Computation models for assessing dynamic effects on underpasses in high speed railway lines

Abstract eng:
The scope of application of the IAPF-2007 Spanish Standard [1] shall include railway structures either with very short spans or embedded in the embankment, whenever the height of the median track running surface over the upper face of deck or over the highest point of its supporting structure is less than 2,5 m. Strictly speaking a dynamic computation of such structures is mandatory except for specific cases stated in paragraph 2.3.2 of Appendix B of said standard. Nevertheless, experience shows that usually this type of structures does not show resonance issues although for a significant number of cases vertical deck accelerations appear and would be non-compliant with the limits of IAPF because dynamic computation results are conservative whenever simplified models are used. Furthermore the dynamic analysis of this type of structures is difficult due to: a fully three-dimensional behavior (thus the structure cannot be made equivalent to a beam, which is a usual simplification in viaduct analysis), the influence of soil damping in side walls and top slab of structure, the importance of the concept of ‘added damping’ due to vertical vehicle-structure interaction as spans are extremely short, etc. However, the actual construction cost of this type of structures is much lower than a viaduct and thus a costly computational effort leading to assess its dynamic behavior would be hard to justify, for each one of the different scenarios that can occur along a railway line, especially when considering the abovementioned aspects and the need to use complex and customized computation tools. As a solution we propose the application of a simplified computation method allowing a dynamic analysis with a computational cost in accordance to the actual cost of the structure. This paper will present the computation method and several case studies, with added emphasis on the development of modal and harmonic analysis allowing to take into account the three-dimensional behavior of the structure.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket