Portland Interstate MAX Yellow Line

Light Rail - Structure Interaction Analysis

The Interstate MAX Yellow Line, a 5.8-mile segment, connects the Expo Center in North Portland with downtown and the rest of the transit system.  SC Solutions was contracted by David Evans & Associates to perform an independent analysis of the Tri-Met IMAX light rail elevated structures.

An ADINA finite-element model of Section 10c was constructed with each of the four rails modeled discretely and the nonlinear fixity of the rails to the girders was considered.  Construction sequence was also incorporated into the analysis by birthing the rails following the application of dead load to the structure.  This complex 3-D model was analyzed for various types of rolling stock loads, including live load, emergency braking, acceleration and deceleration, rail break and other miscellaneous dead and live loads.  

The SC Solutions team applied all loads in the actual sequence of their occurrence and the rolling stock loads as if the trains were moving along the rail.  By using this approach, the team accounted for braking at intervals equal to the plinth spacing, rail break at each expansion joint, and north and south-bound trains on the track simultaneously.  SC Solutions’ post-processing software was used to rapidly sift through the load combination results and envelope structure and rail demands.  In this manner, we were able to meet a very tight delivery schedule.