Building a Seismic-Ready Bridge – Part 3: End Bents and Hinges

One of the most intriguing areas of the new bridge is where the east and west approaches connect to the main span of the bridge. At these “end bents,” the column-supported approaches meet the cable-supported main span. These two types of structures will react different in an earthquake, so flexible connections are a must.

Special joints (above), designed by the MAURER company of Germany, and built by D.S. Brown based in Ohio, will enable controlled-swivel movements in three directions (vertical, longitudinal, and lateral) at these junctions to compensate for movements between the adjacent structures. This will be the first application of this sophisticated joint for a bridge in California.

Additionally, between each section of the bridge road deck are expansion joints and hinges, allowing each section to move independently to avoid structural damage during major ground shaking.

Within the hingers are shear keys. Similar to an electrical fuse, shear keys are a sacrificial, replaceable element to absorb the bulk of seismic forces. At certain energy levels, they are designed to “trip” to release the force of the quake.

Atop each column are spherical bearings to enable a sliding movement between the superstructure (the bridge deck) and the substructure (the columns).

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