Modal Parameters Identification of Steel Frame Infrastructures


This project was completed during my summer internship (2016 summer) at Georgia Tech.


The Finite Element Analysis (FEA) and Eigensystem Realization Algorithm (ERA) are both widely used as techniques to analyze modal parameters of infrastructures. To demonstrate their efficiency and consistency, two practical steel frame structures were tested. The finite element model was built in sap2000 to generate modal parameters using FEA. Based on the response data under given excitation, modal parameters were derived using ERA. Based on the comparison of modal parameters, certain model-updating techniques were applied to the FE model, in order to obtain better results. Great performance and consistency of final comparison shows efficiency of ERA and the model updating techniques.


Wo, Z., He, J., and Wang, Y. (2016). Comparison of finite element method and eigensystem realization algorithm through the analysis of a steel frame bridge (preprint) [PDF]

Presentation Slides [PPT] [PDF]

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The Eigensystem Realization ALgorithm (ERA)

The Eigensystem Realization Algorithm (ERA) was proposed by Juang & Pappa in 1985. Their original publication can be searched or cited as below:

  • J.-N. Juang and R. S. Pappa, “An eigensystem realization algorithm for modal parameter identification and model reduction,” Journal of guidance, control, and dynamics, vol. 8, pp. 620-627, 1985

Scanned file of this paper can be downloaded from ResearchGate [PDF]

DIAMOND, a MATLAB toolbox developed by Los Alamos National Lab, is widely used to execute ERA and damage identification [paper]. The source code can be downloaded [here] 

Other useful materials:

  • Juan M Caicedo, “Practical guidelines for the natural excitation technique (next) and the eigensystem realization algorithm (era) for modal identification using ambient vibration”, Experimental Techniques, 35(4):52–58, 2011. [PDF]
  • Zhongyuan’s study notes on ERA [PDF]
  • Zhongyuan’s MATLAB code of ERA [Download]
  • Intro slides by Zhongyuan [PDF]

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