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D&I Railroad - Truss Load Rating AnalysisD&I-Railroad 01_600x400.jpg

D&I Railroad - Truss Load Rating Analysis

CDI was retained by D&I Railroad to perform field inspection and load rating analysis on nine different steel trusses spanning the Big Sioux River on D&I Railroad between Canton, SD and Elk Point, SD. Trusses comprised of pony, through, and quadrangular through trusses, three with pinned connections and six with gusset plate connections. Member and connection load rating analysis was completed for each truss. Field inspection and load rating analysis was completed from January – July 2013. 


Truss spans varied from 123’-0” to 152’-3” and had original construction dates from the years 1899 to 1932, ranging from 82 – 115 years in age at the time of inspection. Field inspection and load rating procedures were completed according to the AREMA Manual and the FRA Bridge Safety Standards – Final Rule, dated July 15, 2010. The FRA requires that each structure be inspected every year with no more than 540 days between inspections. E-ratings (Normal Rating) on each structure were provided to D&I Railroad and recorded in a Bridge Management Program (BMP). 


Field inspections were completed to determine the current condition of each structure. Many of the structures were in fair condition considering their age, but some members warranted a reduction in member strength due to impact damage, section loss, pitting, pack rust, along with many others. Load rating analysis was completed by following the AREMA Manual and also with the use of RISA 3D and RISA Section software. Each truss was modeled and accurate loading information was applied to the model to determine precise member forces in each member and connection of the individual trusses. RISA Section was used to accurately model each built up member section and determine its member cross-sectional properties. Due to the age of the structures, each section was made from individual and readily available materials at the time they were constructed, made up of mainly angles, plates, channels, and lacing, which was then all riveted together. 


Results were obtained and compared to D&I Railroad’s equipment ratings. Modifications and/or speed restrictions were warranted on some of the trusses to allow safe passage of equipment. CDI worked closely with D&I Railroad to get accurate load rating results and to advise on any required modifications to ensure D&I Railroad was compliant with FRA regulations and their track was safe for all equipment.

Project Facts

D&I Railroad - South Dakota