Addition of railroad to the Tagus river suspension bridge

The Tagus River Suspension Bridge in Lisbon, Portugal was opened to four lanes of traffic in 1966, and is now being reconstructed to carry six traffic lanes plus two railroad tracks. The original design for the bridge included a future provision for railroad through the addition of cable stays. During preliminary design for the present strengthening, it was found that a more efficient solution is a system of supplementary externally anchored suspension cables which will be placed above the existing main cables. The trains will run on a new orthotropic floor system located at the bottom chord of the stiffening truss. Construction started in early 1996 and is expected to be completed in 1998. The design included wind tunnel testing, a detailed two-tier seismic analysis, and a time-history analysis of train vibration effects on vehicular passengers.