[UCI-CalIT2] Upcoming Joint Seminar with Dep't. of Civil and Environmental Engineering: Post-Earthquake Structural Assessment by Real-Time Monitoring

[Anna L. SPITZER]

Title:                Post-Earthquake Structural Condition Assessment by Real-Time Monitoring of Dynamic and Static Deformations

 

Speaker:          Erdal Safak, research structural engineer, U.S. Geological Survey

 

Date:               Thursday, Nov. 4, 2004

 

Time:               5 p.m.

 

Location:         3161 Engineering Gateway, UC Irvine

 

Sponsors:       Cal-(IT)² and Department of Civil and Environmental Engineering

Abstract:          The standard approach in structural instrumentation has been to set the instruments to trigger when motions exceed a specified threshold level, so that only the response to large earthquakes is recorded. Recently, a few structures have been instrumented to provide continuous data in real time, recording not only large motions, but also small motions generated by ambient loads. The main objective in continuous recording is to track any changes in structural characteristics and to detect damage. Damage detection typically involves analyses of acceleration response data to see if there are any changes in the structure's natural frequencies. The dynamic response of a damaged structure is nonlinear and in most cases, hysteretic. The natural frequencies rapidly change during the damaging vibrations and are hard to track for short-duration, transient loads such as earthquakes. Moreover, data from earthquakes have shown that even though a structure is damaged, its post-earthquake natural frequency can be equal to its pre-earthquake natural frequency because of hysteretic behavior. Recent real-time data also show that natural frequencies of a structure can change significantly due to soil-structure interaction and environmental factors, such as temperature, rain, wind, etc. Therefore, change in natural frequencies alone is not sufficient to make conclusions about damage. This presentation shows that, in addition to accelerations, continuous monitoring of displacements and rotations can eliminate the deficiencies of acceleration-only monitoring for damage detection. By comparing pre- and post-earthquake displacements and rotations, we can accurately determine the presence of any permanent displacements and rotations in the structure after an earthquake. Such measures of permanent deformations are more reliable than changes in frequencies to evaluate damage.

 

Bio:                  Dr. Safak is a research structural engineer and an internationally known researcher specializing in seismic response of structures, including monitoring, data analysis, system identification and damage detection. He has published more than 100 scientific papers on these subjects, and he serves on many national and international scientific committees and organizations related to seismology and earthquake engineering. Currently, he is involved in the structural health monitoring of two high-rise buildings in the L.A. area that are providing continuous vibration data in real-time. He was instrumental in arranging for monitoring UCI's Cal-(IT)² building.

 

 

Anna Lynn Spitzer

Senior Communications Specialist 

Cal-(IT)²

University of California, Irvine

416 Engineering Tower

Irvine, CA 92697-2800

Office: (949) 824-3317

 

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