Intelligent Design Based On Knowledge Engineering Methodology And Nonlinear Dynamics Research Of Containership Lashing System

Structural design of lashing bridges has become one of the key technologies of container ships.It is a complex subject with multiple disciplines,multiple objectives,and multiple constraints,which mainly relies on the expert experience and key knowledge such as design specifications.The application of knowledge engineering can realize the reuse of knowledge,which can enhance the accuracy and efficiency of structural design.At present,most of the researches and specifications on containers and lashing equipment used in the industry correspond to static situations,which is inconsistent with actual shipping,thus highlighting the imperfections of various classification societies on the structural design specifications of lashing bridges and the gap in experimental research.Therefore,in the present paper,a detailed study on the intelligent design and nonlinear dynamic behavior of the ultra-large containership lashing system is performed.The main work is divided into the following parts:(1)Based on knowledge engineering and three-dimensional design software(CATIA),the digital intelligent design procedure is developed for typical structural form of lashing bridge.A series of knowledge bases such as the design specification database,the expert experience database,the standard part library and the parent ship lashing bridge database have been constructed.Meanwhile,reasoning design based on parent ship lashing bridge structure has been realized.The design process follows the CCS specifications,and can realize self-checking,automatic test report generation and 3D display of the design results.(2)According to knowledge engineering theory,three-dimensional design software(UG NX)and finite element analysis software(PATRAN),a finite element analysis and multi-objective optimization platform for lashing bridge structures was developed.It has the functions of finite element model construction,static strength and modal analysis of the lashing bridge and the vibration response analysis under the excitation of the main engine and the propeller.A multi-objective optimization mathematical model and knowledge base were constructed,and data fusion with the results of finite element analysis were achieved.It can perform multi-objective optimization of the lashing beidge structure's lightweight,statics and dynamics.The optimization results satisfy the requirements of manufacturing,ergonomics and safety.(3)Static strength and modal tests were performed on the 1/10 scaled model of the lashing bridge and transverse bulkhead of a 20,000 TEU ultra-large containership.The mechanical behavior characteristics such as deformation,stress distribution and modal of the structure were measured.A finite element model of the lashing bridge and hull structure was built.The effects of different modeling ranges of transverse bulkheads on the statics and dynamics of the lashing bridge structure are numerically simulated.The difference between the stiffness of the lashing bridge and the recommended values of the CCS and LR specifications is explored.(4)A four-tier 20-ft ISO freight container stack and lashing assembly scaled model was built.Under typical rolling and pitching excitation,the effects of basic variables such as driving excitation amplitude(angle)and frequency,twist lock gap,cargo stowage,the lashing method(internal and external lashing)and stiffness of lashing components on twist lock force(separation force and shear force),lashing force and container stack deformation was analyzed through experiments,numerical simulations and theoretical calculation methods.The study found that,compared with the internal lashing method,the external lashing is more suitable for high stack and heavy stowage plans.Different lashing methods,lashing forces,twist lock forces and twist lock gap exert mutual coupling effects.(5)Through experimental and numerical simulation,the stiffness of the lashing bridge and lashing components of a 20,000 TEU containership was obtained,compared with the recommended values in LR,GL and ABS specification.Besides,the reasons for the differences were explored.The experimental scaled model and the numerical model of the 11-tier single container stack were built.Under the excitation of rolling and pitching,the effects of basic variables such as twist lock gap,lashing stiffness and stack payload on the dynamic response of high-tier container stack deformation were explored,and the experimental and numerical calculation results were compared.The results show that the scaled numerical model can effectively simulate and predict the dynamic mechanical behavior of container stacks during marine transportation.The difference in stiffness between the open and closed end of the container will increase the complexity of the dynamic response of the stack.The twist lock gap is an important factor for the nonlinear dynamic response of the system.(6)Both an experimental test system and a numerical model for the lashing components(lashing bridges,lashing rods and twist locks)and the 11-tier container stack scaled model were built.Under the rolling and pitching motion excitation,the nonlinear dynamic response of deformation,stress and strain of the lashing bridge structure of a 20,000 TEU ultra-large containership was explored.The dynamic characteristics of the lashing bridge structure under typical motion excitation are obtained,and the experimental and numerical results were also compared.The results demonstrate that the gap effect of the twist lock is one of the important factors for the nonlinear dynamic response of the lashing bridge and container stack,and the horizontal gap has a significant effect on the increase of the dynamic response of the stack deformation.Increasing the stiffness of the lashing device can effectively reduce the dynamic response of the system.The innovations of this study are listed as follows:(1)Based on the knowledge engineering theory,a dedicated knowledge base for the design of lashing bridges is constructed.The object-oriented knowledge representation method and mixed knowledge inference method are employed to realize the intelligent design of the lashing bridge structure.The design efficiency of the lashing bridge is improved(2)Based on Froude scaling laws,a four-tier 20-ft ISO freight container stack and lashing assembly scaled model was built.The nonlinear dynamic response of the twist lock force,lashing force and container stack deformation is explored.The mutual coupling effects of various variables within the lashing system were discovered,and the potential causes of container damage and loss during shipping were revealed.(3)Based on the principle of hybrid similarity,a scaled model of the lashing bridge of a 20,000 TEU container ship was designed.Through numerical simulation and physical experiments,the coupling between the transverse bulkhead and the lashing bridge structure was studied,and the nonlinear dynamics study of the 11-tier container stack and lashing bridge was performed.This study found that the nonlinear effect of the twist lock gap is the incentive for the load in the container frame and lashing system to exceed the allowable value.It providing a theoretical basis for the design of the lashing bridge and lashing assemby structure and the further improvement of relevant specifications.