STRUCTURAL ENGINEERING FORUM OF INDIA [SEFI]

nikhil.patelwsm · General Sponsor Joined: 21 Jul 2013 Posts: 30

DEAR SEFIANS,

I AM FACING PROBLEM WITH ONE OF MY PROJECT PLOT SIZE IS 26MX47M, COMMERCIAL BUILDING FOR G+4 STOREY SITE IS NOT IN HILLY AREA, AS PER SOIL REPORT SBC AT 3.5M IS 55 TON/SQM EXCAVATION OF WHOLE PLOT IS DONE AND FOR 8M LEGTH PLOT WE ARE GETTING HARD STRATA AT 3.9M , FOR 25M PLOT WE ARE GEETING HARD STARTA AT 4.5M, FOR REMAINING 4M PLOT WE ARE GEETING HARD STRATA AT 6M. WE HAVE DESIGN ISOLATED FOOTING FOR 4M DEPTH, I HAVE TO REVISED FOR 6M HEIGHT BY PROVIND TIE BEAM AT 3M BELOW GL.
MY DOUBT IS
1) LEVEL DIFFERENCE OF HARD STRATA IS HUGE FOR FOOTING BOTTOM LVL.
2) MINIMUM LVL DIFFERENCE WE CAN KEEP FOR FOOTING BOTTOM LVL.

KINDLY GUIDE ME AND REQUEST ALL SEFIANS (SENIOR PEOFESSIONALS) TO GIVE AN STRUCTURAL SOLUTION.

vikram.jeet · General Sponsor Joined: 26 Jan 2003 Posts: 3706

As per actual strata status described by you :
8m length Hard strata at 3.9m depth
25m length harf strata at 4.5m depth
Remaining 4.0m  length hard strata at 6.0m

The founding level of all columns (except those in 6.0m depth zone) shall be taken as 4.5 m
Only those column footings be taken deep  falling in 6.0 m depth zone,,,

Since design is based on 4.0m depth,  it may not alter moments much,, but for 6.0m  depth,, tie beams to be introduced,,