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# RE: Tilt-up In-Plane Shear

• To: <seaint(--nospam--at)seaint.org>
• Subject: RE: Tilt-up In-Plane Shear
• From: "Jake Watson" <jwatson(--nospam--at)utahisp.com>
• Date: Tue, 24 Jun 2003 21:33:47 -0600

I may be barking up the wrong tree here, but I think Ben said it best.  Just because you ASSUME the structure will remain elastic, doesn't make that assumption reality.  Furthermore, if you are assuming that the panel and all its connections will remain elastic, you should probably re-think that assumption.  The panel itself may remain elastic, but I would bet most of the foundation connections wont.  Secondly, strength design and seismic design are not necessarily tied together.  Do I have do ASD if I check wind forces?

The difference in concrete is that there is not an equivalent ASD seismic section.  Doing ASD does not get you off the hook for considering plastic sections and yielding.  It merely gives you another analogy for the material.  So as soon as the code writers provide you with ASD seismic provisions for concrete, you can use finish your analysis in ASD. :)

Jake Watson, P.E.
Salt Lake City, UT
-----Original Message-----
From: ASQENGG2(--nospam--at)aol.com [mailto:ASQENGG2(--nospam--at)aol.com]
Sent: Sunday, June 22, 2003 10:18 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Tilt-up In-Plane Shear

Everybody is caught into Strength Design (LRFD) that we forgot the reason why such seismic provisions of the code were written in the first place.  It was clearly explained in the Commentary of the Seismic provisions of the ACI code the reason why the provisions are written.  The provisions are necessary for structures that undergo inelastic behavior.  Let's go back to basic.  The ASD use fc = .45 f'c and fs = .4 to .6 of fy.  As long as the loads are within the anticipated loads there can be no chance that the structures designed under ASD will undergo inelastic behavior. The steel will undergo yielding but not beyond the allowable range.

I have not seen any concrete tilt-up buildings that were damaged due to in-plane shear (only out of plane loads). And I have seen hundreds of damaged buildings after the Northridge earthquake.

I think I was misunderstood.  The only reason why I compared the ASD against LRFD to SMRF vs. OMRF is the added requirements you need when designing SMRF.  The OMRF will behave closer to elastic while the SMRF undergo inelastic behavior the same way as concrete that were designed using LRFD.

I wish the people who know the history or participated in the first ACI Seismic Provisions will have time to comment on this piece.

Thanks,

A.S.Quilala

In a message dated 6/20/2003 4:18:00 PM Pacific Standard Time, gmadden(--nospam--at)attbi.com writes:

Sorry, but you are incorrect.

You need to design concrete *shearwalls* for 1921.6 of the UBC.

ASD does not mean NO YIELDING will take place. SMRF and OMRF are not ASD vs. LRFD in steel.

-gerard

Santa Clara, CA