COMPARISON OF MEASURED AND COMPUTED ULTIMATE STRENGTHS OF FOUR HIGHWAY BRIDGES

FOUR DECK GIRDER HIGHWAY BRIDGES IN TENNESSEE, LOCATED IN AN AREA TO BE FLOODED AS A PART OF A TVA RESERVOIR, WERE TESTED TO FAILURE UNDER STATIC LOADING. THE ULTIMATE LOAD FOR EACH BRIDGE, DEFINED AS THE MAXIMUM LOAD-CARRYING CAPACITY OF THE BRIDGE, WAS MEASURED. THIS MEASURED LOAD WAS COMPARED TO LOADS THAT WERE COMPUTED BY STRAIN COMPATIBILITY RELATIONS IN WHICH ACTUAL STRESS-STRAIN PROPERTIES OF THE MATERIALS WERE USED AND THE ENTIRE BRIDGE INCLUDING CURBS WAS ASSUMED TO ACT AS A WIDE BEAM SPANNING BETWEEN SUPPORTS, AND BY THE 1971 INTERIM SPECIFICATIONS OF AASHO, IN WHICH THE CAPACITIES OF ALL GIRDERS WERE SUMMED. IN BOTH METHODS, A FLEXURAL MODE OF FAILURE WAS ASSUMED. ALSO, THE LOAD CAUSING FIRST PERMANENT SET WAS COMPUTED AND COMPARED WITH THE MEASURED LOAD. THE ANALYSICAL METHOD BASED ON STRAIN COMPATIBILITY PREDICTED THE ULTIMATE CAPACITY OF 3 OF THE BRIDGES WITHIN 9 PERCENT. EACH BRIDGE FAILED IN A FLEXURAL MODE. COMPOSITE ACTION WAS LOST IN THE PRESTRESSED CONCRETE BRIDGE PRIOR TO FLEXURAL FAILURE, WITH A RESULTING REDUCED LOAD CAPACITY. THE LOADS BASED ON AASHO SPECIFICATIONS GAVE A LOWER BOUND TO THE ACTUAL ULTIMATE LOADS FOR EACH BRIDGE. THE LOAD CAUSING FIRST PERMANENT SET IS LESS READILY IDENTIFIABLE, EITHER THEORETICALLY OR EXPERIMENTALLY, THAN IS THE ULTIMATE LOAD. THE METHOD GIVEN IN THE AASHO SPECIFICATIONS FOR LIMITING OVERLOAD ON THE BASIS OF FIRST PERMANENT SET APPEARS REASONABLE. /AUTHOR/

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 38-49
  • Monograph Title: Loading history of bridges
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00209706
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Aug 7 1972 12:00AM