huangyhg

allowable foundation settlement values
hi:
does anyone know what allowable settlement and differential settlement values are given to the geotechnical engieer to determine allowable bearing pressures for rafts / footings / piles. any book reference in this regard will be helpful.
do we usually specify 1" total settlement and 1/2" differential settlement between foundations? what if we have high rise buildings 60 and above, does that settlement criteria gets more stringent?
can we have raft foundation when all surrounding areas have bored pile foundation?
nad
many authors and eurocode 7 doesn't talk about sattlements but relative rotations. in en 1997-1, annex h you could find this text:
the maximum acceptable relative rotations for open framed structures, infilled frames and load bearing or continuous brick walls are unlikely to be the same but are likely to range from about 1/2000 to about 1/300, to prevent the occurrence of a serviceability limit state in the structure. a maximum relative rotation of 1/500 is acceptable for many structures. the relative rotation likely to cause an ultimate limit state is about 1/150.
some authors have good practical experience with using 1/300 as a limit.
drile007
thanks drile007, for valuable information, which pretty much matches with my understanding.
nad
you might want to check out m.j. tomlinson's book foundation design and construction, 6th edition, table 2.7 titled: "limiting values of distortion and deflexion of structures". it is a comprehensive table.

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