Evaluation and Repair of Insufficiently-Reinforced Precast Concrete Double Tee Members

A parking garage constructed using precast double tees supported by structural steel experienced an overload condition from snow removal operations that resulted in severe cracking and localized failures. Structural analyses of the affected members revealed insufficient shear reinforcement in the precast concrete shallow dapped end regions. Subsequent surveys revealed a significant number of additional cracked double tees. An inspection and testing program was developed to assess the ability of the as-built double tees to resist code-prescribed loads. The program included ground penetrating radar (GPR) to locate reinforcement on a statistically relevant sample and full-scale load testing on selected double tees that represented approximately 90 percent of the population. The load tests demonstrated double tees with similar conditions were capable of resisting code-prescribed loads, limiting repairs to only those locations, where existing conditions were not comparable to those present in the load-tested members. Guidelines based on crack width and location were developed for assessing the need to repair individual double tees.