SOLUTION

Through WJE's inspection of the failed area, it was determined that the panel failures were a result of the accumulated load of the limestone cladding combined with accumulation (and confinement) of corrosion scale, which caused the panels to displace outward until the bearing stresses at the kerfs were high enough to fail the stone panels.

The originally proposed limestone panel repair design posed scheduling challenges within a tight construction timeline and failed to meet historic tax credit criteria. Rather than installing bolts through the limestone and terra cotta back-up and into steel framing at the interior, the final repair approach reintegrated the limestone and the terra cotta back-up from only the exterior, using adhesive anchors to secure the limestone to the terra cotta back-up, which maintained the original load path and minimized the need for supplemental strengthening of systems that were not originally designed to carry limestone cladding loads. Through-face adhesive anchors were designed based on test data and load analysis and were used at virtually all limestone panel configurations due to the potential that the existing anchors were corroded and no longer functioning. Every limestone panel was stabilized from the exterior with no need to perform work at the interior, allowing the interior restoration efforts to go forward unimpeded. Additional repairs included full restoration of the polychromatic terra cotta and replacement of unstable brick masonry.