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Masonry lap length

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I am interested to know what masonry cover you use for bond beam corner
bars or vertical filled cells with 2 bars (1EF). It seems like the K
value would be quite low say 2" and hence the lap length very long
(since our value it is divided by K.) Or am I missing something?

Adam wrote:
The ACI530-99 code had only ASD included with the ld = 0.002*db*fs 
equation.  However, the 2000 IBC over-ruled this equation and used the 
more cumbersome equation ld = 0.16*db^2*fy*gamma/(K*fm'^1/2).  In 
addition, the 2000 IBC included a procedure for strength design that had

a similar equation for ld.  According to one ACI530-99 committee member 
it was a mistake to use the latter equation for ASD, it was only 
applicable to strength design.  I agree with Bill Sherman that this does

not make sense.

The ACI530-05 uses the equation ld = 0.13*db^2*fy*gamma/(K*fm'^1/2) for 
both ASD and strength design.  Now, the 2006 IBC overrules this equation

for ASD and reverts to ld = 0.002*db*fs with the important exception 
that when the calculated stress in the bar is greater than 80% of the 
allowable stress then ld shall be increased by 50%.  I don't know about 
you, but almost all of my masonry designs result in steel controlled 
sections when using ASD, thus ld must be increases by 50%.

The IBC uses the equation ld = 0.13*db^2*fy*gamma/(K*fm'^1/2)for 
strength design.  This results in shorter lap lengths (most of the 
time).  Therefore, I have now begun using strength design for masonry. 
This has resulted in much more economical designs in overall rebar use 
as well as lap lengths.


Adam Vakiener, P.E.
Structural Engineer
Southern A&E, LLC

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