Date: October 22, 2004

Time: 3:00 pm

Location: GCATT Room 325

Speaker(s): Professor Laurence Jacobs

Title: Application of Time-Frequency Representations for the Nondestructive Evaluation of Civil Infrastructure

Abstract:
As the nation's infrastructure system ages, the ability to detect progressive and catastrophic failure events in civil engineering structures becomes a critical reliability and safety issue. Current nondestructive evaluation (NDE) methods for the inspection of construction materials do not have the degree of accuracy, reliability and repeatability necessary for the quantitative evaluation of the remaining strength of an existing structure. Critical issues that complicate the interrogation of civil engineering components include their size, complexity and the heterogeneous nature of civil engineering materials. This seminar will discuss unique signal processing issues associated with the NDE of civil infrastructure. The first application will examine the use of time-frequency representations to interpret ultrasonic guided waves. This class of ultrasonic signals can be extremely complicated, exhibiting dispersion and containing multiple modes. Laser ultrasonic techniques are then combined with a time-frequency representation to experimentally measure the dispersion curves of a concrete component repaired with a fiber reinforced composite plate. Finally, the attenuation of individual modes in a complementary layered system is examined using time-domain ultrasonic signals measured at multiple spatial locations. This technique is tested on an aluminum plate with water half-space on one side, and is shown to capture changes in the multi-mode attenuation over a broad frequency range.

Bio:
Professor Jacobs' research focuses on the development of quantitative methodologies for the nondestructive evaluation of structural materials. After receiving his B.S. in Civil Engineering from Lafayette College, Dr. Jacobs worked for two years in the aerospace industry and for one year as a structural engineer. He received his Ph.D. (Engineering Mechanics) from Columbia University in 1987, and worked for one year as an Office of Naval Technology Postdoctoral Fellow prior to coming to Georgia Tech in 1988. At Georgia Tech, Professor Jacobs was promoted from Assistant to Associate Professor (of Civil Engineering) and received tenure (both in 1994) and to Professor in April 2000. Dr. Jacobs has been the Associate Chair for Undergraduate Programs in the School of Civil and Environmental Engineering since 1995, and has had a joint appointment with the G.W.W. School of Mechanical Engineering since 2002. Dr. Jacobs has authored/co-authored over 120 papers in refereed journals and conference proceedings and is a past Associate Editor of ASCE's Journal of Engineering Mechanics and currently on the editorial board of NDT&E International.

Date:	October 22, 2004
Time:	3:00 pm
Location:	GCATT Room 325
Speaker(s):	Professor Laurence Jacobs
Title:	Application of Time-Frequency Representations for the Nondestructive Evaluation of Civil Infrastructure
Abstract:	As the nation's infrastructure system ages, the ability to detect progressive and catastrophic failure events in civil engineering structures becomes a critical reliability and safety issue. Current nondestructive evaluation (NDE) methods for the inspection of construction materials do not have the degree of accuracy, reliability and repeatability necessary for the quantitative evaluation of the remaining strength of an existing structure. Critical issues that complicate the interrogation of civil engineering components include their size, complexity and the heterogeneous nature of civil engineering materials. This seminar will discuss unique signal processing issues associated with the NDE of civil infrastructure. The first application will examine the use of time-frequency representations to interpret ultrasonic guided waves. This class of ultrasonic signals can be extremely complicated, exhibiting dispersion and containing multiple modes. Laser ultrasonic techniques are then combined with a time-frequency representation to experimentally measure the dispersion curves of a concrete component repaired with a fiber reinforced composite plate. Finally, the attenuation of individual modes in a complementary layered system is examined using time-domain ultrasonic signals measured at multiple spatial locations. This technique is tested on an aluminum plate with water half-space on one side, and is shown to capture changes in the multi-mode attenuation over a broad frequency range.
Bio:	Professor Jacobs' research focuses on the development of quantitative methodologies for the nondestructive evaluation of structural materials. After receiving his B.S. in Civil Engineering from Lafayette College, Dr. Jacobs worked for two years in the aerospace industry and for one year as a structural engineer. He received his Ph.D. (Engineering Mechanics) from Columbia University in 1987, and worked for one year as an Office of Naval Technology Postdoctoral Fellow prior to coming to Georgia Tech in 1988. At Georgia Tech, Professor Jacobs was promoted from Assistant to Associate Professor (of Civil Engineering) and received tenure (both in 1994) and to Professor in April 2000. Dr. Jacobs has been the Associate Chair for Undergraduate Programs in the School of Civil and Environmental Engineering since 1995, and has had a joint appointment with the G.W.W. School of Mechanical Engineering since 2002. Dr. Jacobs has authored/co-authored over 120 papers in refereed journals and conference proceedings and is a past Associate Editor of ASCE's Journal of Engineering Mechanics and currently on the editorial board of NDT&E International.