Potential Solutions
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Transcript of Potential Solutions
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Potential SolutionsPotential Solutions
Goals for Design – What are we concerned Goals for Design – What are we concerned about?about?– Primary Goal: Get the deck on successfullyPrimary Goal: Get the deck on successfully
Stability during deck pourStability during deck pour Girder plumbnessGirder plumbness Deck thickness, cover, smoothnessDeck thickness, cover, smoothness
– Secondary GoalSecondary Goal Design efficiencyDesign efficiency
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Potential Solutions- Background:Potential Solutions- Background:Current DesignsCurrent Designs
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Potential Solutions- BackgroundPotential Solutions- BackgroundCurrent DesignsCurrent Designs
“On skewed structures, in order to accommodate differential dead load deflections of adjacent stringers that exceed ½ inch at any intermediate crossframe location, the erection bolt holes in the crossframe members should be detailed as slotted holes. Hole dimensions shall be 1/16” wider than the nominal bolt diameter and ¾” longer than the nominal bolt diameter. Holes in the stiffeners shall be 3/16” larger than the diameter of the erection bolts. Final bolting and welding shall not be completed until after the deck concrete has been placed.“
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Potential Solutions- Background:Potential Solutions- Background:Current DesignsCurrent Designs
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Potential SolutionsPotential Solutions
One obvious solution – reduce or eliminate skewOne obvious solution – reduce or eliminate skew
Solution 1 – Erect Girders PlumbSolution 1 – Erect Girders Plumb Solution 2 – Erect Girders Out of Plumb (Pre-Solution 2 – Erect Girders Out of Plumb (Pre-
twist girders)twist girders) Solution 3 – Stiffen Superstructure Solution 3 – Stiffen Superstructure Solution 4 – Lean-on BracingSolution 4 – Lean-on Bracing
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Potential Solutions – Potential Solutions – Solution 1Solution 1Erect Girders PlumbErect Girders Plumb Erect girders plumbErect girders plumb Install all crossframes (welded) Install all crossframes (welded) Girders rotate out of plumb during deck placement Girders rotate out of plumb during deck placement Girders will be permanently twistedGirders will be permanently twisted
““Business as Usual” SolutionBusiness as Usual” Solution
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Potential Solutions – Potential Solutions – Solution 1Solution 1Erect Girders PlumbErect Girders Plumb
IssuesIssues How much twist is too much ?How much twist is too much ?
– GirdersGirders– BearingsBearings– CrossframesCrossframes
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Potential Solutions – Potential Solutions – Solution 2Solution 2Erect Girders out of PlumbErect Girders out of Plumb
Erect girders out of plumb (twisted) and Erect girders out of plumb (twisted) and girders rotate to plumb during deck girders rotate to plumb during deck placementplacement
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Potential Solutions – Potential Solutions – Solution 2Solution 2Erect Girders out of PlumbErect Girders out of Plumb
AASHTO/NSBA
Guidelines for Constructability
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AASHTO/NSBA Guidelines for Constructability
Method for Erecting Girders Out of Plumb
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Potential Solutions – Potential Solutions – Solution 2Solution 2Erect Girders out of PlumbErect Girders out of Plumb
IssuesIssues– Steel fit-up during erectionSteel fit-up during erection– Ability of erectorsAbility of erectors– Where has it been done before ? Is it really Where has it been done before ? Is it really
feasible?feasible?– Steel detailing done correctly ?Steel detailing done correctly ?– Potential finger pointing (detailer, erector, designer, Potential finger pointing (detailer, erector, designer,
owner)owner)
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Potential Solutions – Potential Solutions – Solution 3Solution 3Stiffen SuperstructureStiffen Superstructure
Stiffen superstructureStiffen superstructure– Add steel Add steel
Bigger flangesBigger flanges Deeper websDeeper webs
– Add girder line(s)Add girder line(s)– Use shored constructionUse shored construction
Benefit – girder twist reduces with increased Benefit – girder twist reduces with increased girder stiffnessgirder stiffness
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Potential Solutions – Potential Solutions – Solution 3Solution 3Stiffen SuperstructureStiffen Superstructure
Shored ConstructionShored Construction
AdvantageAdvantage– Composite for all dead and live loadsComposite for all dead and live loads
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Potential Solutions – Potential Solutions – Solution 3Solution 3Stiffen SuperstructureStiffen Superstructure
DisadvantagesDisadvantages– Cost of temporary shoringCost of temporary shoring– Need good foundations for shoringNeed good foundations for shoring– Can’t put shoring in trafficCan’t put shoring in traffic– Undesirable to put shoring in waterwayUndesirable to put shoring in waterway– Serious issues with redecking Serious issues with redecking
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Potential Solutions – Potential Solutions – Solution 3Solution 3Stiffen SuperstructureStiffen Superstructure
Example 1: Single span, 150’ span, 60 deg., 50 ksiExample 1: Single span, 150’ span, 60 deg., 50 ksi
Differential Differential DeflectionDeflection
No. of No. of GirdersGirders
Max. Girder Max. Girder RotationRotation
Total Girder Total Girder WeightWeight
No No RestrictionsRestrictions 55 0.99 deg.0.99 deg. 276 k276 k
1” Max.1” Max. 55 0.50 deg.0.50 deg. 443 k443 k
½” Max.½” Max. 66 0.38 deg.0.38 deg. 670 k670 k
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Potential Solutions – Potential Solutions – Solution 3Solution 3Stiffen SuperstructureStiffen Superstructure
Example 2: Single span, 166’ span, 63 deg. SkewExample 2: Single span, 166’ span, 63 deg. Skew
No. of GirdersNo. of Girders Max. Girder Max. Girder RotationRotation
Total Girder Total Girder WeightWeight
66 2.16 deg.2.16 deg. 410 k410 k
88 1.11 deg.1.11 deg. 750 k750 k
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Potential Solutions – Potential Solutions – Solution 4Solution 4Lean-on BracingLean-on Bracing
Lean on BracingLean on Bracing What is it ?What is it ?
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Potential Solutions – Potential Solutions – Solution 4Solution 4 Lean-on Bracing Lean-on Bracing
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Potential Solutions – Potential Solutions – Solution 4Solution 4 Lean-on Bracing Lean-on Bracing
www.steelbridges.org
“Lean-on Cross Frame Bracing for Steel Girders with Skewed Supports”
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Potential Solutions – Potential Solutions – Solution 4Solution 4 Lean-on Bracing - Lean-on Bracing - DefinitionsDefinitions
Internal Lean on Bracing (Solution “4I”)Internal Lean on Bracing (Solution “4I”)
External Lean on Bracing (Solution “4E”)External Lean on Bracing (Solution “4E”)
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Potential Solutions – Potential Solutions – Solution “4I”Solution “4I”Internal Lean-on BracingInternal Lean-on Bracing
X XX
X XX
A
A
Section A-A
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Potential Solutions – Potential Solutions – Solution “4E”Solution “4E”
External Lean-on BracingExternal Lean-on Bracing
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Potential Solutions – Potential Solutions – Solution “4E”Solution “4E”External Lean-on BracingExternal Lean-on Bracing
Top & Bottom Angles, Single Bolt at Each End
Bolted Crossframe
Bolted Crossframe
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Potential Solutions – Potential Solutions – Solution “4E”Solution “4E”External Lean-on BracingExternal Lean-on Bracing
Place Deck – Middle Girders Deflect
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Potential Solutions – Potential Solutions – Solution “4E”Solution “4E”External Lean-on BracingExternal Lean-on Bracing
Install and Weld X-framesRemove
Crossframe; Place Deck
Remove Crossframe; Place Deck
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Potential Solutions – Potential Solutions – Solution “4E”Solution “4E”External Lean-on BracingExternal Lean-on Bracing
Install and Weld X-frames Install and Weld X-frames
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Potential Solutions – Potential Solutions – Solution “4E”Solution “4E”External Lean-on BracingExternal Lean-on Bracing
Place Closure Pour Place Closure Pour
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Miscellaneous IssuesMiscellaneous Issues
BearingsBearings Deck Joints & End CrossframesDeck Joints & End Crossframes Semi-integral bridgesSemi-integral bridges
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Miscellaneous IssuesMiscellaneous IssuesBearingsBearings
Longitudinal slope issuesLongitudinal slope issues
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Miscellaneous IssuesMiscellaneous IssuesBearingsBearings
Cambered Beam Before Deck Placement
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Miscellaneous IssuesMiscellaneous IssuesBearingsBearings
Beam After Deck Placement
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Miscellaneous IssuesMiscellaneous IssuesBearingsBearings
Before Deck Placement
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Miscellaneous IssuesMiscellaneous IssuesBearingsBearings
After Deck Placement
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Miscellaneous IssuesMiscellaneous IssuesBearingsBearings
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Miscellaneous IssuesMiscellaneous IssuesBearingsBearings
Bearing Movement and Restraint IssuesBearing Movement and Restraint Issues
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Miscellaneous IssuesMiscellaneous IssuesBearingsBearings
Longitudinal Displacements
Fixed
Expansion
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Miscellaneous IssuesMiscellaneous IssuesBearingsBearings
Transverse Displacements
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Miscellaneous IssuesMiscellaneous IssuesBearingsBearings
Lateral restraint issuesLateral restraint issues
Fixed Expansion
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Miscellaneous IssuesMiscellaneous IssuesBearingsBearings
Lateral Restraint
Semi-integral Retainers
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Miscellaneous IssuesMiscellaneous IssuesBearingsBearings
Lateral Restraint
Seismic Pedestals
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Miscellaneous IssuesMiscellaneous IssuesBearings - SummaryBearings - Summary
For Skewed / Wide Bridges, May Need to:For Skewed / Wide Bridges, May Need to: Design for individual loadsDesign for individual loads Design for permanent long. & lat. bearing rotationsDesign for permanent long. & lat. bearing rotations Design for additional longitudinal translationDesign for additional longitudinal translation Design for lateral translationDesign for lateral translation Prevent or design for lateral restraint forcesPrevent or design for lateral restraint forces
– Bearing anchors or other restraintsBearing anchors or other restraints– Seismic pedestalsSeismic pedestals– Semi-integral retainers Semi-integral retainers
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Miscellaneous IssuesMiscellaneous IssuesEnd CrossframesEnd Crossframes
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Miscellaneous IssuesMiscellaneous IssuesEnd CrossframesEnd Crossframes
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Miscellaneous IssuesMiscellaneous IssuesEnd CrossframesEnd Crossframes
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Miscellaneous IssuesMiscellaneous IssuesEnd CrossframesEnd Crossframes
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Miscellaneous IssuesMiscellaneous IssuesSemi-integral BridgesSemi-integral Bridges
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Miscellaneous IssuesMiscellaneous IssuesSemi-integral BridgesSemi-integral Bridges
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Miscellaneous IssuesMiscellaneous IssuesSemi-integral BridgesSemi-integral Bridges