huangyhg

cantilevering a steel deck with concrete
i want to cantilever a 2" corrugated 16 gauge steel deck with a total of 4" light load concrete 5' past an on grade footing. the deck will be mechanically connected with 3/4" anchor bolts every 2'. the total length of each sheet of corrugated 16 gauge steel is 25' there are three (3) on grade footing with the middle footing having number 4 rebar sticking up 3' to be bent down onto the corrugated steel. my question is what size mesh should i use and should i tie number 4 rebar to the number 4 sticking up and tie the mesh (size?) to everything and then pour the concrete. will this be strong enough without supporting the cantilever section.? the footing specs 8" above earth 12" wide 30" deep soil rock/clay concrete 6bag 3/8 gravel number 4 every 12" with 4 number 4 running horizontally.
what kind of load you are going to have on this deck? is this a balcony? or you have a wall supporting roof at the edge of deck? or you going to park a truck on this deck?
sorry - the load is a residential patio-not a car park, there will be no additional structures built upon the patio. the patio is on grade with the 5' cantilever extending over a hill.
from asce7-98, live load for balconies equal to 100 psf.
from vulcraft catalog, weight of slab equal to 35 psf.
total moment for 5 ft cantilever equal to m=(ql^2)/2=135*25/2=1690lbs*ft=1.69k*ft
bending stress in deck equal to fb=m/s=(1.69*12)/0.653=31ksi
for deck with fy=33ksi, allowable bending stress fb=0.6*33=19.8ksi<fb=31kso - not good.
working backwards you will find that maximum cantilever shall be not longer than 3.5 ft.
good luck.
whymrg would this calculation included additional steel reinforcement? or is it due to the light load concrete's weight?i am assuming if the additional steel mesh plus rebar will not help and i still want to cantilever the deck/patio to 5' then i will have to run a stringer under the steel deck. thanks

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