Seismic reinforcing of window sills

[McSEpllc]

I have a school building in construction that the GC forgot to install the seismic horizontal reinforcing of the CMU window sill as detailed. ACI 530, section 1.14.2.2.2.1 clearly states requiring that reinforcing.

On the other hand the windows are only 3'-4" wide, less than the 8'-0" width between vertical seismic bars. The seismicity for Western North Carolina is not that great. We have about 300 quakes a year that are very rarely even perceptible and there is no force build-up. In my mind whether the horizontal reinforcing of a 3'-4" wide window sills is in place or not will not change the behavior of the wall or be the cause of a collapse.

Have you had this before and how did you deal with this?

Thanks!

Eric McDonald, PE
McDonald Structural Engineering, PLLC

 

[JedClampett]

The commentary to the code suggests that these requirements have been required historically and performed well in testing. Common sense indicates that it's there to reinforce the bottom course of block to prevent a crack from forming at the discontinuity. To simulate it, maybe you could add a plate or very small channel (C3 or C4?)and anchor it to both sides of the opening with epoxy anchors.