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    Glykas and Das (2001) calculated the energy dissipation on the bow structure during a "head-on" collision with a rigid body, using finite element analysis. Wang et al. (2002) presented an investigation of the longitudinal strength of ships with damages due to grounding or collision accidents.  Scope of analysis The objective of the analysis was to compare behavior of three types of barges: (i) OBP-500W, being a barge operated by the Polish owner ODRATRANS, further referred to as barge A and two innovative barges devel-oped in Project INBAT – (ii) the design developed by the Design Office for Inland Navigation NAVICEN- Framesno. 7, 10 TRUM,  referred  to  as  barge B  and  (iii)  the  design  de-veloped  by  a  team  in  the  Technical  University  of Szczecin, referred to as barge C. More detailed descrip-tion of the barges is given by Guesnet et al. (2004).  Barge A is a typical barge being currently operated. It is a steel barge characterized by  shell structure  reinforced with numerous girders and  stiffeners at  the bottom and sides. Thickness of  the plates of  the outer shell and  the cargo deck is 6 mm. In the regions exposed to increased loading the sides are reinforced by additional stiffeners. The barge has  the  explicit  fore part –  raised, with  fore deck, equipped with the bulkhead, side decks and the aft part. A  firm  transverse beam  is  situated  at  the midship section. Main particulars of the barge are: length overall 45.13 m,  breadth  overall  8.988 m,  depth  1.7 m,  design draught 1.6 m,  frame spacing 0 - 80 0.5 m,  frame spac-ing 80 -91 0.4 m – Fig. 1. Fig. 3:  Cross-section of barge C Authors  believe,  that  the  application  of  nonlinear,  fast transient application of FEA, when  the structure model is isomorphic with physical structure, permits to achieve accurate  results  in  the  analysis of  the  loss of  structural integrity during ship collision.. As the barge structure is relatively simple and small  in size, a detailed computa-tional model may be elaborated relatively easily and the necessary simplifications do not seriously  influence  the accuracy of the results.  Computations  have  been  done  using  the  PAM-CRASHTM computer code which  is a part of  the PAM-SYSTEMTM,  developed  by  the  ESI  Group.  It  is  the computer  code  for  analysis  of  destruction  of  technical objects  by  the  finite  element  method  employing  the explicit  time  integration  scheme.  This  approach  pro-duces the best results for solving the dynamic problems including  contact. Arbitrary  type  of  s  structure  can  be modelled  using  plate,  shell,  solid  and  beam  elements. Functional persity allows to take into account various physical  phenomena  occurring  during  the  collision  of the barges.  Fig. 1:  Cross-section of barge A Barge B is a concept based on a relatively dense double bottom grid made of  thin plates. The  structure  is  stabi-lized  by  foam  filling  the  double  bottom  space.  The cargo deck  is  reinforced using  the  laminate plates with increased thickness of the plating directly exposed to the cargo in the expected larger pressures – Fig. 2.   The problem of the stability of the numerical solution is overcome  assuming  appropriate  time  step  according  to Eq. 1  ρ= ∆Eltminmin   (1) where  lmin  is  the  geometry  discretization  size  (size  of element).  Fine  meshing  -  small  size  of  the  finite  ele-ments  –  thus  leads  to  numerous  time  steps..  Even  so small  step  size  can be  advantageous  since high  resolu-tion  in  the  time domain can be  important  in accurately capturing the non-linear behaviour of system. PAM-CRASHTM  user  may  model  extreme  non-linear behaviour  under  high  transient  load  by  simulation  of elasto-plastic  behaviour  of  material  with  strain  rate, damage effects and rupture any type of material. When  the  software  is  used,  considered models  can  be prepared  using  structural  parts  with  solid,  shell  and beam elements as well as rigid parts. Validated material models  include  common  engineering materials  such  as metals,  composites,  highly  compressible  polyurethane foams and others. Special essential features in mechani-cal  structures  can  be  easily  modelled  –  behaviour  of rivets  and welding, which may  be  critical  for  collapse modes, may also be taken into analysis Fig. 2:  Cross-section of barge B Barge C is an all-steel barge made using the typical for shipbuilding  flat  plates  and  innovative  structural  ele-ments  -  I-coreTM  panels  developed  by  MeyerWerft, being  elements  with  internal  structure  (Roland  and Metschkow, 2002) – Fig. 3. They are composed of  two plates connected by densely situated vertical ribs. A  contact  model  is  the  important  feature  of  PAM-CRASHTM.  It may  be  accounted  for with  the  series  of search algorithms. The friction between areas of contact are taken into account. The integration scheme stability is controlled with Cou-rant  condition  to  avoid  the  numerical  instabilities  and time  step  collapse. Also  subcycling  algorithm may  be used  to  increase  the  calculation  efficiency  through  ex-ploitation advantage of local mesh density.  Finite element modeling and computational procedure Models of barges Computational  models  were  built  using  shell,  solid, beam  and  rigid  elements. Contact  in  collision was  de-tected by the algorithms of PAM-CRASHTM. The model of contact includes friction. Finite  element model was built using  the 3D  structural documentation.  Longitudinal  symmetry  of  the  barges was utilised. The side of the barge which is in collision is  modelled  as  a  deformable  structure  using  3-  or  4-noded  shell  elements  and beam  elements  including  the transverse beam. In the case of analysis of collision, the opposite side of the barge is modelled: (i) in the case of the struck barge using  the shell  rigid elements  to allow to account the influence of water inertia effect while the barge moves perpendicularly  to  the  direction  of move-ment  along  current  direction  –  as  described  in  Section “Model of water”; (ii) in the case of striking barge using the rigid body elements having the mass equal to a half of the lightweight and a half of the actual deadweight. When  grounding  is  analysed,  the  opposite  side  of  the barge is modelled using the rigid body elements having the mass equal to a half of the lightweight and a half of the actual deadweight. Welds  and minor  elements which  do  not  influence  the structural  strength  are  not  modelled.  All  flanges  of floors, girders and stiffeners were modelled using beam elements. To obtain the effect of loading acting on the inner sides of the cargo hold,
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