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Devin Harris – Michigan Tech Chris Carroll – Virginia Tech

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1 Devin Harris – Michigan Tech Chris Carroll – Virginia Tech
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

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

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

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 ≈ ft Deck ≈ 1 in. ( ) 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. ( ) 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 = 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 Approach primarily dependent on B.C.s
Analysis Options Classical Plate Approach Navier Levy Energy (Ritz) Finite Element Approach Shell Solid Grid (line elements) Approach primarily dependent on B.C.s Note: Focus here will be on the FE approach, but the classical plate approach will be used primarily as a validation mechanism 17

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

19 Material Properties Face Plates (Steel) Core (Polyurethane)
Composite Section Young’s Modulus (E -ksi) 29,878 109 Poisson’s Ratio (n) 0.287 0.36 Flexural Rigidity (D) N/A *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)
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) Midpanel Deflection (wmax)

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22 GT STRUDL Models Element Types BPR SBHQ6 IPLS IPQS

23 GT STRUDL Models Mesh Verification

24 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.

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

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

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

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

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

30 GT STRUDL Models Two Dimensional Example

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

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

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

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

35 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

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

37 GT STRUDL Models Model Construction

38 GT STRUDL Models Model Construction ½”

39 GT STRUDL Models Model Construction Stiffness Analysis GTSES GTHCS
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. DPM-w-selfbrn, The module 'SPWNDX' may not be branched to recursively

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41 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

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

43 Model Validation – SPS Panel
Full Scale SPS Panel

44 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”)

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

46 Experimental vs. Shell Model Predictions ANSYS

47 Experimental vs. Solid Model Predictions ANSYS

48 Experimental vs. Solid Model Predictions GT STRUDL

49 Experimental vs. Solid Model Predictions GT STRUDL

50 Model Validation – SPS Bridge
Half-Scale SPS Bridge

51 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”)

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

53 Experimental vs. Shell Model Predictions ANSYS

54 Experimental vs. Solid Model Predictions ANSYS

55 Experimental vs. Solid Model Predictions GT STRUDL

56 Experimental vs. Solid Model Predictions GT STRUDL

57 Comparison of ANSYS and GT STRUDL Models

58 Questions 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 Questions

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

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