adding a steel support on existing stone wall 1

[gmd255]

I'm dealing with an old building that has thick stone walls.
I have an existing RC beam above existing stone wall as shown in attached pictures. The beam is supported on outer walls only.
What I need to do is new timber ceiling that is at the same level as this beam. So I have two timber beams next to existing RC beam (parallel). Perpendicular to this beams I'll attach other timber beams which will form the wooden ceiling.

Since the span is 7 m I have to support new timber beams (green color in the pictures) in the middle. Contractor suggested OPTION B: a steel corbel/console - red in the picture - (on both sides of the existing wall) that will support the timber beam in the middle. I'm not a fan of this solution since the console wont be evenly loaded. Also one side will be loaded before another. I'm intending to do a concrete layer on top of existing stone wall and anchor a steel corbel into it but still... I don't like that idea.

I was thinking more of an OPTION A: installing a steel beam from wall to wall and put a timber beams on it. That way there is no worry about overturning moment and anchoring (like in option B). I will reinforce steel beam cross section with vertical plates where shear forces are the greatest. What's bothering me is that this beams are not really rational/economical since bending moments are pretty small so they will mostly be in shear.

What do you guys think about that?

 

[dik]

Due to the uneven loading, Option A is the better one. It is more difficult to construct and more costly. It may be visually obtrusive.

I like stiffeners, but, I'm not sure the ones shown are required.

Dik

 

[chicopee]

I would explore the use of columns at the center of the timber beams.

 

[gmd255]

columns are not an option

 

[Yt.]

I don't fully understand your question. Stone walls are probably heavy enough to withstand an uneven load from ceiling (almost decoration work over here). Why don't you try to spread the load instead of a concentrated one? Could you sketch the ceiling ?

 

[gmd255]

There is a 3d model

steel beams + timber beams parallel to the existing RC beam

complete ceiling

 

[dhengr]

Gmd255:
Old, existing rubble stone walls are deceptively weak and unstable, unless built really well and bonded together well. Dry laid walls should not really be used structurally. They make great low height retaining walls and fences to be rebuilt every few years. These walls can appear to be fairly stable until you move one or two stones, and then all hell breaks loose. This would apply particularly to opening discrete pockets for new beams all over the place, and casting any sort of a bearing seat in those pockets. Casting a conc. cap on a good sound wall is fairly reasonable, if you can form it and plug the bottom holes so you can actually cast the conc. beam with some rebar. What do you know about the existing conc. beam, its loads, its strength and reinforcing, its foundations, etc., and the wall found. too? Can you move the timber beams in closer to the RC beam to minimize the eccentricity of the two different sized loadings; or even cast the wall cap beam higher and a little wider and properly reinforced, so it actually becomes the bearing level for a sill timber, which then is the bearing for the perpendicular floor joists or beams. It isn’t that the stone walls might not be strong enough, but it takes a trained eye and touch, and considerable experience to make this judgement. A really good stone mason might be as helpful as anyone else in this judgement and determination. What is your engineering background to be making these determinations. Your questions and sketches do not appear to be very encouraging on this latter account. Your last sketches are quite colorful, but not very meaningful. Shut off your computer and put your thinking cap on and your detailing mind set into gear.

 

[gmd255]

dhengr good points... tnx for your suggestions/opinions!

 

[Yt.]

gmd255, dhengr is expressing (somehow) that the sketch give more questions than guidance. Which joints are planning for that?