huangyhg

deep concrete pier - area of rebar required
i'm trying to calculate the area of steel (for rebar) required for a reinforced concrete pier. my shear force is 28 kips, axial loading is 112 kips, and my uplift force is 59 kips. for estimating purposes, my pier is 3' in dia x 28' deep (28.5' oal) with 6" above the ground. soil is sand. i need help calculating the maximum moment on the pier below ground as well as the calculations to determine the area of vertical rebar (dowels) required. thanks
gtower
do you have any geotechnical data available? you need the geotechnical engineer to calculate the point of fixity of your pier. if you have all the necessary soils information you could use a program like l-pile to calculate this yourself. (there are other methods of estimating pof, but this is how i would go about it) once you know the pof you can use that depth as the column length. estimate the steel reinf.( 1% to 8% gross section area from aci, but start with 1%) and run some interaction diagrams (i use pcacol software) to see if your axial load and max moment fall inside the curve.
i strongly recommend you get the l-pile program and a geotech report. are your axial and uplift values shown the actual net numbers. with a 3ft pier and 112 kips axial your soil bearing capacity required on sand is 15.85 ksf assuming no pier side shear resistance from the sand. i suggest you re-think your design with experienced pe's.
thank you both for your comments.
the numbers were hypothetical so i'm sure the pier size was not right. we do have a soil report. the loads included a safety factor. we do not have l-pile or another equivalent software program yet so i'm having to rely on spreadsheet calculations developed by someone else. the spreadsheet i was given has some calculations in it that i can't tell where they are coming from. i am looking for some manual calculations to see if the output makes sense. thanks

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