Original beam in the foreground and the repaired section of the beam in the background.
Failed beam from overload (Three additional failures similar to this one on two beams).
Concentration of snow debris that caused the beam overload.
Completing surface preparation, steeldowel placement and PT placement.
Damaged areas repaired and epoxy injected.
Final stressing of new PT tendons in enlarged section (jack area concrete installed after stressing).
Form and pump formwork set for SCC pumping.
Formwork featured windows to visually monitor filling of annular space.
New enlarged concrete section installed.

Pre-stressed Beam Repair at a Washington, DC Parking Structure

Project Description 

The parking structure of a government office building in Washington, D.C. suffered failure of two post-tensioned beams as a result of overloading. Bringing the six-story, 500,000 square foot post-tensioned structure back into full operation with a cost-efficient, sound repair with minimal down-time was critical to the Owner.

The initial repair option involved removal and replacement of the damaged beams, but this option required extensive shoring. Additionally, the post-tensioned slab above the damaged beams would have to be detensioned. Because the option was costing and lengthy, the Owner looked for alternate means.

Taking the Owner’s requirements for a cost efficient, timely solution into consideration, STRUCTURAL developed an alternate, in place repair plan - 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. 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 newly repaired beams appear very similar to the original beams and met the Owner’s requirements for an aesthetically pleasing, time and cost efficient repair.