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My opinion is that dead load factor 0.6 tries to embed 1.5 safety factor to a combination that has a dead load factor 0.9, using an approach that has generated confusion, e.g. it has been put in the ASD group instead of LRFD group, and most important thing, standards should calibrate factors to...

Thanks phamENG, I agree. Unfortunately we are to use standards + client specs + our specs, and FS,min > 1 has remained very popular in specs. In my opinion it is the set of ASD combs that include 0.6*Dead that has spread confusion. One sees "ASD", thinks he's unfactored, and wants to use FS,min...

Replying to phamENG: with unfactored loads, eq. 1) and 2) would bring to same results only when FS ~ 1, and this is what you show transforming 1) into 2), i.e. assuming they are not inequalities. But they bring different results-design when FS <> 1.

Where's written that you do not meet the seismic requirements when wind governs, and how much should it govern? And should it govern on wind assuming which R value?

An example of numerical difference between 1) and 2), considering unfactored loads and FS,min = 1.5 Foundation 3x3 m, thk 2 m. Water table at top of foundation. Lever for bouy and SW = 3/2 = 1.5 m Moment from SW = 675 kNm Moment from Buoy = 270 kNm External moment from wind assumed as 255 kNm...

Agree, it would be acceptable for me whichever methods between FS,min=1 with factored loads, or FS,min>1 with unfactored loads, but sometimes project specs asks for a mix of them. My fav is FS,min=1 with factored loads, which allows to address uncertainties where they are and how it is needed by...

Dear All, using American standards here. For overturning checks, one gets quite different results if he does 1) or 2): 1) Dead*lever / (Moment,wind + Buoy*lever) > SF,min 2) (Dead - Buoy)*lever / Moment,wind > SF,min In my opinion, 1) is the formally correct approach (note that it brings to...

Thanks Hturkak. This is not really a query about a specific application. More a discussion about understanding the correct approach. My believing is that a seismic design where: * vertical vessel R/I=1 * anchor bolts R=3 * foundation R=3 Will not have sufficient dissipation capacity to achieve a...

I will add ref to ASCE "Anchorage design for petrochemical facilities", 1st paragraph of Section 3.11.5, that reads: Historically, the foundation anchors for tall vertical vessels and stacks have tended to stretch beyond yield when subjected to strong ground motion, which probably prevented...

thanks

Good day, I am trying not much successfully to convince myself that those vertical vessels will perform happily when the following are applied: ** Table 15.4-2, "All steel [...] distributed mass cantilever structures not otherwise covered herein, including [...] skirt-supported vertical vessels...

Ok, I have been thinking some more about this, and now I am of the opinion that the inner corners of the socket do not need detailing of concave corners. That's because it is all filled with grout and concrete, so actually it is not a concave corner facing a void, no push to void is generated...

Hturkak, Area is middle East, American codes are applied. There is a vague note on the dwgs for the vertical surfaces inside the pocket to be roughened. For the records, if I consider just the horizontal reinforcement area at the outer sides of the pocket, the check that was put in the...

Dear All, I am assessing existing sockets per subject for a very small addition on top of a structure and unfortunately I have stumbled upon a wrong rebar detailing for the horizontal bars in the socket walls, internal sides. Let's see if I can paste a sketch. Link The horizontal bars in the...

Thanks a lot!

Thanks for your reply, yes that may help. Unfortunately I don't decide that, can't do.

At ultimate limit state, the design spectrum is divided by "q", while the elastic spectrum is not. You should assess the displacements (for example to prevent structural pounding, which is an ULS thing) using the elastic spectrum, or multiplying the displacement from the design spectrum by q...

Hi All, I am reading ASCE 7-16 and AISC 341-16. I am dealing with OCBF and OMF, so I have R=3.25-3.50, say R=3. Anyway this post could be extended to concrete SFRS as well. In those codes there's no requirement for designing the foundations for seismic forces stronger than those that the...

Thanks for your replies.

Well dead loads are normally physically tied to the structure. That section C 12.7.2 speaks about live loads and, ok, for these it make sense to some extent to consider only a part of the vertical load as seismic mass.