Tech Briefs

Seismic Evaluation of the Cooper River Bridge (by SC Solutions, Inc., California)

The design of the new Cooper River cable-stayed bridge in Charleston, South Carolina, was analysed by SC Solutions, California, using ADINA. The structure has a main span, two side spans and two anchor spans, for a total suspended span length of about 1005-m. It is currently the largest cable-stayed span in North America. The two diamond shaped towers (of height about 175-m) support a deck carrying 8 traffic lanes and a pedestrian walkway/bikeway. The main span utilizes a composite concrete deck with I-shaped steel edge girders. The pedestrian walkway/bikeway is cantilevered outside of an edge girder. The high level approaches also utilize composite steel construction with steel girders. Both high approaches are jointless over their full lengths, about 1326-m on the Charleston side and 637-m on the Mount Pleasant side.

Design checks of the seismic performance of the bridge were made, including the inelastic time history analysis of the main span unit and the West and East high level approach structures combined in a single model. This "global" model had about 55,000 degrees of freedom, and was subjected to spatially varying ground motion time histories.

Some details are that all towers and piles were modeled using ADINA moment-curvature elements; soil-structure interaction was modeled explicitly with plasticity-based truss elements; and pushover analyses of the stand-alone tower/foundation models were conducted to validate the characterizations of the physical behaviors.

The animation above shows the central part of the bridge under seismic loading (with the movements magnified 50 times). Such nonlinear simulations of course not only require the use of a powerful and reliable analysis tool — ADINA — but also a strong engineering experience in the modeling of seismic problems.

Central part of the Cooper River Bridge

Pushover analysis of bridge towers