Seismic analysis and base isolation retrofit design of a steel truss vertical lift bridge

摘要

Bridges with steel superstructures are frequently ideal candidates for seismic retrofit utilizing base isolation. The seismic assessment and retrofit design of the Three Mile Slough Bridge included both the evaluation of a conventional retrofit scenario and a base isolation retrofit scenario. The structure is a five span riveted steel truss bridge with a vertical center lift span attached to the top of each 100 ft lifting tower by steel cables. The comprehensive analysis model had the following properties: 1. Non-linear springs captured soil-foundation structure interaction (SFSI); 2. Moment-curvature elements modeled reinforced concrete pier columns and capbeams; 3. Inelastic truss elements modeled isolation bearings; 4. Cable elements modeled the cable supporting the counterweight. This paper discusses a non-linear time history analysis using ADINA. Also, the modeling and evaluation of the performance in the isolation bearings is discussed.