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Arun Bhimani, S.E.PresidentLiftech Consultants Inc.
Crane Loads & Wharf Structure Design:Putting the Two TogetherAAPA Facilities Engineering SeminarJanuary 2006 – Jacksonville, Florida
Erik Soderberg, S.E.PrincipalLiftech Consultants Inc.www.liftech.net
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Crane Size Growth:1st Container Crane & Jumbo Crane
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Crane Service Wheel LoadsWaterside Operating Wheel Loads
Year Manufactured
Whe
el L
oad
(t)
0102030405060708090
100
1960 1970 1980 1990 2000
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Crane LoadsCrane loads increasingCodes becoming more complexConsequences of misapplication more severeChance of engineering errors increasing
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Presentation OutlineThe Problem – Overview Wharf Designer’s PerspectiveCrane Designer’s PerspectivePutting the Two TogetherQ&A and Feedback
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The Problem – Overview
Crane Purchaser
WharfDesigner
CraneSupplier
PortConsultant
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Crane Purchaser DifficultiesPurchaser specified
“Allowable wheel load: 200 kips/wheel”
Suppliers submitSupplier A 180 k/wheelSupplier B 200 k/wheelSupplier C 220 k/wheel
Which suppliers are compliant?
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Crane Supplier DifficultyPurchaser specified
Allowable wheel load: 200 kips/wheel
In some cases, linear load (kips/ft)
Not definedOperating or out-of-service?
Unfactored or factored?
Wind profile?
Increase for storm condition?
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Wharf Designer DifficultyClient provides limited crane load data
No loading pattern
No basis given – Unfactored or factored?
Same loads given for landside and waterside
No details of wind or seismic criteria
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Wharf Designer Perspective
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Wharf Designer PerspectiveCodes and Design Principle
Crane Girder Design
Design for Tie-down Loads
Crane Stop Design
Seismic Design Considerations
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Codes and Design Principle
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Design Codes & Standards Crane
FEM, DIN, BS, AISC …, Liftech
Wharf StructuresACI 318 Building Code and Commentary ASCE 7-05 Minimum Design Loads for Buildings and
Other StructuresAISC Steel Construction
Manual
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Design Principle - Wharf Structure Design
Required Strength ≤ Design Strength
Required Strength = ∑ Service Loads * Load Factors
Design Strength = Material Strength * Strength Reduction Factor Ф
Load Resistance Factored Design (LRFD)
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ACI 318
Load Factors Concrete Ф FactorsTen0.900.90
Comp Shear0.75/.7
00.70/.65
0.850.75
D L Wto 2002 1.4 1.7 1.32002+ 1.2 1.6 1.6*
* 1.3 if directionality factor is not included
Load Factors & Ф Factors
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Generally use service loads
Factor of safety typically 2.0 for operating
1/3 increase for storm wind or overload
Design Principle – Soil CapacityAllowable Stress Design
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Crane Girder Design
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Required Crane Geometry DataSill BeamTie-downs
Stowage pin
Bumper
(n-1) S
C craneLn = number of wheels per cornerS = average wheel spacing
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Typical Wheel Loading Geometry
Typical Wheel Spacing
7 at 5’
9’ 7 at 5’
40’ 4’ 40’Recommended Wheel Design Load Geometry
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Dead Loads and Live LoadsWharf LoadsD – Wharf structure self weightL – Wharf live load, includes containers and yard equipment (does not control)
Crane Loads (ASCE 7-05)D – Weight of crane excluding lifted loadL – Lifted load or rated capacity
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ACI Load Factors – Crane Loading
ACI 318 Load FactorsYear D L Compositeto 2002 1.4 1.7 1.452002+ 1.2 1.6 1.30
Some designers treat crane dead load as live load and use the 1.6 factor. This results in 23% overdesign; 1.6 / 1.3 = 1.23.
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Example Combination Table: Service Wheel LoadsMode Operating Stowed
WOP1 WOP2 WOP3 WOP4 WS1 Dead Load DL 1.0 1.0 1.0 1.0 1.0 Trolley Load TL 1.0 1.0 1.0 1.0 1.0 Lift System LS 1.0 1.0 1.0 1.0 Lifted Load LL 1.0 1.0 1.0 Impact IMP 0.5 Gantry Lateral LATG 1.0 Op. Wind Load WLO 1.0 1.0 Stall Torque Load STL 1.0 Collision Load COLL 1.0 Storm Wind Load WLS 1.0 Earthquake Load EQ
50 x S 70 x S Allowable Wheel Loads (tons/wheel)
LS WS 65 x S 90 x S
S = Average spacing, in meters, between the wheels at each corner.Example: S = 1.5 m, Allowable LS Operating = 50 t/m * 1.5 m = 75 t/wheel
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Example Combination Table: Factored Wheel LoadsMode Operating Stowed
WOP1 WOP2 WOP3 WOP4 WS1 Dead Load DL 1.2 1.2 1.0 1.0 1.2 Trolley Load TL 1.2 1.2 1.0 1.0 1.2 Lift System LS 1.2 1.2 1.0 1.2 Lifted Load LL 1.6 1.6 1.0 Impact IMP 0.8 Gantry Lateral LATG 0.8 Stall Torque Load STL 1.0 Collision Load COLL 1.0 Storm Wind Load WLS 1.6 Earthquake Load EQ
60 x S 80 x S Allowable Wheel Loads (tons/wheel)
LS WS 75 x S 100 x S
S = Average spacing, in meters, between the wheels at each corner.Example: S = 1.5 m, Allowable WS Storm = 100 t/m * 1.5 m = 150 t/wheel
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Tie-down Design
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Multiple Tie-downs at a Corner
Uneven tie-down forces
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Causes of Uneven Distribution Some reasons why forces are not evenly distributed:
Crane deflection
Contruction tolerances
Wharf pins not centered
Links not perfectly straight due to friction
Undeflected Shape
Deflected Shape
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Tie-down LoadsManufacturers typically provide the service corner uplift force
Needed data:
Factored corner uplift force
Distribution between tie-downs
Direction of force (allow for slight angle)
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Crane Stop Design
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Bumper Load Provided by Manufacturer
Rated Bumper ReactionBumpers sized for collision at maximum gantry speed
Does not address runaway crane
H
0
5
1 0
1 5
2 0
2 5
3 0
3 5
4 0
-1 4 9 1 4 1 9 2 4
Displacement
HV slow
V gantryV runaway
crane
Displacementmetering pin
gas
oil
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H= maximum load that can develop, i.e. the load at which the crane tips.
D = crane weight
H = approximately 0.25 x D per stop
Recommended Crane Stop Design Load
H
D
DH
Tipping Force
Stability Stool
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Wharf Seismic Design – Crane LoadingThe mass of typical jumbo A-frame cranes can be ignored
For certain wharves and cranes, a time-history analysis may be necessary
Large, short duration wheel loads can be ignored
Localized rail damage may occur
The crane may derail
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Crane Designer Perspective
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Crane Designer Perspective
Basic LoadsStorm Wind LoadLoad Combinations and FactorsTie-down Loads
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Basic Loads
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Dead and Live Loads
DL: Crane structure weightTL: Trolley structure weightLS: Lift System Weight
LL: Rated container load
Dead Loads Live Loads
Crane
Rated Load
Lift System
Trolley
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Inertial LoadsIMP: Vertical impact due to hoist
acceleration
LATT: Lateral due to trolley acceleration
LATG: Lateral due to gantry acceleration
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Overload
COLL: Collision
SNAG: Snagging headblock
STALL: Stalling hoist motors
Normally do not control
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Environmental Loads
WLO: Wind load operating (In-Service)
WLS* : Wind load storm (Out-of-Service)
EQ: Earthquake load
*Often a major source of discrepancies
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Wind Load, Out-of-Service
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WLS: Out-of-Service WindWind Force = ∑A x Cf x qz
A = Area of crane elementCf = Shape coefficient (including shielding)
qz = Dynamic pressure, function of:
Mean recurrence interval (MRI)
Gust duration
, where Vref is a location-specific, code-specified reference wind speed
Exposure (surface roughness)
2refV Need to
clearly specify
From wind tunnel testing
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Shape Coefficient, Cf
Empirical values: FEM, BSI, etc.
Wind tunnel tests are more accurate
Boundary layer
Angled wind effects
Shielding effects
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Angled Wind
0 45 90 135 180Rea
ctio
n
Wind Direction, Degrees
Wind Tunnel Test Liftech Equations
Fx Fz
FxFz
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WLS: Mean recurrence interval (MRI)Wind Force = ∑A x Cf x qz
A = Area of elementCf = Shape coefficient (including shielding)
qz = Dynamic pressure, function of:
Mean recurrence interval (MRI)
Gust duration
, where Vref is a location-specific, code-specified reference wind speed
Exposure (surface roughness)
2refV Need to
clearly specify
From wind tunnel testing
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Mean Recurrence Interval
Years in OperationMRI 1 10 25 50
.10 .99
.87
.64
.39
.04
.02
10010 yrs
.01
.64
.34
.18
.10
.93 .99997
25 yrs .64 .9850 yrs .40 .87100 yrs .22 .64
Probability of Speed Being Exceeded
Example:Chance of 50-yr wind being exceeded in 25 years: 40%
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WLS: Gust durationWind Force = ∑A x Cf x qz
A = Area of crane elementCf = Shape coefficient (including shielding)
qz = Dynamic pressure, function of:
Mean recurrence interval (MRI)
Gust duration
, where Vref is a location-specific, code-specified reference wind speed
Exposure (surface roughness)
2refV Need to
clearly specify
From wind tunnel testing
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Gust Duration
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Wind Speed vs. Gust DurationV t
/ Vho
ur
Gust Duration (seconds)Ratio of probable maximum speed averaged over “t” seconds to hourly mean speed. Reference, ASCE 7-05.
( )
( )46.1
52.104.11
min103
min103
sec3
min10min103
VV
VV
VV
VV
VVhourly
hourly
=
⎟⎠⎞
⎜⎝⎛=
⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛=
Example: converting 10-min speed to 3-sec speed
1.04
1.52
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Code Gust DurationsCode definitions of basic wind speed
Code Gust Duration MRI
EN 1991-1-4
10 min 50 yrs
FEM 1.004 10 min 50 yrs
ASCE 7-02 3 sec 50 yrs
HK 2004 3 sec 50 yrs
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Typical Pressure Profiles
Shape of profile depends on surrounding surface roughness
0
25
50
75
100
125
150
175
200
500 1000 1500 2000Wind pressure, Pa
Hei
ght,
m
Smooth gradient
Stepped profile
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Variation in WLS
Variable Variation Effect on V Effect on F *7.5% 15.6%
113%
10-20%
46%
5-10%
MRI 25 to 50 yrsGust duration
3 sec to 10 min
Profile Open terrain to ocean exposure
*See later slides for effect on calculated tie-down load!
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Recommendations for Specifying WLS
Return Period Use 50-yr MRIBasic wind speedGust duration Use local civil codeProfileOther factorsShape coefficients Wind tunnel tests
Do not mix and match between codes for pressure and load factors !
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Corner Reactions – Angled Wind
Do not use spreadsheet !
Use frame analysis program
Frame stiffness is significant to reactions
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Load CombinationsCrane Design
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Load Combinations
Load combinationsOperatingOverloadStorm wind (out-of-service)
Design approaches Generally Allowable Stress Design (ASD)
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Operating Condition Loads
DL: Crane weight*
LL: Rated container load
IMP & LAT: Inertial loads
WLO: Wind load, in service
*Excluding Rated Load
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Out-of-Service & Overload
DL: Crane weight*
WLS: Wind load storm (out-of-service)
Overload Conditions (in and out-of-service)
*Including trolley and lift system
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RecommendationsRequesting crane wheel load data
Specify wind criteriaAsk for basic loadsCombine per ACI load factors
Requesting crane bidsProvide factored load tablesAsk to fill in tablesSpecify allowable factored loads
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Tie-down Loads
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Tie-Down Failures
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Wind Load & Crane Reactions
FD
wind
Fstow pin
F tie-down
Fgantry
AB
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Error in Calculated Tie-down Force
MomentRightingMomentgOverturnin
BD
hFwind ==
2
γ
( ) ( )1
11
21
211
,
,
−−+
=
⎥⎦⎤
⎢⎣⎡ −
⎥⎦⎤
⎢⎣⎡ −+
=γ
γeBDhF
A
BDhFeA
FF
Wind
Wind
CalculatedTiedown
ActualTiedown
Error in calculated tie-down force:if “e” = error in wind force,
DFwind
Fstow pin
Ftie-down
Fgantry
AB
Ratio of moments:
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Error in Tie-down ForceTi
edow
n Fo
rce
Rat
io(A
ctua
l/Cal
cula
ted)
, Overturning Moment / Righting Momentγ
0
1
2
3
4
5
1 2 3
20% error in V
10% error in V
5% error in V
No error in V
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Example:
Error in calculated tie-down force = 74% !
Tied
own
Forc
e R
atio
(Act
ual/C
alcu
late
d)
, Overturning Moment / Righting Momentγ
0
1
2
3
4
5
1 2 3
20% error in V
10% error in V
5% error in V
No error in V
Error in wind speed = 10%; γ = 1.4Error in wind pressure = 21%
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Stability Load Factors
Load FactorACI
0.90.91.3*
BSI FEMDead Load 1.0 1.0TL + LS 1.0 1.0Wind Load, 50-year MRI
1.2 1.2
* 1.6 with ASCE 7-02 “directionality factor”
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Uplift: Factored vs. Service
Service FactoredLoad Load
Factor
Dead Load -500 x 0.9 =
x 1.3 =
-450
Wind Load +450 +585Calculated Uplift -50 +135
“No Uplift” “Uplift”
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Putting the Two Together
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Problem RecapCrane supplier and wharf designer work with incomplete and inconsistent data
Reasons:
Crane supplier generally uses Service Load approach
Wharf designer generally uses Factored Load approach
Neither knows what basis the other uses
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Solution
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Missing
Link
Crane Purchaser
WharfDesigner
CraneSupplier
Port
Crane purchaser provide or facilitate detailed information
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Obtain From Wharf DesignerAssumed wheel arrangement
Service or factored
Load factors
Load combinations for operating, overload, and out-of-service conditions
Complete wind criteria
Allowable wheel loads, kips/ft** Crane supplier tends to provide kips/wheel
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Example Combination Table: Service Wheel LoadsMode Operating Stowed
WOP1 WOP2 WOP3 WOP4 WS1 Dead Load DL 1.0 1.0 1.0 1.0 1.0 Trolley Load TL 1.0 1.0 1.0 1.0 1.0 Lift System LS 1.0 1.0 1.0 1.0 Lifted Load LL 1.0 1.0 1.0 Impact IMP 0.5 Gantry Lateral LATG 1.0 Op. Wind Load WLO 1.0 1.0 Stall Torque Load STL 1.0 Collision Load COLL 1.0 Storm Wind Load WLS 1.0 Earthquake Load EQ
50 x S 70 x S Allowable Wheel Loads (tons/wheel)
LS WS 65 x S 90 x S
S = Average spacing, in meters, between the wheels at each corner.Example: S = 1.5 m, Allowable LS Operating = 50 t/m * 1.5 m = 75 t/wheel
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Example Combination Table: Factored Wheel LoadsMode Operating Stowed
WOP1 WOP2 WOP3 WOP4 WS1 Dead Load DL 1.2 1.2 1.0 1.0 1.2 Trolley Load TL 1.2 1.2 1.0 1.0 1.2 Lift System LS 1.2 1.2 1.0 1.2 Lifted Load LL 1.6 1.6 1.0 Impact IMP 0.8 Gantry Lateral LATG 0.8 Stall Torque Load STL 1.0 Collision Load COLL 1.0 Storm Wind Load WLS 1.6 Earthquake Load EQ
60 x S 80 x S Allowable Wheel Loads (tons/wheel)
LS WS 75 x S 100 x S
S = Average spacing, in meters, between the wheels at each corner.Example: S = 1.5 m, Allowable WS Storm = 100 t/m * 1.5 m = 150 t/wheel
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Ask Crane Supplier ForWheel arrangement
Wheel loads for individual loads
Combined wheel loads for operating, overload, and out-of-service conditions
Complete wind criteria used and basis for shape factors
Individual and corner factored loads for tie-downs including direction of loading
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Example Design Basic Load Table Wharf Designer needs from Crane
Supplier
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Recap
Obtain detailed crane and wharf design dataStick to one crane design codeStick to one wharf design codeUse consistent design basis
Facilitate communication
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Q & A
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Thank you
Crane Loads & Wharf Structure Design:Putting the Two Together
This presentation will be available for download on Liftech’s website:
www.liftech.net
Arun Bhimani, S.E.PresidentLiftech Consultants Inc.www.liftech.net
Erik Soderberg, S.E.PrincipalLiftech Consultants Inc.