Suspending elegance with Bond Cables
Through a public participation process, the city of Eugene, Oregon approved the design and construction of a new pedestrian bridge over Willamette River. The suspension cable type bridge was the most suitable to minimize the environmental impact and provide also an architecturally elegant structure. The project featured a curved ramp into the park, a midspan observatory platform and a 6.5 m wide deck creating a dramatic suspension bridge and a new architectural landmark.
Construction included cast-in-place approach spans, 23 m cable-stayed intermediate spans, and a 103 m long suspended main span. The structure approach incorporated 19-0.6" multistrand bonded tendons using a combination of MA anchorages, bond-head anchorages, and 180° loop tendons. Construction on the suspension bridge began with the installation 38-0.6" tendons acting as temporary erection cables.
Steel pylons were erected to support the main suspension cables each consisting of 43-0.6" strands with multiple layers of corrosion protection. The strands were internally greased and sheathed in HDPE, installed in a galvanized carrier pipe, and cement grouted upon completion. The main cables were anchored at both ends with the well-known DYNA Bond® anchorage system. The suspended portion of the bridge deck was composed of 44 precast segments longitudinally post-tensioned after erection with 19-0.6" multistrand bonded tendons.
The erection of the deck was developed from the stress-ribbon structure technology that produced an extremely rigid deck structure with only 0.42 m maximum panel thickness. First the mid-span island segments forming the observation platform were erected. They were shifted along temporary cables supported at the abutments. After the erection of these segments, the main suspension span cables were installed. Cables were pulled and tensioned to the required lengths to transfer the dead loads from the temporary cables to the suspension ones. The shorter spans were erected following a similar procedure.