Scope of Work
The following areas should be addressed as part of the independent structural review:
- Review Sound Transit conceptual proposals for stray current mitigation and recommend areas of further investigation, and design milestones through PE and final design. Specifically, designs for isolating stray current that avoids corrosion of the steel reinforcing and other metal elements of the existing floating bridge and transition spans.
- Review Sound Transit standard drawings for the light rail track and power system. Determine the extent of impact to LRT track system (including catenary poles, track ties, and safety rails) installation from embedded steel and moisture from lake effect on the bridge. Recommend design approaches for attaching the LRT track system to the pontoon, elevated roadway, and transition span decks that maintains the reinforcing steel, post-tensioning cables, other metallic imbeds; and limits existing concrete installation damage to an acceptable levels. Identify LRT operational factors, if any, from the avoidance of embedded steel bridge components during LRT track system installation should the material preclude full track system (bolts, plinths, ties) installation.
- Review the previous load test data, perform preliminary analysis as required to evaluate structural feasibility and recommend additional analysis needed to determine the operational “storm” limitation on the floating bridge in combination with LRT dead and live loads. Review weight mitigation measures for sufficiency of loads.
- Assess impact of weight mitigation measures on bridge life, effects of LRT track system on existing maintenance and operations policies, recommend new policies, maintenance criteria and potential work force and cost increases needed to accommodate LRT beyond existing bridge maintenance practices and budget, and recommend any additional analysis.
- Review the effects (including eccentricity) of the LRT dead/live loads and rails on the transition span expansion joints, bridge decks, and other bridge elements and make recommendations for design criteria.
- Review the proposed rail expansion joint design and provide any additional comment or suggestions to accommodate anticipated joint movements and any associated modifications to the bridge.