CMU REINFORCEMENT TOLERANCE REQUIREMENT QUESTION

[zrck99]

I am designing a storm shelter using fully grouted 8" cmu block reinforced at each face in each cell with #5 vertical bars. The first page of the attached pdf shows my proposed reinforcement layout at bond beam locations over doors where I need the bond beam to be able to span vertically for gravity loads and horizontally for out of plane wind loads. The second page of the attached pdf is rom the Reinforced Masonry Engineering Handbook, 8th Edition. I am wondering if the general consensus would be that the 1/2" allowable tolerance that I am providing between the 1/2" clear cover for grout and the face of my vertical bars is what is being required here... Does anyone see something incorrect about me specifying and designing to these "d" distances?

 

[r13]

Design clearance = stated clearance (7.2.4.1) + construction tolerance (table 7.2). Unless fine grout is permitted, the minimum clearance = 1/2" + 1/2" = 1".

 

[masonrygeek]

I believe you are correct, but also recognize that ASTM C90 spec for block allows a face shell to be 1 1/4" thick.

 

[JLNJ]

That layout is pretty tight and somewhat optimistic with regard to rebar placement, especially when you consider construction tolerance. I would try like crazy to make it work with one vertical rebar layer. I would not stagger the horizontal bars.

Your construction drawings should show the rebar where you want it, not where it might be with the construction tolerance.