Research On Ultimate Strength Of Two-way Orthogonal Multi-stiffened Plates

Ship hull is the thin-walled structure, which composed by stiffened plates and framework. The stiffened plates are the basic composite of a ship hull. The research on the mechanical properties of the stiffened plates is the basic work to study ultimate bearing capacity of ship hulls. According to the arrangement of stiffeners, stiffened plates include transverse stiffened plates and longitudinal stiffened plates. With the trend of high-speed of ship and the requirement of lightness of ship weight, as well as the usage of high strength material, on the premise of meeting safety and applicability requirements, optimum design of ship structures is an important factor to control ship structure weight. The control of ship structure weight is also the key of ship design. Decrease the plate thickness can make prominent effect towards lightening the structural weight, however which will cases the decline of local strength, stability and local vibration of the stiffened panels, and will cases welding deformation. A new type structure of hull stiffened plates—wo-way orthogonal multi-stiffened plates, which are used in high-speed ship. Two-way orthogonal multi-stiffened plate is a kind of structure that some orthogonal stiffener welded on plates along the longitudinal and transverse respectively. The adjacent longitudinal and transverse strong girders are the boundary of multi-stiffened plates, which can deal with those contradictions such as hull weight and strength, rigidity, vibration, craft, and so on.Two-way orthogonal multi-stiffened panel is different from transverse stiffened plates and longitudinal stiffened plates that recommend usually by domestic and international high-speed ship rules. Due to there no explicit rules in domestic high-speed ship specification, when adopt this type stiffened panels, it is necessary that designers choice the distribution form and its sectional dimensions of multi-stiffened panel, and then applies the finite element analysis to make strength check, certainly, which bring a lot of inconvenience for designers, so it is necessary to study the ultimate strength of the two-way orthogonal multi-stiffened plates.This thesis adopt the finite element analysis software, based on the theory of orthotropic plates, carried out series of finite element nonlinear calculation and analyzed those calculation results. This thesis presents two more simple, reasonable and precision formula for forecasting the ultimate strength of two-way orthogonal multi-stiffened plates; the formulas provide a convenient way to forecast the ultimate strength of two-way orthogonal multi-stiffened plate in practical engineering.In this thesis based on extensive references and the research about ultimate strength of multi-stiffened plates in domestic and aboard, this thesis expounds some related theory of non-linear computation and the theory of orthotropic plates. The thesis introduced two formula of ultimate strength of multi-stiffened plates. The first one is based on the elastic buckling stress, and the other one introduced three parameters, longitudinal column slenderness ratioλx, transverse column slenderness ratioλy,and plate slenderness ratioβ, the second formula is a function about the three variable parameters. Those formulas proposed have more precision and bring great convenience for the design and calculation of ship structure.