Abstract:

Globally, high-rise developments in urban settings have become venue of choice for both business and residence. This has brought about trends toward structures with increasing heights, lighter and more slender construction whose performance is sensitive to complex wind environments. This has also posed new challenges in designing structural systems with adequate stiffness and damping to ensure acceptable performance in survivability, serviceability and habitability. Quantification of aerodynamic loads on these structures is central to the assessment of these performance limit states. This seminar will address related topics and emerging developments with a focus on recasting of the gust loading factor, introduction of 3-D gust loading factors, an example of aerodynamic loading data base, trends in codes and standards, importance of full-scale monitoring, analysis of coupled building response and effectiveness of auxiliary damping systems.

Current trends in long span bridges is towards spanning long bodies of water, like the Strait of Messina, in Italy using cable supported bridges. With the increase in span length, natural frequencies and the ratio between the fundamental frequencies in torsion and vertical modes have decreased significantly. This leads to increased coupling between the vertical and torsional motions under strong winds. As a result, analysis of buffeting and flutter response of long span bridges generally requires consideration of multimodal response and aerodynamic coupling. This seminar will briefly address highlights of recent developments in the coupled flutter and buffeting analysis of long span bridges.

Biography:

Dr Ahsan Kareem, the Robert M. Moran Professor of Engineering, Department of Civil Engineering and Geological Sciences, first came to Notre Dame in 1990 from the University of Houston, where he had been serving as Professor and Director of the Structural Aerodynamics and Ocean Systems Modeling Laboratory. Ahsan received his bachelor＊s degree with distinction from Pakistan University of Science and Technology, followed by a Master＊s degree from the University of Hawaii through a joint program at MIT under the Fulbright Program and his doctorate from Colorado State University.

Ahsan＊s research interests cover a wide spectrum of topics in Civil Engineering, with his primary work focusing in probabilistic structural dynamics, fluid-structure interactions, risk assessment and structural safety, and particularly the mitigation of natural hazards〞specifically earthquakes, waves and wind. Through the use of computer models coupled with laboratory and full-scale experiments, Ahsan can better understand the impact of natural hazards on the built environment and develop mitigative strategies to enhance the performance and safety of structures.

His work has made significant contributions to the existing literature, with more than 160 technical articles in refereed journals and over 80 in other refereed/reviewed publications. These research efforts have been further distinguished by numerous honors, including one of the first Presidential Young Investigator Award from the White House Office of Science and Technology in 1984. In 1997 he received the Engineering Award from the National Hurricane Conference for his contributions to the development of safer, more hurricane-resistant construction, while being named in 1998 as Distinguished Alumnus of Colorado State University for his overall services to the field of Engineering. Most recently, Ahsan received the 1999 Munro Prize for the best paper award from the international journal, Engineering Structures, for a paper he co-authored with his former graduate student. He is inaugural recipient of the ASCE＊s Jack E. Cermak Medal for outstanding contributions to wind effects on structures in 2002. He also received 2005 Robert H. Scanlan Medal for outstanding contributions to engineering mechanics.

In addition to his research interests, Ahsan is active in a number of organizations and editorial boards, serving as Editor-in-Chief for an international journal, Wind and Structures, past associate editor for the Journal of Engineering Mechanics, past associate editor of the Journal of Structural Engineering, guest editor of the Journal of Wind Engineering and Industrial Aerodynamics and Structural Safety and currently serves on the editorial board of five international journals by Elsevier.

Ahsan has helped to shape the direction of a number of organizations devoted to the advancement of engineering as a service to society, particularly in his role as former President of the American Association for Wind Engineering and Regional Secretary for North and South America through the International Association of Wind Engineering. He is also chair of the Executive Committee of the Engineering Mechanics Division of the American Society of Civil Engineers, overseeing the technical activities of that division. In addition, he has served on several panels and the Committee on Natural Disasters through the National Research Council of the National Academies of Sciences and Engineering.

Throughout his career, Ahsan has chaired several national and international conferences and technical committees, delivering numerous keynote lectures. As a result of his vast experiences in Civil Engineering, he has been invited to give lectures throughout the world at a variety of professional meetings, trade organizations, R&D centers, and colleges and universities, including the Crom Lectureship at the University of Florida. His graduate students are well placed both in academia and industry. He has serves as senior consultant to several major oil, insurance, and consulting engineering companies, as well as the United Nations.