178 rsj - fitting joists at a vertical offset

[RonnyRaygun]

Bearing stays the same, shear increases

Shear stays the same - shear capacity reduces

 

[^woody^]

We have only discussed 3 options so where does last come from?

Have a think, there is at least one more obvious one.

 

[^woody^]

If it works perectly well structurally (which can be proved) and avoids the cost of hangers, why should it be a 'last resort option'?

Shear madness

 

[RonnyRaygun]

How about timber fixed to the web, 100mm timber plate on top of the beam, joist hanger nailed to the timber plate

Anyone got any more options? (This could go on and on )

 

[^woody^]

How about timber fixed to the web, 100mm timber plate on top of the beam, joist hanger nailed to the timber plate

Anyone got any more options? (This could go on and on )

C3

You can't then build on top of the plate.

 

[RonnyRaygun]

C3

You can't then build on top of the plate.

Oh I see - I needed to start at the beginning

 

[^woody^]

SMH

 

[Dereekoo]

Shear stays the same - shear capacity reduces

The design shear force due to the load stays the same, the unit shear force to be taken by the section increases

 

[AngleEyes]

Why would they exclude that possibility?

The wall that the steel beam wll support already exists, therefore any lateral re-positioning of that beam is not possible, or is minimal.
The wooden joists also already exist, therefore it's not possible to stretch the lower half of the joists to fit into the web of the steel beam.

 

[Dereekoo]

The wall that the steel beam wll support already exists, therefore any lateral re-positioning of that beam is not possible, or is minimal.
The wooden joists also already exist, therefore it's not possible to stretch the lower half of the joists to fit into the web of the steel beam.

Op talks of things being fitted ( future tense) hence whilst wall/beam cannot be moved joists are open to length as required

 

[AngleEyes]

Op talks of things being fitted ( future tense) hence whilst wall/beam cannot be moved joists are open to length as required

The OP's post:

Hi, I'm having a 178 x 102 rsj (160 x 45 internal web) fitted to support an existing wall and want the existing joists (50 x 150mm) to be attached slightly higher than the rsj.

 

[Dereekoo]

I stand corrected, thanks

 

[tony1851]

OP doesn't say why, or what height, the floor joists are to be in relation to the UB.

It might be possible to cut a small amount of timber from the underside of the joists once the wall is out, to enable the UB to be pushed higher,
though probably no more than 50mm - subject to checking shear on the reduced section.

Is it to reduce the downstand apperance? Maybe a smaller section could work, eg 152 x152, or even a 100mm SHS if the span wasn't too great.

Would help if the OP came back to elaborate?

 

[OrangeJuice09]

Hi, Thanks for the help - The reason why I wanted the 178 x 100 a little lower is because I wish the Existing ceiling height to be dropped from 2.6m to 2.5m. The 178 fits into a larger steel 203 x 203, once the 178 is tropped then so can the 203. On the new parts of the single storey extension which has a flat roof, the steels would be the correct height for the new joists and ceiling height. With the existing space (3m x 3m) I can add a false ceiling to hide the steels. Hope that makes sense.

 

[^woody^]

That's as clear as some of the suggestions posted.