Transcript Final Presentation.ppt

Structural Analysis of Bridge
Gusset Plates:
Steel vs. Composite
RPI Master’s Project
Stephen Ganz – August 2012
Problem Description
•
The objective of this project is to compare the performance differences in
metallic and composite plates by performing structural analyses on the
vertical section of a Warren truss bridge
Material performance is based on stresses and deflections
•
The materials chosen are A36 Carbon Steel and HexPly 8552 IM7 prepreg
composite
•
This will be accomplished by comparing results from computer generated
Finite Element Analyses.
•
Requirements for the bridge is based on federal and state regulations
Steps to Completion
•
Develop Bridge Model
•
Develop Gusset Plate Detail Dimensions
•
Calculated loads based on bridge model
– Dead Load
– Live load
•
Constructed a working 2D FEA model of a Warren truss bridge
•
Perform a Mesh Study
•
Determine Best Evaluation Method to Analyze Composite Plates
•
Run Analyses & Compare Results based on FS and Deflections
Bridge and Plate Details
•
As previously mentioned, the vertical section is a Warren Truss with verticals. It’s length was
arbitrarily chosen, but it’s height and width are based on state and federal requirements
•
Gusset plates were selected to be 2 inches thick
Loads
•
Loads were based on the overall dimensions of the bridge model as well as state and federal
requirements for vehicles. This included weights of the trusses, sidewalks, snow, vehicles and
road deck.
Total Load (W) is 576,636 lbs
Total Dead Load 297,201 lbs
•
•
•
•
Trusses – 101,721 lbs
Sidewalk – 43,500 lbs
Roadway – 205,200 lbs
Floor and Roof Joists – 98,759 lbs
Total Live Load – 279,435 lbs
• Vehicles – 188,235 lbs
• Snow – 182,400 lbs
Model Development
•
The best way to produce accurate results is to include the truss members
– By using a coarse mesh for the trusses their presence comes at very little
computing cost
– Tie constraints bond the the trusses to the plates to simulate a weld
C
A
Pinned End
G
E
D
B
W
5
I
i
F
W
5
K
J
H
W
5
Surftract  1153psi
W
5
L
W
5
Roller End
Loads were applied as surface tractions (psi)
at the 5 locations shown
Mesh Study & Failure Method
Mesh studies were carried for both steel and composite models
–
•
This was done by varying the mesh density of the plates until a convergence of stress or
TSAI-WU criteria was observed
Developing an accurate way of calculating Factors of Safety for the
composites (CFAILURE)
Plate C
0.300
0.250
TSAIW
•
0.200
0.150
0.100
0.050
0.000
0
200
400
600
Elem ents
800
1000
1200
CFAILURE
•
This field output request has been selected as the tool to provide the
necessary results from FEA to base composite failure on
•
CFAILURE is a built in feature in Abaqus that can allow the user to view
results based on Maximum Stress Theory, Maximum Strain Theory, TsaiHill and Tsai-Wu criterion
Factors of safety are calculated as 1/TSAIW for each layer
•
Defining the failure stresses in Abaqus (Edit Material -> Suboptions -> Fail Stress)
FEA Results
•
A36 Steel Model
•
Composite Models
[0 90]S
[0 45 90]S
Shown here are the maximum values for
stress in the A36 Steel Model and maximum
TSAIW values in the composite models
Factors of Safety for Steel are based on Von
Mises stress
Factors of Safety for Composite model are
based on TSAIW values
[0 15 30 45 60 75 90]S
Deflections Illustrated x100
•
A36 Steel Model
•
Composite Models
[0 90]S
[0 45 90]S
The best performing composite model
deformed nearly twice as much as A36 steel.
[0 15 30 45 60 75 90]S
Factors of Safety
The table below lists the factors of safety based on failure for all the FEA models.
The factors of safety are based on peak stresses or maximum TSAIW values for
that particular model
Steel displayed the highest factor of safety, outperforming the best composite by
approximately 30%.
Table 4: Factors of Safety
Steel Model
Von-Mises Stress
Max allowable
FS
12668
58000
4.58
TSAIW
Max allowable
FS
HexPly [0 90]S
0.296
1
3.38
HexPly [0 45 90]S
0.286
1
3.50
HexPly [0 15 30 45 60 75 90]S
0.400
1
2.50
A36 Carbon Steel
Composite Models
Deflections Illustrated x100
The best performing composite model deformed nearly twice as much as A36 steel.
Table 5: Deflections
Steel Model
U magnitude
U1
U2
0.454
0.180
-0.447
HexPly [0 90]S
0.890
0.329
-0.879
HexPly [0 45 90]S
0.833
0.331
-0.816
HexPly [0 15 30 45 60 75 90]S
0.944
0.377
-0.921
183%
183%
183%
A36 Carbon Steel
Composite Models
Lowest % over steel
Outcomes
•
The A36 Carbon Steel Gusset plates outperformed those made from
HexPly 8552 IM7 Carbon Fiber composite material based on failure
margin and deflections
•
This is primarily due to ther orthotropic nature of composites
–
•
HexPly 8552 IM7 is much stronger than steel when loaded longitudinally, but it is only
about half as strong as A36 in the transverse directions.
Composites do have desirable qualities, but they are not suited for this
application in which a plate is loaded in up to 6 different directions.
References
1.
Kulicki, J.M. “Bridge Engineering Handbook.” Boca Raton: CRC Press, 2000.
2.
Abaqus Technology Brief TB-09-BRIDGE-1. “Failure Analysis of Minneapolis I-35W Bridge
Gusset Plates,” Revised: December, 2009. Web. July, 2012.
http://imechanica.org/files/Architecture-SIMULIA-Tech-Brief-09-Failure-Analysis-MinneapolisFull.pdf
3.
Meyers, M. M. “Safety and Reliability of Bridge Structures.” CRC Press, 2009.
4.
Najjar, Walid S., DeOrtentiis, Frank. “Gusset Plates in Railroad Truss Bridges – Finite Element
Analysis and Comparison with Whitmore Testing.” Briarcliff Manor, New York, 2010.
5.
State of Connecticut Department of Transportation. “Bridge Design Manual.” Newington, CT
2003.
6.
Kinlan, Jeff. “Structural Comparison of a Composite and Steel Truss Bridge.” Rensselaer
Polytechnic Institute, Hartford, CT, April, 2012. Web. July, 2012.
http://www.ewp.rpi.edu/hartford/~ernesto/SPR/Kinlan-FinalReport.pdf
7.
Budynas, Richard G. and Nisbett, J. Keith. “Shigley’s Mechanical Engineering Design 9th
Edition.” McGraw-Hill, New York, NY, 2011.
References
8.
American Standard for Testing and Materials - Standard Specification for Carbon Structural
Steel, ASTM A36/A36 M. ASTM International, West Conshohocken, PA 2008.
9.
Gibson, Ronald F. “Principles of Composite Material Mechanics Second Edition.” Boca Raton,
FL: Taylor and Francis Group, 2007.
10. Abaqus/CAE 6.9EF-1. “Abaqus User Manual.” Dassault Systèmes, Providence, RI, 2009.
11. Portland Cement Association. Unit Weights, 2012. Web. July 2012
http://www.cement.org/tech/faq_unit_weights.asp
12. Beer, Johnston. “Vector Mechanics for Engineers Statics and Dynamics 7th Edition.” New York,
NY. McGraw-Hill, 2004.