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Re: Height of Building/Shear Wall design

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Thanks Paul.  I think the Local Authorities might expect me to design according to local codes though in the approval or peer review process (I am told the seismic provisions in the UBC97 or later IBC codes are generally acceptable in California) - as much as I would love to design to the NZ code which seems to offer a lot more flexible if not rigorous design approach. 
Tim.

>>> pfeather(--nospam--at)SE-Solutions.net 28/09/2005 2:20:30 am >>>
The height limitation is measured from grade, not basement level.  If the 
sight is sloping then a "grade line" will be established for building height 
reference. This is usually worked out with the local building authority and 
will vary depending on jurisdiction.

The 97 UBC is ten years out of date.  There are no provisions similar to 
what you describe for the New Zealand code.  The shear and boundary zone 
trigger limits contained in chapter 21 are intended to limit strain to .003 
similar to column design for a design level earthquake.  A more direct 
strain based approach related to the development of plastic hinging was 
introduced in the 97 UBC, but went no further with the code cycle 
developments and resulting political wrangling.

If you design to New Zealand standards you are familiar with you will meet 
the UBC requirements.


Paul Feather PE, SE
www.SE-Solutions.net 
pfeather(--nospam--at)SE-Solutions.net 
----- Original Message ----- 
From: "Tim Shannon" <Tim(--nospam--at)nsw.meinhardt.com.au>
To: <seaint(--nospam--at)seaint.org>
Sent: Monday, September 26, 2005 5:30 PM
Subject: Height of Building/Shear Wall design


> Hello
> I am looking for a some advice on table 16-N of the 1997 UBC  - as a New 
> Zealand Engineer I am not really sure the background for some of the 
> height limitations.
> I have a "theoretical" building in a zone 4 region with a height of 260 
> feet from basement slab to roof.  UBC97 table 16-N will allow a maximum 
> height of the building  to be 240 feet for a Concrete Shear-Wall only 
> system.   Accordingly I would require a combined SMRF and Shear Wall 
> system for over 240 feet - unless this height was not measured from the 
> lower basement level.
> Question 1 - If I have a rigid basement structure and shear walls only as 
> the lateral resisting system above "ground" level the height from ground 
> level to the roof is only 230 feet, so does this justify a shear wall only 
> system given it is under 230 feet measured from ground level?
>
> Another question I have relates to  Shear Design of Concrete shear walls - 
> the UBC does not seem to consider in depth that shear walls will have 
> Potential Plastic Hinge Zones at the wall base just like a "beam-column 
> joint" might have in a ductile moment resisting frame at the column 
> ace  - I cannot find any attempt to try and suppress undesirable "shear 
> yielding" through capacity design in the instance of flexural yielding at 
> the base of the shear wall.  When I am designing the shear strength for a 
> ductile wall in New Zealand I would always design shear capacity of 
> ductile walls to overstrength according to capacity design principles with 
> a much reduced shear strength contribution from the concrete - is this not 
> required in the UBC, am I missing something?  Or would I just follow the 
> normal simple shear design rules in Section 1921 of the UBC97.
> Any replies would be much appreciated.
> Thanks
> Tim.
>
>
>
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