The Tower Heist: Planning a Successful High-Rise Slab Edge Repair

After only six years of service, a 6-foot long narrow piece of concrete spalled off an exposed slab edge of a 680-foot tall high-rise in Texas, and fell 160 feet to the podium below. The spall was attributed to premature corrosion at the drip edge. The building featured approximately 9,200 feet of exposed slab edge over its height. Given the potential risk to safety and property of additional concrete spalls, the Owner requested forensic investigations, which (1) identified other areas with signs of similar distress and (2) determined the underlying problem of low reinforcement cover at the drip edge was pervasive. In response, repair options were developed to address the problem and restore intended durability. Given the building height, difficult exterior-only access, downtown environment, and post-tensioning anchors along the slab edge, the repair design and construction both had unique challenges to consider and overcome. The engineer and contractor worked collaboratively on nearly all aspects of the project to develop effective and constructible repairs for the slab edges. The repairs consisted of structural replacement of the slab edges with GFRP reinforcement and new waterproof coating, which were completed in summer 2019 after approximately 16 months of construction.

Learning Objectives:

1. The underlying problem that required repair
2. Repair design challenges
3. Repair construction challenges, and
4. Importance of collaboration to avoid and address field challenges.