• 100% Satisfaction Guarantee
StructuralEng, Consultant
Category: Structural Engineering
Satisfied Customers: 7076
Experience:  Structural Engineer
59685895
Type Your Structural Engineering Question Here...
StructuralEng is online now

# Live and Dead Bearing foot span of triple 2x12 PT lumber Building

### Customer Question

Live and Dead Bearing for 24 foot span of triple 2x12 PT lumber
Building foot bridge to span 24 feet and using 3 sets of these triple 2x12 beams to form a four foot wide base of the bridge.
Submitted: 1 year ago.
Category: Structural Engineering
Expert:  StructuralEng replied 1 year ago.
Hello. How are you doing? I'll be happy to assist you.
Expert:  StructuralEng replied 1 year ago.
You need to know the live load capacity of the bridge?
Customer: replied 1 year ago.
Yes, we want to be sure these 3 sets of tripled up 2x12s will support the 2x6 top decking materials and then what live load it will support.
Expert:  StructuralEng replied 1 year ago.
Will all plies of 2x12 be the full 24' length?
Customer: replied 1 year ago.
No, we plan to use 2 x 12 x 12foot pices interwoven together and then glued and bolted to make triple wide beam. so 2 2x12x12 end to end with one 2 x 12 x 12 in center and 2 x12 x 6 foot on each end, then third layer is 2 more 2 x 12 x 12 foot end to end. all this bolted together and glued.
Expert:  StructuralEng replied 1 year ago.
What I can do is this. I can give you the capacity assuming three double 2x12. Interweaving them the way you describe is common, but is a very different behavior and is heavily reliant upon connections to transfer forces across the butted ends. At best, ***** ***** two 2x12 working for you where two are butted together, and you'll need to be sure the connections are designed in a way to make it true that you have two and not less.Is that reasonable?
Customer: replied 1 year ago.
Yes, should reasonable.
Expert:  StructuralEng replied 1 year ago.
Assuming a dead load of 15 psf, that would give you a live load capacity of 30 psf, assuming doug-fir no. 2 pressure treated