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Re: strengthening of floor joists with FRP's??

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Actually, this could be an interesting project. Normally we sister in members and use the effective elastic properties (EI) to determine loadsharing fractions. In a typical floor system, though, there is a 3/4" top "flange" which gets carefully ignored in determining the performance if the system. By utilizing a sufficient shear interface at the subfloor-Ijoist interface, and verifying that the shear capacity at the web-flange interface is sufficient, the addition of a tensile material on the bottom chord with the proper shear transfer mechanism would utilize more of the existing material. If the application of the FRP is relatively simple and durable, this could seriously reduce structural cost of the in place retrofit.

I would be concerned about the (1) shear transfer mechanism between the wood and FRP over a long period and (2) the maximum shear allowable at the web-flange interface. I hope we'll find out the results of the design.

Jordan



Drew Morris wrote:
I don't see how strengthening the bottom chord alone will work. Don't you have to look at the connections of the web members to the chords and how the chords are spliced if not continuous? You may be able to make the joist into a plywood box beam by adding plywood to each side of the joist and adding a metal strap along the bottom chord. Also, can you add or sister in new joists?


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