Time-dependent Considerations of I-35W St. Anthony Falls Bridge including Long-term Monitoring

309 Pages·2014·17.13 MB·English

by  Catherine French

Modeling and Monitoring the
Long-Term Behavior of

Post-Tensioned Concrete Bridges
Catherine E.W. French, Principal Investigator
Department of Civil, Environmental and Geo- Engineering
University of Minnesota

November 2014
Research Project
Final Report 2014-39
To request this document in an alternative format call 651-366-4718 or 1-800-657-3774 (Greater
Minnesota) or email your request to [email protected]. Please request at least one
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Technical Report Documentation Page
1. Report No. 2. 3. Recipients Accession No.
MN/RC 2014-39
4. Title and Subtitle 5. Report Date
Modeling and Monitoring the Long-Term Behavior of November 2014
Post-Tensioned Concrete Bridges 6.

7. Author(s) 8. Performing Organization Report No.
Catherine E.W. French, Carol K. Shield,
Brock D. Hedegaard
9. Performing Organization Name and Address 10. Project/Task/Work Unit No.
Department of Civil, Environmental and Geo- Engineering CTS Project # 2013008
University of Minnesota 11. Contract (C) or Grant (G) No.
500 Pillsbury Drive SE
Minneapolis, MN 55455 (C) 99008, (wo) 42

12. Sponsoring Organization Name and Address 13. Type of Report and Period Covered
Minnesota Department of Transportation Final Report
Research Services & Library 14. Sponsoring Agency Code
395 John Ireland Boulevard, MS 330
St. Paul, MN 55155
15. Supplementary Notes
http://www.lrrb.org/pdf/201439.pdf
16. Abstract (Limit: 250 words)
The time-dependent and temperature-dependent behavior of post-tensioned concrete bridges were investigated
through a case study of the St. Anthony Falls Bridge, consisting of laboratory testing of concrete time-dependent
behaviors (i.e., creep and shrinkage), examination of data from the in situ instrumented bridge, and time-dependent
finite element models. Laboratory results for creep and shrinkage were measured for 3.5 years after casting, and the
data were best predicted by the 1978 CEB/FIP Model Code provisions. To compare the in situ readings to constant-
temperature finite element models, the time-dependent behavior was extracted from the measurements using linear
regression. The creep and shrinkage rates of the in situ bridge were found to depend on temperature. An adjusted
age using the Arrhenius equation was used to account for the interactions between temperature and time-dependent
behavior in the measured data. Results from the time-dependent finite element models incorporating the full
construction sequence revealed that the 1990 CEB/FIP Model Code and ACI-209 models best predicted the in situ
behavior. Finite element analysis also revealed that problems associated with excessive deflections or development
of tension over the lifetime of the bridge would be unlikely. The interactions between temperature and time-
dependent behavior were further investigated using a simplified finite element model, which indicated that vertical
deflections and stresses can be affected by the cyclic application of thermal gradients. The findings from this study
were used to develop an anomaly detection routine for the linear potentiometer data, which was successfully used
to identify short-term and long-term artificial anomalies in the data.
17. Document Analysis/Descriptors 18. Availability Statement
Bridges, Monitoring, Finite element method, Time dependence No restrictions. Document available from:
National Technical Information Services,
Alexandria, Virginia 22312
19. Security Class (this report) 20. Security Class (this page) 21. No. of Pages 22. Price
Unclassified Unclassified 309
Modeling and Monitoring the Long-Term Behavior of
Post-Tensioned Concrete Bridges

Final Report

Prepared by:

Catherine E.W. French,
Carol K. Shield,
Brock D. Hedegaard
Department of Civil, Environmental and Geo- Engineering
University of Minnesota

November 2014

Published by:

Minnesota Department of Transportation
Research Services & Library
395 John Ireland Boulevard, MS 330
St. Paul, MN 55155

This report represents the results of research conducted by the authors and does not necessarily represent the views
or policies of the Minnesota Department of Transportation or the University of Minnesota. This report does not
contain a standard or specified technique.

The authors, the Minnesota Department of Transportation, and/or the University of Minnesota do not endorse
products or manufacturers. Trade or manufacturers’ names appear herein solely because they are considered
essential to this report.
Acknowledgements
Numerical computations were performed using resources provided by the University of Minnesota
Supercomputing Institute.
Table of Contents

Chapter 1: Introduction ................................................................................................................................. 1

1.1 Problem Statement .............................................................................................................................. 1

1.2 Research Approach and Outline ......................................................................................................... 1

1.3 Bridge Description .............................................................................................................................. 2

Chapter 2: Instrumentation ........................................................................................................................... 4

2.1 Overview ............................................................................................................................................ 4

2.2 Static System: VWSGs and Thermistors ............................................................................................ 4

2.2.1 Superstructure VWSGs ............................................................................................................... 4

2.2.2 Superstructure Thermistors ......................................................................................................... 6

2.2.3 Data Collection for the Static System ......................................................................................... 8

2.3 Dynamic System: Linear Potentiometers ........................................................................................... 9

2.3.1 Linear Potentiometers .................................................................................................................. 9

2.3.2 Data Collection for the Dynamic System .................................................................................. 10

Chapter 3: Concrete Material Testing ......................................................................................................... 14

3.1 Compressive Strength and Modulus of Elasticity ............................................................................ 14

3.1.1 MnDOT Testing ........................................................................................................................ 14

3.1.2 UMN Testing ............................................................................................................................. 15

3.1.3 Cemstone Testing ...................................................................................................................... 15

3.2 Tensile Strength ................................................................................................................................ 16

3.3 Creep and Shrinkage ......................................................................................................................... 16

3.4 Coefficient of Thermal Expansion ................................................................................................... 17

3.4.1 UMN Laboratory Testing .......................................................................................................... 17

3.4.2 In Situ Testing ........................................................................................................................... 17

3.4.3 Results Summary ....................................................................................................................... 23

3.5 Unit Weight ...................................................................................................................................... 23

3.5.1 Sample Preparation.................................................................................................................... 23

3.5.2 Testing Procedure ...................................................................................................................... 24

3.5.3 Results ....................................................................................................................................... 24

Chapter 4: Time-Dependent Behavior of Concrete .................................................................................... 25

4.1 Phenomena of Creep and Shrinkage ................................................................................................. 25

4.1.1 Concrete Creep .......................................................................................................................... 25

4.1.2 Concrete Shrinkage ................................................................................................................... 27

4.1.3 Review of Time-Dependent Studies on Existing Structures ..................................................... 27

4.2 Material Parameters for Time-Dependent Models ........................................................................... 28

4.3 ACI Committee 209 ......................................................................................................................... 31

4.3.1 Creep ......................................................................................................................................... 31

4.3.2 Shrinkage ................................................................................................................................... 33

4.3.3 Comments on Original Calibration of the ACI-209 Time-Dependent Model ........................... 34

4.3.4 Derived Material Properties for FEM Input .............................................................................. 35

4.4 B3 ..................................................................................................................................................... 35

4.4.1 Creep ......................................................................................................................................... 35

4.4.2 Shrinkage ................................................................................................................................... 38
4.4.3 Comments on Original Calibration of the B3 Time-Dependent Model .................................... 38

4.4.4 Derived Material Properties for FEM Input .............................................................................. 39

4.5 CEB/FIP Model Code 1978 .............................................................................................................. 39

4.5.1 Creep ......................................................................................................................................... 39

4.5.2 Shrinkage ................................................................................................................................... 41

4.5.3 Comments on Original Calibration of the 1978 CEB/FIP Time-Dependent Model ................. 42

4.5.4 Derived Material Properties for FEM Input .............................................................................. 42

4.6 CEB/FIP Model Code 1990 .............................................................................................................. 43

4.6.1 Creep ......................................................................................................................................... 43

4.6.2 Shrinkage ................................................................................................................................... 45

4.6.3 Comments on Original Calibration of the 1990 CEB/FIP Time-Dependent Model ................. 46

4.6.4 Derived Material Properties for FEM Input .............................................................................. 46

4.7 GL2000 ............................................................................................................................................. 47

4.7.1 Creep ......................................................................................................................................... 47

4.7.2 Shrinkage ................................................................................................................................... 48

4.7.3 Comments on Original Calibration of the GL2000 Time-Dependent Model ............................ 48

4.7.4 Derived Material Properties for FEM Input .............................................................................. 49

4.8 AASHTO LRFD Bridge Design Specifications ............................................................................... 49

4.8.1 Creep ......................................................................................................................................... 50

4.8.2 Shrinkage ................................................................................................................................... 52

4.8.3 Comments on Original Calibration of AASHTO Time-Dependent Provisions ........................ 53

4.8.4 Derived Material Properties for FEM Input .............................................................................. 54

4.9 Summary........................................................................................................................................... 54

4.9.1 Discussion of Basic and Drying Creep ...................................................................................... 55

4.9.2 Discussion of Shrinkage ............................................................................................................ 55

4.9.3 Discussion of Volume-to-Surface Ratio and Predrying ............................................................ 56

4.9.4 Applicability and Usability of Models ...................................................................................... 57

Chapter 5: Validation of Time-Dependent Properties ................................................................................ 58

5.1 Aging Compressive Strength ............................................................................................................ 58

5.2 Aging Elastic Modulus ..................................................................................................................... 59

5.3 Shrinkage .......................................................................................................................................... 59

5.4 Creep................................................................................................................................................. 60

5.5 Summary and Conclusions ............................................................................................................... 62

Chapter 6: Time-Dependent Finite Element Modeling ............................................................................... 64

6.1 Time-Dependent Finite Element Model Overview .......................................................................... 64

6.1.1 Geometry and Mesh .................................................................................................................. 64

6.1.2 Material Properties .................................................................................................................... 67

6.1.3 Construction Staging Sequence ................................................................................................. 67

6.1.4 Loading ...................................................................................................................................... 71

6.2 Modeling Time-Dependent Behavior of Viscoelastic Materials ...................................................... 72

6.2.1 Kelvin Chain Model for Viscoelastic Materials ........................................................................ 73

6.2.2 Post-Widder Theorem and Curve Fitting the Compliance Function ......................................... 74

6.2.3 Rate-Type Creep Model in Elastic Finite Element Analysis ..................................................... 77

6.2.4 Implementation of Shrinkage Strains ........................................................................................ 79
6.2.5 Relaxation of Post-Tensioning Steel ......................................................................................... 79

6.2.6 Summary of Kelvin Chain Approximation in Finite Element Implementation ........................ 80

6.2.7 Exceptions to Kelvin Chain Model Methodology ..................................................................... 83

6.2.8 Validation of Kelvin Chain Approximation .............................................................................. 88

6.3 Modeling Time-Dependent Behavior of Composite Materials ........................................................ 90

6.3.1 Effects of Mild Steel on Concrete Time-Dependent Behavior .................................................. 90

6.3.2 Adjustment of Kelvin Chain Creep Methodology for Composites ........................................... 91

6.3.3 Summary of Kelvin Chain Approximation for Composite Materials ....................................... 95

6.3.4 Validation of Time-Dependent Modeling of Composite Materials ........................................... 96

6.3.5 Summary and Conclusions ........................................................................................................ 98

Chapter 7: Examining Measured Data for Time-Dependent Behaviors ................................................... 100

7.1 Extraction of Time-Dependent Behavior using Linear Regression ................................................ 100

7.2 Temperature Dependence of Time-Dependent Phenomena ........................................................... 103

7.2.1 Temperature Dependence of Concrete Aging ......................................................................... 103

7.2.2 Temperature Dependence of Basic Creep ............................................................................... 104

7.2.3 Temperature Dependence of Shrinkage and Drying Creep ..................................................... 106

7.3 Time-Dependent Behavior in Measured Data ................................................................................ 106

7.3.1 Evidence Showing Temperature Dependence of Time-Dependent Behavior ......................... 106

7.3.2 Temperature Correction of Time-Dependent Behavior in Measured Data ............................. 109

Chapter 8: FEM Results for Time-Dependent Behavior........................................................................... 112

8.1 Comparison of Finite Element Model with Measured Data ........................................................... 112

8.1.1 Longitudinal Deflections ......................................................................................................... 112

8.1.2 Concrete Strains ...................................................................................................................... 115

8.1.3 Vertical Deflections ................................................................................................................. 116

8.1.4 Longitudinal Concrete Stresses ............................................................................................... 118

8.2 Uncertainty in Estimating Time-Dependent Behavior ................................................................... 121

8.2.1 Discussion of Creep and Shrinkage Uncertainty ..................................................................... 121

8.2.2 Investigating Time-Dependent Uncertainty using FEM ......................................................... 123

8.2.3 Accounting for Uncertainty of Time-Dependent Behavior in Design .................................... 124

8.3 Summary and Conclusions ............................................................................................................. 125

Chapter 9: FEM Investigation of Thermal Effects on Time-Dependent Behavior ................................... 127

9.1 Methodology................................................................................................................................... 127

9.2 Validation of Temperature-Dependent FEM .................................................................................. 129

9.3 Effects of Cyclic Thermal Input on Time-Dependent Behavior..................................................... 130

9.3.1 FEM Model Construction ........................................................................................................ 130

9.3.2 Investigated Thermal Variations ............................................................................................. 132

9.3.3 Results ..................................................................................................................................... 134

9.4 Summary and Conclusions ............................................................................................................. 138

Chapter 10: Protocol for Long-Term Monitoring System ........................................................................ 142

10.1 Extrapolation of Time-Dependent Data ....................................................................................... 143

10.1.1 Bayes’ Theorem .................................................................................................................... 143

10.1.2 Bayesian Regression .............................................................................................................. 144

10.1.3 Bayesian Prediction ............................................................................................................... 146

10.1.4 Long-Term Bayesian Predictions on Linear Potentiometer Data .......................................... 147
10.2 Short-Term Anomaly Detection ................................................................................................... 149

10.2.1 Criteria for Short-Term Anomaly Detection Algorithm........................................................ 149

10.2.2 Summary of Short-Term Check Method ............................................................................... 150

10.2.3 Validating Short-Term Check Methodology on Existing Data ............................................. 151

10.2.4 Validating Short-Term Check with Artificially Induced Perturbations ................................ 152

10.3 Long-Term Anomaly Detection ................................................................................................... 154

10.3.1 Criteria for Long-Term Anomaly Detection Algorithm ........................................................ 154

10.3.2 Summary of Long-Term Check Method ............................................................................... 158

10.3.3 Validating Long-Term Check on Existing Data .................................................................... 158

10.3.4 Validating Long-Term Check for Artificially Induced Perturbations ................................... 159

10.4 Summary and Conclusions ........................................................................................................... 160

Chapter 11: Summary and Conclusions .................................................................................................... 163

11.1 Interactions between Temperature and Time-Dependent Behavior ............................................. 163

11.1.1 Method for Separating Time- and Temperature-Dependent Behavior .................................. 163

11.1.2 Temperature-Dependent Rates of Time-Dependent Phenomena .......................................... 164

11.1.3 Impact of Cyclic Temperatures on Time-Dependent Behavior ............................................. 165

11.2 Long-Term Behavior of St. Anthony Falls Bridge ....................................................................... 167

11.3 Anomaly Detection Routine for Structural Monitoring ................................................................ 168

11.3.1 Detecting Short-Term Anomalies.......................................................................................... 168

11.3.2 Detecting Long-Term Anomalies .......................................................................................... 169

11.3.3 Present Drawbacks and Topics for Future Study .................................................................. 170

11.4 Efficacy of Investigated Time-Dependent Models ....................................................................... 171

References ................................................................................................................................................. 173

Tables ........................................................................................................................................................ 177

Figures ...................................................................................................................................................... 202

Appendix A: Proof of Rate-Type Creep Methodology

Appendix B: Validation of Time-Dependent FEM of St. Anthony Falls Bridge

Appendix C: Investigation of Simplified Construction Staging Procedure
List of Tables
Table 1.1: Casting dates of CIP spans ....................................................................................................... 177
Table 1.2: Casting and erection dates of the precast segments ................................................................. 178
Table 1.3: Load stages during construction .............................................................................................. 179
Table 2.1: Summary of gage types and locations ..................................................................................... 180
Table 2.2: VWSG and thermistor labeling, locations, and connections ................................................... 181
Table 2.3: Channel configuration for CR10 data collection during construction ..................................... 185
Table 2.4: Linear potentiometer labeling and locations ............................................................................ 186
Table 3.1: MnDOT test results for superstructure concrete compressive strength ................................... 187
Table 3.2: UMN test results for superstructure concrete compressive strength and modulus of
elasticity ................................................................................................................................................. 187
Table 3.3: Cemstone test results for superstructure concrete compressive strength and modulus of
elasticity ................................................................................................................................................. 188
Table 3.4: Superstructure concrete tensile strength measured by UMN ................................................... 188
Table 3.5: Creep sample loading and unloading ....................................................................................... 189
Table 3.6: Summary of coefficient of thermal expansion using UMN laboratory specimens .................. 189
Table 3.7: Averaged coefficient of thermal expansion by location using VWSG data ............................ 190
Table 3.8: Average superstructure coefficient of thermal expansion using LP data ................................. 190
Table 3.9: Summary of concrete coefficient of thermal expansion .......................................................... 190
Table 4.1: Mix design for superstructure and pier concrete ...................................................................... 190
Table 4.2: Volume-to-surface and reinforcement ratios for concrete elements in Span 1 ........................ 191
Table 4.3: Volume-to-surface and reinforcement ratios for concrete elements in Span 2 ........................ 192
Table 4.4: Volume-to-surface and reinforcement ratios for concrete elements in Span 3 ........................ 193
Table 4.5: Volume-to-surface and reinforcement ratios for concrete elements in piers and barrier
rails ........................................................................................................................................................ 194
Table 4.6: Coefficients for increase in concrete strength with time (ACI 209R-92, Table 2.2.1) ............ 194
Table 4.7: Ultimate shrinkage correction for duration of curing (ACI 209R-92, Table 2.5.3) ................. 194
Table 4.8: Summary of model inputs required for time-dependent behavior of superstructure
concrete .................................................................................................................................................. 195
Table 4.9: Summary of model inputs required for time-dependent behavior of pier and barrier rail
concrete .................................................................................................................................................. 196
Table 4.10: Humidity dependent coefficients φ , λ, and ε from 1978 CEB/FIP Model Code ............... 197
f1 s1
Table 6.1: Analysis Steps for Erection Procedure .................................................................................... 198
Table 6.2: Summary of post-tensioning stresses ....................................................................................... 199
Table 6.3: Approximation coefficients for creep terms β (t – t ) and β(t) of 1978 CEB/FIP Model
d 0 f
Code ....................................................................................................................................................... 199
Table 6.4: Approximation coefficients for shrinkage term β(t) of 1978 CEB/FIP Model Code ............. 199
s
Table 7.1: Fit parameters for Northbound Span 1 LP data using unadjusted time ................................... 200
Table 7.2: Fit parameters for Northbound Span 3 LP data using unadjusted time ................................... 200
Table 7.3: Fit parameters for Southbound Span 1 LP data using unadjusted time ................................... 200
Table 7.4: Fit parameters for Southbound Span 3 LP data using unadjusted time ................................... 200
Table 8.1: Load cases and corresponding multiple presence factors used for investigation of
critical Service I and Service III vehicular live loading ........................................................................ 201