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Evaluation of the Sandwich Plate System in Bridge Decks Using a Plate Approach

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

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Evaluation of the Sandwich Plate System in Bridge Decks Using a Plate Approach

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

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

  3. SPS for Civil Structures

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

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

  6. Half-Scale Bridge (VT Laboratory) • Span ≈ 40 ft; width ≈ 14.75 ft • Deck ≈ 1 in. (3.2-19.1-3.2) • 8 SPS panels • Transversely welded/bolted • Bolted to girders (composite) • 2 girder construction

  7. Shenley Bridge (St. Martin, QC) • Completed - November 2003 • 7 days of total construction • Span ≈ 74 ft; width ≈ 23 ft • Deck ≈ 2 in. (6.4-38-6.4) • 10 SPS panels • Transversely welded/bolted • Bolted to girders (composite) • 3 girder construction

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

  9. Sequence of SPS Construction ERECT BARRIERS COAT DECK LAY ASPHALT

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

  11. Cedar Creek Bridge (Wise County, TX) • 2-Lane rural road • SPS Deck (integral girders) • Span = 3@50 ft • Width = 30 ft • Deck ≈ 1-5/8 in. • 5/16”-1”-5/16”

  12. Fabrication Process

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

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

  15. 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

  16. SPS Plate Representation

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

  18. 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

  19. Material Properties *Dt = 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.

  20. Element Validation (Generic) Midpanel Deflection (wmax) Givens: • Boundary Conditions: Fully Restrained • Material Properties: E=29,000 ksi; n=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)

  21. GT STRUDL Models Element Types SBHQ6 BPR IPLS IPQS

  22. GT STRUDL Models Mesh Verification

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

  24. GT STRUDL Models Two Dimensional Example 60 in. One Layer 60 in.

  25. GT STRUDL Models Two Dimensional Example 60 in. Two Layers 60 in.

  26. GT STRUDL Models Two Dimensional Example 60 in. Three Layers 60 in.

  27. GT STRUDL Models Two Dimensional Example 60 in. Four Layers 60 in.

  28. GT STRUDL Models Two Dimensional Example 120 in. 120 in.

  29. GT STRUDL Models Two Dimensional Example

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

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

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

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

  34. GT STRUDL Models Boundary Conditions/Symmetry Reduced Model: 86,400 Elements102,487 Joints307,461 DOF Full Model: 345,600 Elements406,567 Joints1,229,844 DOF

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

  36. GT STRUDL Models Model Construction

  37. GT STRUDL Models ½” ½” Model Construction

  38. Stiffness Analysis GTSES GTHCS GT STRUDL Models The GTHCS solver partitions the global stiffness matrix into hyper-column blocks of size VBS, 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. Model Construction DPM-w-selfbrn, The module 'SPWNDX' may not be branched to recursively

  39. Summary of Element Validity All Elements are capable of Modeling thin plates, but consideration must be given to mesh density. Especially, thru thickness density for solid elements • 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

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

  41. Model Validation – SPS Panel Full Scale SPS Panel

  42. 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”)

  43. Experimental vs. Shell Model PredictionsANSYS CASE II (Fixed @ Beams) CASE I (SS) CASE III (Fixed)

  44. Experimental vs. Shell Model PredictionsANSYS

  45. Experimental vs. Solid Model PredictionsANSYS

  46. Experimental vs. Solid Model PredictionsGT STRUDL

  47. Experimental vs. Solid Model PredictionsGT STRUDL

  48. Model Validation – SPS Bridge Half-Scale SPS Bridge

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