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Need some URM advice -Reply

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Dennis,

>From Table A-1-E of the latest version (1997) of  UCBC Appendix 1-
retrofit standard for URM bearing wall buildings: 

 1.1 Plywood sheathing nailed directly over existing straight sheathing
with ends of plywood sheets bearing on joists or rafters and edges of
plywood located on center of individual sheathing boards- 225 lbs. per
foot (3283 N/m)

 1.2 Plywood sheathing nailed directly over existing diagonal sheathing
with ends of plywood sheets bearing on joists or rafters- 375 lbs. per
foot (5473 N/m)

1.3 Plywood sheathing nailed directly over existing straight or diagonal
sheathing with ends of plywood sheets bearing on joists or rafters with
edges of plywood located over new blocking and nailed to provide a
minimum nail penetration into framing and blocking of 15/8 inches - 75
percent of the values specified in Chapter 23 of the Building Code

As a side note, the Los Angeles Division 88 has different standards for
diaphragm capacity when used for strength or stiffness. The strength
criteria uses the blocked diaphragms values of Table 23-1-J-1 while the
stiffness check (DCR) uses a maximum of 225 pounds per foot. Note that
UCBC  Appendix 1 uses only 75% of the UBC values in Chapter 23. This
is actually identical to LABC Division 88 because the LABC is actually
75% of the UBC Chapter 23 values. UCBC Appendix 1 allows higher
capacities in the DCR check. Also note that the "Special Procedure" is
optional in the UCBC Appendix 1 while the DCR check of Division 88 is
mandatory for all design methods.

Tim McCormick. P.E.
City of Los Angeles