U.S.-Australia Cooperative Science: Development of Force-Frequency Shifting for Low Frequency Structural Vibrations Testing

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0115593TretheweyThis award supports a three year collaborative research project between Professor Martin Trethewey of the Pennsylvania State University and Professor Leonhard Koss of Monash University in Victoria, Australia. This project will undertake a study of the development of Force Frequency Shifting (FFS) for low frequency structural vibrations testing. Experimental vibration testing of civil and architectural structures has proven helpful in health assessment and in developing vibration absorbers for troublesome facilities. These target systems are characterized by having 1) low natural frequencies, 2) large mass, and 3) high damping. These conditions create a demanding set of vibration excitation specifications for experimental modal testing or active control applications. The vibration excitation problem stems from the inherently difficulty in creating high amplitude forces at low natural frequencies. The goal of the research is to develop and evaluate a novel low frequency vibration excitation technique ultimately suitable for vibration excitation of civil, architectural, and heavy machinery structures. Through a mechanical modulation process, a component of an efficiently generated high frequency excitation force is shifted to a low frequency. It is this shifted low frequency excitation signal that is the focus of this research. The project brings together the efforts of two laboratories that have complementary expertise and research capabilities. The value of vibration testing of large-scale systems has developed a proven track record of delivering valuable information in relation to a number of varied issues. Research in this are could assist in the assessment of bridge structural health, building occupant acceptability, wind excited motion, earthquake isolation performance and floor vibration for sensitive installations such as medical MRI equipment. The project advances international human resources through the participation of graduate and undergraduate students. Through the exchange of ideas and technology, this project will broaden our base of basic knowledge and promote international understanding and cooperation. Results of the research will be published in international scientific journals and will also be presented at scientific meetings in the U.S. and abroad.