Sloping roof without support at centre

[sachintoi]

IS it possible to design a sloping roof (as shown in fig)?
if yes please help in placing of beams.]
thanks

 

[Studiot]

Yes, but the weight of the sloping roof will cause a tendency to spread outwards, pushing out on the walls.

Two ways to counteract this outward thrust are to make the joints at the roof and walls truly rigid.
This is called a portal frame.

Another way is to place a tie across the two sloping sections of roof.

 

[sachintoi]

Yes, but the weight of the sloping roof will cause a tendency to spread outwards, pushing out on the walls.

Two ways to counteract this outward thrust are to make the joints at the roof and walls truly rigid.
This is called a portal frame.

Another way is to place a tie across the two sloping sections of roof.

PLEASE elaborate

direct example with respect to fig will be great

 

[sachintoi]

Y

Another way is to place a tie across the two sloping sections of roof.

WILL the tie be sloping or horizontal (column to column)

 

[Studiot]

Portal frames are the type you see in modern steel framed buildings, where you can see the steelskeleton from the inside.

Ties normally go across horizontally.
They are usually just above the top of the wall, where they are most efficient. Sometimes they can be further up, to about halfway up the rise of the roof. They are often combined with the ceiling support.

 

[sachintoi]

will the ties go in both direction or just along the walls where slab rest?

 

[Studiot]

The ties go across from wall to wall, not along the walls.

How else could they tie the walls, or rafters together?

 

[sachintoi]

will providing beams as shown in new fig solve the problem?
http://img692.imageshack.us/i/beams.jpg/

 

[Studiot]

No, I'm sorry I'm not at home, or even in my home country so I cannot draw it for you.

The ties must connect opposite walls near the top or opposite rafters near the bottom. Ties can be much thinner than beams.

 

[sachintoi]

ok , which fig(new) shows correct ties left or the right?

http://img809.imageshack.us/i/ties.jpg/

 

[sachintoi]

ok, which fig (new) shows the correct tie left or right?
http://img809.imageshack.us/i/ties.jpg/

 

[Studiot]

The upper left hand drawing is fine. and would provide support for a conventional ceiling.

The upper right hand position is OK, but a V shaped tie is not. A light horizontal member at this location would also work.

 

[JaredJames]

Not sure which country you're in, but you might want to check building regulations before you attempt this on your own. I know there's something on it in the UK.

 

[sachintoi]

sorry but v shape is not a tie but just a arrow pointing towards the sloping ties under the roof (forgot to make it red)
sorry for being careless

so both fig are correct
i think right one will suit my needs
PLEASE CONFIRM

 

[Studiot]

The horizontal element you have labelled tie in the top left hand drawing is a fine tie.

It is in the plane of the section drawing and pulls the tops to the two wall towards each other.

There is no tie shown in the top right hand drawing, so this is not OK. I repeat elements at right angles to the drawing cannot be ties. You should redraw the sloping section of the roof so it looks like the letter A.

 

[sachintoi]

It is in the plane of the section drawing and pulls the tops to the two wall towards each other.

.

In my case it need to pull beams right.

so ties should be horizontal and cannot be sloping.and what about their spacing and dimensions in general.something like 23 cm* 30cm in cross section with a spacing of 3 to metres (column to column)

can i use make it a ribbed slab(sloping beams under slab) so there is no need for ties?

also can you suggest ebooks,books, and other web sources that illustrate various types of RCC roof slabs( like hip roof, pitched roof) and the beam & column arrangment for them.

Hope i am not troubling you too much
thanks

 

[JaredJames]

I'm slightly concerned about the fact you don't seem to understand the basics of roof design and yet you're trying to do it. Potentially catastrophic to your home at best.

You need cross members. If you look at roof design on any new houses you will see the characteristic A shape. It's there for a reason.