"Non-Linear Rail/Structure Analysis for the

Elevated 'WMATA' Section F-8 Guideway"

by

Kare Hjorteset

Project Engineer

BERGER/ABAM Engineers Inc.

Federal Way, WA

Abstract

The Washington Metropolitan Area Transit Authority (WMATA) started extending the southern portion of the Green Line in 1996 and is now just finishing the line for train traffic. In association with Whitman Requardt & Associates, BERGER/ABAM prepared the guideway design of the elevated structure called Section F-8. The elevated structure section consists of 4,000 feet inbound and 4,000 feet outbound of single-lane structure, which includes an elevated station and elevated double crossover. BERGER/ABAM was responsible for the complete aerial structure preliminary design, load analysis, and final post-tensioning design. As part of the load analysis, the interaction between the continuous welded rails (CWR) and the elevated structure was modeled using GT STRUDL.

The interaction between the CWR and the elevated structure takes place through the direct-fixation rail fasteners, which have a non-linear force/displacement relationship. Therefore, the structure is modeled using non-linear modeling technique. Typically, the interaction forces are caused by temperature changes in the CWR and the elevated structure that produces strain changes and subsequently displacement changes between the CWR and the elevated structure. These interaction forces were predicted by applying appropriate temperature loads to the non-linear GT STRUDL model. In similar fashion, rail breakage was modeled in GT STRUDL, as well.

The following topics will be discussed during the presentation:

1. Overview of the project.

2. GT STRUDL modeling technique for direct-fixation rails.

3. Design criteria for CWR

a. Temperature loads

b. Rail stress limits for fatigue considerations

c. Rail gap-opening limitation in case of rail breakage to avoid derailment of train

4. Forces in fasteners, rails, and columns caused by temperature loads and rail breakage

5. Rail gap-openings caused by rail breakage.

 

Biographical Data

Mr. Hjorteset is a project engineer for BERGER/ABAM Engineers Inc. with over 14 years of experience. Previously, he worked 4 years with Berdal Strømme A.S. and Veritec A.S. in Norway. His professional experience includes design, analysis, inspection, cost estimating, and field engineering. Projects include buildings, transit, marine, and offshore structures.

 

Education

 

MS Civil and Structural Engineering, University of Washington, 1990

MS Civil Engineering, The Norwegian Institute of Technology, 1985