IV. Case Study

1. The Vincent Thomas Bridge, San Pedro, CA

The Vincent Thomas Bridge is located in San Pedro, CA. It serves as an artery in Los Angeles harbor. Instrumented by
California Strong Motion Instrumentation Program, dynamic measurements of this bridge of both ambient and earthquake
excitations at various time spans have been studied by different groups of researchers using different identification
techniques. There was also finite element modeling for this bridge; seismic retrofit was also undertaken at the bridge.
The structure itself is a long span cable suspension bridge. The earthquake records include the Whittier (1987) and
Northridge (1994) earthquakes. The unique instrumentation and research history of the bridge has made it very well known
in the community of system identification in structural engineering. It might be considered as a benchmark problem which
was developed throughout many researchers’ efforts and evolves naturally through the time. It will be very interesting
to see how a real-world infrastructure can be modeled in different perspectives.

General information
Facts
Link to  CalTran
Seismic Retrofit

A preliminary study on this bridge can be found -
An analysis of the dynamic characteristics of a suspension bridge by ambient vibration measurements
Abdel-Ghaffar, A. M. and Housner, George W. (1977) An analysis of the dynamic characteristics of a suspension bridge
by ambient vibration measurements.

Finite Element Modeling of the bridge can be found in this study –
“Seismic Performance Evaluation of Suspension Bridges”,
Niazy, A. M., Ph.D. thesis, University of Southern California, 1991.

A system identification study based on a time domain approach can be found -

System Identification of the Vincent Thomas Suspension Bridge Using Earthquake Records,
Smyth, A.W., Pei, J.S., and Masri, S.F., Earthquake Engineering and Structural Dynamics, 32, 339-367, 2003.
System Identification of the Vincent Thomas Suspension Bridge Using Earthquake Records
System Identification and Damage Detection of a Long-Span Suspension Bridge based on its Dynamic Response
to Major Earthquake Excitations,
Smyth, A.W., Masri, S.F., Abdel-Ghaffar, A.M, and Nigbor, R.N., 12th World Conference on Earthquake Engineering,
Auckland, New Zealand, Oct. 2000

Another system identification approach based on the ERA and OKID can be found – 

Obtaining Refined First-Order Predictive Models of Linear Structural Systems,
Lus, H., Betti, R. and Longman, R.W., Earthquake Engineering and Structural Dynamics, 31, 1413-1440, 2002.
Identification of Linear Structural Systems Using Earthquake-Induced Vibration Data,
Lus, H., Betti, R. and Longman, R.W., Earthquake Engineering and Structural Dynamics, 28, 1449-1467, 1999.
Damage Identification in Linear Structural Systems

Another study available online on the Vincent Thomas Bridge can be found here –
Seismic Analysis of Long-Span Suspension Bridges

 2. ASCE SHM (Structural Health Monitoring) Benchmark Problem

This benchmark problem has several phases using both simulated and experimental data of a multi-story building model
at various “health” stages including undamaged and damaged to different degrees. It provides a platform to evaluate
various system identification techniques in modeling a linear structural system when the measurements are contaminated
with noise. Problem descriptions, data sets, publications and minutes can be downloaded in this well-maintained website.

For other benchmark problems in structural control, a quick reference can be made to Dr. Satish Nagarajaiah’s webpage.