There is a new program called DP-Vault intended for the preliminary design of precast sectional underground vaults. It uses AASHTO criteria for HS20 and HS25 loading and will design top slabs, sectional walls and base slabs using plate analyses based on the tables in the PCA publication. Contact...
Portland Cement Association publication "Rectangular Concrete Tanks" has a description of this method. I agree that no more than 10 -12 degrees should be used, nor should any more than that be necessary to acheive a reasonable safety factor against floatation.
http://www.portcement.org/
The Portland Cement Association (www.portcement.org) has a publication entitled "Underground Concrete Tanks" that contains general design and construction guidelines. Another reference is ACI 350 "Environmental Engineering Concrete Structures".
Thank you Ginger and Ron. The concept that is being applied is similar to that used for computing loads in a narrow pipe trench installation. However, in that case you have the fill material acting against the undisturbed sides of the trench. Since there are different settlements, the friction...
I have run into some spread footing designs for 3-sided precast bridges and arch elements where overburden loads were reduced by multiplying the active soil pressure times the friction coefficient against the column of soil above the footing. In some cases this vitually eliminates the overburden...
I agree that ACI 350 is a valid requirement for such structures but it should be specified in the contract documents, otherwise I don;t believe the precaster is obligated to apply that standard. 2" cover is not really necessary for precast elements, however due to the low w/c ratio and...
I routinely check for floatation of precast manholes and vaults and typically use the buoyant weight of the column of soil over the top of the base extension to resist uplift. Such calculations are generally conservative since neither skin friction or the friction angle of the soil are...
I agree with developing horizontal steel as you describe. We use either corner bars or, in the case of rectangular precast tanks, "U" bars around the ends and developed into the long wall with a proper splice. The questions is whether this bent bar is considered a "hook", if...
A question has come up regarding the horizontal wall rienforcement in underground precast tanks. If the bars are bent 90 degrees at the corner, does this constitute a hook subject to the requirements of Art. 12.5 of ACI 318? I don't believe it does but I cannot find a definative reference that...
A question has come up regarding the horizontal wall rienforcement in underground precast tanks. If the bars are bent 90 degrees at the corner, does this constitute a hook subject to the requirements of Art. 12.5 of ACI 318? I don't believe it does but I cannot find a definative reference that...
