AN EXAMPLE OF THE USE OF WIND TUNNELS FOR INVESTIGATING THE AERODYNAMIC STABILITY OF BRIDGES

THE LONGS CREEK BRIDGE IS A CABLE-STAYED, ORTHOTROPIC GIRDER BRIDGE HAVING A MAIN SPAN OF 713 FT. 4 IN. AND A TOTAL LENGTH OF 1092 FEET. WHEN ERECTED IT WAS OBSERVED THAT THE BRIDGE WOULD VIBRATE IN VERTICAL FLEXURE WHEN THE WIND VELOCITY NORMAL TO THE BRIDGE WAS IN THE RANGE 25 TO 30 MPH. AMPLITUDES AS HIGH AS 8 IN. WERE OBSERVED. A TEMPORARY SOLUTION FOR DAMPING THE MOTION WAS DEVISED. WIND TUNNEL INVESTIGATIONS WERE THEN UNDERTAKEN TO OBTAIN A PERMANENT AERODYNAMIC SOLUTION AND IT WAS FOUND THAT THE BEHAVIOR OF THE BRIDGE COULD BE DUPLICATED IN THE MODEL EXPERIMENTS. VARIOUS MODIFICATIONS TO THE EXTERNAL SHAPE WERE EXAMINED, SOME OF WHICH SUCCESSFULLY ELIMINATED THE VIBRATION. THE MODIFICATION FINALLY ADOPTED INCLUDED SOFFIT PLATING BETWEEN THE GIRDERS AND TRIANGULAR EDGE FAIRINGS WHICH CONSIST OF A HORIZONTAL EXTENSION OF THE SOFFIT PLATING AND A SLOPING WEB. SINCE BEING MODIFIED THE BRIDGE HAS BEEN EXPOSED TO SEVERE WINDS, INCLUDING SOME WHICH WOULD HAVE PREVIOUSLY CAUSED MOTION OF THE BRIDGE. NO MOTION OF THE MODIFIED BRIDGE HAS YET BEEN OBSERVED. /RATAOC/

• Supplemental Notes:
  • 32 Pp, 12 FIG, 13 REF
• Corporate Authors:

  National Research Council, Ottawa /Can

  ,    
• Authors:
  • Wardlaw, R L
  • Ponder, C A
• Publication Date: 1969-10

Subject/Index Terms

• TRT Terms: Aerodynamics; Amplitude (Physics); Damping (Physics); Girder bridges; Stability (Mechanics); Velocity; Vibration; Wind; Wind tunnels
• Uncontrolled Terms: Change; Model tests
• Old TRIS Terms: Wind velocity
• Subject Areas: Bridges and other structures; Highways;

Filing Info

• Accession Number: 00208223
• Record Type: Publication
• Source Agency: Roads & Transportation Assoc /Canada
• Files: TRIS
• Created Date: Sep 13 1971 12:00AM