Wednesday, November 16, 2011

Re: Unreinforced Masonry Wall from 1965

I am guessing that it was potentially done with the so-called "empirical design" method...i.e. what is now chapter 5 of the MSJC.  If so, then you likely will definitely not get it to work with actual rational engineering methodologies of chapter 2 (ASD) or chapter 3 (strength).  You may not even get it to work under the current empirical provisions in the current MSJC because they may have changed a little bit.

Is it an interior or exterior wall?  If exterior, then it is possible that wind load provisions have changed enough over the 40 or so years that design wind loads are potentially higher than what codes may have required back in 1965.



On Nov 14, 2011, at 5:05 PM, Daniel Popp wrote:


We have a renovation project in a low seismic area (SDC B). The 27-foot-tall exterior walls are unreinforced ungrouted (hollow) 8" concrete masonry interwoven with 4" brick face shells (12" nominal thickness). The occupancy is changing from Category 2 to Category 3 (>300 people in one space), so we are obligated to check the existing walls. However, due to the height, I cannot make them work using the "unreinforced masonry" provisions in MSJC Section 2.2.

Does anyone have any idea how the original engineer may have made these walls work in 1965? It strikes me that the code provisions for unreinforced masonry have probably not changed much in 50 years (seismic regions excepted). The owner is very sensitive to budget (who isn't these days?), so I'd like to find a way around an costly retrofit.

Thanks for your input,
Dan Popp, S.E.