Carroll Harris Presentation

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

Devin Harris – Michigan TechChris Carroll – Virginia Tech

A Comparison BetweenANSYS and GT STRUDL Models

Project Overview

POLYURETHANE CORE

STEEL FACEPLATES

POLYURETHANE CORE

STEEL FACEPLATES

SPS Introduction

Design Approach

Element Validation

ANSYS Models

GT STRUDL ModelsComparison

SPS for Civil Structures

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

Prefabricated Decks/Bridges

• Fabricated panel – limited girder configuration• Wide girder spacing • Larger cantilevers• Fast erection

Structured Panel Deck

Slip-Critical Bolt

WeldedConnection

Cold-FormedAngle

Built-up orWide Flange

Section

Polymer Core(Unexposed)Steel Face Plates

Panel Edge Plate(Cold-Formed Angle)

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

4'-10" 5'-1" 4'-10"

Top Flange PlatePL 0.625 x 6 x 480

Bottom Flange PlatePL 1 x 6.4 x 480

Diaphragm Angles 2 x 2 x 0.31

Top and BottomSandwich Plate

PL 0.125 x 60 x 177.2

Girder WebPL 0.25 x 21.4 x 480

Elastomer Core0.75 x 60 x 177.2

Bent AnglePL 0.19 x 7.9 x 177.2

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

LAY PANELSERECT GIRDERS& BRACING

Sequence of SPS Construction

BOLT PANELS TO BEAMS & TOGETHER

WELD DECK SEAM

COAT DECKERECT BARRIERS

Sequence of SPS Construction

LAY ASPHALT

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

WeldedConnection

Wide FlangeSection

Polymer Core(Unexposed)Steel Face Plates

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”

CL OFBRIDGE

SEEDET "3"

2% SLOPESPS 516" - 1" - 5/16"

DET "A"SEE

32'-414"

10'-0"

30'-0"

2% SLOPE

6'-218" 10'-0"6'-21

8"

CLEAR ROADWAYCL OF

BRIDGE

SEE DET "1"GUARDRAIL

6'-314" 6'-31

4" 6'-314" 6'-31

4"6'-314"

DET "2"SEE

C 15 x 33.9C 15 x 33.9C 15 x 33.9 C 15 x 33.9C 15 x 33.9

NOTE SPACING IS AT TOP & CTROF GIRDER TOP FLANGE

2%TYP

2%TYP

Fabrication Process

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

Research Objective

• To develop a simple design procedure for SPS decks for bridge applications

SPS Deck Design ApproachAASHTO 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

Plastic hinges

Strip W

idth (

S)

Equivalent Strip

Equivalent Strip on Rigid Girders

Slab-Girder Bridge

Slab Section Cut-out

Arbitrary Loading

Deck Continuity

Cut-out

Plate Representation of Bridge Deck

Edge BCsSimplified

Edge BCsSimplified

Arbitrary Loading

Slab-Girder Bridge

Slab Section Cut-out

Arbitrary Loading

Deck Continuity

Cut-out

Plate Representation of Bridge Deck

Edge BCsSimplified

Edge BCsSimplified

Arbitrary Loading

Simple Support Fixed Support

Traffic Direction

SPS Plate Representation

Analysis Options

• Classical Plate Approach– Navier– Levy– Energy (Ritz)

• Finite Element Approach– Shell– Solid– Grid (line elements)

Approach primarily dependent on B.C.s

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

Material Properties

Face Plates (Steel)

Core (Polyurethane) Composite Section

Young’s Modulus (E -ksi)

29,878 109

Poisson’s Ratio () 0.287 0.36

Flexural Rigidity

(D)N/A

3 3 3

22

2 22 23 11

c c cp

t p ccp

t t ttD E E

3 33

2 2

2 22 23 1 1

c ccp p p

c c

eqt p c

t t tE t E

D

2

3

12 1t eqequiv

total

DE

t

*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.

tp

tc

tp

a

b

q

Fixed Edge

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)

40.00126classical

q LwD

Midpanel Deflection (wmax)

0.95

1.00

1.05

1.10

1.15

1.20

1.25

1.30

1.35

1.40

1.45

1.50

1 10 100Span/thickness ratio (L/t)

SHELL 63 SHELL 91 / 93 SOLID 45 SOLID 95 / 191IPLS IPQS BPR SBHQ6

Convergence Comparison of ANSYS and STRUDL Elements (Square Fixed Plate with Uniform Load )

wm

idsp

an(F

E)

/wm

idsp

an(c

lass

ical

) Shell 91 / 93

Shell 63 IPQSSolid 95 / 191

Solid 45

IPLS

BPR

SBHQ6

GT STRUDL ModelsElement Types

BPR SBHQ6

IPLS IPQS

GT STRUDL Models

Mesh VerificationIPLS Element Validation

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

1.5

1 10 100 1000

L/t Ratio

dFE

A/d

CLA

SS

ICA

L

IPLS 6x6x6

IPLS 3x3x3

IPLS 2x2x2

IPLS 1x1x1

IPLS 2x2x1

GT STRUDL Models

Two Dimensional Example

60 in.

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.

GT STRUDL Models

Two Dimensional Example

60 in.

60 in.

One Layer

GT STRUDL Models

Two Dimensional Example

60 in.

60 in.

Two Layers

GT STRUDL Models

Two Dimensional Example

60 in.

60 in.

Three Layers

GT STRUDL Models

Two Dimensional Example

60 in.

60 in.

Four Layers

GT STRUDL Models

Two Dimensional Example

120 in.

120 in.

GT STRUDL Models

2D Element Comparison Example

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

0 5 10 15 20 25

Number of Longitudinal Divisions

d FEA/d

Cla

ssic

al

IPLQ 1 Layer

IPLQ 2 Layers

IPLQ 3 Layers

IPLQ 4 Layers

Two Dimensional Example2D Element Comparison Example

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

0 5 10 15 20 25

Number of Longitudinal Divisions

d FEA/d

Cla

ssic

al

IPLQ 1 Layer

IPLQ 2 Layers

IPLQ 3 Layers

IPLQ 4 Layers

IPQQ 1 Layer

IPQQ 2 Layers

GT STRUDL Models

Aspect Ratios (IPLS vs. IPQS)

Small Aspect Ratios Large Aspect Ratios

SPS Models

• Case I– Simple Support on all edges

• Cold-formed angles – assume minimal rotational restraint

Girder Line

Girder Line

Panel Length

GirderSpacing

Simple Support Fixed Support

SPS Models• Case II

– Simple supports perpendicular to girders– Fixed supports along girders

• Rotation restrained by girders & cold-formed angles

Girder Line

Girder Line

Panel Length

GirderSpacing

Simple Support Fixed Support

SPS Models• Case III

– Full restraint on all edges• Rotation restrained by girders & cold-formed angles

GirderSpacing

Panel Length

Girder Line

Girder Line

Simple Support Fixed Support

GT STRUDL Models

Boundary Conditions/SymmetryFull Model:

345,600 Elements406,567 Joints1,229,844 DOF

Reduced Model:

86,400 Elements102,487 Joints307,461 DOF

GT STRUDL Models

• Simple – Simple• Simple – Fixed• Fixed – Fixed• 2” Thick Plate• 1” Thick Plate• Symmetry

Model Construction

GT STRUDL Models

Model Construction

GT STRUDL Models

Model Construction

½” ½”

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 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.

0.95

1.00

1.05

1.10

1.15

1.20

1.25

1.30

1.35

1.40

1.45

1.50

1 10 100Span/thickness ratio (L/t)

SHELL 63 SHELL 91 / 93 SOLID 45 SOLID 95 / 191IPLS IPQS BPR SBHQ6

Convergence Comparison of ANSYS and STRUDL Elements (Square Fixed Plate with Uniform Load )

wm

idsp

an(F

E)

/wm

idsp

an(c

lass

ical

) Shell 91 / 93

Shell 63 IPQSSolid 95 / 191

Solid 45

IPLS

BPR

SBHQ6

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

Suggested Improvements

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

Model Validation – SPS Panel

Full Scale SPS Panel

Model Validation – SPS Panel

10'-0"

9'-9" 10'-0" 9'-9"

5'-11"

2'-1" 2'-1"

• 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”)

Experimental vs. Shell Model PredictionsANSYS

0

10

20

30

40

50

60

70

80

90

-0.6-0.5-0.4-0.3-0.2-0.10.0

App

lied

Load

(kip

)

Deflection (in.)

Measured SS Plate (Case I) Fixed @ Beams (Case II) Fully Fixed (Case III)

Load vs. Mid-panel Deflection - Full-Scale Panel (ANSYS)

Case III Case IICase I

Experimental vs. Shell Model PredictionsANSYS

Experimental vs. Solid Model PredictionsANSYS

0

10

20

30

40

50

60

70

80

90

-0.6-0.5-0.4-0.3-0.2-0.10.0

App

lied

Load

(kip

)

Deflection (in.)

Measured SS Plate (Case I) Fixed @ Beams (Case II) Fully Fixed (Case III)

Load vs. Mid-panel Deflection - Full-Scale Panel (ANSYS)

Case III Case IICase I

Experimental vs. Solid Model PredictionsGT STRUDL

Experimental vs. Solid Model PredictionsGT STRUDL

0

10

20

30

40

50

60

70

80

90

-0.8-0.7-0.6-0.5-0.4-0.3-0.2-0.10.0

App

lied

Load

(kip

)

Deflection (in.)

Measured SS Plate (Case I) Fixed @ Beams (Case II) Fully Fixed (Case III)

Load vs. Mid-panel Deflection - Full-Scale Panel (GT STRUDL)

Case III Case II Case I

Model Validation – SPS Bridge

Half-Scale SPS Bridge

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”)

9 3,6,8

GIRDER "B"

GIRDER "A"

XX= STRAIN GAGES

X = DISPLACEMENT TRANSDUCERS (WIRE POT OR DIAL GAGE)= STRAIN GAGES LOCATED ON OPPOSITE FACE

"G" "G"

ELEVATION "G-G"

4,5

13

4

61,22

63

4

5

6

5

2

40 ft

4.84

ft5.

09 ft

4.84

ft

17

12 3

9 78

5 ft

5

7

4 7

Panel 1 Panel 2 Panel 3 Panel 4 Panel 5 Panel 6 Panel 7 Panel 8

Experimental vs. Shell Model PredictionsANSYS

Experimental vs. Shell Model PredictionsANSYS

0

5

10

15

20

25

30

-0.7-0.6-0.5-0.4-0.3-0.2-0.10

Load

(kip

)

Midspan Deflection (in.)

Measured SS Plate (Case I) Fixed @ Beams (Case II) Fully Fixed (Case III)

Case II Case I

Load vs. Mid-panel Deflection - Half-Scale Bridge (ANSYS)

Case III

Experimental vs. Solid Model PredictionsANSYS

0

5

10

15

20

25

30

-0.7-0.6-0.5-0.4-0.3-0.2-0.10

Load

(kip

)

Midspan Deflection (in.)

Measured SS Plate (Case I) Fixed @ Beams (Case II) Fully Fixed (Case III)

Case IICase I

Load vs. Mid-panel Deflection - Half-Scale Bridge (ANSYS)

Case III

Experimental vs. Solid Model PredictionsGT STRUDL

Experimental vs. Solid Model PredictionsGT STRUDL

0

5

10

15

20

25

30

-0.8-0.7-0.6-0.5-0.4-0.3-0.2-0.10

Load

(kip

)

Midspan Deflection (in.)

Measured SS Plate (Case I) Fixed @ Beams (Case II) Fully Fixed (Case III)

Case IICase I

Load vs. Mid-panel Deflection - Half-Scale Bridge (GT STRUDL)

Case III

Comparison of ANSYS and GT STRUDL Models

0

0.25

0.5

0.75

SPS Panel SPS Bridge

Maximum SPS Panel Deflections @ Peak LoadMeasured vs. FEA

Measured GT STRUDL Solid ANSYS Shell ANSYS Solid

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

Acknowledgements

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