I'm working on a building that is designed with piers on either side of a 6-foot-wide door. Each pier has four #8 vertical bars in each block (two in each cell), and the engineer is requiring #3 stirrups at 8 inches on center. It would be a lot easier if I could use #9 wire to make the stirrups. If I use the same amount of steel, is that acceptable?
Using such large bars (four #8 bars is really a lot) in masonry is not typical and can cause serious problems in construction with placing the bars and grouting the pier. Engineers should use caution when calling for such high levels of reinforcement and should consider the impact on constructability and whether the element is approaching an over-reinforcement condition. A larger number of smaller bars will typically provide the same capacity and will perform better when subjected to overloads.
Getting the stirrups placed properly with all this reinforcement will be difficult. However, according to the MSJC 1999 Building Code Requirements for Masonry Structures (ACI 530/ASCE 5/TMS 402) in paragraph 220.127.116.11(a), longitudinal reinforcement in a column must be enclosed by lateral ties at least 1/4 inch in diameter. No. 9 wire is less than 1/4 inch and therefore cannot be used. Pilasters in masonry walls, discussed in paragraph 2.1.5, must meet the column criteria where the vertical reinforcement is provided to resist axial compressive stress.