Research On Simplified Calculation Method & Acceptance Criteria For Hull Deflection Of Inland Navigation Vessels

In recent years,there is a developing tendency of large-size and lightweight design of vessels to gain more economic benefits or reduce risk of losing money.For inland navigation vessels,the ratio of ship length to depth L/D and breadth to depth B/D are often limited by the confined waterways,thus leading to the continuous growth of ship length.As a consequence,the bigger L/D ratio,and the more flexible hull.Although ship classification societies usually have established regulations to check longitudinal strength of vessels,there is still possibilities that accidents occur caused by excessive hull deflection due to lack of reasonable criteria with respect to hull rigidity.To avoid problems caused by objectionable deflection,great importance should be attached to the maximum deflection of inland navigation vessels.In this present thesis,the investigation deals with the determination of permissible hull girder deflection of a large number of European inland navigation vessels(which refer to tankers and dry cargo vessels in this study)as well as Chinese river-to-sea vessels under the worst possible scenario of all operating conditions.The simplified analytical method applicable to inland navigation vessels is proposed on the basis of summary and analysis of the impact of shearing deflection,distribution of moment inertia and deflection modification caused by change of the bending moment on hull girder deflection.Further,formulated criterion are put forward,and it may recommend to be considered as a default value to be implemented in the Rules for Inland Navigation Vessels.Moreover,the hull girder deflection of typical Chinese new generation of River-to-Sea container vessels are determined and analyzed to make a summary of characteristics and major differences between European and Chinese inland navigation vessels.The general research contents are developed according to the following:(1)Problems that may arise from excessive longitudinal deflection and methods to obtain hull girder deflection are summarized.General overview is made in relation to maximum hull girder deflection criterion in current ship classification rules and engineering practice,and existing problems are discussed and summed up.(2)By means of comparative study on the key factors that affect hull girder deflection,a simplified analytical method suitable for the deflection calculation of modern inland navigation vessel is put forward.Meanwhile,the feasibility of simplified analytical method is verified by comparing with the finite element method calculation results.Further,the automatic calculation program in VBA code is developed for batch computing of all the series of sample vessels.(3)Apply the developed methodology with program for analytical determination of the hull girder deflection to European standardized vessels.The maximum hull girder deflection,in the form of a simplified analytical prediction formula,considering vital influence factors,including principal dimensions,bending moments,and so on.(4)Take typical Chinese inland navigation vessels as example,determinate its maximum deflection and discuss the major differences between current European and Chinese inland navigation vessels.Suggestions with regard to deflection restrictions are given to rules for inland navigation vessels.