Elasto-Plastic Behavior and Buckling Analysis of Steel Pipelines Exposed to Internal Pressure and Additional Loads

The currently valid worldwide standards allow for taking into consideration plastic deformations in order to achieve a higher degree of utilization. The maximum plastic strains, which can be allowed for steel pipes subjected to internal pressure and additional loads, are particularly interesting. In this paper results of investigations on the elasto-plastic bearing behavior of steel pipelines subjected to internal pressure and bending are presented. Four-point bending tests on eight steel pipes were carried out in order to make the buckling analysis in the elasto-plastic range possible. Finite-element-models were checked by test results for the application on buried pipelines. Taking into account bedding conditions of the pipeline in the soil was made possible. Furthermore, an analytical method based on the differential equation for beams with longitudinal tensile force and variable bending stiffness was developed. It is suitable to determine the elasto-plastic bearing capacity for internal pressure and bending. The collapse due to plastic shell buckling is considered by a limit criterion based on critical strains.