RE: masonry development length equations

The 1999 MSJC did had development length for ASD as 0.0015*db*Fs.  This comes out for be 36*db for grade 60 steel.  It did not have Strength Design.

 

The 2002 MSJC keep the same value for ASD.  Strength Design was introduced in 2002 and the development length was defined as 0.13*db^2*fy*gamma/(K*sqrt(f'm)*phi).

 

In the 2005 MJSC, the Strength Design development length remained the same except that you did not divide by phi anymore.  And ASD was changed to the same value as the Strength Design.  I remember that this was a deliberate attempt to harmonize the ASD and SD provisions.  I will note that the gamma value for #6 and #7 bars reduced from 1.4 to 1.3 but stayed the same for other bar sizes.

 

The 2008 MSJC keeps both the same.

 

I remember that there was some issue with the development lengths and/or splice lengths, but I honestly don't recall the details.  I seem to recall that the IBC choose to modify something in this area, but don't recall what it was or if it was in the 2003 or the 2006 edition.  If you REALLY want to know, then I can ask someone more knowledgeable than I.

 

Regards,

 

Scott

Adrian, MI

 

 

-----Original Message-----
From: Christopher Banbury [mailto:cbanbury@arkengineering.net]
Sent: Tuesday, July 17, 2007 11:42 PM
To: seaint@seaint.org
Subject: RE: masonry development length equations

Thanks Scott, I’m mostly curious as to why the Florida Building Code might have reverted to the old ‘02 ld equation for ASD even though the ‘05 has been officially adopted otherwise.

I heard a rumor that the ’05 equations were intended to address deficiencies in areas where seismic loads govern the design and that lap lengths could be unnecessarily large for areas where wind loads typically govern the design. Curiously, the FBC retains the new ’05 ld equation for Strength Design.

Perhaps you can confirm or deny this.

Thanks.

 

 

 

Christopher Banbury, PE

President

 

Ark Engineering, Inc.

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