Rainbow Bridge

The 605-foot-long design draws inspiration from Long Beach’s history as a dynamic seaside town with its active port and local attractions. The form is conceived as an abstraction of a breaking wave with a deck that is composed of multifarious elements that typify a boardwalk environment, such as the paving, seating, and landscaping.

Construction was a concerted effort and we worked closely with Arup to engineer the bridge. Originally, the bridge called for 80 or more uniquely formed rib beams, but to bring the cost down we had to modify the steel geometry and concrete profile in a way that just one shape could achieve a similar dynamic form when placed in repetition. As it is today, the project is formed by a top frame of 76 custom-welded bent-steel ribs, and a base of approximately 1,200 cubic yards of poured-in-place concrete.

As we mentioned above, the structural design of the bridge is based on a standard Caltrans bridge template with concrete supports and a box beam spanning between columns. We dissected the main components of this boilerplate scheme and then reinterpreted our findings in a more playful and innovative way. This more sophisticated rendition addresses the site’s unique geometry and answers the city’s call to integrate more landscaping by programming a park into the path of the bridge. Similarly, we used the guardrail as an opportunity to add vibrancy to the bridge; the hull-like formation has been married with the grace and uniformity found in waves, while the LEDs were affixed to cables to convey a net-like feeling of the rigging of a ship. The bridge maintains a very streamlined profile even as all of these different details come into play.

The bridge’s two defining features are most certainly its wave-inspired steel framing and its dynamic lighting fixture. The fixture is a unique specification selected by our design team, custom developed alongside Carl Stahl Architektur. As we began construction, our contractor wanted to replace the lighting system with a different manufacturer they had worked with previously. We, however, were more than confident in the superiority of the Carl Stahl piece—we just needed to make a case for its appropriateness.

To do this, we set up a performance test on site and involved all of the project stakeholders—this included the owner (representatives from the City of Long Beach), the lighting designer, and the contractor. All parties had a chance to evaluate the fixture we chose against the contractor’s, and following the demonstrations, it was unanimously decided that our fixture was the better option.

The lights themselves are quite unique in that we worked with Carl Stahl, and the steel cable provider to develop two custom node clips that could either fasten the lighting system or tension the stainless steel canopy. Although the pieces serve two different functions, they are aesthetically analogous and appear as one succinct system. The design also allows for ease of installation and replacement flexibility.

This project is unique in that we used the most up-to-date software to 3D model and document the bridge, but we were required to translate this complex design into 2D drawings that a public works contractor2 could use to build the bridge within budget, and with the limited technology available to them.

Our working title for this project was Riptide but the City of Long Beach opted to christen it the Rainbow Bridge, which we’ve come to understand references the nearby Rainbow Lagoon. While we would have much preferred our moniker be made official, we understand that a rainbow is far less threatening than a riptide. And ultimately, making this bridge a reality was about both innovation and getting individuals out of their comfort zone. We are grateful to have worked with such a talented, open-minded, and motivated team.

Although budget constraints3 largely shaped the design approach and construction, they did not affect the quality of what we were able to create. We managed to build something that is not just very architectural, but artistic and dynamic in function. Today, visitors and locals can use the bridge not just to get from point A to B, but utilize the span for respite, community, and revelry.