Craig Foster, Civil and Materials Engineering and Sandeep Jain and Dimitri Azar, Ophthalmology and Visual Science, Philip Iannoccone, Children’s Memorial Hospital Primary Grant Support: NIH, UIC
Problem Statement and Motivation • • • Collagen cross-linking stiffens corneas weakened by keratoconus
Finite element modeling can help optimize procedure
We are developing models of normal, keratoconic, and and collagen cross-link treated corneas to determine quantities such as strain, stress, stiffness, and and shape under intraocular pressure. One major goal is to examine how the mechanical state of stress and strain influences patterns observed in cell formation and migration, including spiral formation in the epithelium. A second goal is to develop a model that can be used to predict the outcome of a specific treatment regimen of collagen cross-linking on a specific patient.
Cross-linking increases number of bonds between collagen fibers
Key Achievements and Future Goals
Technical Approach •
Multiscale models are developed using the stiffness curves of collagen fibrils oriented in different directions in the cornea (see below) and implemented in a finite element code.
•
Once the traction-free geometry is determined, the intraocular pressure is added, and displace, strain, stress and other quantities of interest are determined.
• • •
Development of anisotropic models based fibril orientation completed Parameter fitting and experimental validation under way Future work includes extending models to keratoconicc corneas and determining effect on cell pattern formation
Shear stress in a preliminary cornea model
Approximate orientations of collagen in the cornea
Sheng-Wei Chi, Department of Civil and Materials Engineering, UIC Primary Grant Support: UIC
Problem Statement and Motivation
Initial trial
Construction of muscle model from a stack of images
Characterization of material properties of tendon from in vivo MRI
Isometric study on the mechanics of passive materials in muscle
•
The patient-specific computational modeling requires tremendous efforts to convert medical images to a 3D geometric representation and to a finite element mesh.
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The study aims to develop an image-based computational framework for modeling biological systems, such as, the musculoskeletal system.
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Seamlessly integrate CAD geometric representation with numerical simulation.
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Develop effective and accurate computational methods for modeling problems that exhibit fundamental difficulties, such as, incompressible, contact, and extremely large deformation problem.
•
Understand better how muscles function and predict muscle force output.
Key Achievements and Future Goals
Technical Approach • • • •
Finite element analysis with mixed formulation Levelset based autonomous image segmentation 3D muscle morphology using levelset methods Anisotropic hyperelastic model for muscle 2
“3D Modeling of Complex Muscle Architecture and Geometry”, Dissertation, S.S.Blemker
W I1 , I 2 , I 4 , I 5 W I 3
total fiber
I1 I1 I 31/ 3 ,
I 2 I 2 I 32 / 3 ,
I 4 I 4 I 31/ 3 ,
I 5 I 5 I 32 / 3
3
act pass iso t f fiber * f fiber *
Anisotropic hyperelastic constitutive model for muscle
a0
1
Levelset based image segmentation
•
Develop an image-based computational framework.
•
Develop a levelset based method to autonomously construct the 3D geometry of muscle from images.
•
Reveal and explain complex strain mechanics in the aponeuroses of contracting skeletal muscle.
•
Study the passive material influence on the deformation and force output of skeletal muscle.
•
The future work is to develop a multiscale constitutive model for muscle active contraction.
Kouros Mohammadian, PhD, S. Yagi, J. Auld, and T.H. Rashidi (PhD Candidates), CME, UIC Primary Grant Support: NIPC/CMAP, FACID, and IGERT (NSF) Synthetic Population
Activity Generation Model
Problem Statement and Motivation
Synthetic City
•
Traditional four step travel demand models are widely criticized for their limitations and theoretical deficiencies
•
These problems lead the model to be less policy sensitive than desired
•
Travel is derived from participation in activities. This fact is not accounted for in 4-step models. Therefore, there is a need for a better modeling approach
•
An activity-based microsimulation travel demand model is considered that simulates activity schedules for all individuals
Activity Scheduling Model
ADS/HTS Surveys
Synthesized Population
Policy scenarios
Executed Schedules Activity-Based Modeling
Activity/Travel Microsimulation
Activities/ Tours/Trips
Travel Demand
Highway/Transit Network Assignment Policy Analysis
Vehicle/Fuel Condition
Emission Model
Key Achievements and Future Goals
Technical Approach • • •
• •
The modeling framework utilizes both econometric and heuristic (rulebased) approaches All human activities are related to broad project categories which have a common goal (e.g., Work, School, Entertainment, etc.) and tasks and activity episodes that are required to reach that goal are modeled Activity participation is modeled at household/individual level (microsimulation) Explicit representation of time/space of occurrence for all travel episodes, linked to associated activities Activity scheduling model is linked to a population synthesizer, rescheduling and resource allocation models, and a regional network microsimulation and emission models
• • • •
• •
A comprehensive multi-tier activity-based microsimulation modeling system is developed. A new population synthesizer is developed. Activity scheduling/rescheduling decision rules are developed and applied to adjust the simulated daily activity patterns. Intra-household interaction rules are developed and applied to account for joint activity generation and household maintenance activity allocation problems. Transferability of activity scheduling/rescheduling decision rules across different spatial and temporal contexts are evaluated. The microsimulation model is applied to evaluate future transportation policy scenarios.
Sheng-Wei Chi, Department of Civil and Materials Engineering, UIC Primary Grant Support: UIC
Problem Statement and Motivation
Progressive penetration processes and predicted damage and contact surfaces
•
Increasing demands are placed on materials and structures to withstand complex phenomena due to extreme loads such as impact and penetration.
•
Key issues needed to be addressed in penetration simulation include high strain rate, extreme large deformation, material fracture, and fragment impact.
•
The study aims to develop a multiscale meshfree approach for modeling fragment penetration into concrete.
•
The ultimate goal is to understand better the phenomena in the penetration process and to predict the structure response under extreme loads.
Comparison of experimental and numerical damage patterns
Key Achievements and Future Goals
Technical Approach • • • •
Semi-Lagrangian Reproducing Kernel Particle formulation in which the point discretization follows the material while the radius of interaction of a point is fixed in Euler coordinates. Levelset enhanced kernel contact algorithm Image-based meso-scale concrete fracture simulation Microstructure informed damage model Meshfree discretization
p
0
Schematic of image-based meso-scale concrete fracture simulation
•
Develop a levelset enhanced kernel contact algorithm that does not require a predefined contact surface.
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Develop an image-based computational approach to effectively construct a computer model based on cross sectional images.
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Develop a concrete constitutive model based on the damage evolution in the meso-scale via the energy bridge theory.
•
The future Goal of this study is to take into consideration multi-physics phenomena in penetration simulations, including: • • •
Thermo effects Rate effects on concrete and projectiles Shock wave
Sybil Derrible, Assistant Professor, Department of Civil and Materials Engineering Primary Grant Support: University of Illinois at Chicago
Problem Statement and Motivation •
With increasing urbanization and growing environmental concerns, public transportation systems will expand in cities all over the world.
•
Current planning practices have limitations, and in particular they omit the topological network feature of transit.
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Inspired from complex systems thinking, the first step is to identify any inherent patterns, common to all transit systems.
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The second step is then to explain any differences in metro network topologies.
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Eventually, we should aim to “steer” relevant metrics in desirable directions for more sustainable and livable cities.
Key Achievements and Future Goals
Technical Approach •
Characterized metro systems according to their State, Form and Structure
•
Developed a methodology to analyze metros as complex systems
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Observed hidden yet relevant patterns common to all metro systems
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Studied the relationship between ridership in network properties.
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Future goals: apply a similar methodology to all transportation modes.
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For more information, visit our webpage: http://www.uic.edu/~derrible/
•
Translate a metro system into a network with a set of nodes (transfer stations and termini) and links (rails). • Calculate relevant topological metrics such as degree of connectivity, cyclomatic number, scaling factor, betweenness centrality. • Plot and observe the evolution of these metrics with network size. • This figure shows one metric (quad. coeff. of cumulative distribution of betweenness centrality) as a function of size, clearly depicting two regimes in metro network topologies.
Farideddin Peiravian, PhD Candidate, and Sybil Derrible, Assistant Professor Department of Civil and Materials Engineering Primary Grant Support: University of Illinois at Chicago
Problem Statement and Motivation
Population
Buildings
Roads
Intersections
City of Chicago Feature Pop+Empl Density Floor Area Density Road Length Density Intersection Density
Radius (km)
Fractal Dimension
R2
tstat
Significant?
1 to 10 11 to 21 1 to 10 11 to 21 3 to 10 11 to 21 3 to 10 11 to 21
1.36 0.73 1.20 0.70 0.21 0.09 0.39 0.19
0.99 0.98 0.99 0.99 0.98 0.95 0.98 0.95
-77 -22 -66 -45 -13 -11 -15 -13
Yes Yes Yes Yes Yes Yes Yes Yes
The characteristics of an urban system is the aggregated outcome of numerous individual and collective choices during its history. The idea is that no matter how a system has evolved, from a larger perspective it has an inherent order, a characteristic of complex systems. The spatial spread of various elements of an urban system exhibit selfrepeating patterns. Although such elements are not directly comparable, using a fractal approach to analyze them offers the provision of a measurable metric, i.e. fractal dimension, enabling one to gage how they co-exist and interact within the built environment. Objectives • Analyze the characteristics of different elements of an urban system • Determine and compare the fractal representations of those elements • Explore the reasons behind such similarities and differences
Key Achievements and Future Goals
Technical Approach • • • • • • • • • • • • •
Selected Chicago for case study, and the “Loop” (CBD) as its center Chose Population+Employment, Gross Floor Area, Road Length, and Number of Intersections as representative elements of the city Obtained the data and removed uninhabited areas (water bodies, etc.) Created 1 km equi-distance rings around the center Clipped the data according to the intersecting ring Calculated the amount of each feature within each ring Created buffers around the center with radial increments of 1 km Calculated the density of each feature within the buffers Plotted the densities versus radius and observed the “Power Law” trend, which is a manifestation of fractal property Plotted log-log diagram of density of each feature versus radius Performed piecewise linear fitting of data based on trend changes Calculated the fractal dimension of each linear segment Performed statistical significance tests to validate the results
• • •
• •
Showed that cities (example: Chicago) are complex systems in which dissimilar features indeed possess inherent order and fractal characteristics which can be captured, quantified, and compared Showed that the spreads of Population+Employment as well as Gross Floor Area in a same city are directly correlated and in fact have very similar fractal dimensions Showed that the distributions of the road network as well as the intersections within a city are directly correlated and in fact have very similar fractal dimensions Used fractal properties to identify the hidden changes in the topology of the urban system, which was otherwise hard to identify. Presented a fractal approach to the characterization of complex urban systems, which can be used in future to identify system deficiencies.
Craig Foster, Civil and Materials Engineering, B.V. Venkatarama Reddy, IISc., Bangalore, India Primary Grant Support: NSF
Problem Statement and Motivation • • •
Though they have been used for millennia, the structural behavior of earthen materials such as rammed earth and stabilized mud block is not well understood. Such materials may fail by diffuse plasticity, fracture along weak interfaces, and fracture through the bulk material. Advanced finite element modeling can help elucidate structural failure modes, limit states, and help design safer, more economical structures.
Stabilized mud block (top, left) and rammed earth (right) buildings
Key Achievements and Future Goals
Technical Approach • • •
Using enhanced finite elements with embedded discontinuities, we can simulate the changing stress and strain as walls are loaded, and model fractures passing through the bodies. The complex material behavior will be fit to bulk and interface constitutive models. Experiments for parameter determination and validation performed with the help of Professor BVV Reddy’s group at IISc, Bangalore.
• • • •
Development of material models and implementation to finite element codes Experimental determination of material properties Validation of large-scale bending and shear experiments Examination of shear behavior of earthen walls Fracture of a stabilized mud block wall in bending
Yield surface of continuum plasticity model
Yield surface for fracture model
Investigators: Kouros Mohammadian, J. Auld, and B. Karimi, CME; and K. Kawamura, CUPPA Primary Grant Support: Illinois Department of Transportation
Problem Statement and Motivation
Legend HSR station HSR line
•
Currently, there are four statewide long-distance travel modes competing across Illinois and its neighboring states: Car, Amtrak, Bus, and Airplane. Each of these travel modes, depending on their attributes such as fare and travel time, attract a specific share of passenger ridership.
•
High-speed (up to 220mph) train is studied as a new alternative travel mode to estimate what percentage of travelers would choose it as their travel mode and how it would affect other modes.
Model Region
Key Achievements and Future Goals
Technical Approach •
A micro-simulation approach was employed to simulate all long distance trips across the study area at person level for the base year and future target year.
Census
Land Use
Synthetic Population
Long Distance Trip Generation
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Total annual ridership of high-speed train was estimated for the base year and for a target year.
•
High-speed train mostly attracts travelers from car and airplane modes.
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An economic model to maximize revenue while maintaining high ridership was also developed and various fare structures were examined.
•
The simulation tool is used to examine various policy scenarios.
HH Survey Trip Distribution Intercept Surveys
Mode Choice
Ridership
Investigators: Kouros Mohammadian and Zahra Pourabdollahi, CME Primary Grant Support: Illinois Department of Transportation (IDOT) & National Center for Freight and Infrastructure Research and Education (CFIRE)
Problem Statement and Motivation •
An efficient freight transportation system could have considerable positive impacts on the economy
•
Freight models and related public policy tools are far behind the logistics and technological advances
•
Freight transport modeling frameworks should be revised in a way that captures the basis of decision making process across the supply chain
Key Achievements and Future Goals
Technical Approach •
•
Develop activity based microsimulation freight transportation framework which simulates decision making process in freight market at a very disaggregate level
•
Incorporate behavioral logistics choice models (supplier selection, shipment size choice, mode choice, shipping chain choice) into the framework
•
•
Simulate the commodity flow between each pair of firms and determines characteristics of each individual shipment
•
Internet-based establishment survey is used to gain insight into decision making process and model logistics choices
•
• • •
Behavioral logistics choice models are developed in the design process to improve freight movement analysis A detailed dataset is collected through the internet-based establishment survey and is used to develop logistics choice models A traffic simulation module will be incorporated directly in the microsimulation model Data simulation techniques are also being improved Simulation results should be validated with the real observed data Policy scenarios should be developed and examined
Nabin Kafle, PhD student and Bo Zou, Assistant Professor Department of Civil and Materials Engineering
Problem Statement and Motivation • Flight delay is a serious problem in the US and causes airlines and passengers tens of billion dollars each year • A significant portion of flight delay stems from delay propagation from earlier flights, but the formation mechanism and the influencing factors are not well understood
DFW
12:50
86
2 14:03
20:40 20:42
21:30
22:56
13:04
14
DCA 16:25 16:42 17:10 17
8
17:18
LAX
00:30
01:35
65
Technical Approach • Formulation and application of a flight-level analytical model to trace the formation of initial delay and how initial delay of an early flight propagates into the subsequent flights throughout a day • Development of flight propagation performance metrics based on the initial delay and delay propagation results from the analytical model • Estimation of truncated regression models to quantify the impacts on delay propagation of an aircraft of system –wide operational performance and buffer times on the ground and in flight schedules
• This research contributes to enhancing the research community’s modeling capability for flight delay propagation and enriching the understanding of spatial-temporal characteristics of the formation and propagation of flight delays in the US
Key Achievements and Future Goals • A new framework for analyzing flight delay propagation is established • The framework is successfully applied to the US domestic network to identify the delay propagation patterns
0
23 13:40
600000
11:10
Minutes 400000
DEN
200000
20 10:50
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Hours of day
New Departure Delay
• Important policy implications are derived from the modeling outputs
Propagated Arrival Delay
Ahmadreza Talebian, PhD Student and Bo Zou, Assistant Professor Department of Civil and Materials Engineering Grant Support: Illinois Department of Transportation (through Urban Transportation Center)
Problem Statement and Motivation • The state of Illinois has launched the High Speed Rail project connecting Chicago and St Louis using track infrastructure shared by passenger and freight rail • It is important to understand the costs and benefits of different stakeholders (travelers, shippers, passenger rail agency, freight railroads) on the shared corridor • This research aims to develop an integrated planning model for optimal rail service to enhance stakeholders’ and policy makers’ understanding of the costs and benefits and engagement in HSR development
Technical Approach • Formulate hyper-graph based binary integer programs to determine optimal train schedules that minimize: 1) System total cost encompassing both passenger and freight side costs 2) Passenger- and freight-side cost sequentially given that HSR has higher priority One of the optimal train • Develop efficient solution schedules procedures to solve the optimal trains schedules
Key Achievements and Future Goals • Optimal train schedules for the future Chicago-St Louis HSR corridor are generated under a variety of service conditions • Evaluation of the impact of speed heterogeneity and service frequency on system overall performance, and welfare distribution among different parties • Exploration of best options for future infrastructure investment to accommodate future demand growth