The condition of the post-tensioning systems of seven precast segmental box girder structures on three separate WMATA lines were evaluated due to the discovery of cracked HDPE ducts during a routine inspection. The evaluation included non-invasive and invasive visual inspections, vibration testing, visual inspection with the aid of a borescope and structural evaluations. Corven Engineering worked on Bridges J2e, E6f and F10a. The seven precast segmental box girder structures were constructed in the 1980’s and 1990’s and erected using the span-by-span method of erection. Post-tensioning tendons are, in general, external to the concrete and have a draped profile. Spans range from 49′-3″ to 151′-0″. The J2e and F10a bridges have one singe box girder supporting two tracks, and the E6f Bridge has two box girders, each supporting one track.
In conjunction with Gannett Fleming, Corven Engineering performed inspection of the post-tensioning systems. The team also developed the work plan, load rating analyses and final post-tensioning evaluation report for the bridges.