Causes and prevention of splitting/bursting failure of concrete crossties: a computational study

PDFTech ReportRailroad tiesPrestressed concrete tiesFailure analysisFinite element methodRailroad safetyStress crackingRailroad tracksUnited StatesJohn A. Volpe National Transportation Systems Center (U.S.)Yu, HailingJohn A. Volpe National Transportation Systems Center (U.S.)United States. Federal Railroad Administration. Office of Research, Development, and TechnologyAGR-INFRASTRUCTURE-RailroadsNTL-RAIL TRANSPORTATION-Rail SafetyNTL-RAIL TRANSPORTATION-RAIL TRANSPORTATIONVolpe National Transportation Systems Center, Technical Reference CenterConcrete splitting/bursting is a well-known failure mode of concrete crossties that can compromise the crosstie integrity and raise railroad maintenance and track safety concerns. This paper presents a computational study aimed at better understanding the main contributing factors to this failure mode. Finite element models are developed for concrete crossties with different geometric and reinforcement configurations. The investigated factors include: steel reinforcement type, concrete release strength, presence of fastener shoulders, and cyclic dynamic loading. Five steel reinforcements with various surface geometries, including a smooth wire, three indented wires and a seven-wire strand, are studied. Three concrete release strengths are applied at 3,500, 4,500 and 6,000 psi, respectively. Static analyses of pretension release and dynamic analyses of repeated rail seat loading are conducted. The study concludes that low concrete release strengths, accompanied by underdeveloped steel-concrete bond for prestress transfer, are responsible for initial concrete material degradation patterns that can further deteriorate under cyclic dynamic loading and develop into macroscopic cracks consistent with the field observations. Based on these findings, this paper recommends (1) sufficiently high concrete release strengths during production and (2) development and implementation of a qualification test standard with dynamic loading cycles to ensure long term splitting/bursting performances of concrete crossties