Research On The Ultimate Strength Of Plate Girders With Perforated Web On The Condition Of Initial Defects

Plate girders are widely used in ships,and their ultimate strength is related to the safety and reliability of hull structures.However,in the actual ship design and construction process,in order to meet the requirements of component layout and installation,it is often necessary to open holes in the web of plate girders,which will cause stress concentration in the opening area,lower the effective bearing area of components,reduce the flexural and shear properties of components,and ultimately weaken the ultimate strength of components.Plate girders are often subjected to axial compression and bending moment loads,causing the typical loads of plate girders are cargo weight and water pressure.In this paper,the ultimate strength of plate girders with perforated web under compression and bending loads is studied by using the non-linear finite element method,and the influence of initial welding defects is considered in the calculation of ultimate strength.Firstly,the influence of initial defects(including initial deformation and welding residual stress)on the ultimate strength of plate girders with perforated web is discussed and analyzed in detail.The results shows that initial deformation has a great negative effect on the ultimate strength of plate girders with perforated web,among them,the influence of plate shape defect is about 9%,the influence of lateral displacement defect is about 5%,and that of column type defect is about 1%.The influence of welding residual stress on the ultimate strength of plate girders with perforated web is very small.When initial deformation and welding residual stress coexist,the reduction of ultimate strength of plate girders with perforated web is less than the sum of the two defects.Secondly,for plate girders with single waist circular hole,the influence of opening parameters,such as longitudinal location,height and size,on the ultimate strength of plate girders is discussed,and the failure modes of plate girders are analyzed.The results show that the longitudinal location of the opening has a great influence on the ultimate strength of plate girders;the ultimate strength of plate girders decreases with the increases of the opening height;and when the opening size increases,the ultimate strength of plate girders decreases.The failure modes of plate girders are put forward: bending failure in the middle span area,bending failure in the middle span area without opening,and failure of four plastic hinges around the opening.Finally,for plate girders with multiple waist circular holes,the influence of spacing,height and size of the holes on the ultimate strength of the plate girders is discussed,and the failure modes of the plate girders are analyzed.The results shows that the influence of spacing on the ultimate strength of plate girders is related to the size of openings;the increase of the height and size of openings will weaken the ultimate strength of plate girders.The failure modes of plate girders are put forward: bending failure in the middle span area,bending failure in the middle span area without opening,failure of four plastic hinges around opening,bending failure in the middle span area and failure of four plastic hinges around opening in the end region.