Research On Structural Systems Reliability Of Thin Shell

The thin shell structure is more and more widely used in the aerospace, aviation,shipbuilding, construction and other fields. The designers are most concerned about the issuethat whether the thin shell structure could perform the specified functions under the stipulatedconditions and within the limited time. For this, the structural reliability analysis is importantobviously. This article’s content is how to apply the reliability theory to the thin shell structureanalysis, which also attracts many researchers’ attention.Considering the elastic thin shell structure, this paper takes research on the structuralsystem reliability under random loads. Firstly, the finite element model of the thin shellelement is built. According to the deformation characteristics, triangular thin shell element isequivalent to the combination of the triangular plane stress element and triangular bendingsheet element. Then, on the basis of deducing stiffness matrix respectively, the thin shellelement stiffness matrix is formed by above two stiffness matrix under the superpositionprinciple. The global stiffness matrix, the coordinate transmitting matrix and the stiffnessequation’s solution are given. Lastly, using FORTRAN language is to write the correspondingfinite element programs, meanwhile, the solution is reliable by comparing with the simulationresults of ANSYS.Based on the ideal elastoplastic assumptions of thin sheet structure, when a certaincomponent is failure, according to three main stress and reverse node force, using theprograms form the safe margin equation automatically. Considering that the external load andthe material strength are the random variables, using the first order second moment methodgets the reliability index. Utilizing the improved branch-bound method is to search thedominant failure modes, which increase the calculation efficiency greatly. The dominantfailure modes is equivalent to a series system model, and then using PNET method calculatesthe reliability index and failure probability of the structural system.Finally, writing the reliability analysis program according to the above theory is toprovide some important reference for the follow-up work.