Finite element analysis of contributing factors to the horizontal splitting cracks in concrete crossties pretensioned with seven-wire strands.

Details

• Creators:
  Yu, Hailing
• Corporate Creators:
  John A. Volpe National Transportation Systems Center (U.S.)
• Corporate Contributors:
  United States. Department of Transportation. Federal Railroad Administration
• Subject/TRT Terms:
  • Bond strength (Materials)
  • Bonding
  • Finite element method
  • Railroad ties
  • Prestressed concrete ties
  • Simulation
  • Wire
  • Stresses
  • Stress cracking Crossties
• Publication/ Report Number:
  JRC2017-2256
• Resource Type:
  Research Paper
• Geographical Coverage:
  United States
• Corporate Publisher:
  American Society of Mechanical Engineers
• Abstract:
  This paper employs the finite element (FE) modeling ; method to investigate the contributing factors to the “horizontal” ; splitting cracks observed in the upper strand plane in some ; concrete crossties made with seven-wire strands. The concrete ; tie is modeled as a concrete matrix embedded with prestressing ; steel strands. A damaged plasticity model that can predict the ; onset and propagation of tensile degradation is applied to the ; concrete material. An elasto-plastic bond model developed inhouse ; is applied to the steel-concrete interface to account for the ; interface bond-slip mechanisms and particularly the dilatational ; effects that can produce the splitting forces. The pretension ; release process is simulated statically, followed by the dynamic ; simulations of cyclic rail seat loading. The concrete compressive ; strength at which the pretension in the strands is released, or ; release strength, affects both the concrete behavior and the bond ; characteristics. Three concrete release strengths, 3500, 4500 and ; 6000 psi, are considered in the simulations. Concrete tie models ; without and with a fastening system are developed and simulated ; to examine the effect of embedded fastener shoulders and ; fastener installation. The fastener shoulders are seated relatively ; deeply reaching between the two rows of strands. ; There is instant concrete material degradation adjacent to ; the strand interfaces near the tie ends upon pretension release. ; Without the fastening system in the model, the 3500 psi release ; strength leads to a high degree of degradation that is coalesced ; and continuous in the upper and lower strand planes, ; respectively. The damage profiles with the higher release ; strengths are more discrete and disconnected. Dynamic loading ; appears to increase the degree of degradation over time. In all ; cases, the upper strand plane is not dominant in the degree or the ; extent of material degradation, in contrast to the field ; observations that the horizontal splitting occurred in the upper ; strand plane only. ; Further simulations with the fastener model at 3500 psi ; concrete release strength indicate that the fastener installation ; process does not worsen the damage profile. However, the ; presence of fastener shoulders in the concrete matrix changes the ; stress distribution and redirects more concrete damages to the ; upper strand plane, while leaving disconnected damages in the ; lower strand plane. Under repeated dynamic rail loading, this ; potentially reproduces the exact upper strand plane, horizontal ; cracking pattern observed in the field. Subjected to further ; experimental verification, the FE analyses identify three ; contributing factors to the horizontal macro-cracks occurring at ; the specific upper strand level: (1) relatively low concrete release ; strength during production, (2) embedded fastener shoulders that ; redistribute concrete damages to the upper strand plane, and (3) ; a sufficiently large number of dynamic rail loading cycles for the ; microscopic damages to develop into macro-cracks. The number ; of dynamic loading cycles needed to produce macro-cracks ; should increase with the increased concrete release strength.
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• Format:
  PDF
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/12461/dot_12461_DS1.pdf
• File Type:
  [PDF - 1.05 MB]
• Collection(s):
  Volpe Center ; Federal Railroad Administration
• Main Document Checksum:
  urn:sha-512:9ea9870516ae81145eb5b5a8e2639fda91e550a3203be416e3052539918ff7ef98e37af808910ef35b5b9ce4564e028f939ec31b07d368c9679ba4576ba7e620