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Dr. Maria Feng, UCI civil engineering professor and researcher, explaining the sensors and vibration control on the Vincent Thomas Bridge.

GOOD VIBRATIONS: SENSORS CLOSELY MONITOR CALTRANS' BRIDGES
by  Maria Raptis
Issue Date: 11/2006

Statewide, Caltrans is working with academia experts to monitor the "health and wellness" of California's bridge structures.

Currently, Caltrans has a contractual agreement with the University of California at Irvine (UCI) for research involving the study of advanced vibration monitoring sensors that collect real-time data from traffic, wind and earthquake-induced vibration and movement on highway bridges, including here in District 7 on the Vincent Thomas Bridge in San Pedro.  

 

UCI Professor Masanobu Shinozuka, Chair, Civil and Environmental Engineering, and a world-renowned expert in earthquake and structural engineering, is leading the study.  He is responsible for the development of a computer model that will interpret much of the data analysis.  Dr. Maria Feng, a civil engineering professor and researcher at UCI’s Henry Samueli School of Engineering, has developed vibration sensors that will help to gauge and monitor the “health and wellness” of Caltrans’ bridges.

 

Earthquakes are a prime consideration in the design and retrofit of bridges on California’s transportation system which makes Caltrans’ Structure Design Services and Earthquake Engineering office in Sacramento responsible to define seismic hazards for structural projects.  “Sensor-based structural health monitoring is an emerging research area with a great potential to improve bridge safety,” said Li-Hong Sheng, Caltrans’ Senior Bridge Engineer. 

 

In order to predict performance in extreme events (especially since the Loma Prieta Earthquake in 1989), this engineering branch has for several years continued to sponsor research and development with universities.  “The Department is working closely with industry experts and academia to apply strategies to preserving and monitoring the safety and integrity of Caltrans’ bridge structures,” said Frank Quon, Deputy District Director, Operations. 

 

In District 7, and encompassing 2.2 miles of State Route 47, the Vincent Thomas (VT) Bridge in San Pedro was designed by Caltrans (then known as the California Division of Highways) who also owns and maintains it. The bridge has official duties having been dedicated as the City of Los Angeles’ welcoming monument to visitors and ships.  Today, this bridge carries a considerable volume of truck traffic from the southernmost slips of the Port of Los Angeles onto the Terminal Island Freeway (47) and eventually to the southern end of the Long Beach Freeway (SR-710) -- as well as commuters, residents and sightseers.  About 100,00 vehicles use the 43-year-old landmark suspension bridge daily.

 

Last month, while standing at the height of the VT Bridge deck, Dr. Feng, along with research associates and students, placed sensors, as small as a fingernail, onto fiber-optic cables that lead to a laptop computer. Within seconds, the sensors spat out data in the form of zig-zag vibration waves like that of a lie detector machine.  Caltrans plans to use such vibration data for real-time damage detection and to verify the seismic performance of the retrofitted bridge.  “The significant challenge that must be met is to acquire meaningful information concerning the structural health and measured data,” says Dr. Feng.

 

Recently, Dr. Feng was interviewed by the producers of “Wired Science,” a new KCET (PBS affiliate) television program, in conjunction with Wired Magazine, in preparation for a show featuring this VT Bridge research project, scheduled to air in January, 2007.

 

 “With proper interpretation,” added Sheng, of Caltrans’ Structure Design Services, “the data from the sensors can also reveal problems with the bridge structure, whether due to aging, deterioration or a destructive event, thus providing early warnings.”  His short answer to why it is important to invest in this research and development, he simply responds, “To improve mobility in California.” 

 

For more information on Dr. Feng’s research activities, visit her website at www.mfeng.calit2.uci.edu.

 

 

 

Real-time monitoring technology using sensors play an important role in minimizing maintenance and maximizing longevity and safety. The sensors and fiber optic cables link up to the laptop computer where the data is collected to analyze.