Case Studies : Cooper River Bridge : Conceptual Design Alternatives

HNTB was responsible for exploring steel alternatives for the Cooper River Crossing while another firm was responsible for exploring concrete alternatives. Therefore, this case study will focus on the steel alternatives.

Each steel design alternative is based on a 780 foot main span, which accommodates the 700 foot wide navigation channel, plus the 60 foot diameter pier protection devices (dolphins) at the base of each pier. Once the span length was decided, "several alternative bridge types for the steel alternate crossing of Cooper River were considered:"

  1. Parallel Chord Continuous Truss
  2. Tied Arch
  3. Variable Depth Continuous Truss
  4. Steel Box Girders
  5. Cable Stayed Girders
  6. Truss Tied Arch
  7. Cantilever Truss

HNTB's experience with bridges on numerous channel crossing projects, and initial cost studies on all alternatives, permitted elimination of some bridge types from detailed consideration. While technically feasible, and in some cases of striking appearance, the last four bridge types listed for the Cooper River crossing were deemed unable to compete economically at this site. The parallel chord continuous truss, tied arch, and variable depth continuous trussare believed to offer a more practical solution for this crossing. These three alternate designs are shown in Drawing 1.


Drawing 1

Only these three alternatives were given further detailed consideration for the Cooper River Bridge. (ref. 4)

No figures for this section.