Working Paper 2A.3:
Structural Assessment of Rail on the Bay Bridge
Bay Bridge Rail Alternatives Study
Metropolitan Transportation Commission
Nelson/Nygaard Consulting Associates
Ove Arup & Partners
LTK Engineering Services
Simon Martin-Vegue Winklestein Moris
and Associated Consultants
22 October, 1999
I. Executive Summary
As part of the Bay Bridge Rail Feasibility Study, this working paper reports on the available structural capacity and needed structural improvements for restoring rail on the San Francisco - Oakland Bay Bridge. This study is restricted to the seismically retrofitted West Spans, Yerba Buena Island and the proposed East Spans replacement currently being designed.
Over the 60+ year life of the structure, significant changes have been made with the 1959 removal of rail, the proposed replacement of the East Spans, and recently awarded seismic retrofit contracts for the West Spans. The potential next phase in the Bay Bridge's history, the addition of rail, would overshadow previous engineering and construction work except the original construction completed in 1936.
Four rail options were defined in Working Paper 2A.2 for this study. The vehicle types and weights ranged from BART, the lightest (least structural impacts based on vehicle weight) at 1,170 pounds per linear foot (plf) of track, to the new 'Acela' train sets developed for the Northeast Corridor 'High Speed' service weighing 1,800 plf.
Rail would not be travelling at high speeds over the bridge. Due to vertical and horizontal geometric restrictions, the operating speeds are estimated for this study to be roughly 50 miles per hour.
A. West Spans
The following ar the main findings form assessment of the West Spans:
B. East Spans
Review of the design criteria and the bridge deck cross-sections has yielded the following information on the East Spans:
C. Yerba Buena Island
Very preliminary costs place the structural work alone in the $3.3 billion range. Again, this is just the costs to improve the structure without actually providing the track, track fasteners, power systems and signaling. This price covers the length from Harrison Street and out Rincon Hill near the San Francisco Anchorage, up onto the west spans, through Yerba Buena Island, across the East Spans to the Toll Plazas in the Oakland.
E. Future Study
This study concludes with approximate alignments of rail routes and projected ridership for the various rail systems. One very direct way of deciding to pursue rail on the Bay Bridge would be to compare the estimated construction costs with other means of bringing rail across the Bay, particularly tunneling or another bridge crossing.
Findings in this report should be viewed as extremely preliminary. In-depth analysis of the seismically retrofitted structures must follow this feasibility study. The analysis should use three-dimensional non-linear models to capture the full behavior and strength of the western spans under service loads and seismic excitation. Costs should be re-evaluated once details of the widening, strengthening and seismic retrofit have been developed.