PIPE-CONCRETE CENTRALLY-LOADED SUB-COLUMN OF A STEEL COLUMN FOUNDATION

A new progressive solution is considered, which consists in improving the design and static calculation of the strength of the elements of the sub-column part of a pipe-concrete foundation, in simplifying the design of a sub-column made of structural concrete of increased and high strength and a thin-walled metal pipe, using it in the form of a permanent formwork as a working element of a composite structure, in reduction of labor intensity and terms of performance of works of the zero cycle. An algorithm is proposed for designing elements of a precast-monolithic reinforced concrete foundation for a column, including a pipe-concrete sub-column, its fl ange connection with a steel column from above and with a foundation slab from below. Thin-walled pipe metal is an economical casing for in-situ concrete.

A FEA Method for Mathematical Calculation and Prediction Analysis Cross-sectional Ovalization of Tubes under Rotary Straightening

The section flattening phenomenon (namely Bazier effect) will occur in the large bending deformation stage of thin-walled pipe in the continuous straightening process. The maximum section flattening amount and the residual section flattening amount are important process parameters, which are the basis for calculating the subsequent process parameters of the flattening circle, and directly determine the roundness of the final pipe and the product quality. However, it is hard to be obtained by the theoretical or experimental methods. Therefore, based on the structure and process parameters of the leveler, a finite element model was built to simulate the section flattening process. Then, ANSYS/LS-DYNA software was used to dynamically simulate the bending flattening phenomenon of thin-walled pipe in the continuous straightening process, and the stress and strain nephographic of the flattening deformation zone was obtained. By recording the position curve of the key nodes in the preventing process, the section flattening amount of the thin-walled pipe in the large bending deformation stage in the continuous straightening process was determined. The simulation results show that the dynamic simulation method can effectively predict the section flattening of thin-walled pipe in the process of continuous straightening.

Elastic-plastic bending of the pipeline under combined loading

Рассмотрена задача упругопластического деформирования тонкостенной трубы при комбинированном нагружении изгибающим моментом, осевой силой и внутренним давлением. Решение задачи осуществлено по разработанной методике с помощью математического пакета Matcad численным методом, основанным на деформационной теории пластичности и безмоментной теории оболочек. Для упрощения решения предложено сведение двумерной задачи к одномерной задаче о деформировании балки, материал которой имеет различные диаграммы деформирования при сжатии и растяжении в осевом направлении. Проведено сравнение с результатами численного решения двумерной задачи методом конечных элементов в упругопластической постановке. Результаты расчета по инженерной методике совпадают с точным решением с точностью, необходимой для практического применения. Полученные результаты упругопластического решения для изгибающего момента в сечении трубопровода при комбинированном нагружении позволяют уточнить известное критериальное соотношение прочности сечения трубопровода с кольцевым дефектом в сторону снижения перебраковки. Применение разработанной методики позволяет ранжировать участки трубопровода с непроектным изгибом по степени близости к предельному состоянию при комбинированном нагружении изгибающим моментом, продольным усилием и внутренним давлением. The problem of elastic plastic deformation of a thin-walled pipe under co-binned loading by bending moment, axial force and internal pressure is considered. The problem is solved by the developed method using the Matcad mathematical package by a numerical method based on the deformation theory of plasticity and the momentless theory of shells. To simplify the solution of the problem, it is proposed to reduce a twodimensional problem to a one-dimensional problem about beam deformation, the material of which has different deformation diagrams under compression and tension in the axial direction. Comparison with the results of numerical solution of the two-dimensional problem with the finite element method in the elastic plastic formulation is carried out. The obtained results of the elastic-plastic solution for the bending moment in the pipeline section under combined loading make it possible to clarify criterion ratio of the strength of the pipeline section with an annular defect in the direction of reducing the rejection. Application of the developed approach allows to rank pipeline sections with non-design bending in the steppe close to the limit state under combined loading of the pipeline with bending moment, longitudinal force and internal pressure.

Prediction of actual limit stresses in a thin-walled pipe loaded with internal pressure and axial tension

If a thin-walled pipe loaded with internal pressure and tension allows the appearance of plastic trains, then the uniform plastic stability loss with the emergence of a local plastic deformation zone is considered the limit state, the corresponding stresses are considered as the limit. Correct prediction of the stress-strain state at the moment of strain localization requires taking into account the actual size of the loaded pipe and the calculation of true stresses. The article proposes the implementation of the method of predicting the limit values of true stresses that appear in the pipe at different ratios of internal pressure and axial tension. The physical and mechanical properties of the material, the type of stress state and the change in the actual dimensions of the loaded element are taken into account.

Experimental Study of Features of Thin-Walled Pipes Sizing in the Line of a Pipe Rolling Plant with an Automatic Mill

The aim of the study is to establish the actual level of working loads on the roll drive line of the sizing mill installed as part of the PRP-220 with an automatic mill, when switching to the production of steel pipes from increased strength group. The study is based on a complex experimental and theoretical analysis. After the processing of the results of experimental studies a comparison of the most loaded sizing route for a thin-walled pipe with a diameter of 244.5 mm and a wall thickness of 8.9 mm (D/S = 27.5) made of steel of strength group “D” was made with the route for a pipe with a diameter of 177.8 mm and a wall thickness of 9.2 mm (D/S = 19.3) from steel of strength group “E”. Graphs of the observed processes are presented, as well as calculated predictive values of sizing of thin-walled pipes for steel of strength group “E”, obtained on the basis of an experimental-theoretical analysis of the growth of flow stress. Recommendations have been given for improving the equipment of the PRP-220 sizing mill for the production of pipes with increased diameters from steels of increased strength groups.

Repair of Leaks in Thin Wall High Pressure Pipelines Using Composite Reinforcing Technologies

A study was conducted to evaluate two composite repair technologies used to reinforce severe corrosion and thru-wall leaking defects in thin-walled pipe materials; conditions where the welding of conventional Type B steel sleeves cannot be conducted. This program involved the reinforcement of simulated 85% corrosion defects in 6.625-inch × 0.157-inch, Grade X52 pipe materials subjected to cyclic pressure and burst testing. The test matrix also included repaired pipe samples with thru-wall defects that were pressurized using nitrogen gas and buried for 90 days. The program was comprehensive in that it evaluated the following elements involving a total of 81 reinforced corrosion defects. • Corrosion features with a depth of 85% of the pipe’s nominal wall thickness in thin-walled pipe material (i.e., 0.157 inches, or 4 mm). • Thru-wall defects having a diameter of 0.125 inches (3 mm). • Repairs made with leaking defects having 100 psig (690 kPa) internal pressure. • Strain gage measurement made in non-leaking 85% corrosion defects; it should be noted that the remaining “15%” ligament was 0.024 inches (0.6 mm); to the author’s knowledge, no high-pressure testing has ever been conducted on such a thin remaining wall. • Long-term 90-day test that included pressurization with nitrogen gas, followed by relatively aggressive pressure cycling up to 80% SMYS followed by burst testing. This is the first comprehensive study conducted by a major transmission pipeline operator evaluating the performance of competing composite technologies used to reinforce severe corrosion features with thru-wall defects. The reinforcement of leaks has not been accepted by regulatory bodies such as the Canadian Energy Regulator (CER), or the U.S. Pipeline and Hazardous Materials Safety Administration (PHMSA). A goal of the current study is to validate composite repair technologies as a precursor to regulatory approval. The results of this study indicate that viable composite repair technologies exist with capabilities to reinforce leaks in pipelines that experience operating conditions typical for gas transmission systems (i.e., minimal pressure cycling).

Experimental and Numerical Analysis of Ratcheting Behavior of SS 316 L Thin-Walled Pipes Subjected to Cyclic Internal Pressure

This paper investigates ratcheting behavior of SS316 L thin-walled steel pipes subjected to cyclic internal pressure experimentally and numerically. Numerical simulations were performed using abaqus software, and nonlinear isotropic/kinematic hardening model. According to experimentations, it was found that the ratcheting strain is only significant in the hoop direction of a pipe subjected to cyclic internal pressure. The effects of pressure amplitude and mean pressure on ratcheting behavior of thin walled pipe in hoop direction were studied experimentally and numerically, and it was observed that increasing the pressure amplitude and mean pressure increased the percentage of ratcheting strain. Another important point about the results was the dominance of pressure amplitude on mean pressure. The results showed that at higher mean pressures the effect of pressure amplitude on increasing the percentage of ratcheting strain was greater. Finally, the experimental and numerical results were in good agreement.