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 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 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.
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 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.
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.
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.
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.
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 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.