DEVELOPMENT AND EVALUATION OF BREAK-AWAY COLUMNS FOR SIGN BRIDGES

TESTS ARE REPORTED OF A BREAK-AWAY SUPPORT FOR OVERHEAD SIGN BRIDGES AT THE TEXAS TRANSPORTATION INSTITUTE'S HIGHWAY SAFETY RESEARCH CENTER. BREAK-AWAY FEATURES ARE EMPLOYED AT THE BASE OF EACH SUPPORT COLUMN. THE UPPER END OF THE COLUMN IS BOLTED TO THE TOP CHORDS OF THE SIGN BRIDGE TRUSS, AND THE COLUMN IS ATTACHED TO THE BOTTOM CHORDS OF THE TRUSS BY A PIN CONNECTION. WHEN THE SUPPORT COLUMN IS STRUCK BY AN ERRANT VEHICLE THE BASE CONNECTION DISENGAGES, THE VEHICLE LOAD NEAR THE BASE PRODUCES A SHEARING FORCE AT THE UPPER CONNECTION CAUSING THE BOLTS TO SHEAR, AND THE COLUMN PIVOTS ABOUT THE PIN CONNECTION. THE SUPPORT SWINGS UPWARD, CLEARING THE VEHICLE. THE PENDULUM BEHAVIOR OF THE COLUMN PRODUCES A SUBSTANTIAL IMPACT FORCE ON THE LOWER CHORDS OF THE TRUSS. AN ENERGY ABSORBING DEVICE WAS DESIGNED TO DISTRIBUTE THIS LOAD TO THE TRUSS MEMBERS. TEST RESULTS SHOW THAT THE SUPPORT COLUMNS, OVERHEAD TRUSS, AND THE ENTIRE STRUCTURE HAVE SUSTAINED THE IMPACT FORCES PRODUCED BY VEHICLES COLLIDING AT 25 TO 55 MILES PER HOUR, HEAD-ON AND AT AN ANGLE OF 15 DEGREES. A MATHEMATICAL SIMULATION WAS DEVELOPED OF THE SUPPORT POST WHICH PREDICTS IMPACT BEHAVIOR. OUTPUT FROM THIS MATHEMATICAL MODEL WAS VERIFIED BY SIX FULL-SCALE CRASH TESTS.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/oclc/1587330
• Supplemental Notes:
  • pp 10-11, 3 FIG
• Authors:
  • Olson, R M
• Publication Date: 1970-4

Media Info

• Serial:
  • Texas Transportation Researcher
  • Publisher: Texas Transportation Institute
  • ISSN: 0040-4748

Subject/Index Terms

• TRT Terms: Breakaway supports; Crash tests; Crashes; Energy absorption; Impacts; Mathematical models; Overhead traffic signs; Testing
• Subject Areas: Highways; Research; Safety and Human Factors;

Filing Info

• Accession Number: 00220938
• Record Type: Publication
• Files: TRIS
• Created Date: Jul 27 1970 12:00AM