I need to design a footing for a large vertical vessel in a highly
seismically-active area. Soils are good, though, and allow the footing pad
to be 20'x20'x36." The loads (including considerable weight and seismic
shear and uplift/pullout) are applied through three baseplates @120 degrees
connected to a 12'x12'x4'-6" pedestal centered on the footing. The pedestal
height is dictated by the technological process.
Within the contact areas I installed rebar cages similarly to short tied
"columns." I also tied the tops of the three "columns" together with rebars
to resist considerable shear.
Unsure about the reinforcement of the rest of the pedestal. Both the ACI
0.0018 and Caltrance's 0.0025 reinforcement ratios appear to be excessive.
Any thoughts about how to reinforce the pedestal away from the areas of
contact (apparenly, minimum reinforcement)?
Steve Gordin, S.E.
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