CHAPTER 22 SUBSTRUCTURES - Indiana 22 SUBSTRUCTURES Uses of Integral and Semi -Integral End Bents...
Transcript of CHAPTER 22 SUBSTRUCTURES - Indiana 22 SUBSTRUCTURES Uses of Integral and Semi -Integral End Bents...
CHAPTER 22
SUBSTRUCTURES
Old Chapters– 66: Foundations– 67: Bents, Piers and Abutments– 68: Retaining Walls (not published)
New Chapters– 22-1: Foundations– 22-2: Abutments, Bents, Piers and
Bearings– 22-3: Earth Retaining Systems
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Revisions and Updates– Chapter 22-1: Foundations
Limit States and Resistance Factors Maximum Axial Nominal Geotechnical Pile
Resistances Rn max for HP and shell piles Additional structural considerations for scour Seismic design
– Chapter 22-2: Abutments, Bents, Piers and Bearings
Limit States and Resistance Factors Load Combination and Load Factors New Section on Semi Integral End Bents
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– Chapter 22-3: Earth Retaining Systems Limit States and Resistance Factors Fill Walls
– Cast-in-place Reinforced Concrete Cantilever– Retaining Walls with or without Ground Reinf– Prefabricated Modular Gravity Wall– Reinforced Soil Slopes
Cut Walls– Soldier Pile Wall– Drilled Shaft Wall– Anchored Wall– Soil Nailed Wall– Micropile Wall
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Benefits of Integral and Semi-Integral End Bents
Eliminate expansion jointsReduce future maintenance costsReduce construction costsEffective way to accommodate seismic forces (dampening effect)
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Uses of Integral and Semi-Integral End Bents
Chapter 22 describes integral end bent limitations.Use integral end bents whenever possible.Use semi-integral end bents when integral end bents are not possible.
Skew angle > 30 and/orBridge Length > 500 ft or Expansion Length > 250 ftTwisting or racking of the bridge should be analyzedRehabilitating existing bridge with battered pile
Use expansion end bents as a last resort.
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Details of Semi-Integral End Bents
Method 1Use keyway with expanded polystyrene and anchor plateUse polychloroprene joint membrane behind end bent
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Details of Semi-Integral End Bents
Method 2Use elastomeric bearing pad and expanded polystyreneUse polychloroprene joint membrane behind end bent
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Interior Pier Requirements
Designed for vertical load.Designed for transverse lateral load (stream, earth, wind; usually minor).All longitudinal lateral loads distributed to end bent embankments.Piers can be either:
fixed (frame bents, hammerhead, on pile caps) with movable bearingsextended pile bentswall pier on a single row of piles (extended pile bent with large cap)
save money on foundations and cofferdamsfriction of approach slab help resist longitudinal forces
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Beyond the Maximum
BFS designing an integral bridge on the US 31 Kokomo Bypass that is 810 ft and zero skew.Edward Wasserman, Tennessee DOT designed a 1175 ft curved, jointless bridge on State Road 50 over Happy Hollow Creek.
Forces at end bents were less due to curvature
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References
Massachusetts Department of Public Works “Integral Bridge Seminar”presented by Steve Weintraut and Martin Burke, Jr.
“The Emergence of Semi-Integral Bridges”by Martin Burke, Jr.
“The Structure Movement Systems Approach to Effective Bridge Design”by Martin Burke, Jr.
“Design of Integral Concrete Bridges”by Martin Burke, Jr.
“Jointless and Smoother Bridges”by Professor Robert Frosch
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BEARINGS
Minimize Bearing Pad Sizes– Minimize different types and sizes
INDOT Specs require extra bearing pad for each size and type.
Cost savings can be realized by using the same bearing pad– Shim Thickness
Shims in elastomeric bearings should be 12 gage (0.1046”) Old standard of 3/32” (0.09375”) should not be specified