Estimating Deterioration in the Concrete Tie-Ballast Interface Based on Vertical Tie Deflection Profile: A Numerical Study
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Estimating Deterioration in the Concrete Tie-Ballast Interface Based on Vertical Tie Deflection Profile: A Numerical Study

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English

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  • NTL Classification:
    AGR-INFRASTRUCTURE-Railroads;NTL-RAIL TRANSPORTATION-Rail Safety;NTL-RAIL TRANSPORTATION-RAIL TRANSPORTATION;
  • Abstract:
    In ballasted concrete tie track, the tie-ballast interface can

    deteriorate resulting in concrete tie bottom abrasion, ballast

    pulverization and/or voids in tie-ballast interfaces. Tie-ballast

    voids toward tie ends can lead to unfavorable center binding

    support conditions that can result in premature concrete tie

    failure and possible train derailment. Direct detection of these

    conditions is difficult. There is a strong interest in assessing the

    concrete tie-ballast interface conditions indirectly using

    measured vertical deflections.

    This paper seeks to establish a link between the vertical

    deflection profile of a concrete tie top surface and the tie-ballast

    interface condition using the finite element analysis (FEA)

    method. The concrete tie is modeled as a concrete matrix

    embedded with prestressing steel strands or wires. The

    configurations of two commonly used concrete ties, one with 8

    prestressing strands and the other with 20 prestressing wires, are

    employed in this study. All models are three-dimensional and

    symmetric about the tie center. A damaged plasticity model that

    can predict onset and propagation of tensile cracks is applied to

    the concrete material. The steel-concrete interface is

    homogenized and represented with a thin layer of cohesive

    elements sandwiched between steel and concrete elements.

    Strand- or wire-specific elasto-plastic bond models developed at

    the Volpe Center are applied to the cohesive elements to account

    for the interface bonding mechanisms. FE models are developed

    for both original and worn concrete ties, with the latter assuming

    hypothetical patterns of reduced cross sections resulting from

    abrasive interactions with the ballast. Static analyses of

    pretension release in these concrete ties are conducted, and

    vertical deflection gradients along tie lengths are calculated and

    shown to correspond well with the worn cross sectional patterns

    for a given reinforcement type.

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