AN INVESTIGATION OF LOAD DISTRIBUTION CHARACTERISTICS AND LOAD CAPACITY OF SMALL TIMBER BRIDGES

BRIDGES WITH TIMBER DECKING ARE USED EXTENSIVELY THROUGHOUT THE SECONDARY ROAD SYSTEM IN NORTH CAROLINA. HOWEVER, SUCH BRIDGES PRESENT A MAINTENANCE PROBLEM DUE TO THE LOOSENING OF THE TIMBER DECKING CAUSED BY THE ACTION OF REPEATED MOVING LOADS. THE PROBLEM IS GENERALLY, AND TEMPORARILY CORRECTED BY REDRIVING THE PLAIN SHANK SPIKES WHICH ARE USED DURING CONSTRUCTION. A MORE POSITIVE METHOD OF SECURING THE DECKING IS OBVIOUSLY NEEDED. THE FOLLOWING REPORT COVERS A LABORATORY STUDY AND ANALYSIS OF TIMBER JOINTS CONNECTED WITH FOUR TYPES OF NAILS AND AN ADHESIVE. THESE JOINTS WERE SUBJECTED TO STATIC PULL- OUT TESTS AND TO FATIGUE TESTS AT 20, 40, 60 AND 80 PERCENT OF THE STATIC PULL-OUT LOAD. THE NAILS WHICH WERE TESTED WERE THE PLAIN SHANK TYPE, A HELICALLY THREADED /SCREWTITE/ NAIL, AN ANNULARLY THREADED /STRONGHOLD/ NAIL, AND A CEMENT- COATED PLAIN SHANK NAIL. THE ADHESIVE WAS DURO-LOK 150, A THERMOSETTING EMULSION. THE TIMBER USED IN THE INVESTIGATION WAS PRESSURE-CREOSOTED SOUTHERN PINE. ANALYSIS OF THE STATIC TEST DATA SHOWS THAT THE THREADED TYPE CONNECTORS HAVE SIGNIFICANTLY GREATER HOLDING POWER. THE CONNECTORS IN DESCENDING ORDER OF THEIR ULTIMATE STRENGTH UNDER STATIC LOADING ARE STRONGHOLD, SCREWTITE, CEMENT-COATED, AND PLAIN SHANK. THE REPEATED LOAD FATIGUE TESTS INDICATE THE SAME ORDER OF RELATIVE STRENGTH, BASED ON THE NUMBER OF CYCLES TO CAUSE A 1/2 INCH SEPARATION OF THE JOINT. THE PERFORMANCE OF THE ADHESIVE TYPE CONNECTION SHOULD NOT BE COMPARED WITH THE ABOVE DATA. HOWEVER, THE STATIC TESTS DO SHOW THAT THE ADHESIVE WILL BOND TREATED TIMBER TO A LIMITED EXTENT IF IT IS APPLIED UNDER CONTROLLED CONDITIONS. /BPR/

  • Supplemental Notes:
    • Hps-hpr 1/1/, BPR-9, NC ERD-110-Q
  • Corporate Authors:

    North Carolina State University, Raleigh

    Raleigh, NC  United States  27695
  • Authors:
    • Zia, P
    • MCDONALD, D
  • Publication Date: 1966-1

Subject/Index Terms

Filing Info

  • Accession Number: 00207781
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 1 1994 12:00AM