. most basements are not indepenent retaining walls, but rather are braced by the basement slab & 1st floor. perhaps the plan checker does not realize the basement wall is self supporting.
it appears that you designed the wall at rest - which means that it is imparting a load on the diaphragm. if so you must account for it in the diaphragm. how does this shear get out of the diaphragm? if the opposite wall also has soil on it then you have a balanced condition where you actually have compression accross the diaphragm. if the soil is on 3 sides of the house then the load will have to be taken out in shear in the diaphragm. either way i would bump up my diaphragm capacity by 60 plf as the code official is requesting to satisfy their requirements. if you think that's conservative - that's fine. i can't think of a building that fell down because the engineer was conservative.
the footing sizes seem weird!
if you are using ibc the 60 psf loading from the ssoil comes from
table 1610.1 (c) for relatively rigid walls, as when braced by floors, the design lateral soil load shall be increased for sand and gravel type soils to 60 pounds per square foot per foot of depth. basement walls extended not more than 8 feet below grade and supporting flexible floor systems are not considered as being relatively rigid walls.
your 9' height precludes you using the exception.
do your anchor bolts work for transfering load into the floor framing? my experience has been that it is difficult to get 1/2" diameter bolts to work if you are designing the basement walls to span vertically between the footing and the floor diaphragm.

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