Ask John Report: Timber cap replacement

摘要

Thanks to all of the AREMA Committee 10 and 7 members for their assistance in preparing this report. Today's rail traffic has seen an increase in both load limits and track speeds. One result of this trend is the record number of timber pile cap failures. To be sure, these caps can be replaced in-situ as shown below, but it is critical to ask why they are failing. Timber bridges have a useful life expectancy of approximately 60 years or longer and components of older bridges are naturally deteriorating and must be replaced. However, many of the timber caps are failing in shear and many of those are newer timbers. While some might argue that new timber caps do not have the structural strength required for today's loading and should be replaced with concrete caps, are there other factors that need to be considered?