Research On Residual Ultimate Strength Of Hull Stiffened Panels With Cracks

The ultimate strength of the hull structures is one of the most important index to expressing the safety and reliability of the ships.Stiffened panel is one kind of basic structural components of the ships as well as offshore structures.Great attention has been given to the ultimate strength evaluation of stiffened panels by many researchers in recent years.Age-related damages will gradually emerge on stiffened panels in transportation,among which crack is a common type of damage which causes invalidation.The ult imate strength analysis of cracked stiffened panels could lay a foundation for the condition assessment and health monitoring over the lifetime cycle of ships,which is inevitable for the damage tolerance design and reliability design.Therefore,the research on the residual ultimate strength of hull stiffened panels with cracks is of high theoretical and practical value.Previous researches mainly focused on center or edge through cracks,few considerations have been given to the random locations of cracks.The exist ing formulas are very limited in applications as they are mostly based on plate with cracks of varying length and angle.In order to obtain the formula which can be applied in engineering practice,this paper systematically studies the residual ult imate strength of stiffened panels with cracks under longitud inal compressive loading through a series of nonlinear finite element analyses.Main contents are as follows.(1)One type of stiffened panel calibrated by ISSC in 2012 is chosen as research object for the convenience of comparison.N umerical analysis on the ult imate strength of intact stiffened panels are performed considering the effects of model range,boundary condition,init ial imperfection and mesh size.The optimal model which satisfies the calculation accuracy and efficiency is obtained through comparing with the results of calibration.(2)The case of single through crack is investigated for the optima l model.Secondary development of ABAQ US is implemented based on Python language to achieve the purpose of pa rametric modeling and analysis wit h the length,orientation angle and position of crack as well as the thickness and deformation amplitude of plate as variables.(3)Some influence laws of crack characteristics are summarized and an empirical formula of ult imate strength reduction factor is obtained by mult iple regression analysis of calculated data.It is found that the influence of crack location on the residual ult imate strength is significantly depended on where the crack locates in the range of plate buckling half wave.The obtained calculation formula of ultimate strength reduction factor comprehensively considered the crack length,orientation angle and posit ion,which has high value in the engineering practice.