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A Load Rating of a 3 Span Continuous Deck-toThrough Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Meeting Michael B. Murdock, P.E. Structural Engineer August 6, 2013 Where We Are Headed New Features of VIRTIS 6.2 Added 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 Analysis Chord member force verification for both dead and live loads Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 2 New Truss Rating Analysis Capabilities of Br|R New Truss Rating Analysis Features Added in VIRTIS version 6.2 Truss-Counters – tension only members Chord Member Eccentricity – at connections Floor 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|R AASHTOWare BrDR 2013 User Group Conference 3 New Truss Rating Analysis Capabilities of Br|R New Truss Rating Analysis Features Added in VIRTIS version 6.2 Half-Deck Configuration – user-defined deck locations along truss Available Main Member Configurations for Truss Superstructures Deck Through New Half-Deck Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 4 Main Member Configuration Deck Truss Configuration Deck defined along truss’s upper panel points Deck Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 5 Main Member Configuration Through Truss Configuration Deck defined along truss’s lower panel points Deck Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 6 Main Member Configuration Half-Deck Truss Configuration Deck defined along user specified panel points Deck Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 7 O’Neal Bridge Rating in Br|R O’Neal Bridge Florence, Alabama US Rte 43 over Tennessee River Constructed 1939 4 lanes of traffic Length: 2070.5’ Spans: 14 6 Simply Supported Approach Spans 5 Deck Truss Spans Main 3 Span Continuous Deck-toThrough Truss Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 8 O’Neal Bridge Rating in Br|R O’Neal Bridge Complexities Deck-to-Through truss configuration Unsymmetrical deck profile Deck Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 9 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|R AASHTOWare BrDR 2013 User Group Conference 10 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|R AASHTOWare BrDR 2013 User Group Conference 11 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|R AASHTOWare BrDR 2013 User Group Conference 12 O’Neal Bridge Rating in Br|R Truss Live Load Live 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|R AASHTOWare BrDR 2013 User Group Conference 13 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|R AASHTOWare BrDR 2013 User Group Conference 14 O’Neal Bridge Rating in Br|R Truss Modeling Assumptions Chord 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|R AASHTOWare BrDR 2013 User Group Conference 15 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|R AASHTOWare BrDR 2013 User Group Conference 16 Truss Load Verification – GTSTRUDL Assumptions Truss Load Verification Verification of new analysis capabilities of VIRTIS Past O’Neal Bridge Analysis Structural Evaluation of Gusset Plates Complete in Fall of 2009 GTSTRUDL analysis of main truss to determine chord member forces Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 17 Truss Load Verification – GTSTRUDL Assumptions Previous GTSTRUDL Assumptions Plane Frame Structure A truss structure cannot define axial loads that do not occur at panel points Occurs 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|R AASHTOWare BrDR 2013 User Group Conference 18 Truss Load Verification – GTSTRUDL Assumptions Gross Section Properties Similar Loading Conditions All 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|R AASHTOWare BrDR 2013 User Group Conference 19 Truss Load Verification – Lower Chord Members Dead Load Comparison Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 20 Truss Load Verification – Lower Chord Members Live Load Comparison Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 21 Truss Load Verification – Lower Chord Members Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 22 Truss Load Verification – Upper Chord Members Dead Load Comparison Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 23 Truss Load Verification – Upper Chord Members Live Load Comparison Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 24 Truss Load Verification – Upper Chord Members Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 25 Truss Load Verification – Diagonal Chord Members Dead Load Comparison Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 26 Truss Load Verification – Diagonal Chord Members Live Load Comparison Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 27 Truss Load Verification – Diagonal Chord Members Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 28 Summary Comparision Dead Load Difference Lower Chord Members: Upper Chord Members: Diagonal Chord Members: 2.7% 3.1% 0.5% Live Load Difference Lower Chord Members: Upper Chord Members: Diagonal Chord Members: 1.1% 1.3% 1.5% VIRTIS typically produced slightly greater member loads Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 29 Conclusions New features of VIRTIS 6.2 (Br | R) Beam elements in modeling of Floor Trusses Half-Deck structure system configuration Allows for more complex Truss Structures to be modeled O’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|R AASHTOWare BrDR 2013 User Group Conference 30 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 Load Rating of a 3 Span Continuous Deck-to-Through Truss Bridge in Br|R AASHTOWare BrDR 2013 User Group Conference 31