After the highly publicized reports from this past summer regarding the failure of 32 anchor rods on the eastern span of the new Bay Bridge, the highly regarded concrete contractor, Conco was retained by the general contractor, American Bridge/Fluor Enterprises, Inc. JV, to assist with the repair work. Based on their earlier performance with other critical and technically challenging components of the new bridge structure, Conco was the logical choice. “Every aspect of this project had complex technical challenges.” said Brian Petersen, the contractor’s Project Director, and “Conco’s skill and expertise was a great asset to our team.”
The defective anchor rods were supposed to secure the bridge deck to the concrete crossbeam support. Since the failed rods were embedded and inaccessible, replacement was not feasible. After extensive collaboration and analysis, a fix was designed. It involved a complex series of steel saddles and post-tensioned (PT) jacket walls that would provide the required clamping force to secure the bridge deck framing to the E2 crossbeam. Temporary steel shims were inserted into the stabilizers while the repairs were being done, and in order for the Labor Day opening to go forward as planned. “The SAS bridge is part of a world-class megaproject which features a large amount of challenging concrete work associated with temporary support structures that are not part of the completed bridge,” noted Jim Klinger, Conco’s project manager.
For this very complicated problem, Conco’s first task was to close in a steel-framed trestle platform to give work crews access to the site and eliminate the potential for materials to fall into the San Francisco Bay. Once the platform was complete, crews roughened the crossbeam surface and epoxied over 3,000 drilled dowels into place. Reinforcing steel and PT cable ducts were then installed by Harris Salinas. Conco crews followed behind them, placing custom-made PT trumpet blockouts and setting forms for the jacket walls.
The concrete jacket wall structures were placed in three pours totaling 380 cubic yards. Due to restricted access and rebar congestion, much of the concrete had to be pumped 250 feet and then injected into the forms through ports at strategic locations. Conco worked closely with concrete supplier, Central Concrete, to develop an injectable SCC mix with silica fume that would meet the project’s specifications. A full-scale mockup was constructed and successfully tested to ensure the long-distance pumping and injection of the highly-flowable SCC mix would work.
“Almost all of the concrete work items Conco was asked to perform by ABFJV were custom, one-of-a-kind scopes that we will probably never see again,” said Klinger. In late November, the third and final injection was finished and the repairs were completed successfully.
Conco is a leading supplier of concrete services for the Western United States. As one of the leading commercial concrete contractors in the Bay Area, we have been involved with large-scale projects in the area including the new 49ers Stadium. Our concrete services include commercial, educational, parking and other construction development as well as public works projects and highways.