NEW DESIGN APPROACH TO LONG-SPAN OVERHEAD SIGN STRUCTURES

THE USE OF IMPROVED LONG-SPAN SIGN STRUCTURES IS REQUIRED TO MEET THE HIGHER SAFETY AND ALIGNMENT STANDARDS FOR MODERN HIGHWAYS. CURRENT SPECIFICATIONS IMPOSE RESTRICTIVE LIMITATIONS ON ALLOWABLE DEAD-LOAD DEFLECTIONS FOR SUCH STRUCTURES. THE BASIS FOR THESE LIMITATIONS INVOLVES THE ASSUMPTION THAT BOTH THE FUNDAMENTAL VIBRATION FREQUENCY OF THE STRUCTURE AND THE VORTEX SHEDDING FREQUENCY ARE IN HARMONY AT A DESIGN WIND SPEED OF 80 MPH. A STUDY WAS CONDUCTED TO EXAMINE THIS ASSUMPTION. THE RESULTS SHOW THAT IT DOES NOT HOLD FOR THE BASIC EQUATIONS APPLYING SPECIFIC PARAMETERS FROM ACTUAL STRUCTURAL DESIGNS. STANDARD LIGHT-GAGE STEEL POLES WOULD NOT HAVE BEEN DEVELOPED HAD SUCH A LIMIT ON THEIR DEFLECTION BEEN REQUIRED. THEREFORE, A CONSISTENT PHILOSOPHY WITH RESPECT TO THE DESIGN OF ROADWAY LIGHTING POLES AND OVERHEAD SIGN STRUCTURES IS DESIRABLE. DESIGNS FOR MONOTUBULAR STRUCTURES WERE COMPLETED FOR CLEAR SPANS UP TO 200 FT., SUFFICIENT TO SPAN 10 LANES OF DIVIDED TRAFFIC WITH ADEQUATE SAFE OUTSIDE SHOULDER CLEARANCE AND CAPABLE OF SUPPORTING FOUR FULL-SIZE FREEWAY SIGNS. SEVERAL SUCH STRUCTURES INVOLVING SPANS AS LONG AS 156 FEET WERE BUILT AND WERE IN SERVICE FOR 2 TO 3 YEARS. THE PERFORMANCE O THESE STRUCTURES IN WINDS OF GUST SPEEDS AS HIGH AS 65 MPH HAS BEEN EXCELLENT. IT IS CONCLUDED THAT MORE LIBERAL ALLOWABLE DEAD-LOAD DEFLECTIONS ARE PERMISSIBLE SINCE THIS NEW FREEDOM IN DESIGN MAKES POSSIBLE SIMPLE, EFFICIENT, SAFE, AND ATTRACTIVE LONG- SPAN HIGHWAY SIGN STRUCTURES. /AUTHOR/

• Record URL:
  • http://onlinepubs.trb.org/Onlinepubs/hrr/1971/346/346-001.pdf
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/isbn/0309019575
• Supplemental Notes:
  • Sponsored by Committee on Traffic Safety Barriers and Sign, Signal and Lighting Supports and presented at the 50th Annual Meeting. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
• Authors:
  • Pelkey, Ron E
• Conference:
  • 50th Annual Meeting of the Highway Research Board
  • Location: Washington District of Columbia, United States
  • Date: 1971-1-18 to 1971-1-22
• Publication Date: 1971

Media Info

• Media Type: Print
• Features: Appendices; Figures; References;
• Pagination: pp 1-10
• Monograph Title: Design of Sign Supports and Structures
• Serial:
  • Highway Research Record
  • Issue Number: 346
  • Publisher: Highway Research Board

Subject/Index Terms

• TRT Terms: Bridge members; Deflection; Design; Length; Overhead traffic signs; Specifications; Static loads; Structures; Traffic signs; Ultimate load design; Velocity; Wind
• Uncontrolled Terms: Bridge spans
• Old TRIS Terms: Limits; Wind velocity
• Subject Areas: Bridges and other structures; Design; Highways;

Filing Info

• Accession Number: 00203578
• Record Type: Publication
• ISBN: 0309019575
• Files: TRIS, TRB
• Created Date: Sep 13 1971 12:00AM