Minimum Concrete Bearing Wall Reinforcing 1

[msquared48]

I have a project where 6" concrete interior bearing walls are used in a hotel building constructed in 1958. The drawings showing the wall steel placed in the center are mostly unreadable, but it appears that WWF was used in the center. The size is not readable.

I am dealing with a difficult jurisdiction that requires proof of everything - not an uncommon problem, but still a problem, nevertheless. I can assume minimum steel in the wall and compute the PhiPn value from section 14.5 using the minimum reinforcing shown in 14.3.2(c), but that is an assumed level of reinforcing, not the actual.

The project is in a hich seismic region, so an unreinforced wall analysis will not fly. I feel that we will eventually find out what the reinforcing is, but I think that it will be less than the minimum per current ACI requirements.

My question is, considering that we will find for the reinforcing, considering the 33% increase provision for beams where less than minimum steel is allowed to be provided (10.5.3), is there any such provision for walls? I can find none, but it seems reasonable to get a reduced value for less reinforcing.

Any thoughts?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[msquared48]

Another consideration is that realistically this wall sees no flexure, with the vertical load well within the kern area of the wall.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[JAE]

Mike,

I don't think there is any exception to ACI chapter 14 min. wall reinf. requirements.

My only suggestion would be that, since this is an existing wall, and if you could show that under the seismic event, the reinforcement (once you find what it is) would work under a P-M column interaction check, then perhaps you could convince the code official that it would be OK.

The concern would be that under the seismic event, would flexural bending get applied to the point where cracking occurs, and perhaps yielding of the reinforcement, such that instability would occur.

 

[msquared48]

OK. Thanks JAE. Had to try...

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com