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Abstract In this paper the effect of two types of common initial geometric imperfections on the reliability of steel frames is investigated. These imperfections are the coordinates of connection nodes and crookedness of members. Most finite element reliability analyses in past literature neglect this source of uncertainty. For this purpose static nonlinear pushover structural analysis is used from which reliabilities are estimated based on FORM and Monte Carlo sampling methods. Furthermore to investigate the importance of uncertain parameters, reliability sensitivity analysis is performed by use of the direct differentiation method which has been implemented in the object oriented software framework Open Sees. It is demonstrated that some of these geometric imperfections have significant influence on reliability assessment of steel frames.

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Abstract: The effect of two types of common initial geometric imperfections on the reliability of steel frames was investigated. These imperfections are the coordinates of connection nodes and crookedness of members. Most of the finite element reliability analyses in the past haveneglect this source of uncertainty. For this purpose, static non-linear pushover structural analysis was used in the present work from which reliabilities were estimated based on the FORM and Monte Carlo sampling methods. Furthermore, to investigate the importance of uncertain parameters, reliability sensitivity analysis was performed by the use of direct differentiation method, which was implemented in the object oriented framework of OpenSees software. It was demonstrated that some of these geometric imperfections have significant influence on the reliability assessment of steel frames.

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When a cylindrical shell subject to a compressive load, because of various imperfections happened during processes as manufacturing, handling, assembling and machining, buckling occurs in loads lower than corresponding static failure load. Still many of cylindrical shell structures are designed against buckling based on experimental data introduced by NASA SP-8007 as conservative lower bound curves. In the manuscript, non-linear methods of Modified Linear Buckling Modeshape Imperfections (M-LBMI) and Simple Perturbation Load Imperfections (SPLI) for composite cylindrical shell with and without cutout are investigated. In order to evaluate the numerical results composite cylinder with stacking sequence of [90/+23/-23/90] are manufactured by using filament winding method and buckling tests are performed under axial loading. Non-linear numerical results in cylinder with and without cutout are close together and have good agreement with experimental data. . It was concluded that buckling load predicted by SPLI and modified LBMI method on cylinder with cutout is close to result of case without apply geometric imperfections. In summary, it was concluded that cutout on the cylinder body act as an imperfection to trigger buckling of the structures so there is no need to apply geometrical imperfections.