A Partnership in Research and Outreach David A. Lange, CEAT Director Department of Civil and Environmental Engineering.

ILLINOISUniversity of Illinois at Urbana -Champaign


A Partnership in Research and Outreach

David A. Lange, CEAT DirectorDepartment of Civil and Environmental Engineering





CEAT OverviewHistory

• Began in 1995 as FAA COE (Barry Dempsey, Director)

• Original focus on pavements

• Broadened to wildlife hazards, lighting technology

• Partnership with O’Hare Modernization Program began in 2004



OMP, FAA and UIUC in partnership

O’HareModernization

Program

FederalAviation

Administration

Subgrade issues

Materials & Pavements

Outreach

Subgrade & pavements

Wildlife issues

Anti-icing

Outreach



Our OMP Partner• $6.6B program

– 35 miles of runways, taxiways

– 2.2M cu yds of PCC– 29M cu yds of earthwork

• Modern, parallel runway configuration

• Massive earthmoving, construction, hydraulic, environmental impact challenges



OMP objectives• Technical objectives

– Illuminate technical issues at O’Hare– Lead to cost-effective solutions

• Outreach objectives– Reach contractor community– Deliver educational programs



OMP Projects• Technical

– Subgrade stabilization -- Erol Tutumluer & Marshall Thompson

– Raw Materials -- Leslie Struble– PCC Pavement -- Jeff Roesler & David Lange

• Outreach– College support is vital -- Minosca Alcantara, Eve

Earles, John Popovics– Focus: MBE/WBE, Contractors, Education



FAA Projects• Pavement Research Program

– Moisture curling of concrete slabs for airfield applications• D.A. Lange and J.R. Roesler

– Materials Testing for NAPTF Base/Subbase and Subgrade Layers• E.Tutumluer

– Fatigue and Fracture Behavior of Airfield Concrete Slabs• J.R. Roesler, S.P. Shah, B. Mu

– Anti-icing Coating Self Cleaning Properties and Wearing Characteristics Study at ORD

• B.J. Dempsey

– Fatigue in Airport Pavements• S.H. Carpenter

– Design of Flexible Overlay Systems for Asphalt Pavements: Phase II Advanced Model Development

• W.G. Buttlar



FAA Projects (cont.)• Wildlife Research Program

– Bird Strike Advisory System• Ed Herricks

• Outreach Program– Summer COE Internship Program for Minority Graduate Students

• B.J. Dempsey



Moisture curling project• Basic driving force

– Internal capillary stresses imposed under partial saturation

• Water vapor in pores• Water layer contacting solid phases• RH defines magnitude of stress felt by solid

• Material modeling– Hygrothermal forces, shrinkage, creep– Time dependence, inter-dependence

• Structural modeling• Validation using lab tests & NAPTF slab tests



Two cases

• Highly restrained slab Cracking

• Low restraint in slab Curling + Wheel

Load Cracking



UIUC RH-temperature measurement system



Digital sensor packaged for placement in fresh concrete

• Sensirion digital RH/Temp sensor– Absolute accuracy ~±2%

RH and 0.5° C

• Packaging system allows placement in fresh concrete– Small plastic tube with

Gore-Tex cap• Gore-Tex allows vapor

transmission while blocking liquid water



Typical RH gradient

Different depths from drying surface in 3”x3” concrete prism exposed to 50% RH and 23o C

3" x 3" Concrete Prism, 0.50 w/c

60

65

70

75

80

85

90

95

100

0 2 4 6 8 10 12 14

Time Days

Internal RH (%)

1/2"

1/4"

3/4"

Depth from drying surface



Symmetrically drying concrete prism

0

5

10

15

20

25

30

35

40

45

50

0 10 20 30 40 50 60 70

Specimen Width (mm)

Internal RH Change (%)

3 days

5 days

7 days

Surface RH

assumed to be

~ambient



Simple model for shrinkage strains

76mm x-section

Superposition of strains

elcrshT εεεε ++=

εT εsh



Free shrinkage stress gradients

-2

-1

0

1

2

3

4

5

6

0 10 20 30 40 50 60 70

Specimen Width (mm)

Stress (MPa)

A-44

B-44

C-44

D-44

41

38

32

3 days age (2 days of drying)

Modelpredicteddamage

zones

NAPTF SINGLE SLAB15 ft x 15 ft x 11 in. SINGLE SLAB

MSC Patran Geometric Modeling

EACON(UIUC)Stress Analysis

MSC Patran Post Processing

EACON_export.pcl

EACON_import.pcl

Matlab EngineSparse Matrix Solver

Stress Analysis Code for Early Age Concrete

NOTE: EACON is * a 3D Nonlinear FEA code written in C++ * using 20-node solid and 2-node spring element

Unique feature:

EACON handles time and stress dependent material properties

NUMERICAL MODELING

NUMERICAL ANALYSISMaterial Properties Need for Numerical Analysis

■ “Instantaneous” properties E(t), v, fc(t), ft(t)

■ “Delayed” property Creep

■ Hygrothermal strain Volume change due to Temperature & Humidity

X

Z

Y

X fixed

Non-linear spring

( Z only)

Y fixed

NUMERICAL PRACTICEGeometry and Boundary Conditions

X,Y,Z fixed

7.5 ft

7.5 ft

11 in.

Deformation & Ground Contact

Age = 1.5 days , 500x Age = 3 days, 500x

NUMERICAL PRACTICE

Virtual material & surface drying scenario

Max. Principle Stress at edge ( Age = 3.0 days )

460psi

0 psi

NUMERICAL PRACTICE

Virtual material & surface drying scenario

0 7 14 21 28 35 42 49 56 63 70

0

20

40

60

80

100

120

140

160

Time (day)

Displacement( in.

× 1000)

Edge center(B)

Corner (A) NAPTF

EACON

NAPTF SINGLE SLAB ANALYSISLift-up Displacements at corner & edge

Virtual material & measured temperature and humidity history

A

B



Summary• We want to provide:

– a more complete understanding of mechanisms

– new sensor technology– accurate, complete material models– useful software tool for analysis

• Results relate to material selection (e.g. high FA concrete)

A Partnership in Research and Outreach David A. Lange, CEAT Director Department of Civil and Environmental Engineering.

Documents

concrete prismsimple

3x3 concrete prism

node solid

wildlife hazards

naptf basesubbase

vapor transmission

faa coe barry dempsey

magnitude of stress