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1994 UBC vs 1997 UBC Masonry Design

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>From a quasi-lurker.


I have a question about the differences between the 1994 UBC and 1997 UBC
Strength Design of Masonry provisions.


It seems as if the 1997 UBC has reduced the load factors for Masonry, but
kept the same strength reduction (phi) factors.


In 1994:  Section 2108 used the ACI load factors 
U = 1.4D + 1.7L, etc.  

The phi factors for beams, piers, and columns (for example) were listed as:

shear 		phi = 0.6, 
flexure 	phi = 0.8 - Pu/(Ae f'm)   0.6 <= phi <=0.8


In 1997: Section 2108.1.3, Says use the factored load combinations of
Section 1612.2, which are the ASCE-7 load factors.  

U = 1.2D + 1.6L, etc,

However, it seems as if the phi factors have not changed.  For example,
   
2108.1.4.1.1 still says for beams, piers, and columns:
shear 		phi = 0.6, 
flexure 	phi = 0.8 - Pu/(Ae f'm)   0.6 <= phi <=0.8


Is this correct ?   The loads factors have decreased, but the strength
reduction (phi) factors have stayed the same ?

In ACI 318-95, there is one set of phi factors to use with the
"traditional" ACI factors (1.4D+1.7L), and a different, lower set of phi
factors to use with the ASCE factors (1.2D+1.6L).

Am I missing something ?



Thanks,
Ed.S.

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Edwin R. Schmeckpeper, P.E., Ph.D.
Department of Civil Engineering                   Phone  : (208) 885-6702 
University of Idaho                               FAX    : (208) 885-6608
Moscow, Idaho 83844-1022                          E-Mail : eds(--nospam--at)uidaho.edu
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