SEMINARS Page 1 of 7
SEMINARS
Spring 2005
May 12, 2005 - Jeffrey Scruggs, Ph.D. - California Institute of Technology
Structural Control Using Regenerative Force Actuation Networks Many structural control systems make use of semiactive forcing devices; i.e., passive devices with variable mechanical parameters which may be controlled in real-time. This talk reports on structural control systems which dissipate energy electrically, using motors for electromechanical energy conversion, and using controllable circuitry to regulate dissipation. This has advantages over mechanical dissipation methods. If two or more devices are used to control a structure, electrical power can be transmitted from one actuator to another. Also, energy removed from the structure may be stored and reused. Such systems of forcing devices are called Regenerative Force Actuation (RFA) networks. Unlike traditional damping systems, RFA networks can be used to apply non-local and asymmetric damping forces on structures. Methods are presented, by which this more generalized damping capability may be exploited to yield significant reductions in structural responses to seismic excitation, beyond that attainable with passive systems. Additionally, nonlinear feedback controller design methods are discussed which exhibit guaranteed bounds on mean-square structural response quantities in stationary excitation. Finally, this talk reports on current research efforts toward the development of controller design techniques which guarantee bounds on reliability-based performance measures .
Jeffrey Scruggs is currently a Postdoctoral Research Fellow and Instructor with the Division of Engineering & Applied Science at California Institute of Technology. He received his Ph.D. degree in applied mechanics from Caltech in 2004. Dr. Scruggs received the M.S. in Electrical and Computer Engineering (1999) and a B.S. in Electrical Engineering (1997), from Virginia Tech.
May 8, 2005 - James Guest, Ph.D. - Princeton University
Design of Structures and Materials using Topology Optimization Topology optimization is a tool for finding the best solutions to engineering design problems. Such solutions meet specified performance criteria while minimizing cost, weight, and/or selected responses and thus potentially offer tremendous benefits. This seminar will discuss the topology optimization methodology and examine its applications to multi-scale structures ranging from structural systems to the microstructure of materials. The design objectives considered will include maximizing stiffness in linear elastic structures, minimizing power dissipation/drag in creeping fluid flows, and simultaneously maximizing stiffness and permeability in periodic material structures. The problems are discretized using finite elements and are introduced in the context of structural design. Associated numerical instabilities and difficulties, as well as novel techniques developed by the speaker for circumventing them, will be presented. These include a scheme for imposing a minimum length scale on load-carrying elements and a Darcy flow regularization of the moving-boundary no- slip condition in the optimization of fluid transport. The techniques are then extended to design microstructures of periodic materials with extreme properties and prescribed symmetries using inverse homogenization. The stiffness and fluid flow material modules are combined to design a multifunctional material simultaneously optimized for both stiffness and permeability. The designer can tailor the microstructure according to the material's intended use by assigning a relative importance to the competing properties.
James Guest received his Ph.D. degree in April 2005 from the Department of Civil & Environmental Engineering at Princeton University, where he is presently a Lecturer and Research
http://www.ce.jhu.edu/sem -spring -abstracts -2005.htm 9/2/2008 SEMINARS Page 2 of 7
Associate. Prior to his doctoral work, he received a M.S.E. degree from Princeton with a focus in bridge design and a B.S.E. degree in Civil Engineering Systems from the University of Pennsylvania. His research interests include structural optimization, finite element methods, simulation of stochastic processes, innovative structural applications of FRP, and history and aesthetics of structures.
May 6, 2005 - Jannette Frandsen, Ph.D. - Louisiana State University The principle challenge and scientific issue to be addressed is the accurate simulation of moving interfaces, especially free surface water waves, high Reynolds number flows and the fluid interaction with fixed and moving objects. Many large flexible structures exhibit unacceptable movement in water waves and wind fields. The interaction between structure and fluid is typically nonlinear. The challenge is to capture the nonlinearity in the flow field and in the interaction processes to accurately predict full-scale behavior of the structure. Examples of numerical approaches will be presented in relation to the modeling of a variety of hydro- and aeroelasticity problems. The tank sloshing problem will form the basis of discussing free surface nonlinearities. Some new development using a mesoscopic approach will also be introduced. Currently, 2-D single phase fluid-structure interaction models are undergoing validation.
April 19, 2005 - Hiroshi Katsuchi , Yokohama National University
Long-span Bridge Aerodynamics in Japan and Akashi Kaikyo Bridge This seminar introduces long-span bridge technologies in Japan focusing on aerodynamics, which is represented by the Honshu-Shikoku Bridge project including the Akashi Kaikyo Bridge. A wind- tunnel test of the Akashi Kaikyo Bridge with a large 40m long full model was carried out in order to investigate its aerodynamic stability of the world’s longest suspension span of 1,991m. Valuable insight into aerodynamic of long-span suspension bridges provided by the test will be presented. In the latter half, the seminar also presents filed measurement data of the bridge during typhoons and an analytical study on its modal parameters identified from the data.
Hiroshi Katsuchi , Dr. Eng. is an Associate Professor of the Department of Civil Engineering, Yokohama National University in Japan. After graduating from Tokyo Institute of Technology, he worked for the Honshu-Shikoku Bridge Authority where he was involved in a wind-tunnel study of the Akashi Kaikyo Bridge. During the HSBA period, he studied at the Hopkins under Dr. Nick Jones and Dr. Bob Scanlan and obtained MSE in 1997.
April 8, 2005 - Special Seminar - Lijuan (Dawn) Cheng, Dept. of Structural Engineering, University of California, San Diago
Analytical and Experimental Investigation of a Free FRP-Concrete Slab-on Girder Modular Bridge System The critical need for replacing and rehabilitating the nation’s deteriorating and aging bridge inventory has motivated the search for new bridge systems using innovative and more durable materials. Fiber Reinforced Polymer (FPR) composites offer such an opportunity with additional advantages of less weight, substantially reduced erection time and consequent costs of traffic disruption, with the potential for reduced life-cycle costs. Systems to date have been limited to configurations consisting of FRP decks supported on steel or concrete girders. All FRP decks have been found to be more costly than conventional reinforced concrete decks even under the most
http://www.ce.jhu.edu/sem -spring -abstracts -2005.htm 9/2/2008 SEMINARS Page 3 of 7
optimistic assumptions. The use of hybrids incorporating the optimized use of FRP with concrete could be considered as a feasible solution.
A steel-free FRP-concrete modular system has been investigated in this research for slab-on-girder type of bridges. The system consists of a steel-free concrete slab cast on carbon fiber reinforced composite deck panels that are snap-locked to the top of the rectangular box girders made of hybrid E-glass-carbon fiber reinforced composites through snap-in shear stirrups. The components and the overall system are comprehensively characterized through full-scale experiments and use of appropriate computational and analytical investigations. This seminar presents the primary results of this investigation. Both the material nonlinearity in concrete and the progressive failure mechanisms in laminated FRP composites are incorporated in the analysis, which uses specially developed sectional analysis and finite-element based methods. The analysis results show close correlation with performance results from the experimental observations. Further design optimization is conducted using the validated analytical tools. Simplified approach and design recommendations are proposed for using the hybrid system.
April 5, 2005 - Deborah J. Goodings, Professor of Civil Engineering and Co-Director of the Engineering and Public Policy Program, University of Maryland,
New Initiatives at the University of Maryland :
Engineering and Public Policy
Engineering systems is a big picture approach to engineering. Take, for example, energy systems. That’s mechanical engineering to make more efficient engines, that’s electrical engineering for more efficient energy production and transmission, that’s chemical engineering for better use of fossil fuels, and that’s civil engineering for making decisions about hydroelectric dams, environment, transportation networks, and urban planning for megacities. But what pulls them all together for a society to make right choices, to balance near term and long term objectives, to use resources wisely, to factor into decisions a degree of concern with social equity? That is the role of public policy makers, however, public policy makers, even when it comes down to technical decisions, are seldom engineers. Dr. Goodings will sketch out the new graduate degree program for engineers, the practice oriented Master’s degree in Engineering and Public Policy offered jointly by the Clark School of Engineering and the Maryland School of Public Policy at the University of Maryland.
Engineers Without Borders
Traditionally, engineering education has concentrated on theories and methods to apply science to infrastructure needs of the one billion “have’s” on our planet. Issues of sustainability, appropriate technology, and engineering’s role and responsibility in international poverty reduction do not enter into our traditional engineering curricula. Engineers Without Borders, as conceived in the United States, is focused on acquainting engineering students with those issues, through adoption, design, and construction of small, sustainable engineering projects in developing nations. Dr. Goodings traveled with five University of Maryland students to northern Thailand last summer to construct a health clinic for a cluster of Lisu hill tribe villages. She will talk about their trip and the next projects in progress at the University of Maryland chapter, and discuss the hypothesis that being an engineer is not incompatible with being a bleeding heart liberal.
Deborah Goodings is a professor of geotechnical/civil engineering at the University of Maryland. Her research has addressed both extreme event and more mundane geotechnical engineering. She
http://www.ce.jhu.edu/sem -spring -abstracts -2005.htm 9/2/2008 SEMINARS Page 4 of 7
has received the US Army Outstanding Civilian Service Medal, and the National Research Council Fred Burgraff Award for her research, and she is a member of the National Academy subcommittee scoping out future challenges and opportunities for geotechnical engineering. Her newest initiatives at the University of Maryland are the Engineering and Public Policy Program which she co- developed, and which she now co-directs; and the Engineers Without Borders UMCP chapter which she co-founded, and for which she serves as its faculty advisor. Dr. Goodings is a registered professional engineer, a Fellow of ASCE, and a By-Fellow of Churchill College, Cambridge.
April 4, 2005 - Special Seminar - Suren Chen, Ph.D.
Dynamic performance of bridges and vehicles under wind Wind is the most devastating natural hazard and exists in almost all states in the United States. The record of span length for flexible bridges has been broken with the development of modern materials and construction techniques. With the increase of bridge span, the dynamic response of the bridge becomes more significant under external wind action and traffic loads. When strong wind is approaching, these long-span bridges sometimes have to be closed in order to ensure the safety of the bridge as well as the transportation on them due to excessive wind-induced vibrations. Ensuring the safety of the bridges themselves and vehicles in extreme storms and maintaining transportation facilities in an operational service condition can maximize the opening time of the transportation lines. The presentation targets specifically on discussing dynamic performance of bridges as well as the transportation under strong wind.
Dr. Suren Chen graduated from Department of Civil & Environmental Engineering at Louisiana State University with Ph.D. degree in May 2004. Right after his graduation, he started working in a national consulting firm as a civil engineer. Before he came to US, he got his M.S. and B.S. from Tongji University, China, in 1997 and 1994, respectively. Dr. Chen has been working in several research areas including: wind engineering, especially long-span bridge aerodynamics research; structural control and health monitoring; vehicle-structure dynamics and vehicle accident assessment; hazard risk assessment and mitigation. Dr. Chen has about 30 publications related to his research on the professional journals and conference proceedings. During his Ph.D. study, Dr. Chen published 7 journal papers and 8 conference papers. Dr. Chen is a registered professional engineer (PE) of civil engineering in State of Ohio.
March 30, 2005 - Special Seminar - Sharif Rahman, Professor, University of Iowa
This seminar will present a new class of computational methods, referred to as dimension-reduction methods , for predicting statistical moments and reliability of general structural systems subject to random loads, material properties, and geometry. The methods involve an additive decomposition of an N-dimensional response function into at most S-dimensional functions, where S << N; an approximation of response moments by moments of input random variables; and a moment-based quadrature rule for numerical integration. The proposed methods require neither the calculation of partial derivatives of response, as in commonly-used Taylor expansion/perturbation methods, nor the inversion of random matrices, as in the Neumann expansion method. Using these dimension- reduction methods, approximate values of a performance function at arbitrarily large number of input can be generated, enabling subsequent response surface approximation and Monte Carlo simulation efficiently. Due to a small number of function evaluations, the proposed methods are very effective, particularly when a response evaluation entails costly finite element or other numerical analysis. Several numerical examples involving structural and solid-mechanics problems will be presented to illustrate the methods developed. Finally, potential applications for solving large-scale engineering problems will be discussed.
http://www.ce.jhu.edu/sem -spring -abstracts -2005.htm 9/2/2008 SEMINARS Page 5 of 7
Professor Rahman received his B.Sc. degree (Honors) in Civil Engineering from Bangladesh University of Engineering and Technology in 1984, his M.S. degree in Structural Engineering from Purdue University in 1986, and his Ph.D. degree in Structural Engineering from Cornell University in 1991. After four years of professional research at Battelle Columbus Laboratory, he returned to academia in 1995 and is currently an Associate Professor in the Department of Mechanical Engineering of The University of Iowa. His research focuses on computational stochastic mechanics and reliability with engineering applications in civil, mechanical, nuclear, and aerospace structures. He received numerous awards including The University of Iowa Faculty Scholar Award, IASSAR Junior Research Prize, ASEE Outstanding New Mechanics Educator Award, The James N. Murray Outstanding Faculty Award, NSF CAREER Award, and others. Currently, he serves as an Associate Editor of ASME Journal of Pressure Vessel Technology, a member of the editorial board of Engineering Fracture Mechanics, and the Chair of ASME Materials and Fabrication Committee. He has published over 200 technical papers and reports.
March 29, 2005 - Understanding Wind and Rain Induced Stay Cabel Vibrations - Delong Zuo, candidate for the Ph.D degree
Under certain wind conditions, stay cables of cable-stayed bridges have frequently exhibited large- amplitude vibrations. Such vibrations are often associated with the occurence of rain, but large- amplitude vibrations without rainfall have been observed. The mechanisms of these vibrations are still not well understood, and it is unclear where the vibrations occuring with and without rainfall are related. Unless fully addressed, these problems significantly hinder the rational design of effective mitigation countermeasures for the vibrations, which potentially threatens the safety and serviceability of cable-stayed bridges. This study was conducted to understand the mechanisms of wind and rain-induced stay cable vibrations based on full-scale measurements of prototype vibrations in the field and tests of sectional models in the wind tunnel.
A parametric study of the stay cables is first performed based on full-scale measurement data. The Hilbert Transform is used to estimate the modal frequencies of stay cables, revealing that stay cables can essentially be treated as taut strings. The modal damping is assessed based on both ambient vibration and forced vibration data, indicating that the level of damping is very low in stay cables and that it is affected by the dynamic energy exchange between the cables and other structural elements of the bridge.
Observed characteristics of stay cable vibrations, as well as their correlation with wind and rain are presented. Based on these characteristics and correlations, several different types of vibrations are identified. In particular, important similarities between the frequently occurring large-amplitude rain- wind-induced vibrations and the classical Kármán-vortex-induced vibrations are explored and compared to a type of large-amplitude dry cable vibrations, providing significant insights to the mechanisms of these types of vibrations.
To verify the observations in the field, sectional cable models were tested in the wind tunnel, revealing the inherent vortex-induced type of instability of yawed and inclined cables over a range of high reduced velocity. The observations in the wind tunnel are also compared with the results of previous wind tunnel tests reported in the literature.
Based on the understanding from both the field and the wind tunnel, a framework is proposed for modeling of the vortex-induced type large-amplitude vibrations at high reduced velocity. The potential application of this model is also discussed.
http://www.ce.jhu.edu/sem -spring -abstracts -2005.htm 9/2/2008 SEMINARS Page 6 of 7
The observed vibrations are also used to assess the performance of passive viscous dampers and cross-ties in mitigating wind- and rain-wind-induced stay cable vibrations. Recommendations for rational design of these mitigation devices are also provided.
March 22, 2005 - A Tuesday Twofer - Hugh Ellis, Chair, Department of Civil Engineering, The Johns Hopkins University
This seminar presentation will consist of brief overviews of two ongoing research projects:
Current Generation Air Quality Modeling
This work is a product of EPA-sponsored research involving the potential consequences of climate change on ambient air quality in the United States. The presentation begins with a description of the modeling process, starting with meteorologic simulation (using MM5), through emissions processing (using SMOKE) and finally air quality simulation (using CMAQ). Model performance is discussed, specifically in terms of comparisons of ground level ozone simulations with measurements. Recent work is then discussed in which MM5 is driven by the output of a general circulation model (the Goddard Institute for Space Sciences GCM). This portion of the seminar concludes with a brief presentation of ongoing work coupling three modeling efforts: electrical energy generation and dispatch, short and long-term energy demand modeling and the air quality modeling described herein.
Global Infectious Disease Transmission
The spread of infectious disease due to travel has existed for centuries. Analyses of the role of air travel in the spread of disease emerged several decades ago. The work reported in this presentation first considers previous attempts to simulate the 1968/69 global influenza pandemic. Simulation model improvements are described and the improved model is used to demonstrate the global spread of influenza that could occur using year 2000 passenger volumes. The modeling system is then applied to a United States network of cities. Comparisons with surveillance data are shown. Finally, the spread of smallpox in the United States is simulated. A series of sensitivity analyses are presented including scenarios in which air travel is suspended based on number of confirmed cases.
February 15, 2005 - The Sumatra Tsunami in Thailand The Indian Ocean Tsunami of 2004 resulted in more fatalities than any tsunami in recorded history. Thailand, which is within 400 miles of the earthquake epicenter, had many of its well-known tourist beaches attacked by the tsunami, with destruction varying along the coastline.
The American Society of Civil Engineers sent a team of investigators to Thailand (and India and Sri Lanka) to examine the effect of the waves on the infrastructure lifelines and the coastline. This talk discusses the wave's effects on beaches and a port. Pictures will show the extent of the water levels and the resulting damage. Examples of good engineering are compared to bad and some lessons learned for building in a tsunami hazard zone.
Professor Tony Dalrymple is a Willard & Lillian Hackerman Professor of Civil Engineering at this university. His main research interests include: water waves, nearshore hydrodynamics, and coastal processes. He works with a team of engineers on topics such as Smooth Particle Hydrodynamics, Sediment Transport, Water Wave Mechanics, and Free -Surface Hydrodynamics at the Coastal Engineering
http://www.ce.jhu.edu/sem -spring -abstracts -2005.htm 9/2/2008 SEMINARS Page 7 of 7
Laboratory located in the Stieff Building. He also teaches for the department. His classes consist of Coastal Engineering, Dynamics, Introduction to Water Waves, and Coastal Modeling.
http://www.ce.jhu.edu/sem -spring -abstracts -2005.htm 9/2/2008