ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/306849
MAINTENANCE, REPAIR, and REHABILITATION OF CONCRETE BRIDGES Community residents helping to restore some of the decorative sculptures on the Minisa Bridge. As part of the renovation of the Minisa Bridge in Wichita, Kans., its decorations made of Carthalite concrete, unique to the city, were repaired and restored. ASPIRE, Summer 2009 | 39 Updating the 1932 Minisa Bridge along West 13th Street in Wichita, Kansas, involved a variety of unusual challenges. In essence, the bridge was torn away completely in the rehabilitation work, leaving only the sidewalks and ornamental elements on both sides supported by standalone shoring of steel and wood to provide access for children to their school on the other side. The bridge then was reconstructed beginning in January over a major river. The work not only preserved the historic portions of the bridge but opened less than 6 months later, ahead of schedule. All of the stakeholders, including designers, contractors, city officials, city engineers, public-works employees, historical experts, and local school officials realized that partnering would be a key element of the project if it was to succeed. Engineers at Parsons Brinckerhoff had to recreate the plans for the bridge, as the originals were 76 years old and in bad condition. The designers and city both provided great latitude to make formwork and construction decisions, with their approval, so construction could proceed quickly. The ornamental elements were rebuilt using a cast-in-place concrete mix that replicated the original material used for the construction, consisting of Carthalite concrete. Carthalite is essentially white portland cement concrete with colored glass aggregates. The material was made by the Cement Stone & Supply Co. in Wichita and was used to create ornamental sculptures, such as buffaloes and Native American images, as well as unique colors for the bridge. The material appears to have only been used in Wichita, where it was incorporated into 13 buildings, a flagpole base, and the Minisa Bridge. The company still operates, but it does not make the Carthalite concrete, requiring a new approach for the repairs. I-Beams Installed Structural integrity was first restored to the bridge, using precast, prestressed concrete I-beams. Seven spans of nine girders each were erected, ranging in length from 33 ft to 41 ft. A conventional cast-in-place composite concrete deck was used on the girders. Once the main structure was completed, restoration of the historic concrete wingwalls and piers supporting the balustrades was performed. Under consultation with historic-masonry experts, the historic Carthalite mortars and materials were replicated. Restoration work consisted of four phases: joint and crack repair, sculpture repair, recasting, and cleaning. Joints and cracks were repointed and injection-patched with less-dense mortar to allow the concrete to "breathe." Then the historic colored mortars were analyzed and recreated. The original castings had featured crushed-glass aggregates, which required incorporating glass made prior to 1950 PartnershiP Pays Off by Don King, King Construction Co. ASPIRE_Summer09.indb 39 6/5/09 1:55:31 PM