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ASCE 7-16 Section 2.3.4 specifies a minimum of 1.0, but leaves it up to you to determine what that factor should be for your application. Take a look at the commentary.

Yes this is what I've typically done. As you note the Inet equation is only valid for a hole through the neutral axis, otherwise use parallel axis theorem (or autocad) to get Inet and c. The APA tech note you cited is what I use.

That's correct. Anticipate about 1/2 (or less) the concrete shear strength from previous versions. Some exceptions for the size factor for shallow foundations you mentioned. But yes, basement walls will likely be quite a bit thicker than an ACI 318-14 designs.

CSI SAFE is what I use. I resolve moments into discrete point loads along the length of the wall. A useful feature is exporting reactions/load combinations from ETABS into SAFE and then modelling your mat. You typically just need vertical loads from gravity and overturning to design the mat.

The model attached does not have the members modelled as pinned. Select all of the members and release moments at either end.

My third printing has (a) through (e) for shallow foundations. Regardless, 13.2.6.2 only includes one-way shallow foundations which to me means strip footings or grade beams. I believe the size factor is required for pile caps.

I didn't think clause 13.2.6.2 applied to pile caps. Fig. R13.1.1 seems to differentiate pile caps from those types listed in the clause.

I'm digging into ACI 318-19 updated shear provisions for the first time by designing a standard 4-pile pile cap. I've found that by using 318-19 I get a pile cap that has nearly 5x(!!) the amount of concrete as a 318-14 beam design method gives me, because I'm down to about 0.5root(f'c) due to...

Modern construction methods for flat slabs use drop panels for increased shear strength at columns, which is basically what your nice-looking column sketch is getting at, but with less complex/expensive formwork and construction.

I think that was the point jbourne is making. He is implying that in that video the room is already leaning due to collapse of columns (possibly beam) that should have been visible in the tiktok video.

I like the NEHRP version of that paragraph, it is clear it is intended for any transfer diaphragm. The 7-16 12.10.1.1 paragraph seems to imply by the first two sentences that there are instances where there are transfer forces but no HT4: "Always design diaphragms for transfer forces plus...

I'm not sure which points you are referring to not being addressed. Question - in the Moehle diagram above, the setback irregularity mid-height. If those two walls align, it would seem odd to me to consider that an "Out-of-Plane Offset Irregularity". Maybe it could be named something less...

If it is a requirement and the intent is for transfer podiums to be considered Horizontal Type 4, it seems that it should just be explicitly addressed in the code since it is a very common occurrence. And if it was a deliberate change in 7-16, changing the Commentary of Horizontal Type 4 seems...

A recent StructureMag article about when overstrength is used in diaphragm design: Link

My understanding is that the difference between Horizontal Type 4 and Vertical Type 4 is whether the offset in the wall is perpendicular to the wall (Horizontal Type 4) or parallel to the wall (Vertical Type 4). Both would cause the diaphragm / transfer element to carry significant overturning...

Robert, I agree that it is not a Type 4 irregularity, and by code is not required to be designed globally for omega forces per 12.10.1.1. However, I am going to check the diaphragm for omega level forces and see how far off I am as a good engineering check. I am modelling the diaphragm as...

Thanks for the references. I've seen the LATB document, but the PEER/ATC Appendix A is very informative. Seems I've modeled the stiffness conservatively so if I run into troubles designing the whole diaphragm for omega transfer forces I can look to refine a little.

Deker - would you, then, design your entire diaphragm for the overstrength transfer forces (plus it’s own inertial force)? I have basically checked that the overstrength collector force can develop into the diaphragm, but once it’s developed into the diaphragm I no longer have the omega in the...

Js5180 - the free-fall distance at any time “t” would be d=16.1t^2 and velocity would be v=32.2t.

ProgrammingPE, Thank you. The part that makes me wonder is "discontinuity in lateral force-resistance path", because the transfer force path is discontinuous there, even though there is a continuous path through the core walls to the foundation. I've seen examples approaching this either way...