A Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R

AASHTOWare BrDR 2013 User Group Meeting

Michael B. Murdock, P.E.Structural Engineer

August 6, 2013

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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Where We Are Headed

New Features of VIRTIS 6.2Added truss analysis capabilities in fall 2010 (now known as Br|R)

Load Rating O’Neal Deck-to-Through Main Span Truss for ALDOT

Verification of Truss AnalysisChord member force verification for both dead and live loads

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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New Truss Rating Analysis Capabilities of Br|R

New Truss Rating Analysis FeaturesAdded in VIRTIS version 6.2

Truss-Counters – tension only membersChord Member Eccentricity – at connectionsFloor Truss Beam Elements – floor trusses to be modeled using beam elements

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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New Truss Rating Analysis Capabilities of Br|R

New Truss Rating Analysis FeaturesAdded in VIRTIS version 6.2

Half-Deck Configuration – user-defined deck locations along truss

Available Main Member Configurations for Truss SuperstructuresDeckThroughNew Half-Deck

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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Main Member Configuration

Deck Truss ConfigurationDeck defined along truss’s upper panel points

Deck

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Main Member Configuration

Through Truss ConfigurationDeck defined along truss’s lower panel points

Deck

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Main Member Configuration

Half-Deck Truss ConfigurationDeck defined along user specified panel points

Deck Deck

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O’Neal Bridge Rating in Br|R

O’Neal BridgeFlorence, Alabama US Rte 43 over Tennessee RiverConstructed 19394 lanes of trafficLength: 2070.5’Spans: 14

6 Simply Supported Approach Spans5 Deck Truss SpansMain 3 Span Continuous Deck-to-Through Truss

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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O’Neal Bridge Rating in Br|R

O’Neal Bridge ComplexitiesDeck-to-Through truss configurationUnsymmetrical deck profile

Deck

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O’Neal Bridge Rating in Br|R

Truss Modeling Assumptions

DC1 loads distributed by tributary deck area to Stringers

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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O’Neal Bridge Rating in Br|R

Truss Modeling Assumptions

DC2 loads distributed uniformly to Stringers

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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O’Neal Bridge Rating in Br|R

Truss Dead Load Path

String -> Floor Beam / Truss -> Main Truss

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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O’Neal Bridge Rating in Br|R

Truss Live LoadLive load does not follow same load path as dead load for truss

Live load distribution to truss is based on live load distribution factors

Factors are manually calculated according to the lever rule

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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O’Neal Bridge Rating in Br|R

Truss Live Load

Influence line method is used to determine maximum force effects

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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O’Neal Bridge Rating in Br|R

Truss Modeling AssumptionsChord members were defined using built up members with gross section properties

Member connections are “Riveted”All connections are modeled as k=1.0

Deck location was defined using “Mid” panel points along vertical chord members

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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O’Neal Bridge Rating in Br|R

Truss Modeling Assumptions

Deck Location

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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Truss Load Verification – GTSTRUDL Assumptions

Truss Load VerificationVerification of new analysis capabilities of VIRTIS

Past O’Neal Bridge Analysis Structural Evaluation of Gusset Plates

Complete in Fall of 2009GTSTRUDL analysis of main truss to determine chord member forces

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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Truss Load Verification – GTSTRUDL Assumptions

Previous GTSTRUDL AssumptionsPlane Frame Structure

A truss structure cannot define axial loads that do not occur at panel pointsOccurs at floor beam locations on O’Neal Truss Panel points had moment released to simulate truss connectivity

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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Truss Load Verification – GTSTRUDL Assumptions

Gross Section Properties

Similar Loading ConditionsAll dead loads manually calculated and applied as point loads except truss selfweight

Similar to VIRTIS approach

Live load is determined through an influence line approach comparable to VIRTIS approach

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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Truss Load Verification – Lower Chord Members

Dead Load Comparison

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Truss Load Verification – Lower Chord Members

Live Load Comparison

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Truss Load Verification – Lower Chord Members

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Truss Load Verification – Upper Chord Members

Dead Load Comparison

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Truss Load Verification – Upper Chord Members

Live Load Comparison

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Truss Load Verification – Upper Chord Members

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Truss Load Verification – Diagonal Chord Members

Dead Load Comparison

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Truss Load Verification – Diagonal Chord Members

Live Load Comparison

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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Truss Load Verification – Diagonal Chord Members

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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Summary Comparision

Dead Load DifferenceLower Chord Members: 2.7%Upper Chord Members: 3.1%Diagonal Chord Members: 0.5%

Live Load DifferenceLower Chord Members: 1.1%Upper Chord Members: 1.3%Diagonal Chord Members: 1.5%

VIRTIS typically produced slightly greater member loads

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Conclusions

New features of VIRTIS 6.2 (Br | R)Beam elements in modeling of Floor TrussesHalf-Deck structure system configuration

Allows for more complex Truss Structures to be modeledO’Neal Deck-to-Through Truss Bridge

Analysis using “Half-Deck” configuration produces comparable member loads to established industry practices

Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|RAASHTOWare BrDR 2013 User Group Conference

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Load Rating of Deck-to-Through Truss Bridge in Br|R

Questions?

Michael Murdock, P.E.Structural Engineer TranSystems

mbmurdock@transystems.com 804-282-1525