Award of Merit: Strengthening Category
Strengthening of Overloaded Prestressed Concrete Beams
Submitted by Structural Preservation Systems
General Services Administration
ReStl Designers, Inc.
Structural Preservation Systems
During the summer of 2007, the repair contractor completed a unique prestressed beam repair project at a government parking structure in the Washington, DC, area. The project required the repair of two post-tensioned beams damaged after being overloaded by a concentration of snow. The beam failure was first noted in December 2006 by an employee who, while parking, noticed concrete spall debris on the deck. She looked up, saw the cracked beams and exposed prestressing strands, and immediately called 911.
For this project, the repair contractor developed an alternate, in-place repair solution that involved enlarging the damaged beams using self-consolidating concrete (SCC) and post-tensioning with mild steel reinforcement to add strength. As it was impossible to estimate the damaged capacity of the beams, it was assumed that the original reinforcement had yielded and would no longer contribute to the load-carrying capacity of the beam. Therefore, the retrofit would include the same amount of post-tensioning as the original beam and the enlarged section would be joined to the original section with a composite bond in order to restore the desired load capacity.
The repair contractor addressed the customer’s need for a sound, cost-efficient repair with minimal down time. They facilitated detailed analysis of structural elements with review and approval by the engineer-of-record (as well as two additional structural engineer peer reviews), and then safely and successfully completed the repair to the satisfaction of the general contractor, architect, engineer, and owner.