Study On Nonlinear Buckling And Stability Of New Typical Dry Gasholder

New typical gas holder is a large combination of thin-walled shell structure,the gasholder body is a longitudinal and circumferential stiffened cylindrical shell;the roof and the piston are radial and circumferential stiffened shallow spherical shell.Under normal circumstances,the bending of the new typical gas holder under gas pressure is crucial to ensure normal operation of the structure.Meanwhile,for this type large structure,scale model test is unavoidably needed to ensure the pre-research and safe usage.Base on the space shell theory and stripe beam on elastic foundation method(SBEFM),two modified methods for the local bending of the cabinet under internal pressure were developed.Then,based on the scaling law of energy method,the similitude for prestressed vibration and buckling of the stiffened cylindrical panels and shells,the similitude for the linear and the nonlinear buckling,the similitude for free vibration of the stiffened shallow spherical shell and applications of the scaling law for the gasholder body,which are given as follows:(1)Based on the improved discrete stiffened method and stripe beam on elastic foundation method,the bending of the gasholder body under local internal pressure was studied,and the simplified models of the longitudinal stiffened cylindrical shell under local internal pressure and the stripe beam on elastic foundation under uniform load were proposed.Then,the results were compared with those obtained from the smear-stiffened theory and the finite element method.On this basis,the method judging ring stiffened cylindrical shell smeared or discrete was presented.Results showed that SBEFM had applicability,high accuracy,good efficiency than other methods and improved discrete stiffened method was effective when the ring spacing was greater 3.875(Rt)1/2.(2)The generalized similitude requirements and scaling laws considering the prestressed deformation for vibration and buckling were put forward based on the total energy of structural system.Scaling laws of partial similitude were improved by first considering the formulas of stiffness parameters.Some parameters could be changed on the premise that the stiffness scale factors did not change.The equivalent stiffeners of the model with distortion in the material properties of the stiffeners were obtained by solving the nonlinear equations relaxing the similitude equation of the torsional constant of the stiffeners.Results obtained from complete and partial similarity indicated that the results of models could accurately predict those of their prototype.(3)Scaling laws for axiaymmetric free vibraton of stiffened shallow spherical shells were developed based on innovative introduction of the formulas of stiffness parameters.A simple numerical example was analyzed to ensure the validity of derivation.The influence of dimensionless stiffener cross-sectional area,the eccentricity and the moment of inertia was studied for dynamic characteristics of the structure.Complete and partial similarity free vibrations were performed based on the improved scaling laws.Results showed that complete and partial similarity models were able to accurately predict the behavior of their prototype.Section types of stiffeners of the model could be different from the ones of the prototype,when the ratios of the cross-sectional area,first and second moment of the stiffener area to their spacing were similar.This was convenient for the design of experiment models.(4)Based on the energy method,the generalized similitude requirements and scaling laws for the linear buckling of stiffened cylindrical shells were presented.The linear buckling similar simulations of stiffened cylindrical shells under axis and lateral pressure were studied by the finite element method.The validity was guaranteed by verifying numerical examples with references.The influence of similar simulations on the linear buckling of stiffened cylindrical shells with different length-radius ratio,boundary conditions and section types of stiffeners under axis and lateral pressure were performed.Results showed that complete and partial similarity models coule accurately predict the linear buckling behavior of the prototype.The scaling laws are suitable for the stiffened cylindrical shells with different length-radius ratio,boundary conditions and section types of stiffeners under axis and lateral pressure.(5)The scaling laws for the nonlinear buckling of stiffened cylindrical shells were developed based on innovative introduction of the scaling factor of deformation.Firstly,the validity and reliability of the finite-element analysis is guaranteed by verifying numerical examples with references.Subsequently,based on the initial imperfection of the first mode of eigenvalue buckling and ideal disturbance displacement,the similar simulations for the nonlinear buckling of stiffened cylindrical shells(cross section of stiffeners are rectangle or T type)by the finite element simulation.Results showed that complete and partial similarity models could excellently predict the nonlinear buckling behavior of their prototype.The discrepancy of the post-buckling path between the predicted and original was increased with the deviation of Poisson's ratio between the models and theire prototype increased.The scaling laws of post-buckling are suitable for the stiffened cylindrical shells with different length-radius ratio,boundary conditions and section types of stiffeners under axis and lateral pressure.It also provides a reference for truly predicting the nonlinear buckling behavior of the prototype.(6)Despite of the influence of longitudinal columns,the truncated gasholder body with ring stiffener was treated as computing model.Base on the previous research,the similar simulations for the linear buckling,free vibration and the nonlinear post-buckling of the new typical gas holder's body were studied.For both ends clamped,the upper-end simply supported and lower-end clamped truncation gasholder body,the results of the linear buckling and free vibration indicated that complete and partial similarity models could excellently predict those of the prototype when the imperfection factor is relatively small,the results of the similar simulations of the post-buckling showed that the models could only predict the rules for the post-buckling path of the prototype when the imperfection factor is larger enough.The buckling mode shapes are well-matched between the the model and its prototype at the end of the post-buckling path.During the linear analysis,the behavior of smear or discrete of stiffeners was not appeared.During the process of development of the nonlinear post-buckling,the behavior of smear or discrete of stiffeners was obviously appeared as the imperfection factor increased.The developed scaling laws for nonlinear post-buckling are only applied to the smeared-stiffeners gasholder body based on the smear-stiffened theory.