Pivot and slide: Buro Happold’s revolutionary bridge design

How do you ensure stability in a seismic zone? The new Academy Museum of Motion Pictures in Los Angeles lies at the heart of one of the world’s most earthquake-prone regions, posing significant challenges for Buro Happold’s engineers.

We talk to senior structural engineer Andy Rastetter about creating custom, safe and long-lasting bridge designs.

“There is so much complexity to a project like this,” said Andy. “On the one hand we have an historic building to retrofit, trying to keep it as true to the original design as possible. “On the other hand, we have this massive reinforced concrete sphere, supported on base isolators. Two very different projects in one.”

Image: Renzo Piano Building Workshop

Buro Happold is working closely with Pritzker-Prize winning architect Renzo Piano and Gensler on a major renovation of the existing Saban Building and a soaring spherical structure that will house a 1000-seat theater and terrace. The two buildings required very different structural solutions. Due to complete this year, the fully renovated historic Saban building will be connected to the new theater via three bridges. These bridges will be anchored on the Saban Building and designed to pivot, moving with the sphere in the event of an earthquake.

During an earthquake, the theater will move up to five feet in every direction.
Andy Rastetter

How do you connect two such different structures safely? Andy explains, “During an earthquake, the theater will move up to five feet in every direction. To accommodate that, we have developed a series of custom connections that allow the bridge to experience this motion. If the theater moves left and right, the bridge rotates. We use specially coated movement joints made with low friction materials so they can move easily and don’t bind up over time due to corrosion.

“If the theatre moves in the other direction, that is, if it moves towards or away from us, we have designed sliding connections where the bridge attaches to the theater. All of these connections are custom designed by Buro Happold.”

Image: Renzo Piano Building Workshop

Seismic-proof structures

As well as seismic-proof bridges, the two buildings require specialist structural solutions. The Saban Building’s original steel and concrete structure needed strengthening in order to resist an earthquake’s forces (meeting structural requirements for Class A museum space).

After extensive analysis, our engineers decided that the 150-foot-diameter, orb-shaped theater required an unusual base-isolation system, ensuring that during an earthquake, base-isolators allow the theater to move up to 30 inches in any direction.

This is a one-of-a-kind project which required innovative and unprecedented structural solutions. By thinking outside of the box, we have been able to make the architectural dream a reality, and we have created a building that will inspire its visitors for years to come. This will surely be one of Los Angeles’ greatest cultural landmarks.
Andy Rastetter

Want to see more? Watch Andy explain how we’re engineering the Academy Museum of Motion Pictures below:

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