FINITE ELEMENT ANALYSES OF THE EARTH PRESSURES AGAINST A BRIDGE PIER

THE WALLA WALLA DISTRICT OF THE CORPS OF ENGINEERS IS CURRENTLY CONSTRUCTING THE 1300-FOOT LONG GRANDAD CREEK BRIDGE ACROSS THE NORTH FORK OF THE CLEARWATER RIVER IN NORTHERN IDAHO. THIS PAPER DEALS WITH THE EARTH PRESSURES WHICH WILL DEVELOP AGAINST ONE OF THE BRIDGE PIERS AS A RESULT OF THE RELATIVELY STEEP EMBANKMENT SLOPE BETWEEN THE PIER AND THE ABUTMENT STRUCTURE. THE FOLLOWING DESIGN ASSUMPTIONS WERE MADE FOR ANALYTIC PURPOSES: THE PIER ACTS AS A RETAINING WALL OF INFINITE LENGTH, AND ALL OF THE SIDE AND THIRD DIMENSIONAL EFFECTS OF THE FILL BEYOND THE PIER ARE NEGLECTED. THE PIER FOUNDATION WILL BE MODERATELY WEATHERED BEDROCK. LITTLE OR NO HORIZONTAL MOVEMENT OF THE PIER CAN BE TOLERATED; THEREFORE, EARTH PRESSURES ARE COMPUTED FOR THE AT-REST CONDITION. FOR THE FINITE ELEMENT ANALYSIS, THE PIER FACE IS CONSIDERED TO BE A FIXED BOUNDARY. THE EMBANKMENT WILL BE CONTRUCTED OF ROCKFILL OR OF GRAVEL FILL WITH AN OUTER SHELL OF ROCKFILL. THE ANALYTIC PROCEDURE IS DESCRIBED. THE FOLLOWING POINTS ARE EMPHASIZED: (1) THE FINITE ELEMENT APPROACH TO A PROBLEM OF THIS NATURE APPEARS TO YIELD MORE REASONABLE VALUES THAN THE CLASSICAL RANKINE OR COULOMB APPROACHES. (2) THE SHAPE OF THE HORIZONTAL PRESSURE DIAGRAM AGAINST THE PIER RESULTING FROM A STEEPLY SLOPING BACKFILL IS NOT TRIANGULAR AS ASSUMED IN THE CLASSICAL APPROACHES. THE TRUE SHAPE IS PROBABLY UNIQUE TO THE PARTICULAR PROBLEM. (3) THE SOIL PROPERTIES OF THE EMBANKMENT ARE NOT CRITICAL WHEN STUDYING THE METHOD AND PATTERN BY WHICH THE PRESSURES DEVELOP IN A HOMOGENEOUS SECTION. THEY ARE IMPORTANT IN DETERMINING THE MAGNITUDE OF THE STRESSES AND DEFLECTIONS. (4) BY USE OF THE INCREMENTAL CONSTRUCTION PROCEDURE, THE DESIGNER CAN GET A MUCH CLEARER PICTURE OF THE MANNER BY WHICH THE PRESSURES DEVELOP AS WELL AS THE MAGNITUDE OF THE PRESSURES. (5) BY USE OF THE FINITE ELEMENT METHOD THE DESIGNER OBTAINS A COMPLETE PICTURE OF THE STRESSES AND STRAINS AT ANY POINT WITHIN THE SECTION BEING STUDIED. /AUTHOR/

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Filing Info

  • Accession Number: 00236293
  • Record Type: Publication
  • Report/Paper Numbers: pp 63-64
  • Files: TRIS
  • Created Date: Apr 17 1972 12:00AM