Steelwork - Post vs Column

[Tetrarch]

This must be a common situation but I'd like some comment on alternatives. The below picture is just to illustrate the install and there has been no structural calcs yet so the proposed steels are not to scale. 

 

The plan is to open up the back of the house and install a 6.5m fully-opening patio door and remove the internal wall the currently runs North/South. It's a two-storey house so both beams will be replacing supporting walls above.

 

Accepting that some kind of vertical support will be needed. Aesthetically, my view is that a circular pillar (indicated by the yellow circle) is far less obtrusive than a square or raw I-beam. Is there a way to find a comparison between round, square and circular vertical supports cross-section vs compressive load. The actual numbers are not as important as the relative cross-sectional area

 

Regards

 

Tet

 

P.S. Asking for a friend.

 

[Nickfromwales]

Can’t you go for stronger beams and do away with the prop? An SE would look at alternative solutions. I’ve seen longer runs unsupported.

 

Theres a few ways to approach this, so I’d suggest you don’t assume any more, and get some proper professional input. SE for a job this size won’t cost much, but will be the best money you spend, (plus, you’re going to need one later anyways)!!
 

I say get one sooner   

[Tetrarch]

Hi Nick,

 

The beam required to span the gap was ~800kg. The deflection is 160mm which is significantly more than the door supplier specifies

 

I understand that I am out of my depth, but my intuition is that there are multiple compromises with a single beam which can be entirely offset by a single compromise of a single supporting pillar

IF I am correct, then the size of the pillar becomes the entirety of the compromise - hence my question. I'm only interested in the comparison between vertical supports

 

Regards

 

Tet

[markc]

160mm is a ridiculous deflection.

As this is a prop, then you are looking at compressive strength and ability to resist buckling while supporting the load.

6.5m isn’t a big span unless you are very stricter on beam depth.

if you do need to prop, then a rectangular box section is probably to best option as this could be sized and positioned to work with the door frames etc.

[Nickfromwales]

59 minutes ago, Tetrarch said:

Hi Nick,

 

The beam required to span the gap was ~800kg. The deflection is 160mm which is significantly more than the door supplier specifies

 

I understand that I am out of my depth, but my intuition is that there are multiple compromises with a single beam which can be entirely offset by a single compromise of a single supporting pillar

IF I am correct, then the size of the pillar becomes the entirety of the compromise - hence my question. I'm only interested in the comparison between vertical supports

 

Regards

 

Tet

Don't take this the wrong way, but what you've just written is utter tosh. 160mm deflection isn't even what the Severn Bridge has accounted for!!

 

Get an SE involved immediately, as you are severely out of your depth and are just making crazy assumptions.

 

FWIW I really do not think you need any prop or column, and I'd ask the SE to sister 2 beams side by side, across the internal leaf and the end wall, and then beef up the intersecting beam to suit. Or bring another steel further inboard to break up the distance of the intersecting beam. Hard to say without lengths, loads, sectional drawings etc tbh, but an afternoons work for any good SE.

 

As I said, I've seen bigger unsupported spans many times before......

[Tetrarch]

Thank you for the candid feedback.

 

Fat finger:  That deflection is 16mm not 160mm This is entirely my typographical error - for which I apologise

 

One piece of hitherto unprovided information. The North/South beam is 8m long, so there is a significant load on the centre of the East/West beam.

 

This install will definitely need significant professional input. I would still like to know the answer to my original question though......

 

Regards

 

Tet

[markc]

Quick google of steel section properties will give the CSA etc for circular (CHS), Square (SHS), Rectangular (RHS) etc.

[saveasteading]

4 hours ago, Tetrarch said:

The deflection is 160mm which is significantly more than the door supplier specifies

 

No that's wrong. 16mm I might believe.

You need to get expert help and I can't condone your friend trying to guess stuff that is complex.

6 hours ago, Tetrarch said:

The actual numbers are not as important as the relative cross-sectional area

Actual numbers are rather important.

[Nickfromwales]

We're in the danger zone.

 

@Tetrarch, go get the SE involved mate. Nothing that's said on here can be used on your project, and it's getting silly now  

 

A good SE will offer up solutions that you / your friend can't possibly even think up, so do yourself a huge favour and get some professional input plz.