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From page 40... ... 40 This chapter presents five case examples of post-tensioned bridge repairs and related maintenance actions performed by five different public agencies. An attempt was made to gather case examples from a diverse representation of states from different geographic areas. Read the entire page →
From page 41... ... Case Examples 41 Grout Inspections Subsequent to identifying chloride intrusion problems in tendons in other bridges using the same grout, the bridge owner ordered an invasive inspection of a limited number of PT tendons to obtain some grout samples and to assess the tendons for corrosion. The initial investigation was conducted April–May 2012. Read the entire page →
From page 42... ... 42 Repair and Maintenance of Post-Tensioned Concrete Bridges grout irregularities. To characterize the grout irregularity, 87 small holes were drilled at various locations in the tendon profiles to visually characterize the grout with a borescope. Read the entire page →
From page 43... ... Case Examples 43 vacuum-assisted grouting. Stage two consisted of the grout-drying process. Read the entire page →
From page 44... ... 44 Repair and Maintenance of Post-Tensioned Concrete Bridges • Commissioned a research study to evaluate efficacy and feasibility of available repair methods, • Added additional external tendons to provide structural redundancy, and • Performed grout remediation and tendon impregnation to inhibit future corrosion. Overall, the project was a large collaborative effort between the bridge owner, consulting engineers, researchers, and the contractors to effectively remediate tendon corrosion in the Wonderwood Connector Bridge. Read the entire page →
From page 45... ... Case Examples 45 findings as containing "limited information due to form only and no corresponding report" (South Carolina Department of Transportation 2018) Read the entire page →
From page 46... ... Photo credit: Parsons Brinckerhoff. Figure 25. Read the entire page →
From page 47... ... Case Examples 47 In light of these findings, a special in-depth, preliminary investigation was undertaken of the external tendons in both the eastbound and westbound structures (October 2011 Preliminary External Tendon Final Report) Read the entire page →
From page 48... ... 48 Repair and Maintenance of Post-Tensioned Concrete Bridges Actions were taken in 2012–2013 to identify water penetration pathways and to address water intrusion, including injection of improperly filled vent ports, partial depth penetration patches to the deck, and application of methacrylate coating to the top of the deck. Attempts (multiple over the life of the bridge) Read the entire page →
From page 49... ... Case Examples 49 to the rupture of M1 -- included monitoring of the M4 tendon; this monitoring was important in identifying the tendon loss because no other indication had revealed its occurrence. The inspector observed the tendon move a noticeable, unexpected amount under manual excitation by the inspector. Read the entire page →
From page 50... ... 50 Repair and Maintenance of Post-Tensioned Concrete Bridges Construction During construction, two custom gantry cranes were used to facilitate the erection of each bridge span; each 150-ft span could be erected in approximately one week using the cranes. The cranes supported the spans during post-tensioning operations. Read the entire page →
From page 51... ... Case Examples 51 deck underwent grinding in preparation for repair. Unexpectedly, grinding the deck exposed some of the post-tensioning ducts. Read the entire page →
From page 52... ... 52 Repair and Maintenance of Post-Tensioned Concrete Bridges Summary The Veterans' Glass Skyway in Toledo, Ohio, serves a critical section of I-280 over the Maumee River. It features several innovative design concepts and a significant amount of PT. Read the entire page →
From page 53... ... Case Examples 53 borescope inspection via vent tubes that had been incompletely filled with grout or that were completely empty. Evidence of bleed water and grout subsidence was noted. Read the entire page →
From page 54... ... 54 Repair and Maintenance of Post-Tensioned Concrete Bridges were repaired, and the duct was resealed with heat-shrink sleeves. The bridge owner is positive of the efficacy of MFL as a defect detection technique, commenting that all identified locations by MFL did reveal defect. Read the entire page →
From page 55... ... Case Examples 55 Several tendons had been identified in the first 2010 inspection report as suspected of slip; these tendons had been suspected because of changes in the repair material, with an evident change in a crack width in the epoxy coating the connection, between inspections occurring in 2007 and 2010. These tendons were carefully inspected during the subsequent in-depth inspection, but slippage could not be verified as the cause by inspecting the tendon mid-length because the crack in the repair material could have been caused by thermal changes within the structure. Read the entire page →
From page 56... ... 56 Repair and Maintenance of Post-Tensioned Concrete Bridges NDE and corrosion specialist, Siva Corrosion Services, Inc., to assess the grout and prestressing strand in the external tendons and the vertical tendons. The evaluation examined 13 external tendon locations and 18 vertical PT bars. Read the entire page →
From page 57... ... Case Examples 57 Considering the multitude of evaluation methods used to assess the grout, the quality of the grout tested in this inspection was generally good. Though no strands were found to be embedded in such locations, grout near the top of the duct was found to be visually poor (white and chalky) Read the entire page →
From page 58... ... 58 Repair and Maintenance of Post-Tensioned Concrete Bridges The effort is expected to wrap up in 2021 and will assist in both improving the accuracy of load-rating and assessing the structures' durability. Additional efforts, including investment in an acoustic emissions system, and further measurements using magnetic flux leakage are anticipated to be used in conjunction with these efforts to assist the agency's future decision making. Read the entire page →
From page 59... ... Case Examples 59 Photo credit: Corven Engineering. Figure 39. Read the entire page →
From page 60... ... 60 Repair and Maintenance of Post-Tensioned Concrete Bridges Subsequent in-depth inspections were conducted by a consultant; the inspection aimed to further visually inspect, with invasive techniques. The following were targeted for this in-depth inspection: • Previously identified, corroded tendons, • Continuity tendons in the bottom slab haunch in the same general vicinity, • Continuity and draped tendons in the same general vicinity of the bridge, • Selected cantilever tendons, and • Selected anchorages of the bottom slab continuity tendons. Read the entire page →
From page 61... ... Case Examples 61 Less severe damage was identified in adjacent spans; wire breaks were identified, but force was found to have been recovered at some distance from the breakage through friction and grout interlock. Identified damage was severe enough to require bridge closure until the conclusion of the repairs (and the satisfaction of the engineer) Read the entire page →

From page 40...

... 40 This chapter presents five case examples of post-tensioned bridge repairs and related maintenance actions performed by five different public agencies. An attempt was made to gather case examples from a diverse representation of states from different geographic areas.