Reliability Analysis Of Slamming Strength Of The Bottom Near The Bow

Bow bottom slamming of ship is one of the physical phenomena,which often appears during heavy sea conditions. At this instant,bottom plates experience large slamming pressure,which can damage bottom plates. The major content of this thesis is to calculate slamming pressures and ultimate bearing capacities more rationally by probabilistic analysis method,and to estimate the safety by reliability analysis method. For this reason,the following problems are researched emphatically:Firstly,the long-term prediction method for calculating the extreme values of slamming pressure is founded. The effects of sea conditions,ship speeds,traveling directions,loading conditions on the results of long-term prediction are studied. On this basis,the computing process is simplified rationally,so as to this method can be used in practical engineering computations.Secondly,the failure mode of bottom plates for finite element calculation is put forward based on the definition of ultimate states. Calculating and analyzing many calculation modes,the effects of plates' sizes and material mechanical properties on ultimate bearing capacity are discovered. On this basis,the upper-limit solution calculation formula of ultimate bearing capacity gotten by limit analysis theory is modified. The new handy and more accurate formula is established.Thirdly,we calculate basing on the concerned contents of shipping design and building rules of China,America,Norway and Britain respectively,then compare and analyze,in which five bulk cargo ships are taken as examples. Through this,the existing problems and the reasons of those are pointed out. The reliability analysis methods areadopted to calculate the reliability specifications of the practical ships and the reliability specifications that correspond with the rules of the four countries. On the basis of this work,the methods of identifying the target reliability specification are gotten.Based on the above work,the calculation formulae of nominal slamming pressure and the bearing capability of the bottom plates in the rules are modified,and the safety coefficients are evaluated referring to the target reliability specification,then the more reasonable formula of assessing the slamming strength of bottom of the bow is given.