huangyhg

table 18-i-a? ubc lateral beraing pressure "note 3"
i am designing a embedment concrete steel column post, the soil project report give me a 4oo lbs/sq/foot lateral bearing pressure. the code allows increase this value by one additional foot of depth(note 3), but for poles used to support buildings only twice? i am not sure about this note, increase this value only two times or by additional foot.
please clarify this note.
thank you to all of you.
berni.

proper unit for this lateral bearing (aka passive pressure) is pounds per square foot per foot of depth. psf/ft.
this value may go up to 15 times the code listed value (i.e. if the embedment exceeds 15 feet, no additional increase).
this table is made for continuous footings primarily. in case of pole footing (steel embeded in cylyndrical concrete footing to act as a fixity), they are allowing the code values to be doubled as long as upto 1/2" tip displacement does not adversely affect the structure. i know... the wording in the code can use some improvement... hopefully this helps.
question: if there is a soils report, why are you using the 18-i-a table? usually soils report specify all criteria needed for design and if any info is missing, you can request such info in a supplement letter.
if you have values provided by a geotechnical report you don't need to use the ubc minimums. you should only increase the values from the geotechnical report based on his recommendations not based on the ubc table. i typically only use the ubc tables if i am working a small project that does not have a geotechnical report available, and then i use the minimums provided in the ubc.

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