Type 5a or 5b irregularity

[McEngr]

Can someone explain the difference in the shear resulting from the nominal flexural moment? Is this is similar to a concrete SMF of SUM(Mpr)/h = VE when compared with VU ? The SEAOC Volume I does not thoroughly explain this. Thanks!

 

[dakota_79]

Yes: V = 2Mp/h for an individual column. Similar to the check for flexural shear in an EBF link (which of course won't control when e<1.6Mp/Vp). Also similar to the ACI check you mentioned.

 

[dakota_79]

Adding...a weak beam at a level or a weak base plate connection at the foundation can control over nominal flexural strength of the column when looking at determining story strength.

 

[McEngr]

Thanks Dakota. The SEAOC volume 1 covers this for columns. I'm not quite sure how to calculate it (if needed) for shearwalls. I suppose it's the ol' capacity design approach.

 

[dakota_79]

Hmmm. Not sure I'm following, sorry! For a shear wall, the strength of the wall(s) for determining story shear strength would be based on ACI 11.9.5, 11.9.6, or 21.9.4.1 (in-plane shear strength of walls), wouldn't it?

Let me know where you're finding reference to "shear resulting from the nominal flexural moment" for a shear wall, and I'll take a look. But I would think that calc would never really come close to controlling, unless you have an extremely tall and narrow shear wall pier such that it's effectively a column.

 

[McEngr]

Dakota,

My question is this - how does one come up with "Vm" from the SEAOC Volume 1 (page52-53, example 8)?

 

[dakota_79]

Vm=2Mn/h

 

[McEngr]

Ok. Thanks.