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Coronado Bridge: History, Construction & Facts

Instructor: Christopher Muscato

Chris has a master's degree in history and teaches at the University of Northern Colorado.

The Coronado Bridge is being recognized as an important landmark in its region. In this lesson, we'll explore the design and history of this structure, and see why the people of the area are so proud of it.

The Coronado Bridge

There's a simple philosophy found among bridge designers: if a crossing deserves to have a bridge, it deserves to have a great bridge.

Bridges represent technology, triumph over adversity, and ingenuity, so they tend to become important landmarks. Among the crossings to proudly boast a great bridge is the San Diego Bay in California, home to the award-winning San Diego-Coronado Bridge (more often simply referred to as the Coronado Bridge).

It took a while for people to decide whether or not the San Diego Bay really needed a bridge, but once they decided that it did, they knew they wanted a great one.

The Coronado Bridge
Coronado bridge

History

As far back as the 1920s, people were advocating for a bridge to connect Coronado and San Diego over the bay. At the time, however, the US Navy opposed the idea. They were worried that the earthquakes of the region would make the bridge prone to collapsing, which could result in Navy ships being stuck inside the bay.

It took roughly 30 years before the city of Coronado started seriously exploring the possibility of a bridge. By the 1950s, people knew they needed a quicker way to get from Coronado to San Diego.

Design

To design the bridge, California hired Robet Mosher as the principle architect. Mosher's job was to create a bridge that provided adequate transportation across the bay, left ship access to the bay unimpeded, and added an iconic landmark to the cityscape.

Framework

He proposed a basic box and girder style bridge, in which a prestressed concrete and steel deck would sit atop steel girders, resting on towers. To increase the strength and resistance of the bridge, Mosher decided to make an orthotropic roadway, which used a stiffening technique that was new to the USA (it was first used to make battle ships in Europe during World War II).

So, the bridge was strong, and eliminated the need for extra superstructures over the deck to disperse weight. Cars could drive directly on an orthotropic roadway, which made the entire structure lighter.

Aesthetics

In terms of aesthetic design, there are three things that really stand out about this bridge.

The mission-arch towers, as seen during construction
Coronado bridge towers

First are the towers. The bridge rests on 30 towers across the bay, but these aren't ordinary bridge towers. They are supported by a tall and tapered arch, meant to mimic the appearance of the Spanish mission church arches that dominate Southern California. In this way, the bridge acknowledges the architectural history of the region, and seeks to be a part of it.

The second notable design element is the bridge's color: blue. According to Caltrans (the California transportation authority that maintains the bridge), the structure constantly has to be repainted to maintain its distinctive color, but it's worth it. The blue connects the bridge to both sea and sky, natural elements that the bay area people are certainly proud of.

The blue color connects the bridge to sea and sky
Coronado blue bridge

Finally, we need to talk about the path of the bridge. The bridge does not take the shortest route across the San Diego Bay. Instead, it curves; making it longer than it has to be. Why?

At its highest point, the bridge has a clearance of 200 feet, enough to let an empty aircraft carrier pass underneath. However, to achieve this height, the towers supporting the bridge had to get progressively taller from the shoreline to the center. The curve was added to give the bridge the distance needed to achieve its height.

Already, the bridge elevated at a 4.67% grade. Any steeper, and it could become hazardous, so the only option was to make the bridge longer and maintain that grade. People of the region seem to like the curves, however, and the bridge has been applauded for its sleek, elegant design.

The bridge features a nearly 90-degree curve in order to create the length needed to elevate it
Coronado bridge curve

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