Recommendations for Numerical Modeling for Rail-Structure Interaction Analysis

Rail-structure interaction (RSI) analysis is critical for the design of transit bridges and viaducts carrying continuous welded rail. The rail and its supporting structures are subject to different temperature loads and usually have different freedom of movement. The bridge and rail system are connected, and this creates complex, non-linear interaction between the two systems. RSI analysis is prescribed by most transit agencies in North America, especially in the case of long elevated guideways or bridges with curvature and for elevated guideways with direct fixation (non-ballasted) track. There are few guidelines on numerical modeling of the system, and the basis of the small number of recommendations is not clear. There is no consensus in the design codes or literature about which parameters will control analysis or how these parameters should be defined in the analytical models. This study evaluates the impact of three key model inputs on representative transit bridges. The impacts of these parameters are studied through parametric analysis, keeping all other factors constant and examining the effects on axial rail stress, rail break gap, and substructure forces. This study provides guidance to transit structure designers to determine the best method for modeling their structure in a rational manner, with recommendations on how to model rail fastener spring type, spacing of fasteners, and fastener restraint force for tangent and curved alignments.