Repair Cracked Timbers

[Beamman]

Hi

I am working on a project involving heavy timber trusses which have cracked timbers due to drying. The truss connections are steel plates with bolts and 4" diameter shear plates. The cracks run directly through the bolt lines in many of the trusses.

I am considering many different repair options including steel dowels set with epoxy, structural timber screws, external steel rods for tension members.

Does anyone have any experience with this type of repair that could offer some suggestions?

Thanks

 

[JAE]

I repaired similiar trusses at an old hanger building - Air Force structure that had been built in the 1940's as a bomber factory during WW2.

The trusses were glue-laminated top chord and heavy timber diagonals and bottom chord if I remember correctly. The top chord was a bowed chord (bent gluelam). The bottom chord was dried out and cracked in many places. The connections were via split ring shear connectors with through bolts.

We added additional side plates that were connected to the bottom chord with through bolts and then welded on horizontal, continuous tubes to serve as "new" bottom chord members. The tubes were spaced off of the side plates to allow the through bolts to be installed.

This effectively prevented bottom chord tension failure only - we had determined that the bottom chord to diagonal connections were OK.

Trusses spanned about 150 feet if I remember right.

See the attached section/sketch.

 

[hokie66]

I would consider clamping the members across the splits. This should allow the shear plates to continue carrying the load.

Is corrosion in the connections involved? This could be at least part of the cause of the splitting and may require replacement of bolts.