Alternative Support Systems for Cantilever - National Transportation ...

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1. Report No. BDK75 977-04 4. Title and Subtitle 2. Government Accession No. Alternative Support Systems for Cantilever Signal/Sign Structures 7. Author(s) R. A. Cook and K. L. Jenner 9. Performing Organization Name and Address University of Florida Department of Civil and Coastal Engineering 345 Weil Hall / P.O. Box 116580 Gainesville, FL 32611-6580 12. Sponsoring Agency Name and Address Florida Department of Transportation Research Management Center 605 Suwannee Street, MS 30 Tallahassee, FL 32301-8064 15. Supplementary Notes iv Technical Report Documentation Page 3. Recipient's Catalog No. 5. Report Date August 2010 6. Performing Organization Code 8. Performing Organization Report No. 00072913 10. Work Unit No. (TRAIS) 11. Contract or Grant No. BDK75 977-04 13. Type of Report and Period Covered Final Report April 2008-Aug 2010 14. Sponsoring Agency Code 16. Abstract During the 2004 hurricane season, several anchor embedment failures of the support structures of cantilever signal/sign structures occurred. A previous research program determined the cause of these failures was by concrete breakout due to shear on the anchors directed parallel to the edge of the foundation. The purpose of the current research program was to take the knowledge obtained on the previous research program and identify a suitable alternative support structure without the use of anchor bolts. After a literature review and experimental testing, it was determined that an embedded pipe with welded plates was a suitable alternative support structure. The torsion could be adequately transferred to the support structure concrete through the vertical torsional plates and the flexure could be adequately transferred to the concrete through the welded annular plate on the bottom of the pipe. Furthermore, it was determined that the alternative selected was not only a viable alternative to the anchor bolt system, but it had greater strength for a given foundation size than the anchor bolt system. The test specimens were designed to fail by concrete breakout originating from the torsional and flexural plates and to preclude other failure modes. The results of the testing indicated that the concrete breakout was the failure mode for the embedded pipe and plate configuration and that the concrete breakout strength could be accurately predicted using modified equations for concrete breakout from American Concrete Institute (ACI) 318-08 Appendix D. The results of these tests led to the development of guidelines for the design of the embedded pipe and plate configuration. Recommendations for future testing include an alternative base connection that precludes the use of annular plates. 17. Key Word Anchorage, cantilever sign structures, torsion, anchors, wind loads 19. Security Classif. (of this report) Unclassified 20. Security Classif. (of this page) Unclassified 18. Distribution Statement No restrictions Form DOT F 1700.7 (8-72) Reproduction of completed page authorized 21. No. of Pages 212 22. Price
ALTERNATIVE SUPPORT SYSTEMS FOR CANTILEVER SIGNAL/SIGN STRUCTURES Contract No. BDK75 977-04 UF No. 00072913 Principal Investigator: Ronald A. Cook, Ph.D., P.E. Graduate Research Assistant: Kathryn L. Jenner FDOT Technical Coordinator: Marcus H. Ansley, P.E. Engineering and Industrial Experiment Station Department of Civil and Coastal Engineering University of Florida Gainesville, FL August 2010 v
Page 1 and 2: Report No. BDK75 977-04 Date: Augus
Page 3: Metric Conversion Table SYMBOL WHEN
Page 7 and 8: EXECUTIVE SUMMARY During the 2004 h
Page 9 and 10: CHAPTER TABLE OF CONTENTS 1 INTRODU
Page 11 and 12: Torsion Test Data .................
Page 13 and 14: LIST OF FIGURES Figure page Figure
Page 15 and 16: Figure 4-15. Arrangement of the LVD
Page 17 and 18: CHAPTER 1 INTRODUCTION This project
Page 19 and 20: CHAPTER 2 BACKGROUND The following
Page 21 and 22: information obtained in the late 19
Page 23 and 24: these problems. The concern with fa
Page 25 and 26: opposite side, see Figure 2-2 The s
Page 27 and 28: 2.2.4 Helical Pipes This option wou
Page 29 and 30: 2.3 Alternative Foundations from Ot
Page 31 and 32: Figure 2-10. Drilled concrete piles
Page 33 and 34: Figure 2-13. Grouted soil anchors G
Page 35 and 36: The pad and pier foundation, found
Page 37 and 38: comments and recommendations on pre
Page 39 and 40: CHAPTER 3 DESIGN IMPLICATIONS Based
Page 41 and 42: Figure 3-2. Differences between con
Page 43 and 44: 2 [ ] 2 2 ( r ) + 3. 25 ( r ) − (
Page 45 and 46: eakout surface for a single plate,
Page 47 and 48: strength of a headed anchor in tens
Page 49 and 50: Figure 3-9. Schematic of anticipate
Page 51 and 52: Vbfp l e tfp bfp f’c ca1 = the ba
Page 53 and 54: 3.2.2 Equivalent Side-Face Blowout
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computed. See Equation 3-14 below t
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One method to quantify the failure
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• An additional 12-4.5” long, 1
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Applied load Lever arm Figure 4-4.
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Figure 4-8. Isometric view of embed
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Flexural plate breakout area Torsio
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4.2.4 Annular Base Plate Design The
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torsional strength of the lever arm
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4.4 Concrete Block and Tie-Down Des
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Figure 4-13. Arrangement of the LVD
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4.7 Summary of Torsion and Flexure
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foundation displayed the predicted
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Figure 5-5. Specimen at failure 5.1
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Figure 5-7. Torsional moment and ro
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torsional 45 degree crack formation
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Figure 5-11. Widening of concrete b
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Failure cracks widen Bond loosens F
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Rear of shaft Figure 5-14. Load and
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testing, signifying that the predic
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provided in NCHRP Report 412 were i
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6.2.2 Tapered Embedded Steel Pipe a
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Figure 6-3. FDOT Design Standards I
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This option provides a possible alt
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6.2.5 Cast-in-Place Solid Concrete
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This option does have some disadvan
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Figure 6-9. Embedded steel pipe and
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However, the fillet welds are susce
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APPENDIX A TEST APPARATUS DRAWINGS
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Figure A-3. Dimensioned side elevat
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Figure A-5. Dimensioned drawings of
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Figure A-7. Dimensioned plan drawin
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Figure A-9. Dimensioned drawing of
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Figure A-11. Dimensioned view of em
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STIFFENER DESIGN Calculation of Cap
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L breakout Concrete Breakout Equiva
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Abrg L⋅b 7 in 2 := = .5 Nsb 200
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β 1 f c Calculations Using ACI Str
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Determine Flexural Capacity of Roun
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DEVELOPMENT LENGTHS OF FLEXURAL REI
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Short Pipe Design Flexural Strength
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Long Pipe Design Flexural Strength
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Superstructure Assembly Strength -
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Weld Design Tn_blowout Vweld := Tor
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Check_Bolt_Shear := "Sufficient Str
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Check Reinforcement No_Bars_Block_R
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Tie-Down Design Block Properties Wi
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Vmax Total Load that the Tie-down m
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λpf := .38⋅ λpw := 3.76⋅ E F
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Input and Properties Shaft Torsion
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ψcV := 1.4 ψecV := 1.0 ψedV := 1
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lbreakout := L + 2⋅1.5ca1 lbreako
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Rn_weld := Throat⋅FW Rn_weld 11.1
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⎛ ⎜ ⎜⎜⎜⎜⎜⎜⎜ 9.250
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Flexural Capacity of T-Plates Using
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FAILURE EQUATIONS Torsion Threshold
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Required Length of Shaft Based on B
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Design Axial Strength ϕcomp := .90
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Design Axial Strength ϕcomp := .90
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Zp := ⎛ ⎜ ⎝ bp tp⋅ 2 ⎞
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Bolt Properties - D1" ASTM A325 Cen
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CONCRETE BLOCK Concrete Block Desig
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Check Shear Check_Shear_B := "Suffi
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7'-4" 8" 5'-4" 8" 1'-3" Calculate s
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Required Capacity of the Channel As
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Check_Flange_Compact_Unit := "Compa
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Rear of Shaft Face of Shaft Figure
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Bolt slippage ends Predicted failur
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APPENDIX D DESIGN GUIDELINES For th
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The designer should then use this i
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• Determine the angle required fo
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Superstructure Base Connection Foun
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1.5ca1 1.5ca1 Length of bearing are
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Vu = 9.04 kip T .u = 198.88 ft·kip
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Increase threaded rod diameter to 2
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Embedded Pipe and Torsion Plates De
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⎝ ⎠ Check_Breakout_Torsion := "
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Lbreakout := tflex.plate + 2⋅1.5c
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( ) .85 if fc < 4000psi β 1 f c .6
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REFERENCES 1. Cook, R.A., and Halco
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