How to design long span slab with big opening?
How to design long span slab with big opening?
(OP)
Hi everyone..
I have to design a long span roof slab (18m x 12m) with big opening (10 x 3). There is no parapet wall or any other loads on the roof.
Roof height is 5m. Architect doesnt want any downstand or upstand beams in the roof. So should I just take each side as a cantilever slab and design it or take it as 2-way slab and provide cross rebar around the opening?
Thanks in advance
I have to design a long span roof slab (18m x 12m) with big opening (10 x 3). There is no parapet wall or any other loads on the roof.
Roof height is 5m. Architect doesnt want any downstand or upstand beams in the roof. So should I just take each side as a cantilever slab and design it or take it as 2-way slab and provide cross rebar around the opening?
Thanks in advance






RE: How to design long span slab with big opening?
Regardless, if there are supports on all 4 sides, the slab should be designed as a 2-way slab. None of the slab portions in the layout you seem to be describing will act as a cantilever.
Brian C Potter, PE
http://simplesupports.wordpress.com
RE: How to design long span slab with big opening?
At the spans discussed you are going to have a thick slab if this is a single plate arrangement. I would give consideration to making the slab a little thicker and putting in a slab beam on the edge of the opening.
http://www.nceng.com.au/
"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."
RE: How to design long span slab with big opening?
BA
RE: How to design long span slab with big opening?
RE: How to design long span slab with big opening?
RE: How to design long span slab with big opening?
Well we can't change the architect. It'e the client is well loaded ( owns 3 Bentleys), whos insisting him net to let the engineer give downstand beams lolz!I like it because it forces me to learn new/difficult designs.
I'm talking about 200mm reinforced slab and the opening in the slab is for skylight ( aluminium glazed roof system).
How about providing rebar like...bottom shortspan 16-140mm,longspan 16-200mm, top-at supports 16-400mm. Makes sense??
RE: How to design long span slab with big opening?
RE: How to design long span slab with big opening?
RE: How to design long span slab with big opening?
RE: How to design long span slab with big opening?
Best case, assuming continuity exists on all sides of this 18m x 12m roof, each side of the roof extends 4 m or 4.5 m from the support to the skylights. Can a sloping slab (PT) tapering from say 350mm to 200mm at the support be designed to cantilever off the supports? Parallel to the 18m direction, run post-tensioned cables to "pick up" the sagging edge?
RE: How to design long span slab with big opening?
BA
RE: How to design long span slab with big opening?
RE: How to design long span slab with big opening?
Doing this, the beams and slab are hidden within the slab.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: How to design long span slab with big opening?
Being a learning engineer, I've learnt alot of useful and important info and design approches.
Nothing impossible, until we try it eh? We tried to design a long span slab with opening, without having beams but failed! We didn't change the architect but changed the design with upstand beams and covered them with parapet walls
:)