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COMPRESS performs a preliminary
calculation to determine the size of the
anchor bolts. This calculation is
reported under the heading "Anchor bolt
load (operating, corroded + Weight)" and
reports a calculated value for bolt load
"P".
The preliminary calculation is based
on the assumption that the neutral axis
of the resisting section is at the
center of the base ring. However, the
neutral axis actually shifts from the
center of the base ring due to the
different modulus of elasticity of the
steel bolts and the concrete foundation.
COMPRESS reports additional
calculations to determine the resisting
section's neutral axis location and the
resultant tension and compression
forces. The actual maximum steel stress
in the bolts is calculated based on the
shifted neutral axis.
The actual maximum bolt force F is
determined as the product of the
calculated maximum steel stress and the
bolt area. The uncorroded bolt area is
applied because this is conservative (the bolt force when bolt is corroded
would be less).
This force is applied to the analysis
of the compression ring (anchor bolt
chair top plate), gusset plate, and
skirt thickness check.
If the anchor bolt is preloaded, the
force applied to the skirt thickness
check will not include the preload
because this force is directly supported
through the compression ring and gusset
plate to the concrete foundation.
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