1.1 Standard Definitions Acceleration due to gravity; g = 9.81 m/s2
Density of seawater; = 1.025 t/m3 ;Assumed
1.2 Natural Conditions 1.2.1 Tide Level
Current tide levels and the relationship between SITE DATUM and CHART DATUM are shown below: Highest Astronomical Tide; HAT = +1.86 m; CD
Mean Highest High Water; MHHW = +1.47 m; CD Mean Lowest High Water; MLHW = +1.04 m; CD
Mean Sea Level; MSL = +0.89 m; CD
Mean Highest Low Water; MHLW = +0.56 m; CD Mean Lowest Low Water; MLLW = +0.45 m; CD Lowest Astronomical Tide; LAT = +0.13 m; CD Site Datum/Chart Datum; CD = +0.00 m; CD
A maximum surge height of 0.5m above MHHW is taken in addition to a future sea level rise of 0.25m over the design life of the shipyard therefore the high water level used to design the Travel Lift Pier is taken as: Design High Water Level; DHWL = +2.22 m; CD
Assumed seabed/ rock level; BED = -13.5 m; CD ;Refer to section Error: Reference source not found
Cope level; COPE = +3.8 m; CD ;Report RLSRY1-0-17-201-206
1.3 Structure Geometry
Overall thickness of deck; Tdeck = 0.8 m ;Assumed
Thickness of crossbeam; Tbeam = 0.8 m ;Assumed
1.4 Large Vessel Parameters
Max. lift capacity of the boat hoist; Vhoist:1100 = 1100 t ;Cimolai drawing
Displacement, docking condition; MD:large = Vhoist:1100 g = 10791 kN ;Inferred
Deadweight; DWTlarge = 1000 t ;Tb.C-1, App.C, PIANC WG 33
Overall length; Llarge = 75 m ;Client issued
Length between perpendiculars; LBP:large = Llarge = 75 m ;Assumed
Breadth; Blarge = 15 m ;Client issued
Draft, full; Dmax:large = 4.9 m ;Client issued
Draft, docking condition; D:large = 2.5m ;Assumed
Displacement, full; Mmax:large = 2480 t ;Tb.C-1, App.C, PIANC WG 33
Maximum berthing angle; =15 deg ;Cl. 4.7.6.4.1, BS6349-4:1994
Berthing point; ¼ point ;Assumed
Longitudinal windage area above water line, light; AL:large = 465 m2 ;Tb.C-1, App.C, PIANC WG 33
Transverse windage area above water line, light; AT:large = 150 m2 ;Tb.C-1, App.C, PIANC WG 33
Bow radius; Rb:large = 27 m ;Assumed
Navigation condition onto berth; Easy berthing, exposed ;Cl.4.6, BS6349-4:1994 Approach berthing velocity; vlarge = 0.52m/s ;Fig1, curve c, BS6349-4:1994
Figure 1 details the abnormal berthing safety factors recommended in The Guidelines for the Design of Fender Systems: 2002 (PIANC):
Figure 1 - PIANC factors for abnormal impacts Based on the above, the following is assumed:
Abnormal berthing factor of safety; Cablarge = 1.75 ;Tb.4.2.5, PIANC WG 33
Recommendations on allowable hull pressures taken from the same source are given in Figure 2:
Figure 2 - PIANC hull pressure guidance
Therefore based on the above, the following is assumed:
1.5 Small Vessel Parameters
Max. lift capacity of the boat hoist; Vhoist:300 = 300 t ;Cimolai drawing
Displacement, docking condition; MD:small = Vhoist:300 g = 2943 kN ;Inferred
Overall length; Lsmall = 35 m ;Client issued
Length between perpendiculars; LBP:small = Lsmall = 35 m ;Assumed
Breadth; Bsmall = 8.5 m ;Client issued
Draft, full; Dmax:small = 1.9 m ;Assumed
Draft, docking condition; Dsmall = 1.9m ;Assumed
Maximum berthing angle; = 15 deg ;Cl. 4.7.6.4.1, BS6349-4:1994
Berthing point; ¼ point ;Assumed
Longitudinal wind area above water line, light; AL:small = 168 m2 ;RH Data, Appendix B
Transverse wind area above water line, light; AT:small = 53 m2 ;RH Data, Appendix B
Bow radius; Rb:small = 11 m ;Assumed
Maximum hull flare at fender line; “=” <10° ;Assumed
Navigation condition onto berth; Easy berthing, exposed ;Cl.4.6, BS6349-4:1994
Curve C in Figure 1 of BS 6349-4:1994 demonstrates that berthing velocities increase for vessels with lower displacements. Although the graph is not intended for vessel displacements of less than 1000t, since no other guidance is available, the exponential graph has been extended and the velocity estimated for a 300t vessel displacement.
Approach berthing velocity; vsmall = 0.575 m/s ;Fig1, curve c, BS6349-4:1994
Figure 1 details the abnormal berthing safety factors recommended in The Guidelines for the Design of Fender Systems: 2002 (PIANC). As vessels utilising the 300T Travel Lift are much smaller, a larger abnormal berthing factor will be adopted as berthing velocities are likely to be higher.
Abnormal berthing factor of safety; Cabsmall = 2.00 ;Tb.4.2.5, PIANC WG 33
Recommendations on allowable hull pressures taken from the same source are given in Figure 2. Since allowable hull pressures will be higher for smaller vessels, the design of fender panels will only consider vessels utilising the large Travel Lift as this will provide the most onerous design situation.
1.6 Berthing Energy for Large Design Vessel With reference to parameters given in Section 1.1 for the large design vessel: Displacement, docking condition; MD:large = 10791 kN ;Inferred
Overall length; Llarge = 75 m ;Client issued
Breadth; Blarge = 15 m ;Client issued
Draft, full; Dmax:large = 4.9 m ;Client issued
Maximum berthing angle; =15 deg ;Cl. 4.7.6.4.1, BS6349-4:1994
Berthing point; ¼ point ;Assumed
Approach berthing velocity; vlarge = 0.52 m/s ;Fig1, curve c, BS6349-4:1994
Distance from bow to point of impact; x = Llarge / 4 = 18.8 m ;Assuming ¼ point mooring
Block Coefficient; Cb = MD:large/(Llarge Blarge Dmax:large g = 0.195
The ship’s radius of gyration; K = ((0.19 Cb) + 0.11) Llarge = 11.02 m
Distance from bow to point of impact; R = ((Llarge / 2 – x)2 + (Blarge / 2)2) = 20.19 m
= 90 - - asin(Blarge / (2 R)) = 53.20 deg ;Refer to Figure 3
Figure 3 - Diagram of Velocity Vector Angles Eccentricity factor;
Ce = (K2 + (R2 (cos( )2))) / (K2 + R2) = 0.506 ;Cl. 4.2.4, PIANC WG33
Using the formula by Vasco Costa:
Virtual mass factor; Cm1 = 1 + (2 Dmax: large) / Blarge = 1.653 ;Cl. 4.2.5, PIANC WG33
Using the Shigeru Ueda formula:
Virtual mass factor; Cm2 = 1 + (( Dmax:large)/(2 Cb Blarge)) = 3.636;Cl. 4.2.4, PIANC WG33
To be conservative, an average value is assumed: Virtual mass factor; Cm = (Cm1 + Cm2) / 2 = 2.645
As fenders are likely to deflect by more than 0.15m and berthing vessels are relatively small, the softness coefficient will be taken as:
Softness factor; Cs = 1.0 ;Cl. 4.2.6, PIANC WG33
Berthing is against an open piled structure therefore the berthing configuration factor will be taken as: Berth configuration factor; Cc = 1.0 ;Cl. 4.2.7, PIANC WG33
Design energy, normal conditions;
Ed:large = 0.5 (MD:large / g) vlarge2 Ce Cm Cs Cc = 199.03 kNm ;Cl. 4.2.1, PIANC WG33
Berthing energy, abnormal impact;
Ev:large = Ed:large Cablarge = 348 kNm ;Cl. 4.2.8.4, PIANC WG33
1.7 Berthing Energy for Small Design Vessel With reference to parameters given in Section 1.5 for the small design vessel: Displacement, docking condition; MD:small = 2943 kN ;Inferred
Overall length; Lsmall = 35 m ;Client issued
Breadth; Bsmall = 9 m ;Client issued
Draft, full; Dmax:small = 1.9 m ;Client issued
Maximum berthing angle; =15 deg ;Cl. 4.7.6.4.1, BS6349-4:1994
Berthing point; ¼ point ;Assumed
Approach berthing velocity; vsmall = 0.57 m/s ;Fig1, curve c, BS6349-4:1994
Distance from bow to point of impact; x = Lsmall / 4 = 8.8 m ;Assuming ¼ point mooring
Block Coefficient; Cb = MD:small / (Lsmall Bsmall Dmax:small g = 0.518
Distance from bow to point of impact; R = ((Lsmall / 2 – x)2 + (Bsmall / 2)2) = 9.73 m
Angle between the velocity vector and the line joining the point of contact and the centre of mass; = 90 - - asin(Bsmall / (2 R)) = 49.1 deg ;Refer to Figure 3
Eccentricity factor;
Ce = (K2 + (R2 (cos( )2))) / (K2 + R2) = 0.634 ;Cl. 4.2.4, PIANC WG33
Using the formula by Vasco Costa:
Virtual mass factor; Cm1 = 1 + (2 Dmax:small) / Bsmall = 1.447 ;Cl. 4.2.5, PIANC WG33
Using the Shigeru Ueda formula:
Virtual mass factor; Cm2 = 1 + (( Dmax:small)/(2 Cb Bsmall)) = 1.678;Cl. 4.2.4, PIANC WG33
To be conservative, an average value is assumed: Virtual mass factor; Cm = (Cm1 + Cm2) / 2 = 1.563
As fenders are likely to deflect by more than 0.15m and berthing vessels are relatively small, the softness coefficient will be taken as:
Softness factor; Cs = 1.0 ;Cl. 4.2.6, PIANC WG33
Berthing is against an open piled structure therefore the berthing configuration factor will be taken as: Berth configuration factor; Cc = 1.0 ;Cl. 4.2.7, PIANC WG33
Design energy, normal conditions;
Ed:small = 0.5 (MD:small / g) vsmall2 Ce Cm Cs Cc = 49.16 kNm ;Cl. 4.2.1, PIANC WG33
Berthing energy, abnormal impact;
Ev:small = Ed:small Cabsmall = 98 kNm ;Cl. 4.2.8.4, PIANC WG33
The above confirms that the largest design vessel exerts the greatest berthing energy. Maximum design energy, normal conditions;
Ed:max = max (Ed:large, Ed:small) = 199.03 kNm
Maximum design energy, abnormal impact; Ev:max = max (Ev:large, Ev:small) = 348.30 kNm
1.8 Fender Design Manufacturing Tolerances
Assuming Supercone fenders then technical data from a typical fender manufacturer suggests the fender’s energy absorption and the resulting reaction can vary by ±10%, refer to specification extracts in Appendix F.
Temperature Factor
Data from the World Meteorlogical Organisation on typical Qatar air temperatures is reprodiced in Table 1. Table 1 - Maximum & minimum Qatar air temperatures
DAILY MINIMUM DAILY MAXIMUM January 12.8 21.7 February 13.7 23.0 March 16.7 26.8 April 20.6 31.9 May 25.0 38.2 June 27.7 41.2 July 29.1 41.5 August 28.9 40.7 September 26.5 38.6 October 23.4 35.2 November 19.5 29.5 December 15.0 24.1
Maximum annual temperature; Tmax = 41.5 deg
Minimum annual temperature; Tmin = 12.8 deg
Interpolating between the temperature factors stated in the manufacturer’s literature contained in Appendix F gives:
Maximum temperature factor at 41.5 deg Celsius;
TFTmax = 0.926 - ( ((0.926 – 0.882) / (50 – 40)) (Tmax – 40) ) = 0.919
Minimum temperature factor at 12.8 deg Celsius;
TFTmin = 1 + ( ((1.056 – 1) / (23 – 10)) (23 – Tmin) ) = 1.044
Velocity Factor
According to the manufacturer’s specification contained in Appendix F, for steady state deceleration the compression time, t, for a Supercone fender is given by 2d / v where d is the fender deflection and v is the vessel’s impact speed therefore by assuming a fender height:
Estimated fender height; H = 1100 mm
Compression time; t = (2 H) / vlarge = 4.231 s
Tabulated data from the manufacturer’s specification contained in Appendix F indicates that for a compression time of just over 4 seconds, the following velocity factors can be assumed:
Energy velocity factor for the slowest berthing;
VFEVmin = 1.005 - ( ((1.005 – 1.000) / (5s – 4s)) (t – 4s) ) = 1.004
Reaction velocity factor for the slowest berthing; VFRVmin = VFEVmin = 1.004
Angular Berthing Factor
The general arrangement drawing issued by the Client indicates that vessels utilising the smaller 300T boat hoist are 35m long:
Minimum berthing vessel length; Lmin = 35 m ;Assumed
Maximum fender spacing; Fc:max = 0.15 Lmin = 5.3 m ;Fig 8.0, BS 6349-4:1994
Assume fenders are installed at each pile cross head which are likley to have centres of 5m:
Fender spacing; Fns = 5 m ;Assumed
Bow radius angle; = asin(Fns / (2 Rb:large)) = 5 deg
No data is available on likely hull flares flare adjacent to the fender line. Technical data contained in Appendix F suggests that berthing energies are less where hull flares are below 10 degrees therefore to be conservative, a hull flare of 10 degrees will be assumed. With reference to Figure 4:
Flare angle; = 10 deg ;Assumed
Angle factor; AF = 1 ;Fender specification
Figure 4 - Hull flare and bow radius angles Required Energy Absorption
At the maximum temperature of 41.5 deg Celcius,
Minimum energy absorption required; Emax = Ev:max / (AF VFEVmin TFTmax 0.9) = 419.3 kNm
At the minimum temperature of 12.8 deg Celcius,
Minimum energy absorption required; Emin = Ev:max / (AF VFEVmin TFTmin 0.9) = 369.3 kNm
Fender Selection
The combined depth of a pile crossbeam and the overlying deck is 1.6m. This dimension is constrained by the required cope level of +3.8m CD and the DHWL of +2.25m CD. The diameter of the fender would preferably fit within the 1.6m deep zone however since horizontal berthing forces are most onerous in terms of the pile design, concrete sponsons will be detailed to extend above cope level as required to allow the largest diameter of fender with the softest rubber to be selected to keep the magnitude of fender reactions to a minimum.
The SCN1100, type E0.9 Supercone fender will be used. Manufacturer’s literature in Appendix F suggests the following:
Rated energy absorption; Er = 450 kNm
Rated reaction; Rr = 788 kN
Maximum horizontal reaction; Hberthing = Rr 1.1 TFTmin = 904.89 kN
Fenders will be mounted centrally on the outer face of each crossbeam therefore:
Lever arm from the seabed to fender; yberthing = -BED + COPE – ((Tdeck + Tbeam)/2) = 16.50 m
Lever arm from the western berthing face to the fender; xberthing = 1.1 m
Fender panels will be supplied with a polyethylene facings therefore:
Fender coefficient of friction; fender = 0.2 ;Cl. 4.8.5 BS6349-4:2994
Vertical/ longitudinal actions at fender; Vberthing = Hberthingfender = 180.98 kN
We assume that the condition of the fendering system will be monitored and any damage (for instance to the low friction facings) repaired before it can lead to further deterioration.
