Structural Integrity of a Bridge

The California Department Transportation (CALTRANS) funded a research and development project to investigate methods to assess the structural integrity of bridges following earthquakes as well as the structural degradation accumulated over years of use. A project team, consisting of Navcon Engineering, Vibrant Technology & the University of Texas was assembled to develop the basic methodology and conduct two proof of concept tests/analyses.

The "general" approach was to:

  1. develop a finite element model (FEM) of a bridge in its original as-built condition,
  2. conduct a modal test of the bridge in its as-built condition and verify the analytical model,
  3. conduct a modal test following a seismic event and compute a "pseudo" stiffness matrix,
  4. compare the "pseudo" stiffness matrix with the analytical stiffness matrix to identify areas of structural degradation.

The project was conducted by:

  • Navcon Engineering was responsible for conducting the modal tests including the data acquisition and modal analysis.
  • Vibrant Technology provided the modal software and assisted with the modal data acquisition.
  • University of Texas created the finite element models and conducted the degradation analyses.


The photo shows one of the two suspension bridges tested and analyzed during this project. The bridge was excited using two methods, an APS Dynamics Model 400 electro-dynamic shaker and an impact mass. The test data was acquired using a HP 3566A multi-channel analyzer, PCB Piezotronics signal conditioning, accelerometers and force sensors and Vibrant Technology modal software, ME'Scope.