PSI - Issue 20

A.A. Antonov et al. / Procedia Structural Integrity 20 (2019) 270–277 A.A. Antonov et al. / Structural Integrity Procedia 00 (2019) 000–000

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Using equations (5) - (7), equation (8) can be transformed into: σ ��� � � � �� � ��( � � � �⁄�) � � � � ��� � ��� ��� (�⁄�)����(���) � (�⁄�)(� �) � ⁄ � � σ ��� (9) Having determined the maximum local stress in the specific bent sections of the underwater gas pipeline, the structural state and mechanical properties of the welded joint zones are estimated. Subsequently, the comparison of these data allows estimating the stress-strain state, the development level of local elastoplastic deformations in the welded joints of the underwater gas pipeline and their safety taking into account operational factors and changes in temperature conditions of the material deformation in the examined section. This algorithm is at the stage of final development for subsequent testing at linear structures, particularly, in the Hatassy-Pavlovsk underwater crossing of TGPL across the river Lena. 4. Conclusion 1. The following instrumental methods of examination are shown to determine the actual planned-high-altitude position of the underwater crossing of TGPL across the Lena River: • profile sounding by means of the OKO-2 GPR with the AB-150 antenna with an operating frequency of 150 MHz. The depth of sounding is 12 m, the resolution is 0.35 m; • examination of the bottom of the river Lena in the area of the underwater gas pipeline is performed using the Hydra 500E SSS with the following characteristics: average frequency is 500 kHz, resolution is not less than 0.94 cm, the maximum slant range is not less than 60 m, working depth is up to 20 m with a built-in echo sounder; • determination of the actual planned-high-altitude position of the floodplain part of the underwater gas pipeline is accomplished with the RD-8000 line locator. 2. Based on the results of monitoring the changes in the planned-high-altitude positions of the Hatassy-Pavlovsk underwater gas pipeline, the basics of assessing the dynamics of the stress-strain state (SSS) of welded joints of the gas pipelines are summarized. 3. The main principles of the assessment of the stress-strain state of welded joints of the underwater gas pipeline across the river Lena, combining the results of on-sight inspections of the planned-high-altitude position of the gas pipeline in floodplain areas, algorithms for determining the curvature radius of the gas pipeline bend, the statistical distribution of the stress concentration coefficient in the transition zones of the pipe welded joints, determination the maximum local stress in a zone of welded joint at pipeline bend are formulated. Acknowledgements This research has been supported by The Ministry of Science and Education of Russian Federation (Project III.28.1.1). References Aistov, A.S., 1973. On the calculation of the stress state of high-pressure pipes with ovality. Materials of Science and Technology Conference of academic teaching staff of GIIVT (1972-1973 academic years). Gorky, 244-245. (in Russian) Bakhvalov, NS, Zhidkov, NP, Kobelkov, G.M., 2004, Numerical methods. Binom, Moscow. (in Russian) Bronshtein, I.N., Semendyayev, K.A., 1962. Handbook of mathematics for engineers and students of technical colleges. State Publishing House of Physical and Mathematical Literature. (in Russian) Fokin, M.F., Gusenkov, A.P., Aistov, A.S., 1984. Evaluation of the cyclic durability of welded pipes of the main oil and product pipelines. Mashinovedenie 6, 49-55. (in Russian) Gusenkov, A.P., 1979. Durability under isothermal and non-isothermal low-cycle loading. Nauka, Moscow, pp. 295. (in Russian) Gusenkov, A.P., Aistov A.S. 1975. Study of low-cycle strength of large-diameter pipes of the trunk gas and oil pipelines. Mashinostroenie 3, 61 71. (in Russian)