link: 2003, 2005
Spring Semester 2004
Thursday, 3:00-4:00 pm
Mudd 627

March 4, 2004
Prof. Majid T. Manzari (host: Prof. Ling)
Department of Civil Engineering
George Washington University
A Unified Approach to Deformation and Failure Analysis in Geomechanics

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March 11, 2004 (834 Mudd, 11:00-12:00 am)
Prof. Perulmasamy N. Balaguru (host: Prof. Meyer)
National Science Foundation and Rutgers University
Fiber Reinforced Inorganic Polymers (FRIP): An Innovation to Improve the Fire Resistance of High Strength Composites

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March 25, 2004
Prof. Kazunori Uchida (host: Prof. Ling)
Kobe University, Japan
Strain-path Controlled Triaxial Test of Diluvial Clay

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April 8, 2004
Prof. Franz-Joseph Ulm (host: Prof. Meyer)
MIT
What Osteoporosis and Nuclear Waste Disposal Have in Common

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April 13, 2004 (Tuesday; 2:30-3:30, Puppin)
Prof. Geert Degrande (host: Prof. Dasgupta)
Department of Civil Engineering, K.U.Leuven, Kasteelpark Arenberg 40, B-3001 Leuven, Belgium
Development and experimental validation of a numerical model for ground-borne vibrations from underground railway traffic

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April 19, 2004 (Monday, 5:00-6:00 pm; Davis Auditorium)
Burmister Lecture
Prof. Kenji Ishihara
Chuo University & University of Tokyo
Geotechnical Damage in Recent Earthquakes in Japan and Soil Property Characterization associated with Landslides

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April 29, 2004
Prof. Aspasia Zerva (host: Prof. Deodatis)
Drexel University
Spatial variation of Seismic Ground Motion: Estimation, Modeling and Effects on Bridges

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August 12, 2004
Prof. Bernd Zastrau (host: Prof. Meyer)
Institute of Mechanics and Shell Structures, Technical University Dresden, Germany
Textile Reinforced Concrete - on the Development of an Appropriate Mechanical Model

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ABSTRACT
Prof. Majid T. Manzari
George Washington University
A Unified Approach to Deformation and Failure Analysis in Geomechanics 
Analysis and design of civil engineering structures requires a thorough understanding of the constitutive behavior of civil engineering materials such as concrete, steel, and soil.  Considering the fact that in today’s practice various limit states are considered in a typical design process (e.g. limiting deformations under normal loading condition and preventing failure under extreme loading conditions), there is a strong need for analysis tools that are consistent with these limit states and can provide realistic estimations of stress and strain states in these materials as they approach the corresponding limit states.  As far soil is concerned, reliable computational tools for accurate analysis of deformation and failure are scarce.  Moreover, majority of available design methods use separate tools for analysis of deformation and failure.  In this presentation, a unified framework for modeling constitutive behavior of soils in both pre- and post failure regimes is discussed.  The main ingredient of the proposed framework is a nonlinear kinematic hardening plasticity model for granular soils, which can be used to capture the main characteristics of soil stress-strain behavior under a wide range of confining stresses at various relative densities. This basic model is enhanced with higher order micropolar and/or gradient terms to tackle post failure conditions.  The enhanced constitutive model is shown to alleviate the numerical difficulties that are commonly encountered in the collapse analysis of engineering structures using standard continuum mechanics.  Several examples of the performance of the model in capturing constitutive behavior of soils in pre- and post failure regimes are presented.  Examples of application of the proposed modeling framework in various geomechanics problems are also discussed.

About the Speaker: Currently a member of Civil and Environmental Engineering Faculty at the George Washington University, Majid Manzari holds a Ph.D. in civil engineering from University of California at Davis.  He has over 18 years of practical and research experience in the fields of geotechnical engineering, computational geomechanics, and engineering mechanics.

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Prof. Perulmasamy N. Balaguru
National Science Foundation and Rutgers University
Fiber Reinforced Inorganic Polymers (FRIP): An Innovation to Improve the Fire Resistance of High Strength Composites
High-strength composites have been used by the aerospace industry for more than four decades. These composites, fabricated using high strength carbon or glass fibers and organic polymers, have very high specific strength and excellent corrosion resistance. One major disadvantage is their lack of fire resistance. An inorganic polymer that can withstand more than 2000^o F is the subject of this seminar. This relatively new polymer, which is water-based and non-toxic, cures at room temperature and is compatible with commonly used fibers such as aramid, carbon and glass, and infrastructure materials such as, clay bricks, concrete, steel and wood. The polymer was also used to fabricate composite panels using lightweight organic and inorganic cores and balsawood cores. The fiber-reinforced skin provides both strength and fire protection. The composites were evaluated for strengthening brick walls, unreinforced concrete walls, reinforced concrete beams and steel beams. The various studies indicate that this new inorganic polymer composite has excellent potential for broad applications in aerospace, automobile, marine and civil infrastructure. 

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Prof. Kazunori Uchida (host: Prof. Ling)
Kobe University, Japan
Strain-path Controlled Triaxial Test of Diluvial Clay
This research was conducted to examine the response of submarine diluvial clay to triaxial K0-consolidation testing.  To compare with the diluvial clay, the same testing was performed on reconstructed clay samples of kaolin clay.  The difference between this strain-path controlled K0-consolidation testing and the conventional one, and the advantage of this system is described in detail.  Additionally, consolidation characteristics and structural change were investigated using a bender element system. The clay sample was also observed using a scanning electron microscope (SEM) to compare structural changes before and after testing.

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Prof. John W. Hutchinson
Harvard University
Micron Scale Plasticity
Plastic deformation at the micron scale is assuming increasing importance in areas of technical application, including MEMS, thin films and coatings, and structural composites.  Recent experiments have revealed aspects of micron scale deformation that are not present in bulk plasticity.  Of major importance is a strong size dependence whereby the effective yield strength increases with decreasing specimen size when non-uniform straining occurs.  The phenomenon is revealed by indentation hardness tests, by bending and torsion tests, and by straining of thin films bonded to a substrate. In effect, smaller is stronger when the deformation is non-uniform.

    Understanding and characterization of plasticity at the micron scale has emerged over the past decade with contributions from dislocation mechanics and continuum mechanics.  Micron scale effects have been observed in the range from roughly sub micron to tens of microns.  This size range generally dictates that a continuum theory of plasticity is required to deal with applications, since the total number of dislocations is huge.  A formulation will be discussed which fits within the framework for higher order continuum theory laid out by Mindlin forty years ago.  At the current stage of development of micron scale continuum plasticity, further progress calls for fundamental input from dislocation mechanics.  The presentation will review the current status of micron scale plasticity, both experimental and theoretical, and then lay out where the theory is lacking and how improvements would be informed by additional experiments or dislocation mechanics.

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Prof. Geert Degrande
Department of Civil Engineering, K.U.Leuven, Kasteelpark Arenberg 40, B-3001 Leuven, Belgium
Development and experimental validation of a numerical model for ground-borne vibrations from underground railway traffic
Within the frame of the EC funded project CONVURT, a numerical prediction model is developed for subway induced ground-borne vibrations in buildings.
The dynamic tunnel-soil interaction model is efficiently solved with a coupled FE-BE formulation, accounting for the periodicity of the problem
in the longitudinal direction, while the soil-structure interaction problem at the receiver is solved with a classical coupled FE-BE formulation.

The efficiency of the model is illustrated considering two cases in Paris and London that have been selected for in situ measurements to support the
validation of the numerical model.

The results of the vibration measurements at the site in Regent^Ys Park in London during the passage of a test train on the Bakerloo line at a variable
speed between 25 and 50 km/h are commented in more detail. Vibration measurements have been performed on the axle boxes of the test train,
in the tunnel, in the free field (on the surface and at depth) and on several floors of two buildings at a distance of 70 m from the tunnel. The results of
these vibration measurements are presently used to validate the numerical prediction models.

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Franz-Josef Ulm, Department of Civil & Environmental Engineering 
Massachusetts Institute of Technology, Cambridge MA 02139, USA
What Osteoporosis and Nuclear Waste Disposal Have in Common

Bone is remodeled continuously during adulthood through the resorption of old bone by Osteoclasts and the subsequent formation of new bone by Osteoblasts. These two closely coupled events are responsible for renewing the skeleton while maintaining its anatomical and structural integrity. It has long been argued that remodeling and cracking are intimately related.  

The activity of osteoclast and osteoblast cells in bone is a typical example of a biological process that affects the mechanical performance of biomechanical solids. A kinematics imbalance between osteoclast and osteoblast activity leads to severe bone diseases, such as osteoporosis, increasing the risk of bone failure during downfall. While the link between biological processes and chemical effects has been a focus of biochemistry, the integration of biological processes into a consistent framework of mechanics is challenging. The main difficulty arises from the very nature of biological processes: Biological processes are dynamic in nature, and not defined with respect to an equilibrium state, in contrast to both mechanical processes and chemical processes. In addition, the absence of biological conservation laws complicates the direct integration of biological processes into the description of the material behavior.

In this talk, I will investigate how a biological process orchestrated by cells affects strength and stiffness of the solid; and vice versa: how fractures affect the biochemical activity cells develop at the cell-solid interface. I will show that cracks and fractures in the immediate surrounding of cells are a nonrandom remodeling stimulus, initiating the repair of damage in bone, which at the same time reduces by resorption the risk of crack propagation. With this information available, prediction and anticipation of bone diseases becomes possible, that is the understanding of the physics and its interaction with the biochemical process is essential for preventive medical engineering; and beyond: the process of osteoporosis may well be mimicked for the bio-degradation of radioactive concrete of nuclear power plants.

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Lifelines, such as bridges, dams and pipelines, extend for long distances parallel to the ground, and their supports undergo different motions during an earthquake. This spatial variation of the seismic ground motions can induce additional loads in the structure than the ones induced if the motions at the supports were assumed to be identical. The linear and nonlinear seismic response of a typical highway bridge subjected to both spatially variable and identical ground motions at its supports will be presented. It will be shown that there is difficulty in establishing identical input motions that would have the same effect on the bridge as the spatially variable ones, suggesting that spatially variable motions should be applied as excitations at the bridge supports.

The utilization of spatial variability for the seismic response evaluation of lifelines, however, poses the following problem: Its main descriptor, the coherency, is a measure of the phase variability in the data, which is not readily modeled physically. Coherency models are, generally, obtained from statistical analyses of data recorded at dense instrument arrays, are event- and site-specific, and cannot be reliably extrapolated to different sites and events. An alternative approach for the investigation of coherency will be introduced: It will be shown that there exist correlation patterns between the amplitude and phase variability of seismic data recorded at dense arrays around the amplitude and phase of a coherent component, common for all recording stations. Since amplitude variability is easier visualized and modeled than phase variability, this observation provides insight into the underlying causes of coherency and can lead to its physical modeling.

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September 23, 2004 (Thursday, 2:30-3:30 pm) Mudd 337
Wang J-J (with Hoe Ling & Andrew Smyth)
Typhoon (July 2)-Induced Structures and Geotechnical Failures in Taiwan
The presentation will focus on the findings obtained from the reconnaissance trip to Taiwan following the July 2 typhoon. Significant geological, geotechnical and structural failures occurred in the central part of Taiwan following a total rainfall of 2000 mm, which was about one-third of average annual rainfall. Discussions will be made on developing techniques in mitigating rainfall-induced disaster.
[The trip was sponsored by the Public Construction Commission, the Executive Yuan (cabinet) and it was composed of faculty members and students from the Department of Civil Engineering]

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October 14, 2004 (Thursday, 2:30-3:30 pm) Mudd 337
Prof. Rafi Baker (host: Prof. Ling)
Technion-Israel Institute of Technology, Haifa, Israel
Inter-relations Between Experimental and Computational Aspects of Slope Stability Analysis
The basic idea of this talk is based on the following observations: (a) Strength parameters are not 'God given' and their experimental values depends on the range of normal stresses at which the tests are done. (b) Results of slope stability calculations include the distribution of normal stresses on critical slip surfaces. (c) When ordering strength tests most practical engineer do not specify the range of normal stress at which those tests should be done resulting therefore in a mismatch between experimental and relevant normal stress ranges. The talk shows that for certain problems such a mismatch can lead to a very serious under estimate of safety factors. A simple iterative procedure overcoming this problem is presented and discussed.

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Oct. 28, 2004 (Thursday, 2:30-3:30 pm) Davis Auditorium
Prof. Xing Liu (host: Prof. Meyer)
Department of Civil Engineering, Wuhan University, China
China's Three Gorge Dam

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Nov 4, 2004 (Thursday, 2:30-3:30 pm) Mudd 337
Prof. Lori Graham (host: Prof. Deodatis)
Department of Civil Engineering, Johns Hopkins University
Analysis of Materials with Random Microstructure

Material properties in many engineering analyses are generally represented by average, or homogenized, values for calculating macroscopic behavior, a practice that ignores the micro-scale fluctuations in real materials. This assumption of homogenized material properties is based on the existence of a representative volume element (RVE), which is generally valid when considering displacements, average strains and average stresses of structures where the loading and boundary conditions are at a much larger scale than the microstructure. The RVE assumption is less valid, however, for some of the recently emerging applications of composites to very small-scale systems (e.g., MEM’s or thin-film coatings). Further, even for large-scale systems, the homogenized assumption does not yield an accurate measure of local stresses that are often linked to critical structural behavior. This presentation will describe some recently developed techniques for evaluating local mechanical properties and stresses in random composites. Through stochastic simulation, the variability in the local stresses is assessed as a means of evaluating the severity of inherent randomness in composite materials. A two-dimensional finite-element based model is used to describe the effect of random fiber shapes, sizes and configuration on the material response.

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Nov 5, 2004 (Friday, 2:00-3:00pm) Mudd 627
Prof. Tony Songer (host: Prof. Garvin)
Department of Civil & Environmental Engineering, Virginia Tech
Contracts vs. Covenants in Integrated Project Delivery Systems

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Nov 11, 2004 (Thursday, 2:30-3:30 pm)
Prof. Toh-Ming Lu (hosts: Xi Chen and Ling)
Department of Physics, Rensselaer Polytechnic Institute
Physical Self-Assembly and 3D Integrated Nanostructures

Thin film growth front morphology formed by physical vapor deposition is controlled by many factors including surface diffusion and shadowing effects. If shadowing is dominant, such as in the oblique angle deposition configuration, it can lead to many diverse physically self-assembled 3D nano-size structures that are otherwise difficult to produce by any advanced lithographical techniques. In this talk, I will describe fundamental aspects of the formation of a variety of fascinating nanostructured assemblies using the shadowing mechanism. I will also discuss possible applications of these structures in nanoelectromechanical, nanophotonic,  nanofluidic, memory, sensors, and energy devices.

Biosketches     Dr. Toh-Ming Lu, the Ray Palmer Baker Distinguished Professor of Physics, was the former Chairman of the Physics Department at Rensselaer Polytechnic Institute. Currently he is the Director of Rensselaer Center for Advanced Interconnect Systems Technologies where 25 faculty (from 13 universities) and 40 graduate students are involved in advanced on-chip interconnect research. He is Fellow of American Physical Society and Fellow of American Vacuum Society. He is co-recipient of the 2004 Materials Research Society Medal Award.

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Nov 12, 2004 (Friday, 1:30-2:30 pm) Mudd 627
Prof. Pol D. Spanos (host: Prof. Deodatis)
Departments of Civil and Mechanical Engineering
Rice University, Houston, TX
Time-Frequency Analysis Techniques in Earthquake Engineering
Traditional Fourier spectral analysis has been an important tool in earthquake engineering for several decades.  However, it does not readily capture non-stationary features, which are inherently present in ordinary seismic events.  The seminar will focus on modern time-frequency analysis techniques for capturing localized effects and evolutionary frequency content by using wavelets, chirplets, and signal intrinsic modes.  These techniques will be used both for analyzing ground accelerograms, and linear/nonlinear responses of benchmark structures.  Finally, the potential use of these techniques in conjunction with the problem of design spectrum-compatible synthesis of accelerograms, and the development of analytical representations of evolutionary spectra in the Priestley context will be discussed.

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