SEAOC V.2

[MOOK]

I have the following questions about SEAOC V.2

1- Example 1A page 27

Why the over turning moment was calculated using "omega node"? There is nothing in the code says that the non-continued walls should be design using omega node. As far as I know, the columns support this wall should be designed using omega node not the wall itself. '

Any reason for that?

2- Example 1B page 74

In this example, Eventhough the author considered the columns as part of the lateral force resisting system (LFRS), he check the deformation compatibility. I thought we should do the deformation compatibility check for elements that are NOT part of the LFRS. Is there anything in the code about that?

3- Example 2 page 149

In the lower half of the page,

PDL = (15*16/12) + 2(25* 24/12) + 10*27) (16in+8in/2)

What are the 16in and the 8in in the end of the equation came from??

In the last line of the page

What is the factor 0.73 came from?

4- Example 5 page 265

In the beginning of the page

The author used number of bolts n= 4 to determine Vsa. In a similar example in PCA notes, they used n=2.0 because they consider the bolts in Tension are the only bolts that can resist shear.

If we follow what PCA notes, we will get half the value.

Any thoughts about it?

Thanks for your help guys.

 

[kevo_55]

Mook,

1) You're right. This should be for the connections only. I don't know why they check the actual wall for this, but the connections should be for Em.

2) Yes, you must always check deformation compatibility. See section 12.12.4 of ASCE 7-05 for the code requirement. See example 39 of the SEAOC V1 for a good example of the forces generated by movements.

3) I have no idea. They skip way too many steps in this example.

4) It's a different philosophy. The PCA notes show a few different ways to resolve the moment out of a bolt group. One way is to simply couple out the moment between bolts. Another way is to resolve the moment about the edge of the anchor plate. If you choose to do it this way, you will have to use another factor. I think the Yec,N factor.

I hope this helps.

 

[mjbikes]

3) I think it may be the length of wall tributary to the full width bearing studs. The studs are spaced @ 16" and the full width studs either side of the tiedown anchor are used for the bearing area for fcmax (a simplification). So the tributary area for those studs would be 16" + 8" (the next half bay). The details shown in Figs 2-12 and 2-13 don't match (single & dbl studs are reversed).

 

[MOOK]

Thanks a lot Kevo and mjbikes for your time and effort to answer my questions.

2) ASCE 12.12.4 says the following:

For structures assigned to SDC "D" "E", or "F", every structural component NOT included in the seismic force-resisting system in the direction under consideration shall be designed to be adequate for the gravity load effects and the seismic forces resulting from displacement.

So, the code refers to the structures that NOT part of the LFRS as deformation compatibility shall not calculated for any structure. In Example 1B, they considered this column part of the lateral force resisting system and according to the code; we should NOT calculate the deformation compatibility for it.

4) I think you misunderstood my question, let me clarify my question.

In PCA notes Example 34-7. There are 4 anchor bolts subjected to Moment and shear force. Due to the moment, there are 2 bolts are in Tension and the other 2 are in compression. When they tried to determine shear capacity of the bolts, they get the shear capacity of one bolt and then multiplied by "TWO" instead of multiplied by "FOUR" as in SEAOC V.2. The reason for that PCA considers only bolts in tension are the active bolts and they do not consider bolts in compression to resist shear. If we follow that we will get HALF the values in SEAOC.

There is HUGE difference in the two solutions.

 

[kevo_55]

Mook,

For item #2, there is no such thing as wood columns being part of the LFRS. For a wood framed building, the shear walls must be the LFRS. (There could be wood columns taking care of the gravity loads though.) I honestly don't like the problems in volume II, and took a look at example 1B just for fun. The problem itself is wrong. The columns must simply be able to take the gravity loads as well as the forces induced by the lateral deformation of the wood shear walls.

What you are saying is actually true for systems which include its own columns. A good example of this are SMF systems. The deformation compatibility is actually "inside" of the analysis of the frame itself. Unfortunately, wood shear walls with wood columns is not a specified LFRS per ASCE 7-05.

For item #4, I actually don't have the full copy of the PCA notes. What I do have is for ACI 318-02 and only a few pages of the Appx D section. I'm sorry I can't be much help.

Keep up the studying!!