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Re: CONC - Modern concrete frame building -

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Tom Chiu wrote:

> I just got an inquiry about damage assessment on "modern concrete frame
> buildings" after the Northridge earthquake.  The inquiry is that, were
> there any damage suffered by those concrete frame buildings detailed per
> today's standards, meaning prior to 1994 and say after 1982's standards.
> Since I am also interested in this area as well and the responses may
> also benefit everyone, I decide to post the question here.
> 
> I had assessed lots of damaged concrete shear walls, both
> poured-in-place and tilt-up wall panels with large openings type
> buildings But I had not seen damage in the MODERN concrete ductile frame
> buildings yet.  Just getting curious to hear from some of you.

The parking garage at Cal State Northridge incorporated a "modern" 
concrete frame structure and also experienced collapse.  The frame 
itself did not collapse.  Failure initiated due to the inability of 
the interior columns (and possibly the diaphragm) to withstand the 
deformations imposed on the structure by the frames' response to the 
ground motion.

- This is probably the single biggest potential cause of poor 
performance of such structures.  Until the 1997 UBC, the code did not 
provide adequate assurance that non-participating elements would be 
protected under the large deformations that a frame could experience.

A large hotel structure in Guam, designed as ductile concrete 
frame for Zone 3, 1988 UBC requirements collapsed in an eathquake in 
1993.  Both deisgn detailing and construction execution of the design 
were deficient in some ways.

- This is also a concern for such structures.  The design and 
construciton requirements are quite complex.  Failure to execute them 
properly can result in structural failure.
Ronald O. Hamburger, SE
Regional Manager
EQE International, Inc.
San Francisco, California