Department of Civil Engineering
City College of the City University of New York
New York, NY 10031

There is increased awareness towards security of highway bridges from intentional or unintentional blast events.  Hence, a bridge may need to be designed to sustain both seismic and blast events during its lifetime.  This presentation will address critical issues in bridge security, a highly refined finite element model of a Highway Bridge and numerical simulation results on blast load effects on highway bridges.

Professor Agrawal is Professor of Civil Engineering at the City College of the City University of New York, New York, NY 10031.  He received his Ph.D. in Civil Engineering from the University of California, Irvine, in August 1998 and joined the Coty College of New York in September 1998.  He has published more than 50 Journal papers and 100 conference papers.  He is currently the member of executive committee on U.S. Panel of International Association of Structural Control, Executive Committee Member of Northeast Region of the Advanced National Seismic System (ANSS-NE), and Associate Editor of the Journal of Structural Engineering (seismic protective systems) and Journal of Bridge Engineering (Bridge Management, inspection).

Department of Civil Engineering

Auburn University

Understanding the mixing dynamics of dense water within freshwater aquifer systems is an important fundamental research problem.  Analysis of this problem requires the simulation of density coupled flow processes in the presence of both stable (e.g., saltwater intrusion) and unstable (e.g., tsunami/hurricane invasion, dense leachate discharges from landfills or salt ponds) interface conditions.  In this work, we will present multiple experimental datasets to illustrate the dynamics of density coupled flow in saturated groundwater systems under conditions involving stable and/or unstable (or conditionally stable) interfaces.   These datasets are useful for visualizing the fate and transport of the dense fluid discharged within a saturated porous media formation.  In addition, these datasets can also serve as benchmark problems for testing numerical formulations.

The first set of experiments focused on studying the transport patterns of a saltwater wedge within a freshwater aquifer using a laboratory-scale, porous media tank.  Three types of experiments were performed to develop: a) steady-state salt wedge data observed under different hydraulic gradient conditions; b) transient salt wedge data observed under intruding wedge conditions; and c) transient salt wedge data observed under receding wedge conditions.  A numerical model was used to simulate these datasets.  The model results along with the experimental data are presented as benchmark problems for testing density-coupled groundwater flow models.  A worthiness analysis was completed to test the sensitivity of the experimental problem to density coupling effects.  The results of the analysis show that proposed benchmark is a more robust alternative to the traditional Henry problem.  The new experimental datasets can be used to assess the performance of saltwater intrusion models under both steady-state and transient conditions.

The second set of experiments focused on investigating the fate and transport of saltwater deposited by a tsunami wave into a coastal unconfined aquifer.  The laboratory analysis included three types of contaminant sources: (i) a pond-type source, (ii) a beach infiltration source, and iii) a well source.  These sources were specifically used to model the contamination scenarios that could have occurred in the coastal regions of India and Sri Lanka during the December 2004 tsunami event.  The results show that three types of plumes, namely stable, unstable, and highly-unstable plumes, can evolve from the dense saltwater discharged on the top of an unconfined water table.  Among the three plumes the highly unstable plume, which is also a slow moving plume, appears to be the most hazardous since it has the potential to penetrate deep into an aquifer and contaminate a relatively larger aquifer volume.  This experimental dataset provides a preliminary conceptual model for saltwater transport after a tsunami- or hurricane event in a coastal aquifer.

Dr. Prabhakar Clement is a professor and also hold the distinguished Arthur H. Feagin Chair position at the Department of Civil Engineering, Auburn University, Alabama, USA.   Before joining Auburn University, Dr. Clement worked as a senior research engineer at the Battelle Pacific Northwest National Laboratory for over six years and later as a senior lecturer at the Department of Environmental Engineering, University of Western Australia for three years.  Dr. Clement is the lead author of the widely used reactive transport code RT3D; he is also a co-author of the EPA’s natural attenuation screening tool BIOCHLOR.  His current research interests include development of laboratory scale models to visualize groundwater transport processes, modeling of density-coupled flow problems, numerical modeling of metals transport involving surface complexation reactions, derivation of analytical solutions to reactive transport equations, and management of erosion in engineered hydrological systems.  He has authored over fifty peer-reviewed journal articles.  Web site: http://www.eng.auburn.edu/users/clemept/

Department of Civil Engineering
University of Mississippi

Collocation methods incorporate a wide range of numerical methods that use global, instead of local basis functions for interpolation. Some collocation methods, such as the spectral methods (Chebyshev polynomial, Fourier series, wavelet), require a rectilinear grid, thus are limited to simple geometries. Those methods are not amenable to engineering applications. Other methods, such as the Method of Fundamental Solutions (MFS), the Radial Basis Function (RBF) Collocation, and the Trefftz Method, use scattered points in space for collocation; hence are much more “form‐fitting” to the problem geometry. These methods are also “meshless” because no “elements” are involved. This is a much desired feature for industrial applications, because it cuts down the labor intensive mesh and connectivity data generation. It has driven the industry to develop “meshless FEM”. The real strength of the meshless collocation methods is in its (amazingly) high accuracy. Unlike the more popular numerical methods, such as the Finite Element Method (FEM) and the Finite Difference Method (FDM), which use piece‐wise, low‐degree polynomials for interpolation, collocation methods use global and highly smooth functions. Some interpolants, such as multiquadrics (MQ), are infinitely smooth. As a consequence, some methods, such as the multiquadric or Gaussian collocation method, can achieve exponential error convergence,
 . Using a relatively coarse mesh of 20 20, a uniform accuracy of  has been accomplished solving a Poisson equation (Huang, Lee & Cheng, 2007). This accuracy is impossible to accomplish using FEM or FDM, which typically has an error convergence of  . It will require a mesh refinement and computational effort of astronomical order to achieve this accuracy.

Associate Director (Research)
Gulf Coast Research Center for Evacuation and Transportation Resiliency
Department of Civil and Environmental Engineering
Louisiana State University

The two -fluid model is traditionally derived from particle physics at low temperature. Earlier studies have shown that driver behavior has a significant effect on the parameters of the two-fluid model. These parameters can also be used to characterize driving behavior (aggressive/conservative). This presentation describes two studies undertaken by the author and results indicating aggressive behavior during the mornings and on arterial roads having high crash rates. Motivated by these studies, the two-fluid model is derived from expected utility. Using two-fluid model from the various cities in 1990-91 in America this relationship was validated. Also interesting conclusions can be drawn regarding the regimes under which the two-fluid model is valid. Using the data conclusions regarding the average perception of drivers in 1990-91 in America could be drawn. The parameters of the utility model can be utilized to evaluate training and educational programs for new drivers, to ensure that crashes do not occur due to skewed perception, and help improve safety. The utility model has the potential of being used to engineer human driving behavior.

College of Engineering and Mathematical Sciences
University of Vermont
Burlington, Vermont

It has been revealed through recently completed experiments, that the behavior of dissolved compounds in coastal aquifers, both anthropogenic and naturally occurring, is not as classical theory purports. Experiments conducted in intermediate scale apparatus reveal not only that the effects of tides reduce the average concentration of groundwater contaminants that reach the benthic layer dramatically, but also that the flow and transport of solutes in this region are inaccurately represented by classical flow and transport theory. A new mathematical statement of tidally influenced transport in coastal aquifers is proposed.

 

As the nation’s infrastructure system ages, condition assessment of traditional civil engineering materials has become a critical issue for sustainability and economical infrastructure management.  However, existing nondestructive evaluation (NDE) methods for infrastructure applications do not have the degree of accuracy, reliability, and repeatability necessary for the quantitative assessment of civil materials. This seminar reports on recent applications of ultrasonic wave based techniques for the quantitative NDE of civil infrastructure.  Specific examples discussed will include: a combination of laser ultrasonic, signal processing and analytical modeling techniques to examine the propagation of transient Lamb waves in viscoelastic plates (with applications for repaired concrete); the quantitative characterization of the microstructure of cement-based materials using diffuse and coherent ultrasonic waves; and the development of a focused, air-coupled ultrasonic source in a frequency range relevant for civil infrastructure.  The underlying hypothesis of this research is that ultrasonic techniques can be used to make in situ measurements of critical parameters that characterize the current state of, and then to track the degradation of civil infrastructure.

Coastal and Hydraulics Laboratory

U.S. Army Corps of Engineers Engineering Research and Development Center

The degree to which wetlands attenuate surge is the subject of
debate and difficult to assess. The potential of wetlands to reduce storm surge has typically been expressed as a constant attenuation rate, but the actual situation is much more complex.   A numerical storm surge model was applied to assess the sensitivity of surge response to specified wetland loss.  Results suggest that wetlands do have the potential to reduce surges but the magnitude of attenuation is dependent on the surrounding coastal landscape and the strength and duration of the storm forcing. Numerical models that simulate the relevant physical processes can provide valuable information on how to best integrate wetlands for coastal protection. However, while the model applied for this study has displayed skill in estimating surges over wetlands, the formulations are missing key processes
and model advancements are necessary.

 

For the past twelve years, the use of Global Positioning System (GPS) devices has been under development as a potential method to measure the travel behavior of individuals, in preference to the use of any of variety of self-report methods, such as travel diaries and face-to-face interviews. Within the past year or so, devices have progressed to the point that they are readily able to be used as personal tracking devices, and some years of development of software has taken place for processing the data collected by means of personal, portable GPS devices. In work that began at LSU has continued for the past 8 years at the University of Sydney, Professor Stopher and his associates have pioneered the use of GPS surveys to measure travel behavior. In this seminar, Stopher will describe and demonstrate the people to carry the devices with them. The devices collect travel data on a second-by-second basis. This produces large data files that must be processed to obtain information about individual trips from an origin to a destination. Using a number of rules that will be described in the seminar, the stream of data points are first divided up into specific origin-destination movements. Then, using various GPS layers and additional rules, the mode of travel of each of these movements is inferred, along with the trip purpose. The rules that are used in this process will be described. Results of the processing will be shown to indicate the nature of the final processed information. The University of Sydney in a team with a some of  US firms, is about to commence the first large-scale GPS household survey every undertaken, with 4,000 households to be surveyed in Ohio. The seminar will conclude with a brief discussion of this commencing project and some of the additional advances that are expected to result from it, especially in the addition of Artificial Intelligence applications to assist the current processing software.

Director, O.H. Hinsdale Wave Research Laboratory

Oregon State University

Recent failures of coastal highway bridges during storm events have highlighted the need for improved analysis of wave-bridge superstructure interaction.  Large-scale physical models are an effective method of determining the wave forces on the complex geometry of a highway bridge while minimizing scale effects that can be enhanced by air entrainment, turbulence, and other  processes.  This work represents one of the first large-scale physical model tests for wave-in-deck loads using realistic bridge geometries and random wave forcing. Three laboratory experiments were conducted to examine realistic wave forcing on a large-scale model of a highway bridge superstructure in the 104 m-long Large Wave Flume at the O.H. Hinsdale Wave Research Laboratory at Oregon State University.  A 1:5 scale model of a typical section of the I-10 Bridge over Escambia Bay, Florida that failed during Hurricane Ivan in 2004 was used as the test specimen.  The reinforced concrete specimen consisted of six AASHTO Type-III girders with diaphragms, a deck, and railing details. The model was fitted with six tension-compression load cells to measure horizontal and vertical forces as well as overturning moments.  A unique feature of this model was its roller and rail system which allowed the specimen to move freely along the axis of wave propagation to simulate the dynamic response of the structure for two of the experiments (the first experiment was for a rigid structure).  In addition to the load cells, twelve pressure transducers were embedded in both the exterior and interior girders and along the underside of the bridge deck to record the pressure distribution profiles.  The associated hydrodynamics were measured with ten surface piercing wave gages to provide the incident, reflected, and transmitted wave heights.  The model was subjected to both periodic and random waves over a range of water depths. The data are analyzed to study the relative importance of the impulse load versus the sustained wave load, the magnitudes of the horizontal to vertical forces and their time histories to identify the modes of failure.  The data are compared to the empirical methods outlined in Cuomo et al. (2007), Kaplan et al. (1995), and proposed U.S. Federal Highway standards.   Confidence limits are provided for forces due to periodic waves, and the exceedance probabilities of normalized forces are calculated for random waves.  The authors propose a new method that calculates horizontal and vertical forces for random waves based on exceedance probabilities.  The method will calculate a reference force based on wave height, period, and water depth.  The reference force is then factored by a multiplier based on the desired exceedance probability.  This method will help engineers to make decisions regarding the retrofit of existing bridges and the design of new bridges.

Southern University