by Teresa Martin

Several years ago, Norfolk Southern’s Chief Bridge and Structural Engineer, Jim Carter contacted A&A with an idea. He was searching for a more efficient way to produce railroad ties used on open deck rail bridges. The current manual process is time consuming and not always accurate.

bridge tie replacement on open deck rail bridges

Bridge ties can be made of various types of wood but are usually hardwoods such as oak.  Due to environmental conditions and time and wear, they need to be replaced every five to ten years.  When it is time for replacement, either a bridge supervisor or an engineer from Bridges and Structures department will be dispatched with bridge plans in hand.  While they do take vertical measurements, they often do not take horizontal measurements, relying more on the original bridge drawings.  However, the original bridge drawings will likely not take into account any recent repair work or alteration.  The daps, or notches that are cut into the ties in order for them to sit directly on the bridge girders and to account for super elevation are all cut manually, and when made with inaccurate information, are prone to errors and are problematic when installing.

Mr. Carter asked if A&A could develop a more efficient and accurate way to produce the ties that needed to be replaced. He envisioned an automated procedure using a Computer Numerical Control (CNC) machine. A&A would work with tie manufacturers like Stella Jones and Koppers in order to streamline and standardize this process.

After several years, A&A was able to meet the goal of creating a more accurate process. Our staff is safety trained in eRail and Roadway Worker Training. We send our well trained crews to the field with total station instruments and can quickly acquire the information efficiently to achieve a comprehensive set of data to develop a model of the bridge. Through using a combination of programs: AutoCAD Civil 3D, Microstation InRoads and our own in house programming, we compute what it takes to get the optimum vertical and horizontal alignment. We then compute the daps and create a spreadsheet of information that can then be used with a CNC machine in order to cut the ties precisely and efficiently.

bridge tie replacement on open deck rail bridgesWe have found success in the process on projects in Virginia, West Virginia, Kentucky, North Carolina and New York. We envision working with the manufacturers and railroads across the country.

We have written a paper on the entire process that has been presented at the Virginia Railway Association and will be presented at the American Railways Engineering and Maintenance-of-Way Association, and the Railway Tie Association this Fall.

Share This