Research On Simplified Method For Calculating Ultimate Longitudinal Strength Of Ship Structures

Analysis and design of the ultimate longitudinal strength of ship structures is one of the basic tasks in the ship design. Ultimate longitudinal strength of ship structures is an important indicator of the carrying capacity of it. Its accurate assessment and forecasting are related to the safety of the ship. So it is necessary to find out an accurate and convenient method which is used to calculate the ultimate longitudinal strength of ship structures.The essay analysis and calculate on the ultimate longitudinal strength of ship structures base on progressive collapse analysis and Single step ultimate capacity method. There are some count examples in the paper. We attempt to find out a proper method through comparing with the two methods.The progressive collapse analysis is a traditional method. We increase the load on the cross section of the ship step by step until the ship structure damaged. In every step we calculate stress response states of all stiffeners. At last we can get the relationship of flexural torque and circumflexion. Then we can get the ultimate longitudinal strength of ship structures. We also design a simplified calculation system which is developed in visual basic 6.0 development environment, with the Access database connectivity and fortran programs. This system can calculate the ultimate longitudinal strength of ship structures automatically.One step method is a simplified method to calculate the ultimate longitudinal strength of sagging ship structures. This method considers that the reason of the damage of the ship is that the deck get buckling. One step method only consider vertical bend. This method neglect the effect of shear force, torsional load , horizon bend and lateral pressure. We get the ultimate longitudinal strength of ship structures by the way of using empirical formula. To the deck buckling there touch upon the advanced buckling analysis.The two methods are both feasible.