Alternative Support Systems for Cantilever - National Transportation ...

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ACKNOWLEDGEMENTS The authors acknowledge and thank the Florida Department of Transportation for providing funding for this research project. This project was a collaborative effort between the University of Florida and the FDOT Structures Research Laboratory (Tallahassee). The authors wish to thank the FDOT Structures Research Laboratory personnel for constructing the specimen, installing instrumentation, data acquisition, and in general performing the tests required to make this project successful. vi
EXECUTIVE SUMMARY During the 2004 hurricane season, the failure of several foundations of cantilever sign structures occurred along Florida highways. Those failures necessitated a review of the design and construction procedures for the foundations of cantilever sign structures. The failures were determined to be caused by concrete breakout of the anchors subjected to shear parallel to the edge caused by torsional loading. The research team tested a retrofit option using carbon fiber- reinforced polymer (CFRP) wrap and design guidelines for determining the susceptibility of failure for current systems and design of the CFRP wrap retrofit design were created. Having found the failure mechanism, alternative support structures were recommended for future research, which became the basis for the current project. The primary objectives of this research program were as follows: • Identify a viable alternative to transfer load from the superstructure to the foundation other than through anchor bolts. • Provide design guidelines for the alternative selected. In order to complete these objectives, a literature review and experimental program were conducted. The findings of the literature review were used to develop the experimental program. The literature review and the results of the experimental program were used to develop the design guidelines for the alternative selected. In addition to the primary objectives, alternative connections were also identified for consideration for future testing. After a literature review and exploration of other industries’ options, an embedded pipe and plate section was selected as a viable alternative. The clear load path and ability to handle both torsional and flexural load made the embedded pipe and plate section the most ideal alternative. Testing proved that the embedded pipe and plate section was able to transfer the torsional and flexural load to the concrete satisfactorily. Testing also proved that American Concrete Institute (ACI) 318 code equations for concrete breakout from applied shear could be modified to accurately predict the concrete breakout strength of the embedded pipe and plate section. vii
Page 1 and 2: Report No. BDK75 977-04 Date: Augus
Page 3 and 4: Metric Conversion Table SYMBOL WHEN
Page 5: ALTERNATIVE SUPPORT SYSTEMS FOR CAN
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
Page 55 and 56: computed. See Equation 3-14 below t
Page 57 and 58:
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
Page 211 and 212:
REFERENCES 1. Cook, R.A., and Halco
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