Bursting and Spalling in Pretensioned U-Beams - Ferguson ...

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Bursting and Spalling in Pretensioned U-BeamsbyDavid Andrew Dunkman, B.S.C.E.ThesisPresented to the Faculty of the Graduate School ofThe University of Texas at Austinin Partial Fulfillmentof the Requirementsfor the Degree ofMasters of Science in EngineeringThe University of Texas at AustinDecember 2009
Bursting and Spalling in Pretensioned U-BeamsApproved bySupervising Committee:Oguzhan Bayrak, SupervisorJames O. Jirsa
Page 1: CopyrightbyDavid Andrew Dunkman2009
Page 5 and 6: Bursting and Spalling in Pretension
Page 7 and 8: 2.4.2.3 Itani & Galbraith, 1986 ...
Page 9 and 10: 4.2.2.4 Beam 1: Lateral-Bar Burstin
Page 11 and 12: List of TablesTable 2.1 Range of st
Page 13 and 14: Figure 2.25 Mechanical gage points
Page 15 and 16: Figure 3.30 Thermocouple placement
Page 17: CHAPTER 1Introduction1.1 IMPETUS FO
Page 20: At present, current end-region deta
Page 23 and 24: Figure 2.1 Severe cracking in a pre
Page 25 and 26: through use of tensioned, high-stre
Page 27 and 28: As splitting stress is bond-related
Page 29 and 30: Figure 2.6 Effect of bursting & spa
Page 31 and 32: magnitude of the end-region transve
Page 33 and 34: FEA can readily output color maps o
Page 35 and 36: 2.3.1.3 Plastic Analysis of Beam En
Page 38 and 39: force can increase by 400% (Yettram
Page 40 and 41: 2.4 EXPERIMENTAL STUDIES OF BURSTIN
Page 42 and 43: The trial specimens included one 40
Page 44 and 45: mechanical gage (2 in. gage length)
Page 46 and 47: Bursting stress(normalized by prest
Page 48 and 49: proprietary post-tensioning anchors
Page 50 and 51: Though Marshall and Mattock placed
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ectangular beam” (p. 21). At high
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Most beams observed to crack did so
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The behavior of these beams was dom
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2.4.2 Studies of End-Region Transve
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Figure 2.28 I-beams studied by Mars
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transverse forces compared to those
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(a) Actual spalling stress variatio
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stirrups in Gergely, Sozen and Sies
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50% more reinforcement than require
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strength concrete, increasingly hig
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the reinforcement located within th
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Typical crack patterns for the beam
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“Very common”crack locationPred
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Figure 2.38 Typical gage locations
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2.4.2.7 Smith et al., 2008Most rece
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the provided transverse reinforceme
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Itani and Galbraith (1986) reported
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Figure 2.45 Confining reinforcement
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cracks located along lines of prest
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odies relevant to pretensioned conc
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than that in another shape. For thi
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Figure 2.47 Required splitting rein
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No attempt was made in the Tentativ
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No citation is provided in the PCI
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Section Propertiesy b22.4 in.A 1120
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minimum for greater skews. For beam
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treatment (counting the transverse
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Pretensioned/post-tensioned beams h
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Figure 2.57 Harped strands in webs
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transversereinforcementwithin voidp
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2.8 SUMMARYIn this chapter, literat
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3.2.1.1 Linear and Nonlinear Stress
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Empirical expressions can be used t
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where: 0.021 = spalling force,
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3.3 CONCRETE PROPERTIES3.3.1 Concre
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It was reasoned that the dimensiona
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Splitting tensile-strength testing
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For temperature-match curing, therm
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3.4.1 Reinforcing-Bar Mechanical Te
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Grade 60 rebar yielded at 65 ksi an
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Equation 3.10where:ε1,2 = gage str
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Figure 3.17 Typical strand failure
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SouthNorth North120NorthSouthFigure
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Beam 1 also included an additional
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Figure 3.22 Strand strain-gage inst
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Figure 3.25 Interface board used to
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eam has a “hot spot” (measureme
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3.6 BEAM FABRICATION3.6.1 Beam Cast
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Figure 3.33 Installing the interior
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In order to use a pretensioning bed
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standardside-formprofilespecialtape
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Figure 3.41 Strands installed, tens
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Correspondence between the values o
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Figures 3.45 to 3.50 show the fabri
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Figure 3.49 Casting end block (and
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Figure 3.52 Detensioning by gradual
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CHAPTER 4Results & Discussion4.1 OV
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The strain time history for each ga
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1DNorthSouth1E18 ksi1C1C,E1D1521B1B
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Figure 4.4 Beam 1 prestress losses
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crack adjacent to this location was
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The temperatures in the end blocks
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Table 4.4 Beam 2 applied prestressi
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Figure 4.10 Beam 2 prestress losses
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terms of force distribution seems t
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limits were only exceeded at locati
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spalling stresses were measured in
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transverse reinforcement contained
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Based on Figure 4.18, the 4% Pi des
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Uniform and linearly-decreasing tra
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4.3.5 Contributing Factors to High
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stress ratio multiplied by a typica
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Figure 4.25 Relation between total
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4.4.1 Recommended Texas U-Beam Rein
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Figure 4.28 Proposed end-region det
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At present, AASHTO LRFD (2009) lack
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CHAPTER 5Conclusions5.1 SUMMARY OF
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tested at transfer and under shear
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APPENDIX ADatabase of Transverse-Ba
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194Figure A.1 U-beam with skewed en
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196Figure A.3 Shallow Texas bulb te
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198Figure A.5 Lightweight-concrete
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200Figure A.7 Washington bulb tee (
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202Figure A.9 Nebraska bulb tees an
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204Figure A.11 Nebraska bulb tees a
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206Figure A.13 Shallow I-beams
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where:= lower-bound concrete tensil
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B.3.4 Transmission Length (Clause 6
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Equation B.11where:= bursting force
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50High Web gage4030Max Moment heigh
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C.2 CONCRETE RELEASE STRENGTHA bott
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Table C.1 Specimen Design for Beams
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Table D.1 Beam 1 match-cured cylind
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D.1.2 Beam 28Release-Point Cylinder
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Cylinder Strength (ksi)131197Ambien
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D.2 REINFORCING-BAR MODULUS & STREN
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APPENDIX EEnd-Block Temperature Pro
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E.2 BEAM 2T max = 142°F∆T = 30°
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REFERENCESREFERENCED STANDARDSAmeri
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Fédération Internationale du Bét
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Davis, R.T.; Buckner, C.D. & Ozyild
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Lin, T.Y. & Burns, N.H. (1981), Des
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Stone, W.C. & Breen, J.E. (1984),
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VITADavid Andrew Dunkman was born 2
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