Research On Long Deckhouse Contributing To Hull Girder Strength

The main purpose of the thesis is to study the effective factor of the long deckhouses to the longitudinal strength of Naval Ship. Based on 3-D FEM method, the actual stress of each deck is obtained. Then by comparing the calculation results, the effective factor of the long deckhouse contributing to the longitudinal strength is confirmed, so as to provide the numerical values for the deckhouses design. Consequently, the deckhouses can be designed in a more reasonable way.A 3-D FEM model is established according to Guidance for Direct Calculation of Hull Structure and Guidelines for Direct Strength Analysis of Container Ship issued by CCS. Ship motion and wave load transfer functions are calculated by using 3-D surface panel method. According to P-M wave spectrum and global wave scatter diagram, the long-term prediction results of wave load at given loading conditions are gotten by using spectral analysis method. The vertical wave bending moment for the calculation of longitudinal strength is determined from the result of long-term prediction. Wave induced dynamic pressure and inertia force are calculated by design wave method. By imposing the loads on the 3-D model, the quasi-static response FEM analysis of the hull and the direct calculation for the longitudinal strength are carried out.From above calculation, the maximum combined stress of all loading conditions, appeared at the bracket of aft bulkhead in the long deckhouse. The longitudinal stress of the main deck is much smaller at the middle of the long deckhouse and the value turns mush higher near the edge.The longitudinal stress of the deckhouse reaches maximum while it becomes smaller gradually towards two edges. Around frame 54, which is near the cross position of long deckhouse's aft bulkhead and the main deck, the stress is higher.It is shown that the effective factor of the long deckhouse contributing to the longitudinal strength is 85.6%.