Warren Distinguished Lecture Series

Lev Khazanovich
Department of Civil Engineering, University of Minnesota

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Abstract

Characterization of early age behavior of concrete is an important factor in modeling of long-term behavior of concrete pavements.  The presentation deals with three-dimensional micromechanical modeling of concrete creep at early age.  In this formulation, concrete is treated as a two-phase composite material consisting of an aging matrix (cement paste) and elastic inclusions (aggregates). The aging matrix uniaxial creep behavior is described by Bazant’s solidification theory, which models aging by volume growth of non-aging viscoelastic products of cement hydration. The bulk modulus of the matrix is assumed to be time-independent.  

Time-translation non-invariant behavior of the aging matrix complicates determination of effective properties of the composite material.  To overcome this challenge, continuous integral operators are approximated by operators acting in finite-dimensional spaces.  A transformation converting the viscoelastic boundary value problem (BVP) to a series of independent elastic BVPs is introduced.  This along with the Mori-Tanaka scheme was adapted for determining the effective shear and bulk creep operators of the composite material, resulting in rational functions of operators.

Joel Burken
Department of Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology

+ Live Webcast Link *

* Viewers must have the appropriate software installed on their computers to watch the live or archived presentation. For Windows users, please make sure Windows Media Player is installed. Apple users must install Microsoft's Silverlight. For questions or connection issues, e-mail umconnect@umn.edu.

Abstract

Plants interact intimately with their environment. Although stationary, plants extract water, nutrients, carbon, oxygen and all that is needed to be the dominant terrestrial, multicellular biomass on earth. Plants concurrently collect and store chemicals and elements from the surrounding water, air, and soil in the environment, all by harnessing the energy of the sun and wind. To utilize the chemical data stored in plants, new knowledge was necessary. Fundamental breakthroughs in understanding plant-contaminant interactions have led to novel approaches that now being used in the new field of Phytoforensics. Recent breakthroughs range from analytic chemistry to fundamental organic molecule fate, such as an improved understanding of how organic molecules can transport across root membranes. The ‘Rule of 5’ for plant uptake was developed from similar relationships for mammalian drug uptake, and now we can better predict which chemicals can migrate into and through vascular plants. New insight is being gained on in-silico methods to assess potential food pollutants in addition to using plant sampling for forensic purposes in site assessments. 

The primary and most diverse advancements leading to phytoforensic applications are n novel sampling and chemical analysis techniques developed at S&T. Methods have been developed that can assess contaminants in-planta, offering not just screening, but long-term monitoring possibilities. Entirely different methods offer no-solvent extraction methods for non-volatile contaminants (such as RDX, HMX, Perchlorate). Patented methods of placing sampling devices in-planta offer a new chemical monitoring paradigm that has never been available or considered. Using novel plant sampling techniques, data on contaminants in the otherwise obscured subsurface environment can be gathered to help in contaminated-site delineations that are too often costly and inaccurate, thereby improving remediation efficacy and protecting human health.

The same processes are applied proactively in engineered natural systems that are not only effective at meeting treatment targets, but also offer biomass and fiber resources, habitat and ecosystem services, as well as recreation and aesthetic benefits. Policy and ‘total economics’ should be considered in remedial decisions. Plants can be used for a wide range of environmental applications if understood.  We have just never tried to ‘listen to the trees’ regarding the contaminants in our environment, nor have we learned to ask Mother Nature to help fix the problems.

Daniel Noguera
Department of Civil and Environmental Engineering, University of Wisconsin - Madison

Abstract

Understanding the dynamics of microbial communities in engineered biological systems, such as wastewater treatment plants, drinking water distribution systems, bioremediation sites, or biofuel generating reactors is a fundamental requirement to monitor, improve and optimize such processes. Rapid advances in biotechnology over the last two decades has resulted in a constantly evolving molecular biology-based toolkit that is used to investigate microbial community composition and population dynamics.  The methods in this toolkit primarily rely on exploiting the 16S ribosomal RNA (rRNA) gene as a phylogenetic marker that establishes an evolution-based taxonomy of life.

In this presentation, I will describe our participation in the creation and evolution of the toolkit, which includes the development of a mechanistic model of fluorescence in situ hybridization (FISH), a thermodynamics-based approach to design probes for FISH (http://mathfish.cee.wisc.edu), a new method to evaluate the quality of 16S rRNA sequences (http://decipher.cee.wisc.edu), and new approaches to design primers for microbial ecology application of the polymerase chain reaction (PCR).

Henryk Stolarski
Department of Civil Engineering, University of MInnesota

Abstract

(in collaboration with A. Gilmanov and F. Sotiropoulos)

Use of rotational degrees of freedom in the finite element analysis of all structures undergoing bending is convenient to satisfy kinematic compatibility between elements. For that reason, virtually all finite element formulations use rotations as parameters to describe deformation of shells. In general analysis of shells three translations and three or two rotations (depending on the formulation) are used as degrees of freedom at each node of the finite element mesh. Consequently, any formulation retaining only translational degrees of freedom would significantly reduce the associated theoretical and computational effort, and would be very desirable provided its accuracy is comparable to the formulations involving rotations. This is particularly true in the case of large deformation problems where rotational degrees of freedom require special handling (such as exponential maps, Euler angles, Rodrigues parameters, quaternions etc.)

In this presentation a rotation-free formulation for large deformation analysis of shells will be presented. It is an extension of the seminal work of Phaal and Calladine (1992), which dealt with small deformations of plates and shells. It also incorporates modifications of some ideas found in a couple of articles on rotation-free large deformation analysis of shells published in the past twenty years. The key ingredients of the formulation will be explained and discussed in the context of previous contributions on the subject. The accuracy and effectiveness of the approach will be demonstrated via comparisons of the computed results with those obtained by different, more complicated, finite element formulations involving rotations or with (rarely) available analytical solutions.

Joe Goddard
Department of Mechanical & Aerospace Engineering, University California, San Diego

Abstract

“[Granular media] are omnipresent: from the rings of Saturn to the snow of our mountains.
[They] represent a major object of human activities: as measured in tons, the first material manipulated on earth is water; the second is granular matter.”
P.-G. de Gennes “ From Rice to Snow”, 2008 Nishina Foundation Nobelist Lectures, In Lect. Notes Phys. 746, 297-318 (2008).

The past forty years or so have witnessed a resurgence and continuous growth of interest in the mechanics of granular materials, whose scientific origins go back at least to the 18th Century. The subject is relevant to a number of geotechnical and technological processes, such as stability of slopes and natural avalanches, mechanics of desert sands, and vibratory conveying and compaction. The challenge of understanding and mathematically modeling these materials and processes has attracted researchers from a wide array of disciplines, ranging from soil mechanics to theoretical physics, who bring complementary but sometimes opposing philosophies and methodologies to the table.

This lecture provides a broad overview of the field, including the distinguished flow régimes of elastoplastic solid, viscoplastic fluid and viscous gas. The focus here is on the first two, which involve several fascinating phenomena such as Reynolds dilatancy, seismic liquefaction, mesoscopic force chains, shear bands and Faraday patterns on vibrated layers. An effort is made to relate these qualitatively to the geotechnical and technological processes mentioned above.

A brief summary is given of some of the more promising phenomenological continuum models for the elastoplasticity and viscoplasticity of non-cohesive granular media. One conclusion is that multiscale and multipolar continuum models involving additional kinematic degrees of freedom and conjugate hyperstress, may be essential to the rheology of granular media, particularly the elastoplastic behavior. Owing to their typically large particle size, this becomes much more compelling for granular media than for other complex solids and fluids.

Biography

Professor Goddard received his Ph.D. in chemical engineering from the University of California, Berkeley in 1962. He joined the chemical engineering faculty of the University of Michigan in 1963, and in 1976 he accepted the position of Fluor Professor and Chair in the Department of Chemical Engineering at the University of Southern California. He has been Professor of Applied Mechanics and Engineering Science at the University of California, San Diego, since 1991. He has published research in a wide variety of fields, including the mechanics of complex fluids and solids, and the thermodynamics and transport properties of of physical and biological systems. He has served on several editorial boards and U.S. national committees on mechanics. He has been visiting researcher or professor at numerous academic and research institutions, most recently as a Springer Visiting Professor in Mechanical Engineering at the University of California, Berkeley in 2012.

Other professional distinctions include, NATO, NSF and Fulbright Postdoctoral and Senior Postdoctoral Fellowships, 1963-84, Fluor Professor of Chemical Engineering, USC, 1976-91. D.L. Katz Lecturer, University of Michigan, 1983, President of the U.S. Society of Rheology, 1991-93, and the 2012 G.I. Taylor Medal of the Society of Engineering Science.

Joe Labuz
MSES/Miles Kersten Professor
Department of Civil Engineering
University of Minnesota

Abstract

It is evident from a strength test conducted on a specimen of rock that failure is associated with initiation and propagation of fracture. The rock may deform uniformly until a critical condition is reached, and then deformation localizes in a zone that opens and/or slides. Because of the presence of the fracture, a structural size effect on the overall response appears, and energy released from the failure process can be sudden or gradual. Controlling failure is often necessary to achieve safe operations of underground mines, while promoting failure efficiently is a concern in excavating and drilling. Thus, the conditions to initiate and propagate a fracture are often needed for proper designs in rock.

Details of tensile fracture from flexural tests are reported based on the optical methods of speckle interferometry and image correlation, which provide high-resolution measurements of crack displacements. Acoustic emission, which are elastic waves emitted during the fracture process, deliver information on location and mechanism of microcracking. Fracture characteristics such as critical crack opening and process-zone length are highlighted.

An interpretation of shear fracture is discussed in relation to plane strain compression tests, where growth of a failure plane is observed at various stress states. Displacement measurements, AE locations, and thin-section microscopy allowed direct and indirect observations of in-plane propagation, and fracture mechanics was used to determine the shear fracture toughness of the rock.

Luciano Castillo
National Wind Resource Center
Department of Mechanical Engineering, Texas Tech University

Abstract

During the first portion of this seminar, extensive PIV data collected from a scaled down 3 blade, 3 x 5 turbine array is shown. In order to understand how large scale motions play a role in providing mean kinetic energy (MKE) to the array, low dimensional tools based on a proper orthogonal decomposition (POD) are used to analyze the spatially developing velocity field inside the scaled array. From this analysis, modal decomposition of the Reynolds stresses and fluxes of the MKE are constructed. Thus, from these modal expansions it is established that low order modes have large contributions to Reynolds shear stress regardless of analysis domain.  In addition, it will be shown that mean kinetic energy transport resulting from Reynolds shear stress typically serves to bring energy into the array while transport terms associated with Reynolds wall-normal stress typically removes energy from the array. Furthermore, it will be shown that the sum of the first 13 modes for the mean fluxes contributes 75% of the total Reynolds shear stress in the domain.

The concept of coherent transfers of energy is employed here as means to uncover the scales responsible for the entrainment of mean kinetic energy into the array. The major contributions to the MKE entrainment are achieved by large-scale motions associated with sums of the Reynolds shear stress, (idiosyncratic) modes (see figure 1). Thus, the sum of the first 9 modes yield 54% of the total energy entrainment, with scales given by L ~ 13D associated with this sum. It is expected that given a longer experimental setup, the lengths of these large-scale contributions would have been observed to be even bigger. Moreover, a major result from the modal length-scale analysis is that large scale motions or the idiosyncratic modes contain most of the MKE and that the low mode numbers are associated with the small scales. These high order POD modes in the inhomogeneous flow direction (x-coordinate) correspond to the Fourier-like modes and decay as 1/n where n is the mode number (see fig. 1 right). This observation is consistent with studies of wall-bounded flows by Baltzer& Adrian (PoF, 2011).  

From these results, it is clear that scales of the order of the total wind farm size are those which are critical in determining how much power can be extracted from the atmospheric boundary layer. In addition, during this seminar it will be shown that dispersive stresses are also important in the energy entrainment and dissipation in wind arrays with complex topography and where proximity between turbines exists.  

During the second part of the seminar, preliminary PIV results from scaled down experiments of 2 blades versus 3 blades arrays subject to similar conditions in a wind tunnel will be presented. Of primary importance from this data are the differences which exist in the entrainment patterns between 2 and 3 bladed turbine arrays. Finally, a prototype of a wind farm will be shown as means for future collaborations between UMN and TTU. In general, this seminar will stress the importance of understanding turbulence in wind energy. 

Special Warren Lecture in Memory of Robert Dexter

Theodore Galambos
Department of Civil Engineering, University of Minnesota

Abstract

The nation’s interest in the safety of bridges was suddenly reignited by the catastrophic collapse of the I35W Bridge over the Mississippi River in Minneapolis on August 1, 2007. This presentation will focus on the general causes of bridge failures and on how they can be prevented. Most accidents happen during construction, but less frequently collapses also occurred after many years of service. The most terrible events are when a bridge after many years suddenly disintegrates. Examples of both construction and long service failures will be presented. Examples of construction failures to be considered are the Quebec Bridge in Canada and the Yarra River Crossing in Australia. The Firth of Tay Bridge in Scotland, the Point Pleasant Bridge over the Ohio River, and the Minneapolis Bridge disasters will illustrate events on bridges that were in service.

Similarities and differences of these sudden failures will be discussed. Lessons learned and recommendations for preventive actions will then be presented. The main conclusion of the talk will be that the seeds of destruction were sowed already at the initial planning stages of design. Sudden and complete bridge failures are very rare events, fortunately, and the engineering profession has the means to make the probability of failure even smaller.

Biography

Theodore (Ted) V. Galambos, Ph.D., P.E., N.A.E., is Emeritus Professor of structural engineering at the University of Minnesota in Minneapolis, MN. He received BSCE and MSCE degrees from the University of North Dakota in Grand Forks in 1953 and 1954, respectively, and Ph.D.degree in Civil Engineering from Lehigh University in Bethlehem, PA in 1959.

He had an academic research and teaching career at Lehigh University (1959 – 1965), at Washington University in Saint Louis (1965 – 1981) and at the University of Minnesota.

His research areas are: the behavior and design of steel structures, the reliability of structures, structural design standards, and the stability of steel structures. He is author of several technical books and of scores of published articles. He is an honorary member of the American Society of Civil Engineers, and a member of the National Academy of Engineering, the Structural Stability Research Council and the International Association of Bridge and Structural Engineering. He is a registered professional engineer in Minnesota, and Missouri. He holds honorary doctorates from the Technical University of Budapest, the University of North Dakota, and the University of Minnesota. He is one of the 2002 recipients of the ASCE OPAL Award.

Dan Frangopol
Department of Civil and Environmental Engineering, Lehigh University

Abstract

Throughout their service life, civil infrastructure systems are subject to progressive or sudden deterioration in performance. This deterioration may render the use of these facilities unsafe at some point in time. Decisions regarding civil infrastructure systems should be supported by an integrated life-cycle reliability, risk and resilience-based multi-objective optimization framework by considering, among other factors, the likelihood of successful performance, the total expected cost accrued over the entire life-cycle, and restoring as quickly as possible the proper functionality of the infrastructure after a disaster.  Over the last two decades, there has been successful research towards developing procedures for establishing the various vital elements required in this framework. It is noted, however, that a framework for integrating all these elements is lacking. The primary objective of this talk is to present an integrated framework for the life-cycle management of civil infrastructure systems. The elements integrated into the framework include assessment and prediction of life-cycle performance, analysis of system and component performance interaction, maintenance optimization, updating the life-cycle performance by information obtained from structural health monitoring, and optimum decision making based on reliability, risk and resilience. Applications of the proposed integrated framework to life-cycle management of individual bridges and bridge networks are presented.

Biosketch

Dr. Dan M. Frangopol is the first holder of the Fazlur R. Khan Endowed Chair of Structural Engineering and Architecture at Lehigh University. Before joining Lehigh University in 2006, he was Professor of Civil Engineering at the University of Colorado at Boulder, where he is now Professor Emeritus. From 1979-1983, he held the position of Project Structural Engineer with A. Lipski Consulting Engineers in Brussels, Belgium. In 1976, he received his doctorate in Applied Sciences from the University of Liège, Belgium. According to the ASCE video script introduction at his induction as an ASCE Distinguished Member “Dan M. Frangopol is a preeminent authority in bridge safety and maintenance management, structural systems reliability, and life-cycle civil engineering. His contributions have defined much of the practice around design specifications, management methods, and optimization approaches. From the maintenance of deteriorated structures and the development of system redundancy factors to assessing the performance of long-span structures, Dr. Frangopol’s research has not only saved time and money, but very likely also saved lives.”

Dr. Frangopol is an experienced researcher and consultant to industry and government agencies, both nationally and abroad. His work has been funded by NSF, FHWA, ONR, NASA, USACE, AFOSR and by numerous other agencies.

Dr. Frangopol holds two honorary doctorates from Belgium and Romania. He is an Honorary Professor of Hong Kong Polytechnic, Tongji, Southeast, and Tianjin Universities. For his  contributions, Dr. Frangopol has been recognized with several awards, including the T. Y. Lin Medal, Newmark Medal, Khan Life-Cycle Civil Engineering Medal, Croes Medal, Howard Award, and Moisseiff Award, to name only a few.

Dr. Frangopol is devoted to serving the profession, having held various leadership positions in SEI, chaired numerous committees, and is the current founder and chair of the Technical Council on Life-Cycle Performance, Safety, Reliability and Risk of Structural Systems, and chair of the Executive Board of the International Association for Structural Safety and Reliability. He served as the Founding President of the International Association for Bridge Maintenance and Safety and of the International Association for Life-Cycle Civil Engineering.

Dr. Frangopol has left an indelible legacy of work, having authored or co-authored more than 300 books, book chapters, and refereed journal articles, and numerous papers in conference proceedings. He is the founding Editor-in-Chief of Structure and Infrastructure Engineering, a leading peer-reviewed journal.

Shridar Krisnaswamy
Department of Mechanical Engineering, Northwestern University

Abstract

Photoacoustics (also known as laser ultrasonics) deals with the optical generation and detection of stress waves in matter. Typically, the technique uses modulated laser irradiation to generate high frequency stress waves (ultrasonic waves) by either ablating the medium or through rapid thermal expansion. The resulting stress wavepackets are also typically measured using optical probes. Photoacoustics therefore provides a non-contact way of carrying out ultrasonic interrogation of a medium to provide information about its properties. Photoacoustics can be used for the nondestructive imaging of structures in order to reveal flaws in the structure, as well as to obtain the material properties of the structural medium.

In this lecture, the basic principles of laser generation of ultrasound in solids will first be briefly described. Several interesting photoacoustic materials characterization and imaging methods that have been developed at Northwestern University will then be discussed. It will be shown that photoacoustic characterization provides some unique advantages over conventional ultrasonics for applications ranging in scale from ultra-thin films and coatings to macro-scale engineering structures.

About the Speaker

Sridhar Krishnaswamy obtained his B. Tech. from the Indian Institute of Technology, Madras, and his M.S. and Ph.D. from the California Institute of Technology, all in aerospace engineering.   Following a post-doctoral fellowship at the University of California, San Diego, he joined the faculty at Northwestern University where he is currently a Professor of Mechanical Engineering and Director of the Center for Quality Engineering & Failure Prevention.    His research interests are in nondestructive materials characterization, intelligent structural health management, optical metrology and ultrasonics, and more recently, in assisted self-assembly of patterns on thin film structures.