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Re: Tilt-up In-Plane Shear

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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.



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



Santa Clara, CA