DAMPING AND FREQUENCY MEASUREMENTS ON EIGHT BOX GIRDER BRIDGES

Full scale dynamic tests are reported on eight box girder bridges to measure frequencies, damping levels and mode shapes. All the bridges had concrete decks on single or twin steel box girders. The effects of amplitude of movement and temperature of asphalt on damping were examined on four of the bridges. Logarithmic decrement values between 0.023 and 0.18 were measured in the 1st bending modes and between 0.05 and 0.22 in the 1st torsion modes. The results show that no single value of damping applies generally for box girder bridges. No clear relationship was found between asphalt temperature and damping - but this may require further examination for wholly steel bridges. Damping increased with amplitude in the 1st bending mode but this trend was less obvious in the 1st torsion mode. Damping levels were generally similar for nominally identical structures but differences between two of the bridges show that results for one structure cannot be used with confidence to predict damping levels for other structures. It was apparent that support conditions have a significant effect on damping. It is recommended that the factors affecting damping should be examined in detail in laboratory tests in order to obtain an understanding of the mechanism for dissipating energy in bridge structures. (A) /TRRL/

• Corporate Authors:

  Transport and Road Research Laboratory (TRRL)

  Wokingham, Berkshire  United Kingdom 
• Authors:
  • LEONARD, D R
  • EYRE, R
• Publication Date: 1975

Language

• English

Media Info

• Features: Figures; References; Tables;
• Pagination: 30 p.
• Serial:
  • Issue Number: 682

Subject/Index Terms

• TRT Terms: Amplitude; Bending; Box girders; Bridges; Damping (Physics); Deflection; Dynamic tests; Electromagnetic frequencies; Energy; Girder bridges; Measurement; Temperature; Torsion
• ITRD Terms: 6988: Amplitude; 3474: Box girder; 3455: Bridge; 5559: Damping; 5586: Deflection; 213: Energy; 6997: Frequency; 6136: Measurement; 6722: Temperature; 5512: Torsion
• Subject Areas: Bridges and other structures; Construction; Design; Energy; Highways; I24: Design of Bridges and Retaining Walls; I53: Construction of Bridges and Retaining Walls;

Filing Info

• Accession Number: 00131795
• Record Type: Publication
• Source Agency: Transport and Road Research Laboratory (TRRL)
• Report/Paper Numbers: R&D Rept.
• Files: ITRD, TRIS, ATRI
• Created Date: Jun 5 1976 12:00AM