The Lower Bound Dynamic Shakedown Analysis Of Pipeline Structure Based On Drucker-Prager Yield Criterion

The pressure pipeline projects in China are large in scale and are subjected to cyclic loading effects during operation,which inevitably lead to plastic deformation,and it is of great importance to evaluate the safety of such structures.The numerical analysis method of stability theory is an effective calculation tool to predict the mechanical behavior of the members under cyclic repeated loading.The current method of stability analysis for pressure pipelines is based on the Mises yield criterion,which is applicable to metallic materials and is not applicable to non-metallic materials.In order to evaluate the safety performance of non-metallic pressure piping,this paper is based on the theory of stability,and the main work is carried out as follows.First,a dynamic stability lower limit analysis method based on the Drucker-Prager criterion is proposed.Based on the dynamic stability lower limit theorem,the stress compensation method based on the Drucker-Prager criterion is developed,the numerical method for constructing the self-balancing stress field is established,and the dynamic stability lower limit analysis method suitable for non-metallic materials such as concrete and rock is developed.Secondly,the numerical solution algorithm of the dynamic stability lower limit based on the Drucker-Prager criterion is developed and the corresponding procedure is developed.The numerical solution format of the dynamic stability lower limit based on the Drucker-Prager criterion is proposed,the iterative algorithms of the self-equilibrium stress field and dynamic stability multipliers are developed and perfected,and the feasibility and accuracy of the numerical procedures under static and dynamic loads are verified by classical examples.Finally,based on the developed numerical procedures,the stability performance of non-metallic straight and bent pipes subjected to cyclic internal pressure and bending moment dynamics is studied and analyzed.The bending part of the bends has a greater influence on the structural stability performance.The stability load of the non-metallic straight pipe and bend is influenced by the frequency of external excitation,and the stability load decreases significantly near the self-oscillation frequency of the structure.With the excitation frequency away from the self-oscillation frequency of the structure,the dynamic stability load is gradually greater than the static stability load.As the excitation frequency gradually decreases,the dynamic stability load gradually approaches the static stability load.