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Evaluation of the Sandwich Plate System in Bridge Decks Using a Plate Approach Devin Harris – Michigan Tech Chris Carroll – Virginia Tech A Comparison Between ANSYS and GT STRUDL Models

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Project Overview SPS Introduction Design Approach Element Validation ANSYS Models GT STRUDL Models Comparison

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SPS for Civil Structures

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Introduction to SPS Developed by Intelligent Engineering –Maritime industry –Bridge Application (deck) Pre-fab Panels Disadvantages – Cost – Limited application – No design provisions Advantages – Lightweight – Rapid installation – New/rehab

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Prefabricated Decks/Bridges Fabricated panel – limited girder configuration Wide girder spacing Larger cantilevers Fast erection Structured Panel Deck

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Half-Scale Bridge (VT Laboratory) Span ≈ 40 ft; width ≈ ft Deck ≈ 1 in. ( ) 8 SPS panels – Transversely welded/bolted – Bolted to girders (composite) 2 girder construction

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Shenley Bridge (St. Martin, QC) Completed - November 2003 – 7 days of total construction Span ≈ 74 ft; width ≈ 23 ft Deck ≈ 2 in. ( ) 10 SPS panels – Transversely welded/bolted – Bolted to girders (composite) 3 girder construction

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LAY PANELS ERECT GIRDERS & BRACING Sequence of SPS Construction BOLT PANELS TO BEAMS & TOGETHER WELD DECK SEAM

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COAT DECKERECT BARRIERS Sequence of SPS Construction LAY ASPHALT

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Prefabricated Decks/Bridges Simple plate – many girder configuration Small girder spacing Short cantilevers Girders attached to deck in factory Very fast erection Simple Plate Deck

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Cedar Creek Bridge (Wise County, TX) 2-Lane rural road SPS Deck (integral girders) Span = ft Width = 30 ft Deck ≈ 1-5/8 in. 5/16”-1”-5/16”

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Fabrication Process

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Current Bridge Projects New Bridge IBRC – Cedar Creek – Texas – June ‘08

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Research Objective To develop a simple design procedure for SPS decks for bridge applications

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SPS Deck Design Approach AASHTO Deck Design Design Methods –Linear Elastic (Equivalent Strip) –Inelastic (Yield-Line) –Empirical (R/C only) –Orthotropic Plate Limit States –Serviceability –Strength –Fatigue SPS Approach (Layered Plate) –Variable loads and B.C.s –Assume deflection controls

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SPS Plate Representation

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Analysis Options Classical Plate Approach –Navier –Levy –Energy (Ritz) Finite Element Approach –Shell –Solid –Grid (line elements) Approach primarily dependent on B.C.s

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FE Model Approach Shell Model –Advantages Ideal for thin elements Computationally efficient Membrane/bending effects Single thru thickness element Solid Model –Advantages Realistic geometry representation Element connectivity –Disadvantages Element compatibility Element connectivity Stacking limitations* –Disadvantages Can be overly stiff User error (more likely) Complicated mesh refinement

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Material Properties Face Plates (Steel) Core (Polyurethane) Composite Section Young’s Modulus (E -ksi) 29, Poisson’s Ratio ( ) Flexural Rigidity (D) N/A *D t = flexural rigidity for layered plate (equivalent to EI for a beam) *Ventsel, E., and Krauthammer, T. (2001). Thin plates and shells:theory, analysis, and applications, Marcel Dekker, New York, NY.

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Element Validation (Generic) Givens: –Boundary Conditions: Fully Restrained –Material Properties: E=29,000 ksi; =0.25 –Dimensions: thickness=6” (constant); a=b=L [L/t … 1-200] –Load: q = 0.01 ksi (uniform) ANSYS Shell 63 (4-node) Shell 91/93 (8-node) Solid 45 (8-node) Solid 95, Solid 191 (20-node) GT STRUDL BPR (4-node plate) SBHQ6 (4-node shell) IPLS (8-node solid) IPQS (20-node solid) Midpanel Deflection (w max )

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GT STRUDL Models Element Types BPR SBHQ6 IPLSIPQS

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GT STRUDL Models Mesh Verification

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GT STRUDL Models Two Dimensional Example 60 in. IPLQ (2D equivalent of IPLS) Linear Shape Function IPQQ (2D equivalent of IPQS) Quadratic Shape Function A shape function is the relationship of displacements within an element.

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GT STRUDL Models Two Dimensional Example 60 in. One Layer

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GT STRUDL Models Two Dimensional Example 60 in. Two Layers

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GT STRUDL Models Two Dimensional Example 60 in. Three Layers

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GT STRUDL Models Two Dimensional Example 60 in. Four Layers

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GT STRUDL Models Two Dimensional Example 120 in.

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GT STRUDL Models Two Dimensional Example

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GT STRUDL Models Aspect Ratios (IPLS vs. IPQS) Small Aspect RatiosLarge Aspect Ratios

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SPS Models Case I –Simple Support on all edges Cold-formed angles – assume minimal rotational restraint

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SPS Models Case II –Simple supports perpendicular to girders –Fixed supports along girders Rotation restrained by girders & cold-formed angles

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SPS Models Case III –Full restraint on all edges Rotation restrained by girders & cold-formed angles

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GT STRUDL Models Boundary Conditions/Symmetry Full Model: 345,600 Elements 406,567 Joints 1,229,844 DOF Reduced Model: 86,400 Elements 102,487 Joints 307,461 DOF

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GT STRUDL Models Simple – Simple Simple – Fixed Fixed – Fixed 2” Thick Plate 1” Thick Plate Symmetry Model Construction

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GT STRUDL Models Model Construction

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GT STRUDL Models Model Construction ½”

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GT STRUDL Models Stiffness Analysis GTSES GTHCS Model Construction DPM-w-selfbrn, The module 'SPWNDX' may not be branched to recursively The GTHCS solver partitions the global stiffness matrix into hyper-column blocks of size V BS, and stores these blocks on the computer hard drive, with only two of these blocks residing in the virtual memory at a time reducing the required amount of virtual memory space.

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Summary of Element Validity ANSYS Solids –Converged with single thru thickness element ANSYS Shells –Minimal mesh refinement required for convergence STRUDL Plate/Shells –Converged but no multiple layer capabilities STRUDL Solids –Converged with sufficient thru thickness refinement All Elements are capable of Modeling thin plates, but consideration must be given to mesh density. Especially, thru thickness density for solid elements

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Suggested Improvements Layered element for composite materials Redraw Issues in GT Menu Contour plots without mesh Undo Button in GT Menu

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Model Validation – SPS Panel Full Scale SPS Panel

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Model Validation – SPS Panel SPS Plate (0.25” plates; 1.5” core) Support by W27 x 84 beams Loaded to 77.8 k with concrete filled tires (assumed 10” x 20”)

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Experimental vs. Shell Model Predictions ANSYS CASE I (SS) CASE II Beams) CASE III (Fixed)

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Experimental vs. Shell Model Predictions ANSYS

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Experimental vs. Solid Model Predictions ANSYS

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Experimental vs. Solid Model Predictions GT STRUDL

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Model Validation – SPS Bridge Half-Scale SPS Bridge

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Model Validation – SPS Bridge SPS Plate (0.125” plates; 0.75” core) Support by Built-up Girders (depth ~ 23”) Loaded ~ 24 k with bearing pad (9” x 14”)

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Experimental vs. Shell Model Predictions ANSYS CASE I (SS) CASE II Beams) CASE III (Fixed)

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Experimental vs. Shell Model Predictions ANSYS

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Experimental vs. Solid Model Predictions ANSYS

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Experimental vs. Solid Model Predictions GT STRUDL

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Comparison of ANSYS and GT STRUDL Models

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Conclusions SPS deck behavior can be modeled as plate with variable boundary conditions Solid and shell elements are applicable Attention to mesh refinement critical to solid elements Higher order elements significantly increase # DOFs Layered elements ideal for efficiency GT STRUDL and ANSYS yield similar results, but not identical –Future investigation of differences in solid/shell boundary conditions

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Acknowledgements Virginia Department of Transportation Intelligent Engineering (www.ie-sps.com)www.ie-sps.com GT STRUDL Users’ Group Virginia Tech

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