Structural Design and Response in Collision and Grounding

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6.2 DATA FOR MODEL VALIDATIONThe second type of data required by the panel is for modelvalidation. In collision the following data is required:• Collision Scenario• Striking ship• Speed• Displacement• Draft• Bow height• Type• Collision angle• Strike location• Struck ship design• L,B,D,T,∆• Speed• Structural design• h DB , w DS , y LBHD , x TBHD• web spacing, z string , z strut• scantlings• Damage descriptionIn grounding, the following model validation data isrequired:• Grounding Scenario• Geometry and elevation of the rock• Location of the rock relative to the ship'scenterline• Ship speed, draft, displacement and trim• Grounded ship design• Hull type (single hull, double hull, mid -deck, …)• L, B, D, LCG, LCF, GM T , GM L• Waterplane area• Transverse and longitudinal bulkhead locations• Frame spacing, spacing of longitudinal girders• Scantlings• Damage description7 STRIKING SHIP BOW7.1 SIMCOL Bow Model StudyAll of the collision models used thus far in this study, andmost models used by other researchers, assume that thestriking ship bow is rigid. This is changing. Panel workin this area is focused on the following questions andproblems:1. Is the rigid bow assumption rational? Is significantenergy absorbed by the striking ship bow? Is thisenergy variable in different collision scenarios?2. If bow deformation is important, can this problem besolved uncoupled from the side damage problem?3. Identify a simple, but sufficient bow model for futureuse in SIMCOL.4. Develop a course-mesh bow model to speed upLSDYNA modeling for SIMCOL validation.Most collision accidents that result in significantstruck ship damage also result in significant damage tothe striking ship bow. Minorsky’s original analysis [26]considered absorbed energy in the striking bow. Areanalysis of his data indicates that absorbed bow energyin these cases accounted for between 8 and 53 percent ofthe total absorbed energy [30]. More recent studies byReckling [31], Akita and Kitamura [32], and Valsgard andPettersen [33] indicate absorbed bow energies in the rangeof 42 to 55 percent of the total absorbed energy.LSDYNA analyses conducted at Virginia Tech withdeformable bows and sides show absorbed bow energiesin the range of 22 to 44 percent [30]. We mu st concludethat absorbed bow energy can be significant and variable,and therefore should be considered in collision analyses.The availability of this data is extremely limited.Accident data from USCG databases for the period of1980-1998 was screened for sufficiency and applicabilityto this problem. Useful validation cases must include allof the data specified above (scenario, structural design,damage description). In the case of collision, thefollowing additional criteria were applied:• Striking location in struck ship away from bow orstern.• Collision angles of 45-135 degrees.• Penetration greater than one meter.Collection and evaluation of this data is also ongoing.Table 6. Bow Model Test Matrix16
Table 6 lists the bow and struck ship model casesconsidered in the SIMCOL bow model development.Four rigid bow tests were run to validate SIMCOLcalculations. These are labeled R-1 through R-4 in Table6. Ten conventional FEA bow analyses were run tovalidate the simpler intersection bow model results. Theseare labeled C-1 through C-10 in Table 6. Two types ofintersection model analyses were accomplished. Tests I-1through I-4 use closed-form equations from Pedersen[34], Amdahl [35], and Yang and Caldwell [36]. Tests I-5 through I-16 use intersection elements applied inLSDYNA simulations.Simplified LSDYNA intersection-element bowmodels were developed to increase the speed ofLSDYNA finite element solutions used in SIMCOLcollision model validation. In these models, onlyintersections of sides, decks, longitudinal bulkheads andgirders were included in the model with longitudinalstiffener area smeared into plate thickness based onplastic bending moment. Intersection elements aremodeled as truss elements in LSDYNA with materialproperties replaced by properties derived for crushed L, Tand cruciform sections as illustrated in Figure 29 [35].Transverse frames were modeled as normal trusselements. Nodes were only allowed a single degree offreedom in the striking ship longitudinal direction. The150kdwt bulk carrier bow is shown in Figure 30 [34].Figure 31 shows the intersection model for this bow (I-8).Figure 32 shows the conventional fine-mesh FEM for thisbow with beam and panel elements (C-5). Figure 33shows a comparison of the force-indentation plots for theintersection and conventional models (I-8 and C-2). Theresults compare very well. Similar results were obtainedfor the other test cases. It is concluded that the bowintersection model is sufficient for LSDYNA collisionsimulations. Work is continuing to apply these results tothe development of a SIMCOL bow model.Forecastle Deck, 26.0m abl.Tank Top, 20.0 m abl.Collision Bhd.Tl =15.96mDeck (not W.T.), 7.6mabl.LoadedFigure 30 - 150kdwt Bulk Carrier Bow [34]Figure 31 - Bulk Carrier Intersection Element Model [30]Figure 29 - Intersection element Model [35]Figure 32 - Bulk Carrier Conventional FE Bow17
Page 1 and 2: Brown, A.J., Tikka, K., Daidola, J.
Page 3 and 4: 3 PROBABILISTIC FRAMEWORKFigure 2 i
Page 5 and 6: 4.2.2 Method by Wang [15]Dr. Wang d
Page 7 and 8: damage results. Surprisingly, the t
Page 9 and 10: ybeginning of time step nStriking S
Page 11 and 12: location, COG, and detailed structu
Page 13: Ship Type150,000 dwtbulk carrierLen
Page 18 and 19: Force (N)8.00E+087.00E+086.00E+085.
Page 20 and 21: Figure 37 - Macro flow diagram for
Page 22 and 23: enhance resistance to collision. Th
Page 24 and 25: Figure 42 - Load versus lateral ind
Page 26 and 27: Accidental Grounding and Collision

Structural Design and Response in Collision and Grounding

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