ABSTRACT
ABSTRACT: The Gerald Desmond Bridge is a vital link in the nation’s trade infrastructure and a major commuter corridor which connects Long Beach with Terminal Island. The Port of Long Beach intends to replace the existing deteriorating bridge with a 2000 ft long cable stayed bridge with 1000 ft main span and two 500 ft side spans. The 515 ft tall towers, which provide primary means of vertical support to the cable-stayed bridge, are relatively slender tall hollow reinforced concrete sections thus requiring assessment of possible buckling. The buckling resistance of the towers comes from the global structural system with the stay cables providing restraint to the top of the towers and the viscous dampers providing restraint at deck level. The octagonal tower shape at the connection to the pile cap tapers to a diamond in the upper part of the tower. This non-standard tower geometry is a signature architectural statement and can be constructed with fairly simple formwork; however, the constantly variable cross-section is an analytical challenge. The slenderness evaluation captured the unique boundary conditions of the bridge as well as the irregular tower geometry. This paper provides an in-depth discussion of this analysis. The bridge is located in an area of extreme seismic hazard. The non-linear time history analysis of the bridge includes simultaneous tri-axial earthquake accelerations as well as gravitational acceleration. This paper discuss the explicit nonlinear time history analysis performed for tower stability during an earthquake and show the tower remain stable and elastic after Functional Evaluation Earthquake (FEE) and 1000 year return period Safety Evaluation Earthquake (SEE) event.
