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Copyright ©2015 American Institute of Steel Construction. All rights reserved.
This presentation is provided solely for informational purposes and does not constitute conveyance of any intellectual property rights.
This presentation may not be reproduced or redistributed, in whole or in part, without the prior consent of the American Institute of Construction or the National Steel Bridge Alliance.
Notice:
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HNTB CorporationNational Steel Bridge Alliance
A Division of the American Institute of Steel Construction
Steel Bridge Selection
and Design
NSBA Marketing ManagerMatthew Shergalis, PE
Sr. Project Engineer & Office Quality Manager
Burleigh Law, PE
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Steel Bridge Resources
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Steel Bridge Design References
• Basic Design Resources
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Steel Bridge Design References
• Cutting Edge Resources
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Steel Bridge Design References
• NHI 5 day seminar on Steel Bridges• 2016 Course title: LRFD and Analysis
of Curved Steel Highway Bridges
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Economic Analysis
Span to Weight Curves
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New Overpass Construction
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Substructure Layout
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Substructure Layout
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Substructure Layout
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Substructure Layout
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Substructure Layout
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Substructure Layout
Clearance Requirements
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AASHTO/NSBA Collaboration G12.1-2003: Guidelines for Design
for ConstructibilitySteel Bridge Design Handbook: Selecting the Right Bridge Type
Selecting Bridge Type
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• Rolled Beam? Welded Plate Girder?.......It Depends!
• 80 feet is where a plate girder becomes more advantageous from a pounds per foot perspective.
Rolled Beam vs. Plate Girder
Bridge Span Length (ft)Solution Type 0 20 40 60 80 100 120 >140Rolled BeamHomogeneous Plate Girder
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Benefits• Simplified Design.• Simplified Fabrication.• Great for limited depth
requirements: (33” to 36” most economical).
Limitations• 40” depth beams
become less economical.• Must heat curve
– Significant dead load camber will make heat curving difficult.
– Minimum 1200 ft radius for horizontal curvature.
• Depends on rolling schedule.
• Lengths available up to 120’.
Rolled Beams
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Benefits• Will fit the project
constraints.• No availability issues
with regards to typical plate sizes.
• Can cut girder to fit camber and horizontal curvature requirements.
Limitations• More involved design.
Plate Girders
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Rolled Beam vs. Plate Girder
• AASHTO/NSBA Collaboration document G12.1-2003recommends note allowing substitution of plate girder for rolled beam
• Nevada DOT provides language in their Standard Spec.
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Substructure Layout
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Girder Spacing
• Objective: Balance What’s Practical with What’s Economical
Spacing (s) Spacing (s) Spacing (s) Spacing (s)
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• AASHTO-NSBA Collaboration G12.1-2003– Section 1.2: Girder
Spacing• Up to 140’ spans: 10’
to 11’ girder spacings.• Over 140’ spans:
Greater than 11’ girder spacings
– Vertical clearance and owner preferences could be limitations.
Steel Bridge Design Resource
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Deck Overhang
Overhang Distance Girder Spacing
• Objective: Balance girder moments so exterior and interior girders have same plate sizes.
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• Handbook Vol 6.– Section 3.0: Basic
Framing Development• Deck overhangs to be 30%
to 32% of girder spacing.
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Steel Bridge Design Resources
• Span to Weight Charts– Used during preliminary design phase.– Evaluation alternative structures.– Quickly determine relative costs.
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Span - Steel Weight Curves
Bridge Weight (psf) x Bridge Area (sq‐ft) x Historical CostBridge Weight (psf) x Bridge Area (sq‐ft) x Historical Cost
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Economic Analysis
Continuous Span Standards
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Steel Bridge Design Resources
• Continuous Span Standards– Provides preliminary solutions.
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Conceptual Solution – Girder Elevation
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Conceptual Solution - Girder Sizing
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Conceptual Solution - Weight
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Substructure Layout
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Conceptual Solutions
• Input files allow you to develop a solution that fits your project constraints.
www.steelbridges.org/SoftwareRegistration
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Preliminary Design
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• Ensure the output of plate sizes are readily available.
• Consult 2011 MSC Article – Steel Plate Availability for Highway Bridges
Material Availability
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Plate Transitions
• Write down all plate sizes from analysis. If more than 5 plates sizes are listed, consider combining sizes.
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• AASHTO-NSBA Collaboration G12.1-2003– Section 1.5: Flange
Sizing• Limit the number of
plate sizes.• TexasDOT estimates
an 800 to 1000 lbsplate savings to justify shop splice.
Steel Bridge Resource
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Field Sections
• Objective: Balance what can be fabricated practically with what can be shipped.
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Steel Bridge Resource
Field Section Bounding Box• Length: 175 ft. Possible, 80 ft. Comfortable.• Weight: 100 Tons Maximum, 40 Tons No Permit.• Width: 16 ft. Maximum.• Height: 10 ft.
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Field Splices
• Listing field splices as optional gives the fabricator the opportunity to ship larger field sections.
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Crossframe Layout
• Continuous Bracing
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Crossframe Layout
• Lean on Bracing
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Crossframe Layout
• Discontinuous Bracing
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Crossframe Types
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AASHTO NSBA Collaboration G1.4-2006: Guidelines for Design Details
Steel Bridge Design Handbook: Bracing System Design
Steel Bridge Resource
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