I'm interested in input on how to design a braced timber frame with current codes. Specifically, due to a change of use, I've been asked to analyze a historic barn, and bring it up to current seismic code. The barn is constructed of heavy timber frames with knee braces and endwalls sheathed with 1x horizontal board siding. The last versions of the IBC and ASCE7 have eliminated timber frames from the seismic design provisions, except for Cantilevered Column systems. The last code I can find that mentions braced timber frames is the 1997 UBC. The 1997 UBC allowed braced timber frames with R values of 2.8 where the bracing also carries gravity loads, and 5.6 when the braced frames are independent of the gravity loads. So, my dilemma is what, if any, R value to use when analyzing the strength of the existing frames. I guess we could resheathe all the roofs and walls with plywood and install steel moment frames in between the existing frames and ignore the strength of the timber frames, but that would be quite cost prohibitive. Anybody have any input here?
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