Steel Bars and Cables

This set of photographs illustrates some of the steel elements that went into building the San Francisco-Oakland Bay Bridge. The photograph on the upper left shows a welder working on an expansion dam on the western span. Temperature changes, settling, and other factors cause concrete to expand and contract, which can cause the concrete to crack. Expansion dams, or expansion joints, allow concrete to expand and contract without threatening the integrity of the structure as a whole.

The photograph on the upper right shows bundles of reinforcing steel, while the bottom photograph illustrates the scale of the cables used in the western span. These cables, from which the bridge deck is suspended, are composed of 37 strands. Each of these strands are in turn composed of 472 steel wires bound together.

Identification Information: Dept. of Public Works, San Francisco-Oakland Bay Bridge Construction Photographs (F2516:1-93).
Top Left: Expansion Dam, Span W1-W2, 06-02-1936: Box 12 (C5229), photograph 6-2306.
Top Right: Reinforcing Steel, 04/30/1935: Box 15 (C5230), photograph 7-702.
Bottom: South Cable Midspan W2-W3, 08/09/1935: Box 12 (C5229), photograph 6-1201.