Harbor Drive Pedestrian Bridge

The Harbor Drive Pedestrian Bridge was completed in March of 2011 to complete the “Park to Bay Link”. This link provides a pedestrian pathway along Park Boulevard to connect Balboa Park with the San Diego Bay. This bridge was a key part of the link, as it carries pedestrians across six sets of railroad tracks and five lanes of traffic.

This bridge is 550 feet long, with a main span length of 350 feet. This makes it one of the longest self-anchored suspension bridges in the world. A traditional wire cable suspension bridge has large anchorage blocks in the ground on either side of the bridge. The main cables attach to these blocks, and they provide the resistance needed to support the bridge. This is one of the main reasons that suspension bridges are typically built on rock, and that there are very few suspension bridges in the Southeastern USA where the soil isn’t good (note that cable stay bridges are different and can be built on poor soil). In a self-anchored suspension bridge, the main cables are attached directly to the deck at the end of the spans. The tension forces in the main cables are countered by compression forces in the tower and deck, instead of relying on external anchorages. It works very similarly to a tied-arch bridge.

To make it more complicated, the 130-foot-tall tower of this bridge is set at a 60-degree angle, and the concrete bridge deck is curved. The 34 individual suspender cables only attach to the inside of the curve and are attached to the top of the railing instead of the deck. This was done in an effort to make the bridge resemble a sail in order to fit with the city’s nautical history. During design, a steel space truss, a cable-stayed bridge, and an arched steel shell were also considered, but the self-anchored suspension bridge was ultimately chosen due to the aesthetics, cost, and suitability for the site.