FerryLandings Loads
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Transcript of FerryLandings Loads
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Characterizing the Load Environment ofWashington State Ferries & Alaska Marine
Highway Ferry Landings
Andrew T. Metzger, Ph.D., P.E.
Jonathan Hutchinson, E.I.T.
December, 2010
GoTo Meeting
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Scope
Project overview
Assess design criteria for vessel loads on Ferry
Dolphins (AKDOT&PF) and Wingwalls (WashDOT)
Long-term in situ monitoring of active ferry landings
Collect a sample of structure response to vessel loading
Determine design load criteria based on sample
statistics
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Auke Bay Study
Auke Bay Study - dolphins
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Auke Bay Study
Study of loads from vessels
Model fender pile with available geotechnical
information
Measure compression of side-loaded cylinders
Axial strain in tripod piles
Measurements collected at 5Hz
Identify maximum load for event
Collect sample over approx. 1 year of operation
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Auke Bay Study
Study of vessel berthing energy
Distance measurements at 5 Hz during vesselapproach and impact
Estimate impact velocity from distancemeasurements
Energy is estimated with displacementmeasurements and SAP model
Statistics for Vessel impact velocity
Impact energy
Mass + added Mass at impact
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Dolphins monitored:
70 complete berthing events have been collected for Five different vessels.
Monitoring will continue into July, 2011
W2 and E4 monitor Mooring Loads
E1 and E3 monitor Berthing loads
E2 monitors both Berthing and Mooring loads
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Motion Sensors on E1 and E2 Two motion sensors located 10 from
dolphins E1 and E2
Used to measure approach of
berthing vessels at E1 and E2
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LMTs (linear motion transducers) One LMT located adjacent to each
cylindrical fender
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Tide Gage: at E1
Monitors tide
Used to estimate elevation of
ship sponson.
i.e., point of application of load
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Strain Gages on Piling
Gages placed on dolphins:
E1, E2, and E3
Oriented to measure
Axial Strain in piling
Axial force is calculated real-time
and stored in datalogger
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Mooring Instrumentation: Original method: determine mooring forces by
measuring bending stresses in bollards.
Assumption that the primary
stress in the bollards, from
mooring loads, are bending
stresses.
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Data
Data has been collected for 70 berthing events
Datalogger takes measurements continuouslybetween events
Begins to store data when vessel is with ~ 20of E1 motion sensor
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Data
For each event:
Data collection for 10 minutes (3,000 records)
Each day, data is downloaded from Juneau to
Fairbanks via digital cellular modem
For each event:
Data collection for 10 minutes (3,000 records) Each day, data is downloaded from Juneau to
Fairbanks via digital cellular modem
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Vessel Approach Profile: E1
Typical Malaspina
position vs time
Graph for E1
Used to determine
approach velocityNormal to dock for
each per berthing
event.
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Bollard Data for E2
Shows the mooring line
effect on the force in
the Piles
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Time history for:
Malaspina, August 23, 2010on Dolphin E1
LMT
Pile Force
Vessel Motion
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Time History Pile Data: E2
Pile Reaction (Kips)
from Impact
and Springline
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Time History Pile Data: E2
Pile Reaction (Kips)
from Impact
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Berthing Energy
Impact Energy is needed for design vessel
berthing structures
Cannot measure energy directly
Can be inferred from structure response:
2 2
2 2
mv kxE = =
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Berthing Energy
We are directly measuring
Velocity, v
Fender displacement
Using a structural analysis software (SAP) +
available geotechnical information
Related fender displacement to dolphin
displacement
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Berthing Energy
Relating fender displacement to dolphin displacement
Fender stiffness taken from manufacturer data
Tri-pod stiffness modeled with SAP model; accounting for data frompile driving logs
Fender support piles notes from driving logs piles went to bedrock under self weight
Driven another 1-2 feet
soil is poor and likely deformed from previous displacements
Given poor soil condition and relatively long length of piling
Chosen to ignore lateral stiffness probably small compared to fender andtripod stiffness
Personally observed that ANY wave action causes movement in fendersupport piles
E1 Force vs Deflection
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y = 27.66x y = 7.375x y = 5.822x
0
20
40
60
80
100
120
0 5 10 15 20
Force
(Kips)
Deflection (inches)
E1: Force vs Deflection
Tripod
Fender
Combined (Fender +Tripod)
y = 0.3766x2
y = 0.3072x2
y = 0
0
10
20
30
40
50
60
70
80
0 2 4 6 8 10 12 14 16
EnergyAbsorbedbyS
tructure(ft-kips)
Fender Deflection (inches)
E1: Energy vs Fender Deflection
Combined (Fender + Tripod)
Fender
Tripod
1 1 1
2dolphin tripod fender
k k k= +
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Ksys
0
20
40
60
80
100
120
140
160
0 2 4 6 8 10 12 14 16 18 20
FORCE(K
IPS)
TOTAL DEFLECTION (INCHES)
Force vs Fender Displacement
Kt
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Time history for:
Malaspina, August 24, 2010on Dolphin E1
Recall our Extreme Event:
Vessel Motion
Pile Force
LMT
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Fender supportpiling probablycontacted tripod
platform
Evidence of this
occurring (gougesin toe-kick plates;bent cap plates)
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Evidence of this occurring (gouges in
toe-kick plates; bent cap plates)
S d l f l hi 2
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Sap Model of Dolphin E2:
Energy from a berthing vessel is
absorbed by both the fender
AND the tripod structure
Determining Berthing Energy:
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Results
Histograms
Normal Approach Velocity
Berthing Energy
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E1 histograms
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Results
Histograms Berthing Factor, Cb
from
We can represent the kinetic energy as
Where c is a factor representing uncertainty associated with Added mass
Mass of cargo
Other uncertainties
A multiplier applied to the mass to account for uncertainties inberthing energy
( ) 2 2
2 2
am m v kx
Energy+
= =
( )2
2
b vC m v
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Results
Histograms A correction factor histogram will also be constructed
(presently, in the works)
Consistent with heavy shipping industry
Presently, correction factors are hard to find for ferry classvessels
Result is a probability distribution for the correction factor(histogram)
2
2f n e m c s
ME V C C C C=
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Implementation
Statically description of relevant design
parameters
Description of the uncertainty for:
Normal velocity
Impact energy
Correction factor
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Implementation
Any of these parameters can be used for
design end user will have options
Design Energy
Specify acceptable deflection,x
design structure with necessary stiffness
2
2E
k x=
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Implementation
Reliability-based design
Method to account for uncertainty in design
Result is a structure with quantified degree ofreliability
Probability of not failing LRFD approach in structures
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Implementation
Reliability baseddesign
Fit a distribution tohistogram
Identify demandvalue with lowprobability ofexceedance
This will be thedesign value
Implementation
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p
Reliability baseddesign
Design pointchosen forspecified reliability
index
Our new designpoint(s) will becompatible withexisting designcodes:AISC, ACI, NDS
Implementation
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p
Reliability based
design
Reliabilitybased
design criteria formarine structuresdo notexist, presently
Implementationtimeframe:immediate
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Characterizing the Load Environment of
Washington State Ferries & Alaska Marine
Highway Ferry Landings
Thank you so much!