Field testing and finite element analysis for evaluation of railroad bridges

Throughout the centuries, railroads have been the most important means of transportation. The capacity of railroads should be increased with the booming economy. In order to keep in step with an increased demand for freight, goods and services, New Jersey Department of Transportation increased the capacity of existing railroads to be able to increase the freight capacity. In New Jersey, a proposed increase of railcar weight limits from 263,000 lb to 286,000 lb raised additional concerns for the passenger rail systems since the bridges in the passenger rail system were not designed based on the increased freight railcar weight. The effect of increased freight railcars on passenger rail systems must be evaluated.;The impact of the proposed increase freight railcars on three rail road bridges in New Jersey is investigated through the study presented herein. The AREMA Specifications were utilized to estimate the load rating of the bridge. Moreover, strain transducers were implemented to the structural members of Bridge A, one of the selected bridges, to collect strain measurements. Various measurements were performed to measure the deflection in companion with the strain measurements by means of reflective target tapes and Laser Doppler Vibration Unit. A total of 6 tests were performed with the passenger railcars that NJ Transit provided the axle configuration and axle weights.;Additionally, a three dimensional finite element (FE) model was developed to evaluate the behavior of three bridges under 286,000 lb railcar on a software program ABAQUS (Version 6.8.1). The recorded deflection and strain readings from the strain transducers and Laser Doppler Vibration Unit were utilized to calibrate the three dimensional FE model. Results from AREMA evaluation procedure and those from FE Model were compared.;A considerable difference arose between finite element analysis and simple beam analysis based on AREMA Specifications. It was found out that the bridge has more capacity to allow the increase of the freight railcar according to the finite element analysis. A more conservative approach was adopted in AREMA Specifications.