Reinforcing Existing Wood Beams 1

[ChamboEng]

I'm currently working on an existing building where we need to reinforce the existing timber beams to accommodate the new loading condition. Our plan was to sandwich the existing beams with steel and bolt together.

However, due to historic preservation requirements they will only allow us to add steel to one side of the existing beams. Is there anything in the code that states the steel must be added symmetrically to allow for composite action? Can the steel be placed on one side of the existing beams?

Thanks.

 

[BMart006]

If the issue is the aesthetics of having wood due to the historic look, you could always do a flitch plate (wood-steel-wood). This would prevent any unsymmetrical rigidity.

 

[EngineeringEric]

Removing the beam, reinforcing it, reinstalling it really isn't that hard (for an engineer to specify that is). Shoring is always doable

 

[XR250]

However, due to historic preservation requirements they will only allow us to add steel to one side of the existing beams. Is there anything in the code that states the steel must be added symmetrically to allow for composite action? Can the steel be placed on one side of the existing beams?

Not likely any code other than Laws of Physics which will want the beam to rotate so that must be addressed.

 

[ahypek]

Why not reinforce the timber beams with additional timber? That's how I normally deal with alterations and "landmarks."

 

[OldBldgGuy]

What about a cable or rod on the bottom of the beam? What about suspending from above with hanger rods through partitions and a beam or truss in the attic? I know, that may be a completely different configuration than you can do but without seeing your building it's hard to provide a solution. A little imagination can go a long way & that's why you get the big bucks.

 

[KootK]

What are the relative thicknesses of the wood and steel? Is the load delivered to the top of the beams? Will the bearing reaction in the steel be delivered to the support directly or will it be transferred back through the timber. Can blocking, bridging, or bracing be installed on either side of the beam?

One sided reinforcing is often fine in my opinion. You just need to rectify the torsion with blocking/bridging etc or give due account to the resulting torsional stresses.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Nor Cal SE]

Good suggestions by all, one additional thought: if you're concerned about unsymmetrical stiffness of a one-sided steel retrofit, you could look at designing your added steel such that it would have capacity to take all the load, presuming the design magnitude doesn't get out of hand. Therefore, the existing wood beam would simply be "sacrificial", and I think you could neglect any thought of potential torsion/etc. due to unsymmetrical stiffness.