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https://nap.nationalacademies.org/catalog/27432/critical-issues-in-transportation-for-2024-and-beyond

AN EXPERIMENTAL INVESTIGATION OF THE STRESSES, STRAINS AND DEFLECTIONS IN A LAYERED PAVEMENT STRUCTURE SUBJECTED TO DYNAMIC LOADS

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Filing Info

  • Accession Number: 00206647
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 1 1994 12:00AM