Advancements of New Narrows Suspension Bridge Design in Tacoma, Washington

The suspended superstructure of the new Tacoma Narrows Suspension Bridge in Washington State consists of twin welded steel trusses with a continuous and integral orthotropic steel deck measuring over 1 mi in length. AASHTO M270 Grade 50 HPS 50W and HPS 70W steels are the materials of choice. The truss elements are fabricated of both closed-box and open I-sections. The bridge, including major components of the stiffening truss, was designed to allow for a future lower roadway or light-rail transit system. This paper discusses the design aspects of this 5,400-ft suspended superstructure, including the development of design details to satisfy performance requirements for serviceability, fatigue, wind, and seismic loading. Global superstructure and local component computer modeling techniques are presented as they relate to force, fatigue, and displacement demands and overall structural performance for the 150-year design service life. Fabrication and lessons learned are also discussed.