Post-Tensioning Systems for a Self-Anchored Pedestrian Suspension Bridge
In 2011, one of the world’s longest self-anchored suspension bridges was built in San Diego, California: The Harbor Drive Pedestrian Bridge.
The 168m long bridge links the Petco Park baseball stadium with the San Diego Convention Center and permits a safe crossing of the multi-lane Harbor Drive as well as several railroad tracks.
The curved structure with a main span of 107.9m (354ft) includes an approx. 40m high pylon that is post-tensioned with DYWIDAG Strand Tendons. Since the pylon features a 60° incline, it had to be tied back using two stay cables. The back stays consist of waxed and PE sheathed 43-0.6" DYWIDAG Strand Cables that were individually stressed using the Conten stressing system and then grouted.
The main suspension cables consist of waxed and PE sheathed 37-0.6" DYWIDAG Strand Cables inside articulated stainless steel pipe segments. These cables extend upward from each abutment to the pylon tip. The main cables were stressed at the abutments with a multi-strand jack and then grouted. To resist unbalanced torsion due to the eccentric hanger supports, lateral forces acting about 1m above the deck were generated by stressing a 37-0.6" DYWIDAG Tendon that was placed inside a curved heavy wall stainless steel pipe that also acted as part of the bridge railing.
The slender, cast-in-place concrete deck consists of a 1m deep by 3m wide box girder and a 3m overhang slab on one side. It is supported by 34 stainless steel hangers suspended from the main cables. 12-0.6" and 19-0.6" DYWIDAG Strand Tendons with MA Anchorages were used for the longitudinal post-tensioning of the bridge deck.
The extremely complex geometry and extensive use of stainless steel created multiple challenges throughout the design and erection of the cables and the construction of the bridge. DYNA Force® Sensors were necessary during construction in order to monitor loads in the foundation tie-downs, main cables and the back stays throughout the construction process.
This project won the ENR's "Best of the Best" Award.