@phamENG That's a sad day for that engineer.
I've come across this type of framing a few times in old timber structures before SCL, glulam, rolled shapes and all the other fun options we have at our disposal now for open floor concepts. I have never used it for new construction, but if I did...
You could implore an old school method and suspend the floor beams from a steel frame in the roof structure, assuming you've got some aligned walls between the upper levels. Just don't take any requests from the fabricator to separate the load path of the tie rods...
I assume you've already verified the 10% DCR is exceeded per IEBC 807.5. Of course, for old structures it's always fun to try and justify the final statement in that exception accounting for all additions/alterations since original construction [upsidedown].
I'd don't think I'd be anchoring a...
Most HSS these days meets grade C and is often labelled as A500 grade B&C, at least in my area - so I always spec grade C. Calling your local steel supplier to have a conversation is always helpful as well.
XR - interesting. I've seen plenty of crushing perpendicular to grain in sawn lumber beams at supports, but not in SCL. Were those cases in scenarios with excessive moisture?
Similarly, we generally avoid CMU whenever possible due to a lack of competent contractors in the area. If it's a fairly short column a no. 1 6x6PT post with caps and bases, otherwise I would look at a treated SCL or glulam column before jumping to a CIP pier.
Why not just use floor to floor hold-downs (HDU or sim) - you could specify the nuts be backed off to account for the shrinkage. I use straps less and less as most of the framers we work with complain about them getting in the way of just about everything. Sometimes they're inevitable of course.
Appendix 6 is for point bracing. These systems I believe do behave more like continuous bracing where each rafter takes some portion of axial load and transfers it into the diaphragm, so equation A-6-7 but spread out over some distance. You could explicitly design and detail point bracing in the...
Agree with Eng16080 - in the end it's a beam guys, I think we can handle it and the contractor should be able to as well or not take the job. Are there nuances? Yes, limit the deflection as XR suggest, consider the rafter slope and corresponding lateral displacement at the eave. I do wish AISC...
Agreed that some of the details I mention are overkill in certain situations, possibly this one. At a minimum I'm going to provide a DTT or something similar at the chords to tie into the main building, like you would for a deck, where even there we don't rely on the ledger fasteners to transfer...
phamEng - it definitely depends on the project. I'm only going to do the cantilever diaphragm if the client accepts the details required to do so, including removing interior finishes and creating the collectors into the transfer diaphragm - perhaps reinforcing existing shear walls and adding...
phamENG - I have used the same technique for 2-story applications treating both diaphragms as cantilevers and tying them into the roof/floor. I've only done this for relatively small additions, at a certain point, conceivably when the diaphragm no longer satisfies the rigid diaphragm check in...
My first pass with these types of situations is to do as lexpatrie indicates, treating the roof diaphragm as a rigid cantilever providing tension ties back into the floor system. Sometimes that gets tricky with any steps between roof to floor, but it looks like you got a good opportunity to tie...
JustUseSteel - I agree with your interpretation of 9.7.6.4.4 and that the each is saying that neither side shall be greater than 6". I view the position that it's only in regard to one side as being analogous to having a column braced against buckling along one axis but not the other...
Saying the wall has no capacity is very conservative. Typically, residential foundation walls are considered pinned at the top and bottom (whether that's actually justified depends on the details). The capacity needs to be checked in accordance with ACI 318 CH 14 which a structural engineer can...
Generally, no. RISA 3D has its place for me in wood construction in a couple of scenarios: 1) modelling discrete portions of the structure where it is warranted, such as systems with transfer beams. 2) Ambitious lateral systems. You can do a full boar semi-rigid diaphragm analysis with wood...
