ML12153A393
| ML12153A393 | |
| Person / Time | |
|---|---|
| Issue date: | 06/01/2012 |
| From: | Office of the Chief Human Capital Officer |
| To: | |
| References | |
| Download: ML12153A393 (87) | |
Text
ology and Codes ology and Codes Reinforced Concrete Reinforced ConcreteConcrete Techn oConcrete Techn o
Outline OutlineBasic Material PropertiesConcreteReinforcement Reinforced Concrete l 2F l exureBondShearCreep and ShrinkagePrestressed & Post-tensioned Concrete Compression Machine Compression Machine 3
Compression Testing to Compression Testing to Failure Failure 4 Definitions Definitionspsi).in (Area)lbs (LoadStress 2==Area Load g th D 5.)in (LengthOriginal.)in (nDeformatioStrainStressMaximumStrength==Len g High High--Strength ConcreteStrength Concrete 6
Compressometer Compressometer 7
Strain Gage on CylinderStrain Gage on Cylinder 8
Direct Tension Test Direct Tension Test Specimen Specimen 9 Direct Tension Test SetupDirect Tension Test Setup 10 Direct Tension FailureDirect Tension Failure 11 Splitting Tensile TestSplitting Tensile Test 12 13 Characteristics of Characteristics of Concrete Concrete Basic ConceptStrong in CompressionWeak in Tension 14 Factor of 10!!
Load Load--Deformation Characteristics Deformation Characteristics for Concrete for Concrete 15 Demonstration DemonstrationSlotted Styrofoam Model Model Beams 16 Styrofoam Beam Styrofoam Beam --Loaded Loaded Compression 17 Tension Plain Concrete Beam Plain Concrete Beam (no rebar)(no rebar) 18 Plain Concrete BeamPlain Concrete Beam 19 Reinforced Concrete BeamReinforced Concrete Beam 20 Load Load--Deformation Deformation Characteristics for Characteristics for Reinforcing Steel Reinforcing Steel 21 Why Steel?
Why Steel? Strong in tensionDoes not react with concrete 22Compatible thermal expansion and contraction Ductile Bond strength Reinforced Concrete Reinforced Concrete Beam Beam 23 Load Load--DeformationDeformationfor Plain and for Plain and Reinforced Beams Reinforced Beams 24 Reinforced Concrete BeamReinforced Concrete Beam(steel at top)(steel at top) 25 Case Case Study Study 26Stairway LandingPair of Precast Ledger BeamsIf you look underneath
-.
Case Study Case Study 27Remember, this is from underneath!
Rebar Development Rebar Development 28~ 1 3/8"#14 9/8"#9 3/8"#3 Rebar Development Rebar Development 29 Why the ribs?
Rebar Development Rebar Development 30 Bond and Development Bond and Development Length Length Mechanical BondAdhesion Bond 31 Mechanical Bond Mechanical Bond 32 Headed Bars in Tension Headed Bars in TensionHeaded Bars Can Reduce Rebar CongestionTrump Tower Chicago 33Courtesy ERICO Shear and StirrupsShear and StirrupsCrack (Saw Cut) 34 Stirrup (Bungee Cord Thru Drilled Hole in
Beam)
Shear and StirrupsShear and StirrupsAfter Concrete Cracks Shear Load Supported byStirrups(stretching 35 by Stirrups (stretching bungee cord)Held Together by "Stirrup" Diagonal Tension Due to Diagonal Tension Due to Shear Shear 36 Headed Shear Stud Headed Shear Stud Reinforcement Reinforcement 37Courtesy of Hai Dinh, Univ. of Michigan Creep and Shrinkage Creep and Shrinkage"The Rocket Science of Structural Concrete" 38Short-term Elastic Behavior Superimposed over Long-term Inelastic Behavior Creep and Shrinkage Creep and ShrinkageDetermine the Important ParametersUse Analogy of Inflatable Mattress 39 Creep and Shrinkage Creep and ShrinkageShort-term Loads = Elastic 40 Creep and Shrinkage Creep and ShrinkageLong-term Loads = Inelastic 41 Creep and Shrinkage Creep and Shrinkage Important ParametersScale of Element 42 Creep and Shrinkage Creep and Shrinkage Important ParametersScale of Element 43 Creep and Shrinkage Creep and Shrinkage Important ParametersSize of "Openings" = Age and Strength of Concrete 44 Creep and Shrinkage Creep and Shrinkage Important ParametersPressure Differential 45 Creep and Shrinkage Creep and ShrinkagePressure Differential = Relative Humidity 46 Predicted Vertical Shortening vs. Story at 30 Years Demonstration DemonstrationStyrofoam Blocks (Prestressed) 48 Prestressed Concrete:
Prestressed Concrete:General PrinciplesGeneral Principles 49 Tension CompressionNo Tension Methods of PrestressingMethods of PrestressingConcrete MembersConcrete Members
- Pretensioning 50*Post-Tensioning Prestressed Concrete Beams Prestressed Concrete Beams 51 Precast Girders After Detensioning Precast Girders After Detensioning 52 Unloading Girders from Flat Unloading Girders from Flat Bed Rail Car Bed Rail Car 53 Test to Destruction Test to Destruction 54 Flexural CracksFlexural Cracks 55 Sudden Shear Failure Sudden Shear Failure -
-No Shear ReinforcementNo Shear Reinforcement 56 Advantages of Post Advantages of Post--tensioned tensioned Structures StructuresReduced structural depth for lower story heights and reduced dead loadAdditional savings in labor and material for M/E/P, elevator and cladding claddingLong economical spansWide flexibility and variation in designReduced crackingHowever, additional inspections are required Unbonded Tendons Unbonded TendonsThe prestressing strand is prevented from bonding, and is free to move, relative to the surrounding concrete7wirestrands(05 "dia)7-wire strands (0.5 dia.)SheathingAnchor Unbonded Tendons Unbonded TendonsPrestressing force can only be transferred to the concrete through the anchorageCasting: 5" x 2 1/4" typicalWedges Unbonded Tendons Unbonded Tendons Typical Tendon Typical Tendon Profile Profile Banded Tendon Distribution Banded Tendon DistributionResembles a one-way slab (uniform tendons) supported by an embedded beam (banded tendons) along column linesTendons grouped in flat bundles of 4 to 5Accommodatesirregular column pattern Placement at ColumnPlacement at Column#4 bars, typical to match tendon
diameter Place transverse
reinforcing steel belowthebanded below the banded reinforcing steel Curving Curving Banded Tendons Banded Tendons Extreme Curves Extreme Curves Curves in Plan Cause:
- Increased Losses
- High Internal Forces
- Cracking at Openings Extreme Curves
Extreme Curves Corrected Layout Extreme Curves Extreme Curves Punching Shear Punching ShearDetail with tendon group running
directly through l co l umn core 2 minimum
required per ACI
CodeHeaded shear stud
reinforcement Adolphson & Peterson Short Short Column Effect in RampsColumn Effect in RampsCrack in Column Improper Improper Conduit Conduit Acceptable Conduit Acceptable Conduit Beam Column Beam Column Joint Joint --Interior InteriorTendons and beam top steel compete for placement at top of beam Beam Column Beam Column Joint Joint --Exterior ExteriorBeam hooked tops bars compete for space with PT anchorages Beam Column Beam Column Joint Joint --Corner CornerTwo beams framing in at a corner column have even more congestion issuesCoordinate Coordinate Coordinate!
Anchorage Zones Anchorage ZonesBeam-column connections have limited space for anchoring tendons Wider columns for ease of constructionConsider column vertical steel configuration Beam Column Joint Beam Column Joint --Exterior ExteriorCongestion + Poor consolidation
= Problems Beam Column Joint Beam Column Joint --Exterior ExteriorCongestion + Poor consolidation = Problems Consolidation at Anchors Consolidation at Anchors Blow Blow Out Prevention Out PreventionOne tendon exerts ~33,000 pounds of force at the anchor or about the weight of 10 carsRemove penetrations near the anchorage zoneProper concrete consolidation is crucial Restraint Crack Restraint Crack Restraint Crack Restraint Crack Special Inspections Special Inspections Pre-PourVerify PT c.g.s off structural drawingsSupports, midspan, anchorsVerify minimum number of tendons intersect center of column in both directionsRemove conduit, penetrations, etc., by the anchors Special Inspections Special Inspections Pre-PourLook for tendons with extreme
bends, reverse curvature,orodd curvature, or odd configurationsInspect for damage
to sheathing Special Inspections Special InspectionsDuring and after stressing operationInspection of the stressing operation is to be continuous, NOT periodicA deputy inspector is required for each stressing (hjk)crew (eac h j ac k)Measurement of strand tails Elongation Record Elongation Record Building is Human Nature 86
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