Laser vibrometer application on bridge cable tension measurements

To ensure the safety and integrity of tied arch bridges, it is crucial that tension levels in cables do not exceed their design levels. Currently, visual inspection is required since there are no reliable techniques that can accurately determine the tension levels of these cables. A possible approach would be to correlate the vibration measurements with the tensions in these cables. However, due to their long length, access to these cables for mounting contact sensors is not easy. An attempt has been made to use a He/Ne laser vibrometer for non-contact cable vibration measurements on a tied arch bridge. The objectives of this test are to assess the quality of vibration measurements from the He/Ne laser under regular daylight environment and to determine the vibration signatures of these bridge cables under ambient condition. The results of study indicate that using non-contact measurements, a quick and easy prediction of tension levels in bridge cables can be made. This paper presents the results of the study and presents discussion on the advantages of non-contact measurements and possible testing difficulties.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.