U.S. Department of Transportation

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Accelerating Innovation

**Publication No. FHWA-HIF-13-039June 2013**

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This report does not constitute a standard, specification, or regulation.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this report only because they are considered essential to the objective of the document.

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

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9. Performing Organization Name and Address 1 University of Washington, Seattle, WA |
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15. Supplementary Notes |
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16. Abstract The tests provide data regarding the performance of the precast column-to-spread footing connection. The results indicate that the connection, when used with a precast column, is sufficiently strong to support the factored design gravity loads and to resist plastic hinging in the column above the footing. The behavior is emulative of cast-in-place performance. However, the precast column also provides an improved load path for lateral force transfer to the footing, owing to the elimination of outwardly hooked column longitudinal reinforcement. Additionally, the connection performance is adequate without reinforcement passing from the footing into the column, thus simplifying construction. |
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17. Key Words |
18. Distribution Statement |
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9. Security Classif. (of this report) Unclassified |
20. Security Classif. (of this page) Unclassified |
21. No. of Pages 184 |
22. Price |

This report provides technical information from the laboratory testing of three precast column-to-spread footing specimens. These tests were conducted to support the development of a precast bent system for use in high seismic regions.

This report consists of seven chapters.

Chapter 1 provides background and overview material, including the spread footing socket connection concept and the research objective and scope.

Chapter 2 covers the design of the test specimens.

Chapter 3 provides a description of the test setup, instrumentation, and the method of control of the testing process.

Chapter 4 provides definition of the damage states that were observed and an overview of the damage progression that occurred during testing.

Chapter 5 provides the measured response of the three specimens, including material strengths, force and moment vs. displacement plots, curvature distributions, displacement histories, and strain histories. Strain histories are provided for all the principal reinforcement types. Also included are the results of the post-seismic tests of the axial capacity of the foundation.

Chapter 6 covers the analysis of the observed and recorded data, and it provides treatment of various modes of potential failure and how the test results compared relative to those failure modes.

Chapter 7 provides a summary, conclusions, and recommendations.

Appendixes are included to report more detailed information that may be useful in understanding the response of the specimens and the progression of damage

Symbol | When You Know | Multiply By | To Find | Symbol |
---|---|---|---|---|

Length | ||||

in | inches | 25.4 | millimeters | mm |

ft | feet | 0.305 | meters | m |

yd | yards | 0.914 | meters | m |

mi | miles | 1.61 | kilometers | km |

Area | ||||

in^{2} |
square inches | 645.2 | square millimeters | mm^{2} |

ft^{2} |
square feet | 0.093 | square meters | m^{2} |

yd^{2} |
square yard | 0.836 | square meters | m^{2} |

ac | acres | 0.405 | hectares | ha |

mi^{2} |
square miles | 2.59 | square kilometers | km^{2} |

Volume | ||||

fl oz | fluid ounces | 29.57 | milliliters | mL |

gal | gallons | 3.785 | liters | L |

ft^{3} |
cubic feet | 0.028 | cubic meters | m^{3} |

yd^{3} |
cubic yards | 0.765 | cubic meters | m^{3} |

NOTE: volumes greater than 1000 L shall
be shown in m^{3} |
||||

Mass | ||||

oz | ounces | 28.35 | grams | g |

lb | pounds | 0.454 | kilograms | kg |

T | short tons (2000 lb) | 0.907 | megagrams (or "metric ton") | Mg (or "t") |

Temperature (exact degrees) | ||||

°F | Fahrenheit | 5 (F-32)/9 or (F-32)/1.8 |
Celsius | °C |

Illumination | ||||

fc | foot-candles | 10.76 | lux | lx |

fl | foot-Lamberts | 3.426 | candela/m^{2} |
cd/m^{2} |

Force and Pressure or Stress | ||||

lbf | poundforce | 4.45 | newtons | N |

lbf/in^{2} |
poundforce per square inch | 6.89 | kilopascals | kPa |

Symbol | When You Know | Multiply By | To Find | Symbol |
---|---|---|---|---|

Length | ||||

mm | millimeters | 0.039 | inches | in |

m | meters | 3.28 | feet | ft |

m | meters | 1.09 | yards | yd |

km | kilometers | 0.621 | miles | mi |

Area | ||||

mm^{2} |
square millimeters | 0.0016 | square inches | in^{2} |

m^{2} |
square meters | 10.764 | square feet | ft^{2} |

m^{2} |
square meters | 1.195 | square yards | yd^{2} |

ha | hectares | 2.47 | acres | ac |

km^{2} |
square kilometers | 0.386 | square miles | mi^{2} |

Volume | ||||

mL | milliliters | 0.034 | fluid ounces | fl oz |

L | liters | 0.264 | gallons | gal |

m^{3} |
cubic meters | 35.314 | cubic feet | ft^{3} |

m^{3} |
cubic meters | 1.307 | cubic yards | yd^{3} |

Mass | ||||

g | grams | 0.035 | ounces | oz |

kg | kilograms | 2.202 | pounds | lb |

Mg (or "t") | megagrams (or "metric ton") | 1.103 | short tons (2000 lb) | T |

Temperature (exact degrees) | ||||

°C | Celsius | 1.8C+32 | Fahrenheit | °F |

Illumination | ||||

lx | lux | 0.0929 | foot-candles | fc |

cd/m^{2} |
candela/m^{2} |
0.2919 | foot-Lamberts | fl |

Force and Pressure or Stress | ||||

N | newtons | 02.225 | poundforce | lbf |

kPa | kilopascals | 0.145 | poundforce per square inch | lbf/in^{2} |

* SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380. (Revised March 2003)

**CHAPTER 1. INTRODUCTION**

Need for Rapid Construction

Socket Connection Concept

Objectives and Scope

**CHAPTER 2. DESIGN OF TEST SPECIMENS**

Design of Prototype and Test Columns

Design of Prototype and Test Specimen Column-to-Footing Connection

Specimens SF-1 and SF-2

Specimen SF-3

**CHAPTER 3. EXPERIMENTAL PROGRAM**

Loading Setup

Instrumentation

Testing Protocol

**CHAPTER 4. DAMAGE PROGRESSION**

Definitions of Damage States

Preliminary Test Cycles

Factored Axial-Load Tests

Lateral-Load Tests (up to yielding)

Lateral-Load Tests (after yielding)

Axial-Load Testing to Collapse

**CHAPTER 5. MEASURED RESPONSE**

Material Properties

Concrete Strength

Grout Strength

Reinforcement

Friction Correction

Moment-Drift Response

Effective Force

Distribution of Column Curvature

Column Splice

Strains in Column Longitudinal Bars

Strain Profiles along the Height of Specimen

Strain Histories for Bars near Splice

Column Longitudinal Bar Strain Histories in Footing

Footing Strain Corrections

Strains in Bottom Mat of Footing Reinforcement

Strains in Bottom Bars in the North-South Direction (Loading Direction)

Implication of the Effective Width

Strains in Bottom Bars in the East-West Direction

Strains in Diagonal Bars

Strains in Footing Ties

Axial Load-Response

Factored Axial Loading

Ultimate Axial-Load Capacities

**CHAPTER 6. ANALYSIS OF MEASURED RESPONSE**

Footing Response

Footing Flexural Strength

Footing One-Way Shear Strength

Combined Punching Shear and Moment Transfer

Footing Punching Shear Strength

Footing Shear-Friction Strength

Footing Joint Shear

Column Response

Column Axial-Load Capacity

Column Flexural Strength

Column Shear Strength

Column Splice in Specimens SF-1 and SF-2

Damage Progression Models

Effective Stiffness Model

Normalized Moment-Drift Response

Strength Degradation

Energy Dissipation

**CHAPTER 7. SUMMARY AND CONCLUSIONS**

System Concept

Design of Test Specimens

Experimental Testing

Experimental Analysis

Conclusions

Recommendations

**APPENDIX A: SPECIMEN CONSTRUCTION DRAWINGS**

Specimen SF-2

Specimen SF-3

Concrete Strength

Grout Strength

Reinforcement

Stress-Strain Plots for Specimens SF-1 and SF-2

Stress-Strain Plots for Specimen SF-3

Corrugated Metal Ducts

**APPENDIX C: DAMAGE PROGRESSION**

Specimen SF-2

Specimen SF-3

**APPENDIX D: CONSTRUCTION SEQUENCE**

Columns with Projecting Bars

Columns without Projecting Bars

Socket Columns

Long Struts

Short Struts

Figure 1. Diagram. Rapid construction sequence

Figure 2. Diagram. Strut-and-tie models for (a) bent out bars and (b) headed bars

Figure 4. Diagram. Precast column elevation for specimens SF-1 and SF-2

Figure 5. Diagram. Specimen SF-1 footing steel arrangement

Figure 6. Diagrams. Spread footing cross section for (a) SF-1 and (b) SF-2 (section A-4)

Figure 7. Graph. Final criteria design space for specimen SF-3

Figure 8. Diagram. Specimen SF-3 footing steel arrangement

Figure 9. Diagram. Specimen SF-3 spread footing cross-section (section A-5)

Figure 10. Diagram. Specimen SF-3 longitudinal section (section A-7)

Figure 11. Diagram. Test setup

Figure 12. Diagram. Locations of external instruments

Figure 13. Diagram. Locations of strain gauges in the three specimens

Figure 14. Diagram. Locations of strain gauges in the three specimens' cast-in-place footings

Figure 15. Graph. Lateral loading displacement history

Figure 16. Chart. Comparison of specimens' drift ratios for the major damage states

Figure 17. Diagram. Column vertical bar naming convention

Figure 18. Photos. Test specimens after a cycle of maximum drift ratio of 4.28 percent

Figure 20. Photo. Specimen SF-3 footing failure

Figure 21. Photo. Damage on top of footing after test

Figure 22. Diagram. Punching shear profile in the north-south direction (loading direction)

Figure 23. Photos. Specimens at the end of the test program

Figure 24. Equation. Coefficient of friction

Figure 25. Equation. Calculation of the moment at the base of the column

Figure 26. Diagram. Displacements and forces on test specimen used in figure 25

Figure 27. Graph. Specimen SF-1 moment-drift response

Figure 28. Graph. Specimen SF-2 moment-drift response

Figure 29. Graph. Specimen SF-3 moment-drift response

Figure 30. Equation. Effective lateral force

Figure 31. Graph. Specimen SF-1 effective force-displacement response

Figure 32. Graph. Specimen SF-2 effective force-displacement response

Figure 33. Graph. Specimen SF-3 effective force-displacement response

Figure 34. Equation. Calculating the average curvature

Figure 35. Graph. Specimen SF-1 average column curvature

Figure 36. Graph. Specimen SF-2 average column curvature

Figure 37. Graph. Specimen SF-3 average column curvature

Figure 38. Photo. Crack opening measurement pot

Figure 39. Graph. Specimen SF-1 splice interface opening

Figure 40. Graph. Specimen SF-2 splice interface opening

Figure 41. Graph. Strain profiles in S-SW bar in specimen SF-1

Figure 42. Graph. Strain profiles in S-SW bar in specimen SF-2

Figure 43. Graph. Strain profiles in S-SW bar in specimen SF-3

Figure 44. Graphs. Strain-drift relationship 2 inches below the column splice interface

Figure 48. Graph. Thermal effects in strain gauges

Figure 49. Graph. Specimen SF-1 strain profiles in bottom mat of the footing

Figure 50. Graph. Specimen SF-2 strain profiles in bottom mat of the footing

Figure 51. Graph. Specimen SF-3 strain profiles in bottom of the footing

Figure 52. Graph. Specimen SF-1 transverse strains in bottom mat of the footing

Figure 53. Graph. Specimen SF-2 transverse strains in bottom mat of the footing

Figure 54. Graph. Specimen SF-3 transverse strains in bottom mat of the footing

Figure 55. Graph. Specimen SF-1 strains in diagonal steel in footing

Figure 56. Graph. Specimen SF-2 strains in diagonal steel in footing

Figure 57. Graph. Specimen SF-3 strains in diagonal steel in footing

Figure 58. Graph. Specimen SF-1 strains in ties

Figure 59. Graph. Specimen SF-2 strains in ties

Figure 60. Graph. Specimen SF-3 strains in ties

Figure 61. Graph. Column vertical displacement vs. cumulative column drift

Figure 62. Graph. Axial response of specimens SF-1 and SF-2

Figure 63. Photo. Specimen SF-2 after axial load of 817 kips

Figure 64. Diagram. Support conditions

Figure 65. Equation. Shear stress demand

Figure 66. Equation. Nominal shear capacity

Figure 67. Equation. Nominal punching shear capacity including transverse steel

Figure 68. Equation. Nominal punching shear capacity excluding transverse steel

Figure 69. Equation. Nominal shear friction resistance

Figure 70. Equation. Maximum principal compressive stress

Figure 71. Equation. Maximum principal tensile stress

Figure 72. Equation. Principal tensile stress

Figure 73. Equation. Principal compressive stress

Figure 74. Diagrams. Strut and tie models for bent-out bars (left) and headed bars (right)

Figure 75. Photo. Joint region of specimen SF-3 after failure

Figure 76. Equation. Nominal axial-load capacity of the column

Figure 77. Graph. Moment-curvature model.^{(15)}

Figure 78. Equation. Plastic overstrength shear demand

Figure 79. Equation. Nominal shear resistance

Figure 80. Equation. Component of total shear resistance due to concrete strength

Figure 81. Equation. Concrete shear resistance

Figure 82. Equation. Contribution of total shear resistance due to transverse steel strength

Figure 83. Equation. Analytical plastic hinge length

Figure 84. Equation. Damage model for spalling

Figure 85. Equation. Damage model for bar buckling

Figure 86. Equation. Damage model for bar fracture

Figure 87. Equation. Effective modulus of rigidity

Figure 88. Graphs. Normalized equivalent moment-drift response

Figure 89. Graph. Comparison of effective force vs. drift

Figure 90. Equation. Energy dissipation

Figure 92. Graph. Equivalent viscous damping calculated per cycle

Figure 93. Equation. Equivalent viscous damping

Figure 94. Graph. Equivalent viscous damping vs. drift

Figure 95. Photos. Specimen SF-1 (left) and specimen SF-2 (right)

Figure 96. Diagram. Specimen SF-1 column elevation and sections

Figure 97. Diagram. Specimen SF-1 top mat plan view

Figure 98. Diagram. Specimen SF-1 bottom mat plan view

Figure 99. Diagram. Specimen SF-1 sections

Figure 100. Diagram. Specimen SF-2 column elevation and sections

Figure 101. Diagram. Specimen SF-2 top mat plan view

Figure 102. Diagram. Specimen SF-2 bottom mat plan view

Figure 103. Diagram. Specimen SF-2 sections

Figure 104. Diagram. Specimen SF-3 column sections

Figure 105. Diagram. Specimen SF-3 column elevation

Figure 106. Diagram. Specimen SF-3 bottom mat plan view

Figure 107. Diagram. Specimen SF-3 footing sections A7 and A6

Figure 108. Diagram. Specimen SF-3 footing sections A5 and B5

Figure 109. Equation. Calculating yield strain

Figure 110. Graph. Specimens SF-1/SF-2 stress-strain curves for No. 6 bars

Figure 111. Graph. Specimens SF-1/SF-2 stress-strain curve for No. 5 bar

Figure 112. Graph. Specimens SF-1/SF-2 stress-strain curve for No. 4 bar

Figure 113. Graph. Specimens SF-1/SF-2 stress-strain curves for No. 3 bar

Figure 114. Graph. Specimens SF-1/SF-2 stress-strain curves for stirrups (2-gauge wire)

Figure 115. Graph. Specimens SF-1/SF-2 stress-strain curves for spiral reinforcement (3-gauge wire)

Figure 116. Graph. Specimen SF-3 stress-strain curve for No. 7 bar

Figure 117. Graph. Specimen SF-3 stress-strain curve for No. 6 bar

Figure 118. Graph. Specimen SF-3 stress-strain curve for No. 5 bar

Figure 119. Graph. Specimen SF-3 stress-strain curve for No. 4 bar

Figure 120. Graph. Specimen SF-3 stress-strain curve for No. 3 bar

Figure 121. Photo. Corrugated metal duct used in test specimens

Figure 122. Photo. Specimen SF-1 flexural cracks after cycle 4-1 (+1.00/-1.00 target drift ratio)

Figure 127. Photo. Specimen SF-1: damage after the cyclic testing

Figure 128. Photo. Specimen SF-1: no damage to the footing was observed after the cyclic testing

Figure 130. Photo. Specimen SF-2: flexural cracks after cycle 3-2 (+0.83/-0.83 target drift ratio)

Figure 135. Photo. Specimen SF-2: damage after the cyclic testing

Figure 136. Photo. Specimen SF-2: no damage to the footing was observed after the cyclic testing

Figure 145. Photo. Specimen SF-3: full column spalling in cycle 9-1 (+6.16/-6.16 target drift ratio)

Figure 152. Photo. Specimen SF-3: condition of specimen just before last cycle

Figure 156. Photo. Roughened surface of octagonal, bottom portion of column

Figure 157. Photo. Specimens SF-1 and SF-2, column segments formed and ready to be cast

Figure 158. Photo. Specimen SF-3, column formed and ready to be cast

Figure 159. Photo. Specimen SF-1 footing ready to be cast

Figure 160. Photo. Specimen SF-3 footing formwork and reinforcement

Figure 161. Photo. Specimen SF-3 column inserted into footing that is ready to cast

Figure 162. Photo. Specimen SF-3: finishing the footing surface

Figure 163. Diagram. Column detail with projecting bars

Figure 164. Diagram. Socket column concept

Figure 165. Diagram. Long struts concept

Figure 166. Diagram. Short struts concept

Table 1. Strain gauge types used in the specimens

Table 2. Target displacement history

Table 3. Damage state description

Table 4. Damage milestones for all three specimens

Table 5. Average concrete strength on test day

Table 6. Average grout strength on test day

Table 7. Measured mild reinforcement properties

Table 8. Moments and drift ratios at maximum and 80 percent of maximum resistance

Table 9. Effective force and displacement at maximum and 80 percent of maximum resistance

Table 10. Axial load and strains across and near splice interfaces

Table 11. Axial load combinations on the test specimens

Table 12. External forces, displacements, and estimated reactions**.**

Table 13. Footing flexural capacities and demands

Table 14. Footing one-way strength capacities and demands

Table 15. Combined punching shear and moment transfer capacities and demands

Table 16. Punching shear capacities and demands

Table 17. Footing shear-friction capacities and demands

Table 18. Footing joint shear stress capacities and demands

Table 19. Column axial-load capacities and demands

Table 20. Column flexural capacities and demands

Table 21. Column shear capacities and demands

Table 22. Comparison of damage model predictions and observed occurrences

Table 23. Comparison of model prediction and measured effective modulus of rigidity

Table 24. Summary of ratios of footing demands to calculated capacities

Table 25. Slump and air content test results

Table 26. Concrete compressive strengths up to 28 days

Table 27. Concrete compressive strengths on test day

Table 28. Concrete split cylinder strengths on test day.^{1}

Table 29. Grout cube strength on test day

Table 30. Measured mild reinforcement properties

AASHTO | American Association of State Highway and Transportation Officials |

ABC | Accelerated Bridge Construction |

ACI | American Concrete Institute |

ASCE | American Society of Civil Engineers |

BDM | Bridge Design Manual |

Caltrans | California Department of Transportation |

CCC | Compression-compression-compression |

DL | Dead load |

HSS | Hollow structural section |

LL | Live load |

LRFD | Load and Resistance Factor Design |

LVDT | Linear variable differential transformer |

MEF | Maximum effective force |

NEHRP | National Earthquake Hazards Reduction Program |

o.c. | On center |

o.d. | Outside diameter |

OT | Overturning |

PEER | Pacific Earthquake Engineering Research |

PTFE | Polytetrafluoroethylene |

SDC | Seismic Design Criteria |

WSDOT | Washington State Department of Transportation |

Page last modified on July 30, 2013.