Sistering existing Wood beam with Steel 3

[Instance]

I'm removing a support post and wish to sister an existing 6 x 8" wood beam with steel angle. I'm considering thru-bolting the joist to connect the steel angle. Can anyone advise me on how to calculate or practicaly determine the frequency and diameter of the hardware for the thru-bolting? It a 14' span with a 30psf DL and 40 psf LL.

Best regards,
Instance

 

[Ron]

This is a typical flitch plate design. Use plates on either side of the beam instead of angles. You've only given the area unit load. Would need to know the spacing to analyze.

Approach the design to allow the plate to carry the amount of load equivalent to the removal of the column and increasing the span (the former column reaction). Then check deflection. If deflection is more than L/360, add more plate section. Check differential shear between the wood alone and the steel plates alone carrying the same load. Use factor of safety of at least 4 and this will be the size of your thru-bolts to bolt the plates to the wood. Check wood bearing on the bolts and increase size if necessary to cover compression in the wood, plus creep.

Other techniques are used as well. Check structural texts for flitch plate design.

 

[SlideRuleEra]

Here is a paper (free .pdf download) that address your question

http://www.destefanoassociates.com/tech/flitch.pdf

 

[Instance]

Thanks for the advise and the very valuable PDF which describes flitch plate bolting. I've calculated that I could use two 14' 8" x 3/8" flitch plates bolted on the side of the beam to do the job. Ron, the tributary length is 13' on each side if you have time to double check my calculation.

Thanks everyone.

-Mark