Probabilistic Method for Predicting Ship Collision Damage

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pdf0.70.60.50.40.30.20.10USCG Tankers,1992-pres0 5 10 15 20Struck ship speed (knts)Figure 14. Struck ship speed (knots)Exponential (.584)An approximate Normal distribution (µ = 90 degrees, σ = 28.97 degrees) is fit to collision angle data derived from theSandia Report [1998], and is used to select collision angle in the Monte Carlo simu lation. At more oblique angles, there is ahigher probability of ships passing each other or only striking a glancing blow. These cases are frequently not reported.The current IMO pdf for strike longitudinal location specifies a constant value over the entire length of the stuck ship,IMO [1995]. The constant pdf was chosen for convenience and because of the limited available data. Figure 15 shows a barchart of the actual data used to develop the IMO pdf, IMO [1989], and data gathered for cargo ships in the Sandia Study.This data does not indicate a constant pdf. The IMO data is from 56 of 200 significant tanker-collision events for which thestrike location is known. The Sandia data indicates a somewhat higher probability of midship and forward strikes comparedto the IMO data. The IMO tanker probabilities are used in SIMCOL.Probability0.350.30.250.20.150.10.050.0530.0280.3040.2040.2320.299IMO Tanker ProbabilitiesCargo Ship Probabilities0.1790.2480.2320.22100-.2 .2-.4 .4-.6 .6-.8 .8-1.0Location (x/L fwd of AP)Figure 15. Longitudinal damage location probabilities4. RESULTS AND DISCUSSIONFour struck ships are used in the preliminary application of this method. The ships include two 150k dwt oil tankers, onesingle hull and one double hull, and two 45k dwt oil tankers, one single hull and one double hull. SIMCOL input data forthese ships are provided in Table 1 and Table 2. Collision scenario pdfs are used to develop 10000 collision cases that are18
applied to each of the four ships. SIMCOL calculates damage penetration, damage length and absorbed energy for each ofthese cases.Table 1. Struck ship principal characteristicsDH150 SH150 DH45 SH45Displacement, MT 151861 152395 47448 47547Length, m 261.0 266.3 190.5 201.2Breadth, m 50.0 50 29.26 27.4Depth, m 25.1 25.1 15.24 14.3Draft, m 16.76 16.76 10.58 10.6Double bottom height, m 3.34 NA 2.1 NADouble hull width, m 3.34 NA 2.438 NATable 2. Stuck ship structural characteristicsDH150 SH150 DH45 SH45Web frame spacing ,mm 5.2 5.2 3.505 3.89Smeared deck thickness, mm 29.4 28.2 27.6 30.5Smeared inner bottom thickness, mm 37.1 NA 27.8 NASmeared bottom thickness, mm 36.6 44.2 34 38.5Smeared stringer thickness, mm 14.9 NA NA NASmeared side shell thickness, mm 26.7 27.8 24.5 23.6Smeared inner side thickness, mm 28.1 NA 20.1 NASmeared long bhd thickness, mm 25.1 24.5 20 33.4Smeared upper web thickness 12.5 12.5 12.7 19Smeared lower web thickness 14.5 16 12.7 19Figure 16 and Figure 17 are the resulting probability density functions for damage penetration and damage length. Table 3lists mean values for scenario variables, damage penetration, and damage length. The damage pdfs for the four struck shipsare quite similar. Unlike the IMO standard pdfs, penetration in these pdfs is not normalized with breadth. The larger struckships must absorb more energy due to their higher inertia, but structural scantlings are also larger so damage penetrations andlengths for the 150k dwt ships are similar to the 45k dwt ships. Comparing the mean values in Table 3, on the average, thesingle hull ships do have larger penetrations and damage lengths than the double hull ships, and the larger ships have largerpenetrations and damage lengths than the smaller ships.3000Number of Cases2500200015001000SH150 - 2522 cases nopenetrationDH150 - 2533 cases nopenetrationSH45 - 2530 cases nopenetrationDH45 - 2545 cases nopenetration50000 5 10 15 20 25Maximum Penetration (m)Figure 16. Damage penetration pdf19
Page 2 and 3: ABSTRACTThis paper describes a meth
Page 7 and 8: Web frames acting as a vertical bea
Page 9 and 10: where:e i - strain in leg iq bi - b
Page 11 and 12: where j is the number of webs count
Page 13 and 14: collision angle, and extents of dam
Page 15 and 16: Striking ShipBow HEACollision Angle
Page 17: Figure 11. Striking ship displaceme
Page 21: Giannotti, J.G., Johns, N., Genalis

Probabilistic Method for Predicting Ship Collision Damage

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