Study On Ultimate Strength Of Locally Elevated Web Variable Section Open Beam

As the main supporting component in ship structure,it is important to ensure the ultimate bearing capacity of strong beam to guarantee the strength of ship structure.However,in some special ships with a large number of electronic equipment,in order to pass through the complex pipeline system,it is necessary to make holes in the web of the strong beam whose size and position exceed the requirements of the code.In this case,the standard strengthening method can’t guarantee the ultimate bearing capacity of the strong beam,so this paper proposes a special strengthening method to form a variable section open beam by raising the web locally.The influence of opening and variable cross section on the ultimate bearing capacity of variable cross section beams is very complex.In this paper,the ultimate bearing capacity of open beam with variable cross section is studied by experiment and numerical simulation.Firstly,the ultimate bearing capacity tests were carried out on the variable-section beams with open holes and the equal-section beams without open holes,and the failure modes and ultimate bearing capacity of each beam were analyzed.It was found that the ultimate bearing capacity of the variable-section beams with open holes and the equalsection beams without open holes were similar,which proved the effectiveness of the strengthening method of the variable-section beams with open holes formed by local raising webs.The nonlinear finite element method is used to simulate the ultimate bearing capacity of the test model,and the simulation results of load,displacement and stress are compared with the experimental results.Secondly,finite element software ABAQUS was used to establish a series of openhole beam models with variable cross-section to calculate the ultimate bearing capacity.The method of element division was selected and the influence of element size on the calculation results was discussed.At the same time,the initial deformation caused by welding was introduced in the finite element calculation based on the buckling mode.Analysis of finite element calculation results,discuss the opening hole size and position of variable cross-section beams ultimate bearing capacity,and based on this research the height,length of the variable cross-section area,variable cross-section area transition variable cross-section form and variable cross-section area position influence on non-uniform limit bearing capacity of beams,the failure mode of variable cross section beams is: Bending failure in the opening area,plastic hinge failure in the opening area,bending failure in the transition area of variable section,bending failure in the middle of the beam without opening area.Finally,the design criteria of the open beam with variable section are summarized as follows: the height of the open beam is close to the neutralization axis as far as possible,the longitudinal position of the open beam is close to the middle of the variable section area as far as possible,the size of the open beam is 0.7 times the height of the web;The height of the web of variable section should not be more than 1.5 times of the height of the low web(hw),and the length of the area of variable section should not be more than 6.25 times of the length of the opening.The transition Angle of the transition area of variable section should be 2-3,and the connecting form should be linear,and the area of variable section should be as close to the middle of the beam as possible.