Modal analysis of multi-reference impact test data for steel stringer bridges

Catbas F., Lenett M., Brown D., Doebling S., Farrar C., Turer A.

15th International Modal Analysis Conference - Current Horizon for Structural Damage Detection (IMAC), Florida, United States Of America, 3 - 06 February 1997, vol.3089, pp.381-391 identifier identifier

  • Publication Type: Conference Paper / Full Text
  • Volume: 3089
  • City: Florida
  • Country: United States Of America
  • Page Numbers: pp.381-391


A comparative study on the postprocessing of experimental modal data from a full scale steel stringer bridge for damage identification is presented. The bridge was tested before and after removal of one of the bearing plates at one abutment. Frequency Response Functions, measured crt different spatial locations, are used to post-process the data using a Complex Mode Indicator function(CMIF) algorithm. Dynamic properties of the bridge show major differences between the two cases. In addition modal flexibility of the bridge is calculated for the measured degrees of freedom. Modal flexibility of the bridge shows good agreement with static instrumentation results under truck loading. The induced damage is successfully quantified for this loading case. The ''after-removal'' condition data was also post-processed at Los Alamos National Laboratory using the Eigensystem Realization Algorithm (ERA) in order to provide a distant check and correlation for the results. This paper briefly describes the two different algorithms and presents the results in both modal and flexibility space. Further the principal focus of this paper is the post-processing algorithms and one damage index, although a number of different damage identification indices are being used for varying levels and types of damage as part of the ongoing research project.