Precast Bent System for High Seismic Regions: Laboratory Tests of ColumntoDrilled Shaft Socket Connections
Publication No. FHWAHIF13038
June 2013
TABLE OF CONTENTS
CHAPTER 2. DESIGN OF TEST SPECIMENS
 Configuration of Test Specimens
 Design of Prototype and Test Columns
 Design of Specimen ColumntoDrilled Shaft Connection
CHAPTER 3. EXPERIMENTAL PROGRAM
 MomentDrift Response
 Effective Force
 Curvature
 Displacement
 Strains in Column Reinforcing Bars
 Strains in Shaft Reinforcing Bars
 Strains in Shaft Spirals
 NonContact Lap Splices Models
 Column MomentCurvature Analysis
 The StrutandTie Model and Shaft Spiral Design
CHAPTER 7. SUMMARY AND CONCLUSIONS
APPENDIX A: SPECIMEN CONSTRUCTION DRAWINGS
List of Figures
 Figure 1. Diagram. Precast bridge bent construction stages.
 Figure 2. Equation. Spacing of shaft spiral.
 Figure 3. Photos. Column reinforcement (left) and shaftfooting reinforcement (right).
 Figure 4. Photos. Specimen construction (left) and specimen test setup (right).
 Figure 5. Diagram. Test setup.
 Figure 6. Diagram. Locations of external instruments.
 Figure 7. Diagram. Top column displacement comparison for DS1 (top) and DS2 (bottom).
 Figure 8. Diagram. Locations of strain gauges.
 Figure 9. Graphs. Lateral loading displacement history.
 Figure 10. Chart. Comparison of specimens' drift ratios for the major damage states.
 Figure 11. Photo. Specimen DS1 after testing.
 Figure 12. Photo. Specimen DS2 after testing.
 Figure 13. Equation. Moment at the base of the column.
 Figure 14. Diagram. Displacements and forces on test specimen.
 Figure 15. Equation. Determination of axial load lateral displacement.
 Figure 16. Equation. Moment at the base of the column.
 Figure 17. Graphs. Moment vs. drift ratio response.
 Figure 18. Equation. Effective lateral force.
 Figure 19. Graph. Effective forcedisplacement response.
 Figure 20. Diagram. Detailed curvature rods setup.
 Figure 21. Equation. Calculating curvature.
 Figure 22. Graphs. Average column curvature (specimen DS1 and DS2).
 Figure 23. Graphs. Average column curvature (measured by Optotrak) in specimen DS2.
 Figure 24. Graphs. Average shaft curvature for specimens DS1 and DS2.
 Figure 25. Illustration. Displacement types.
 Figure 26. Graph. Rotation comparison at 10 inches above the interface position (specimen DS2).
 Figure 27. Graph. Rotation comparison at 18 inches above the interface position (specimen DS2).
 Figure 28. Graph. Specimen DS1 displacement profile.
 Figure 29. Graph. Specimen DS2 displacement profile.
 Figure 30. Graphs. Displacementdrift response (specimens DS1 and DS2).
 Figure 31. Graphs. Displacementdrift response of shaft (specimens DS1 and DS2).
 Figure 32. Diagrams. Column strain gauge positions.
 Figure 33. Graphs. Strain profiles in reinforcing bars of the column (until 3 percent drift).
 Figure 34. Graphs. Strain profiles in reinforcing bars of column (after 3 percent drift).
 Figure 35. Graphs. Straineffective force relationship of the column reinforcing bars.
 Figure 36. Diagrams. Strain gauge positions in the shaft.
 Figure 37. Graphs. Strain in shaft reinforcing bars in specimen DS1.
 Figure 38. Graphs. Strain in shaft reinforcing bars in specimen DS2.
 Figure 39. Graphs. Strain profiles in the shaft reinforcing bars.
 Figure 40. Graphs. StrainEffective force relationship of the shaft reinforcing bars.
 Figure 41. Graphs. Strain in shaft spiral.
 Figure 42. Diagram. Twodimensional behavioral model for noncontact lap splices.
 Figure 43. Equation. Shaft transverse reinforcement for rectangular columns.
 Figure 44. Equation. Shaft transverse reinforcement for rectangular columns with
 Figure 45. Equation. Volume of shaft reinforcement for rectangular columns.
 Figure 46. Equation. Volume of shaft reinforcement for rectangular columns  expanded equation.
 Figure 47. Equation. Minimum volume of shaft reinforcement for rectangular columns.
 Figure 48. Equation. Inclination angle of the concrete strut.
 Figure 49. Graph. Relationship between the total steel volume in a splice and the inclined angle of struts.
 Figure 50. Diagrams. Proposed threedimensional behavioral model for noncontact lap splices.(18)
 Figure 51. Equation. Shaft transverse reinforcement for circular columns.
 Figure 52. Equation. Volume of shaft reinforcement for circular columns.
 Figure 53. Equation. Volume of shaft reinforcement for circular columns  expanded equation.
 Figure 54. Equation. Minimum volume of shaft reinforcement for circular columns.
 Figure 55. Equation. Inclination angle of the concrete strut.
 Figure 56. Equation. Shaft transverse reinforcement for circular columns under axial load and bending.
 Figure 57. Graph. Momentcurvature analysis (based on expected material properties).
 Figure 58. Graph. Momentcurvature analysis (based on measured material properties).
 Figure 59. Graph. Momentextreme reinforcement tensile strain relationship for column (in specimen DS1).
 Figure 60. Graph. Momentextreme reinforcement tensile strain relationship for column (in specimen DS2).
 Figure 61. Graph. Relationship of moment at the base and extreme reinforcement tensile strain for the shaft.
 Figure 62. Diagram. Strutandtie model proposed by Schlaich and Schäfer.(24)
 Figure 63. Diagrams. Elevation and plan of the strutandtie model for transmitting load from one column reinforcing bar to the three nearest shaft bundles bars.
 Figure 64. Diagram. Tension transfer from column to shaft longitudinal reinforcement.
 Figure 65. Equation. Distributed load determination.
 Figure 66. Equation. Distribution of tension in the shaft reinforcement.
 Figure 67. Diagram. Distributed load applied to shaft spirals.
 Figure 68. Equation. Distance of tensile forces from the neutral axis.
 Figure 69. Equation. Distribution of tension in the shaft longitudinal reinforcement.
 Figure 70. Equation. Distributed load applied to the shaft transverse reinforcement.
 Figure 71. Equation. Equilibrium equation.
 Figure 72. Equation. Distribution of tensile force in the shaft spirals.
 Figure 73. Diagram. Tensile force distribution in tie T2 in tension area.
 Figure 74. Equation. Maximum tensile force in the tie.
 Figure 75. Graph. Relationship of T2max vs. θ.
 Figure 76. Equation. Yield strength of a single spiral wire.
 Figure 77. Diagram. Column elevation.
 Figure 78. Diagram. Column sections.
 Figure 79. Diagram. Shaft and base  longitudinal section.
 Figure 80. Diagram. Shaft and base  transverse section.
 Figure 81. Diagram. Shaft and base reinforcement arrangement.
 Figure 82. Graph. Stressstrain curve for No. 3 bar.
 Figure 83. Graph. Stressstrain curve for No. 5 bar.
 Figure 84. Photo. Specimen DS1  significant horizontal crack in cycle 41 (0.56/0.75 percent drift).
 Figure 85. Photo. Specimen DS1  first significant spalling occurred in the column in cycle 72 (3.00/3.14 percent drift).
 Figure 86. Photo. Specimen DS1  plastic hinge formed in the column in cycle 83 (4.60/4.68 percent drift).
 Figure 87. Photo. Specimen DS1  first noticeable bar buckling in the column in cycle 93 (6.90/6.81 percent drift).
 Figure 88. Photo. Specimen DS1  first column spiral fractured in cycle 101 (8.43/8.27 percent drift).
 Figure 89. Photos. Specimen DS1 column damage after cyclic testing.
 Figure 90. Photo. Specimen DS1 shaft damage after cyclic testing.
 Figure 91. Photo. Specimen DS2  significant horizontal crack in cycle 42 (0.73/0.87 percent drift).
 Figure 92. Photo. Specimen DS2  first diagonal crack in the shaft in cycle 62 (1.87/2.02 percent drift).
 Figure 93. Photo. Specimen DS2  shaft damage when first shaft spiral fractured in cycle 82 (4.59/4.59 percent drift).
 Figure 94. Photo. Specimen DS2  first noticeable prying action in shaft in cycle 92 (6.72/6.83 percent drift).
 Figure 95. Photos. Specimen DS2 shaft damage after cyclic testing.
 Figure 96. Photo. Specimen DS2 column damage after cyclic testing.
List of Tables
 Table 1. Prototype and specimen design dimensions.
 Table 2. Shaft reinforcement.
 Table 3. Target displacement history.
 Table 4. Damage state descriptions.
 Table 5. Damage milestones for all five specimens.
 Table 6. Moment and drift ratio at maximum and 80 percent of maximum resistance.
 Table 7. Effective force and displacement at maximum and 80 percent maximum of resistance.
 Table 8. Comparision of peak column moment.
 Table 9. Concrete strengths for specimen DS1 and DS2.
 Table 10. Tensile strength of spiral.
AASHTO  American Association of State Highway and Transportation Officials 

ABC  Accelerated Bridge Construction 
BDM  Bridge Design Manual 
HSS  Hollow structural section 
LRFD  Load and Resistance Factor Design 
LVDT  Linear variable differential transformer 
MEF  Maximum effective force 
PTFE  Polytetraflouroethylene 
WSDOT  Washington State Department of Transportation 
Notice
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.
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Quality Assurance Statement
The Federal Highway Administration (FHWA) provides highquality 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.
1. Report No. FHWAHIF13038 
2. Government Accession No. N/A 
3. Recipient's Catalog No. N/A 

4. Title and Subtitle PRECAST BENT SYSTEM FOR HIGH SEISMIC REGIONS: LABORATORY TESTS OF COLUMNTODRILLED SHAFT SOCKET CONNECTIONS 
5. Report Date May 2013 

6. Performing Organization Code  
7. Author(s) Hung Viet Tran, John F. Stanton, and Marc O. Eberhard 
8. Performing Organization Report No.  
9. Performing Organization Name and Address BergerABAM, Inc. 33301 Ninth Ave South, Suite 300 Federal Way, WA 98003 University of Washington, Seattle, WA 
10. Work Unit No. (TRAIS)  
11. Contract or Grant No. DTFH6109G00005 

12. Sponsoring Agency Name and Address Federal Highway Administration Highways for LIFE Program  HIHL1 1200 New Jersey Avenue, SE Washington, D.C. 20590 
13. Type of Report and Period Covered Final Report 

14. Sponsoring Agency Code  
15. Supplementary Notes This is a companion report to the final project report, Precast Bent System for High Seismic Regions (FHWAHIF13037). 

16. Abstract This report provides detailed information from the laboratory investigation of two precast columntodrilled shaft largescale tests, including descriptions of the specimen design, testing, data reduction, and conclusions regarding the use of the connection with the precast bent system. The tests provide data regarding the performance of the precast columntodrilled shaft connection. The results indicate that the connection, when used with a precast column, is sufficiently strong to resist plastic hinging in the column above the drilled shaft splice zone. The column reinforcing bars were anchored with headed bar ends to facilitate column strength development. The behavior is emulative of castinplace performance. The specimens tested were based on the minimum practical difference in diameters of the shaft relative to the column. When adequate confinement in the reinforcing cage of the shaft is included in the splice zone, the column can form a plastic hinging mechanism above the shaft without incurring damage in the shaft splice zone. If sufficient confinement is not included, then the resulting behavior is undesirable because the splice zone strength rapidly deteriorates. Recommendations for transverse reinforcement are provided to ensure desirable performance, and these result in more reinforcement in the upper portion of the splice zone than in the lower portion. 

17. Key Words Bridges, earthquakes, accelerated bridge construction, precast bent, connections, drilled shaft foundations, prefabricated bridge elements and systems 
18. Distribution Statement No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161. 

19. Security Classification (of this report) Unclassified 
20. Security Classification (of this page) Unclassified 
21. No. of Pages 125 
22. Price 
APPROXIMATE CONVERSIONS TO SI UNITS  APPROXIMATE CONVERSIONS FROM SI UNITS  

Symbol  When You Know  Multiply By  To Find  Symbol  Symbol  When You Know  Multiply By  To Find  Symbol 
LENGTH  LENGTH  
in  inches  25.4  millimeters  mm  mm  millimeters  0.039  inches  in 
ft  feet  0.305  meters  m  m  meters  3.28  feet  ft 
yd  yards  0.914  meters  m  m  meters  1.09  yards  yd 
mi  miles  1.61  kilometers  km  km  kilometers  0.621  miles  mi 
AREA  AREA  
in^{2}  square inches  645.2  square millimeters  mm^{2}  mm^{2}  square millimeters  0.0016  square inches  in^{2} 
ft^{2}  square feet  0.093  square meters  m^{2}  m^{2}  square meters  10.764  square feet  ft^{2} 
yd^{2}  square yards  0.836  square meters  m^{2}  m^{2}  square meters  1.195  square yards  yd^{2} 
ac  acres  0.405  hectares  ha  ha  hectares  2.47  acres  ac^{2} 
mi^{2}  square miles  2.59  square kilometers  km^{2}  km^{2}  square kilometers  0.386  square miles  mi^{2} 
VOLUME  VOLUME  
fl oz  fluid ounces  29.57  milliliters  ml  mL  milliliters  0.034  fluid ounces  fl oz 
gal  gallons  3.785  liters  L  L  liters  0.264  gallons  gal 
ft^{3}  cubic feet  0.028  cubic meters  m^{3}  m^{3}  cubic meters  35.314  cubic feet  ft^{3} 
yd^{3}  cubic yards  0.765  cubic meters  m^{3}  m^{3}  cubic meters  1.307  cubic yard  yd^{3} 
NOTE: Volumes greater than 1000 l shall be shown in m^{3}  
MASS  MASS  
oz  ounces  28.35  grams  g  g  grams  0.035  ounces  oz 
lb  pounds  0.454  kilograms  kg  kg  kilograms  2.202  pounds  lb 
T  short tons (2000 lb)  0.907  megagrams  Mg  Mg (or "t")  megagrams (or "metric ton")  1.103  short tons (2000 lb)  T 
TEMPERATURE (exact degrees)  TEMPERATURE (exact degrees)  
°F  Fahrenheit  5(F–32)/9 or (F–32)/1.8  Celcius  °C  °C  Celsius  1.8C +32  Fahrenheit  °F 
ILLUMINATION  ILLUMINATION  
fc  foot–candles  10.76  lux  lx  lx  lux  0.0929  foot–candles  fc 
fl  foot–Lamberts  3.426  candela/m^{2}  cd/m^{2}  cd/m^{2}  candela/m^{2}  0.2919  foot–Lamberts  fl 
FORCE and PRESSURE or STRESS  FORCE and PRESSURE or STRESS  
lbf  pounds  4.45  newtons  N  N  newtons  0.225  poundforce  lbf 
lbf/in^{2}  pound per square inch  6.89  kilopascals  kPa  kPa  kilopascals  0.145  poundforce per square inch  lbf/in^{2} 
Notation
A_{tr}  =  Area of shaft transverse reinforcement or spiral (in2) 
A_{l}  =  Total area of longitudinal column reinforcement (in2) 
A_{lsh}  =  Total area of longitudinal shaft reinforcement (in2) 
c  =  Depth to the neutral axis 
D  =  Diameter of shaft spiral (in.) 
d  =  Distance from the extreme compression fiber to the extreme tension longitudinal reinforcement 
e  =  Distance from the inner bar to the outer bar 
E_{a}  =  Modulus of elasticity of reinforcement (ksi) 
f_{r}  =  Concrete modulus of rupture (ksi) 
f_{s}  =  Tensile stress in reinforcement (ksi) 
f_{yt}  =  Specified minimum yield strength of shaft transverse reinforcement (ksi) 
f_{ul}  =  Specified minimum tensile strength of column longitudinal reinforcement (ksi), 90 ksi for A615 and 80 ksi for A706 
l_{ns}  =  Total noncontact lap splice length 
l_{d}  =  Class C tension lap splice length of the column longitudinal reinforcement (in.) 
L_{tr}  =  Distance between the outer bars 
R  =  Radius of shaft spiral (in.) 
s_{tr}  =  Spacing of shaft transverse reinforcement (in.) 
VOL_{s}  =  Total volume of steel, including both longitudinal and transverse in the splice 
ε_{s}  =  Tensile strain in reinforcement (ksi) 
θ  =  Inclination angle of the strut (degree or rad) 
φ  =  Curvature (1/in.) 