Determining the Features of Oscillations in Prestressed Pipelines

This paper considers the structural solution for a main above-ground pipeline with a pre-stressed winding, which makes it possible to improve the efficiency of operation and reduce material consumption. The results from studying experimentally the features in the operation of prestressed pipelines under static operating loads are given. It is shown that the radial movements of the wall of a pre-stressed pipeline are constrained by the strained winding, which prevents its deformation. It was revealed that increasing the tension force of the winding wire reduces circular stresses in the pipeline wall by 1.3...1.6 times and increases meridional ones by 1.2...1.4 times. The experimental study into the models of prestressed pipelines with free vertical and horizontal oscillations has established the dependence of frequency characteristics on the operating conditions and pre-stress parameters. It was found that the envelope amplitude on the oscillogram of free attenuated oscillations takes the shape of an exponent, which indicates the damping effect of the pre-stress. Analysis of the change in the dynamic characteristics of the models depending on the pre-stress force has revealed that the frequencies of free oscillations increase by 1.5÷1.6 times while the oscillation decrement decreases by 1.2÷1.25 times. This paper reports the results of studying the influence of pre-stress parameters on the stressed-strained state of the pipeline model under forced horizontal and vertical oscillations. It is shown that the diagrams of circular dynamic stresses and deformations in the models of a prestressed pipeline are smoother compared to similar characteristics of a conventional pipeline tested at the same experimental parameters. The study results have made it possible to quantify the features in the operation of a pre-stressed pipeline under static and dynamic influences, taking into consideration the pre-stress parameters and operating conditions