Structural Design and Response in Collision and Grounding

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Table 1. SIMCOL EvolutionVersion 0.1 1.0 1.1 2.0 2.1SimulationExternal ModelInternal ModelHorizontalMembersVerticalMembersw/o ruptureof plateVerticalMembersw/ rupturedplateSimulation in time domainThree degrees of freedom(Hutchison and Crake)Minorsky mechanism as re-validated by Reardon and SprungCrake’smodelJones and Van MaterCrake’smodel(Jones)Sweeping segment method to calculate damaged areaand resulting forces and momentsVanMater’sextensionof JonesNeglectedMcDermott / Rosenblatt Study methodsDoes notconsiderdeformationofwebs,frictionforce andthe force topropagateyieldingzoneConsidersdeformationofwebs,frictionforce andthe force topropagateyieldingzoneStrikingbow withlimiteddepthMinorsky method forcalculating absorbedenergy due tolongitudinal motionIn DAMAGE 4.0, the striking ship bow is assumed tobe rigid. DAMAGE Version 5.0 (Released June 2000)includes crushing of the bow.Based on conservation of linear momentum, angularmomentum and energy, the velocities after the impact arecalculated as well as the loss of kinetic energy, which isavailable for the structural deformations.In order to determine the deformation of the bow andthe side, the striking ship is moved into the struck ship insmall increments. In each increment, the total resistanceforces from crushing of the bow and penetration into theside are compared. The actual crushing/penetrationincrement takes place in the ship with lowest resistance.DAMAGE 4.0 considers the material and structuralscantlings of all major structural components for the sidestructure.15913S1S3S5S7S9S11S13S151.80E+011.60E+011.40E+011.20E+011.00E+018.00E+006.00E+004.00E+002.00E+000.00E+00Figure 16. DAMAGE Bow GeometryThe model for the internal mechanics is based on thedirect contact deformation of super-elements. The superelementsused to model the side in DAMAGE are:• Shell and inner side plating (laterally loadedplastic membrane)• Deck and girder crushing• Beam loaded by a concentrated load• X-, L- and T-form intersections crushed in theaxial directionThe bow geometry is defined by eight parameters.Figure 16 shows an example the bow geometry.5.2.3 ALPS/SCOLALPS/SCOL is a coarse-mesh 3-D non-linear finiteelement code using super-elements based on the IdealizedStructural Unit Method (ISUM) [20,21]. The geometry ofthe striking and the struck ships is described in a global(three-dimensional) rectangular coordinate system. Thestress in an ISUM unit is described in a local elementcoordinate system. ALPS/SCOL considers sway and yawof the struck ship with the following assumptions:• The added masses of the striking and the struck shipsare calculated based on ships of similar type and sizeusing a linear strip theory-based computer program.• The striking ship is assumed to be rigid.• The analysis of the external and the internaldynamics is undertaken separately.• The longitudinal velocity of the struck ship is notconsidered.• Since ALPS/SCOL is based on a simplified 3-Dnonlinear finite element approach, damage in thethree directions (i.e., including penetration, verticaland horizontal damage) are considered.• The geometry of the striking ship bow shape isdescribed by gap/contact elements. The bow isassumed to be rigid.• One cargo hold of the struck ship is taken as theextent of the analysis.• ISUM stiffened panel units are used to model thestruck vessel structure.The geometry of the struck ship is described using about600 rectangular or triangular ISUM units. If thedeformation of the struck ship is symmetric, the totaldegrees of freedom in the numerical model are reduced byhalf. Each node has 3 degrees of freedom.Figure 17 shows damage calculated in anALPS/SCOL simulation.Design data required for the striking ship includes adetailed bow geometry description, length, beam, depth,draft and displacement.Design data for the struck ship includes, length,beam, depth, draft and displacement, transverse bulkhead10
location, COG, and detailed structural design andscantlings.Scenario data required includes striking ship velocityand longitudinal location of impact in the struck ship.Energy ratio10,80,60,40,260 Deg.90 Deg.120 Deg.150 Deg.Ship-Ship collision0-0,5 -0,3 -0,1 0,1 0,3 0,5Collision location (d/L)Figure 18 - Energy ratio defined as the ratio betweenenergy released for crushing and the total kinetic energyof the two ships before the collision as function of thecollision location, d, for collision angles equal 60, 90, 120and 150 degrees. The two tankers are identical and havethe same speed prior to the collision [29].Figure 17. Damage from ALPS/SCOL Simulation5.2.4 DTU ModelThe Technical University of Denmark (DTU) modelalso solves the external problem uncoupled from theinternal problem, and applies the calculated absorbedenergy to plastic deformation of the struck ship.Solution of the external dynamics is accomplishedbased on an analytical method developed by Pedersen andZhang [29]. This method estimates the fraction of thekinetic energy that is available for deformation of the shipstructure. The energy loss for dissipation by structuraldeformation is expressed in closed-form expressions. Theprocedure is based on a rigid body mechanism, where it isassumed that there is negligible strain energy fordeformation outside the contact region, and that thecontact region is local and small. This implies that thecollision can be considered instantaneous as each body isassumed to exert an imp ulsive force on the other at thepoint of contact. The model includes friction between theimpacting surfaces so those situations with glancingblows can be identified. Both ships have three degrees offreedom: surge, sway and yaw. The interaction betweenthe ships and the surrounding water is approximated bysimple added mass coefficients, which are assumed toremain constant during the collision.The loss in kinetic energy by the method isdetermined in two directions, perpendicular and parallelto the side of the struck ship. Both right and oblique anglecollisions are considered and both vessels may havevelocity before the collision.The model for the internal mechanics is based on aset of super-elements, where each element represents astructural component. The calculation method is based onthe principle that the area of the struck vessel affected bythe collision is restricted to the area touched by thestriking vessel. The super-elements are:• Lateral plate deflection and rupture. Largedeflections are assumed; this implies that the bendingresistance can be neglected• Crushing of structure intersection elements (X- or T-elements)• In-plane crushing and tearing of plates• Beam deflection and ruptureThe design data for the struck vessel includes length,beam depth, draft, displacement, COG and detailedstructural design and scantlings.The bow of the striking vessel is assumed to be rigid.The basic data for describing the striking ship bow arestem angle, breadth and bow height. The horizontal shapeof the deck and the bottom are assumed to be parabolic. Ifthe striking vessel is equipped with a bulb, this is assumedto have the form of an elliptic parabola.Scenario data required includes striking and struckship velocity, collision angle and longitudinal location ofimpact at the struck vessel.5.3 ApplicationIn order to assess the models’ consistency and sensitivity,they are tested in a series of collision scenarios with arange of struck tanker sizes and designs. The BaselineTanker design is a 150000 dwt double-hull tanker. It wasdeveloped to be consistent with the dimensions of the150000 dwt reference tanker in the IMO InterimGuidelines. HECSALV and SafeHull were used to11
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: ybeginning of time step nStriking S
Page 13: Ship Type150,000 dwtbulk carrierLen
Page 16 and 17: 6.2 DATA FOR MODEL VALIDATIONThe se
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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