HONORABLE MENTION: Parking Structures Category

Repair of Continuum Parking Garage

Austin, Texas

Submitted by Wiss, Janney, Elstner Associates, Inc.

The Continuum Parking Garage in Austin, Texas, is a five-level precast concrete structure that was constructed in 1986. The structure consists of a series of precast, prestressed double-tee beams, supported by spandrel beams on the east and west edges and by vertical load-bearing wall panels along the two interior column lines.

The concrete in portions of the load-bearing precast elements exhibited cracking and a loss of integrity, which material testing attributed to delayed ettringite formation (DEF). This is believed to be the first structure in the United States that required structural repair due to DEF. Other distress in this structure included inclined structural cracking in the spandrel beams near the end supports due to insufficient reinforcing of the spandrel beams.

The distressed portions of the load-bearing precast wall panels were repaired using cast-in-place replacement panel sections with additional reinforcing. The deteriorated panel concrete was removed from the top down, effectively detensioning the prestressing tendons as the removal proceeded.

The cracked spandrel beams were repaired by low-pressure epoxy injection of the cracks followed by supplemental steel reinforcing plates on the inside face of the beams. The contractor’s demolition, shoring, and formwork schemes allowed the reconstruction of the panels in place while the garage was still in service. Furthermore, these repairs were completed without any permanent loss of parking and without an effect on the overall aesthetics of the structure.