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[SEAOC] Re: [SEAOC] Concrete Cracks

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At 07:56 AM 9/19/96 -0800, you wrote:

Jeff Crosier,

If your concrete shear wall is reinforced and properly detailed, you can
calculate a lower bound stiffness for a fully cracked wall using the method
given in Park and Paulay, REINFORCED CONCRETE STRUCTURES, 1975, pp. 315-319.
This lower bound stiffness will maximize the loss of strength you will
calculate using the steps you outlined.

However, I do have some reservations about your overall approach for
calculating the loss of strength of the cracked wall.  The magnitude of the
seismic loading this structure will experience in the next earthquake is a
function of its stiffness, as well as other factors.  The seismic deflection
will therefore not be the same for the uncracked and cracked conditions as
your approach implies.  Why not calculate the wall's strength directly -
instead of this round about way?  Depending on what the crack pattern looks
like, it may be feasible to idealize the cracked wall as a series of
uncracked panels between cracks which can be analyzed as independent shear
walls.  Shear loads would be distributed to each panel according their
relative stiffnesses.

I hope this information is useful.

Walt Sawruk
Wilfred Baker Engineering, Inc.
email: sawruk(--nospam--at)srvr.third-wave.com


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