IMPLEMENTING IMPROVED COMPOSITE TIE DESIGN AND TESTING GUIDELINES INTO THE AREMA MANUAL FOR RAILWAY ENGINEERING

摘要

Engineered polymer composite (EPC) ties offer a potential alternative to solid sawn timber ties (also known as wood ties), particularly in areas of high rot and high decay. Through research sponsored by the Federal Railroad Administration (FRA), in collaboration with the Association of American Railroads' (AAR) Strategic Research Initiatives Program, EPC ties are being studied to improve design and testing recommendations published in the AREMA Manual for Railway Engineering, Chapter 30 - Ties (1). As these ties are made primarily out of plastic, their material properties and behavior differ significantly from timber ties. EPC ties have been implemented successfully in select cases; however, they have an inconsistent performance history. Failure modes of EPC ties have primarily included spike-hole cracking and center cracking. Existing AREMA laboratory qualification testing has not proven effective in identifying these failure modes prior to in-track installation, thus highlighting the need for further study. Recent research has led to an improved understanding of how EPC tie and fastener systems perform and how they should be tested. Updates to EPC tie lateral resistance, bending strength, bending stiffness, and fastening system recommendations are discussed, including two new ballots based on this research and approved for the 2018 AREMA Manual. Ongoing work related to the effects of thermal expansion/contraction of EPC ties and the development of two new EPC tie laboratory fatigue tests are also presented. Implementing research-driven testing methods and best practices will serve as tools for EPC tie suppliers and railroads to evaluate the performance and consistency of improved tie and material designs.