Lake Pleasant WTP West Reservoir – Double Tee Repair And Strengthening
CONTRACTOR: Hunter Contracting Co.
PROJECT OWNER: City of Phoenix
LOCATION: PHOENIX, AZ
BUDGET: $ 1.5 MILLION
COMPLETION: 2020
Repairing large structural components can prove to be an incredibly difficult task due to the complexities that come with handling heavy members and temporarily shoring parts of the structure. In this case, nearly 30 Double-Tees spanning over 58 feet each needed significant repairs. The failure was a bearing failure, which crushed the concrete stem and caused the top slab to sag. This also led to corrosion of the reinforcement. The needed repairs ranged from partially or fully repairing the flange to partially or fully repairing the stem of the Double-Tees. In addition, the damaged Double-Tees would need to be strengthened to increase the load bearing capacity.
Cornerstone decided that using a polymer modified concrete repair would be suitable to return the double tees to their original shape. Additionally, by using high strength Carbon Fibers (CFRP) fabric, we restored the load carrying capacities of the compromised Double-Tees. We also introduced stainless steel brackets at these compromised locations and secured them with new bearing pads.
A conventional solution would have been to perform section enlargement of the double tees by forming and pouring additional concrete. However, this increases the deadload on the structure, requires extensive formwork and field prep work, and takes 28 days before it can be utilized. By using CFRP reinforcement, the same levels of strength were achieved without adding to the deadload, and the members reached their full design capacities within only 24 hours. This made the overall project much less expensive and significantly cut the timeframe of the project. Cornerstone also provided construction management and special inspections to ensure the quality of repairs met the design standards.