Research

Project Number:
01-10

Research Project:
Smart Damping Devices for Monitoring the Health of Bridge Structures

P.I. Name & Address:
Erik Johnson
Assistant Professor
Department of Civil and Environmental Engineering, KAP210
University of Southern California
Los Angeles, CA90089-0193
Tel: (213) 740-0610
Fax: (213) 744-1426
Email: JohnsonE@usc.edu

Project Objective:
The objective of this project is to begin studying how to best use variable stiffness and damping devices to improve structural health monitoring of bridges.

Project Abstract:
Aging infrastructure is a significant concern for today's urban environments.Various reports, including those by the US DOT, have documented the number of bridges in the U.S. that are in less than ideal condition.Monitoring long-term degradation of bridge structures - currently dominated by manual, visual inspection - can be a time-intensive and costly procedure.Determination of the integrity of bridges in the aftermath of a serious earthquake will dictate effective prioritization of post-disaster actions, such as routing emergency crews to affected areas and the rerouting of emergency vehicles and the general public to safe lifelines through the city.

Some autonomous structural health monitoring and damage detection methods based on ambient vibration have been considered for civil engineering structures.Accurate characterization of the health of a structure necessitates precise knowledge of localized damage within the structure.However, current structural monitoring methods that use global structural vibration methods are largely ineffective for detecting localized damage. The methods that can provide localized information require a cost-prohibitive number of sensors distributed throughout the structure.

One promising alternate approach would be through use of incremental changes in the structure stiffness and damping characteristics, but this is not readily accomplished in a conventional structure. A new technology that shows promise for improving the performance of structures subjected to natural hazards is variable stiffness and damping devices (VSDDs). In addition to providing near optimal damping strategies for vibration mitigation, these low-power and fail-safe devices can also provide the parametric changes required for health monitoring.

The focus of this project is to begin studying the use of VSDDs to improve structural health monitoring and damage detection of bridges.VSDD models will be integrated with simple dynamic models of bridge motion.The responses of the combined system due to ambient excitation (e.g., wind, microtremor, etc.) will be simulated.Several structural identification methods will be used to process the simulated responses to determine dynamic characteristics indicative of damage.By changing the type and actions of the VSDDs, multiple "fingerprints" of the structural response will be obtained.It is expected that the integration of VSDD technology with structural health monitoring will capitalize on their synergies to provide structures that are more reliable, have superior performance, and are less-costly to maintain.

Task Descriptions:
1.Develop control-oriented bridge models10/31/01
2.Identify excitation models10/31/01
3.Incorporate controllable discrete-stiffness device into model11/31/01
4.Simulate and collect data12/31/01
5.Use modal analysis to identify structural characteristics02/28/02
6.Incorporate controllable discrete-damping device into model03/31/02
7.Simulate and collect data04/30/02
8.Use ERA or least squares method to identify structural characteristics06/30/02

Milestones, Dates:
Draft Final Report07/31/02

Total Budget:
$50,000

Student Involvement:
One Research Assistant @ 33% time for 9 months
One Research Assistant @ 50% time for 3 months

Relationship to Other Research Projects:
Project is part of infrastructure focus area

Technology Transfer Activities:
Project report will be posted on website

Potential Benefits of the Project:
More efficient bridge monitoring technology

TRB Keywords:
Highway Infrastructure

Primary Subject:
Maintenance and operations

Goals:
Safety, Mobility

Enabling Research:
Sensing and Measurement

Modal Orientation:
Highway Infrastructure