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Public Works

Constructing Bridges and Walls, Part 1 - Piers

pier diagramBridges must be strong. When a long bridge is being constructed, bridge bents – commonly referred to as “piers” – are used to support the bridge.

Piers consist of three main parts: cap, column and foundation.

The pier cap is at the top of a column. The pier cap has a raised portion – the beam seat -- in which the beams of the bridge are positioned.

The 28th / 31st Avenue Connector Bridge Pier has four columns for support. The columns and their caps are both made of concrete that is reinforced with steel.

Since the cap and columns bear the weight of the bridge, the foundation for the columns is very important. The goal is for the weight of the bridge to be “transferred” to the ground below the bridge.

A bridge engineer carefully selects the type of foundation based on many factors including location and subsurface conditions. Pier foundations for the 28th / 31st Avenue Connector Bridge were constructed by drilling a shaft into rock and then filling the shaft with reinforced concrete.

drilled shaft pour column pour cap pour completed bridge pier