#### Peter Dow

**Registered Senior Member**

OK I have a way to estimate the effect of the lost concrete from the 2 x 3" diameter ducts of cross sectional area of about 7 square inches each - 14 square inches for the 2 of them.

14 square inches = 21" x (14/21)" = 21" x 0.66"

so we can estimate the strength loss by subtracting 0.66 from 24 inches

So recalculate for a 21" x 23.33" column

Other values the same

Maximum allowable design (factored) load or capacity, Pu:

Actual load 1615 kips was 145% of the maximum allowable design load of 1112 kips

With something like another 2 x 200 kips from the 2 x 1.75" PT bars, the actual compression load would have been about 1915 kips or 172% of the maximum allowable design load of 1112 kips.

14 square inches = 21" x (14/21)" = 21" x 0.66"

so we can estimate the strength loss by subtracting 0.66 from 24 inches

So recalculate for a 21" x 23.33" column

Other values the same

Maximum allowable design (factored) load or capacity, Pu:

**1112 kips**Actual load 1615 kips was 145% of the maximum allowable design load of 1112 kips

**before**they added even more load with the post-tensioning bars!With something like another 2 x 200 kips from the 2 x 1.75" PT bars, the actual compression load would have been about 1915 kips or 172% of the maximum allowable design load of 1112 kips.

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