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The energy absorption behavior of nested tubes under lateral loading conditions was investigated in this study. Nested tubes are considered as an alternative to energy absorption structures used in many industries including automotive, military, and aerospace. Steel tubes with the same wall thickness and different diameters were used in the experiments. First, experiments of single tubes were carried out, and the deformation behavior of tubes under lateral load was examined in detail. Afterward, experiments were carried out on nested tube samples in which a minimum of 2 and a maximum of 6 tubes were used together in different numbers and sequences. It was seen from the experiments that the best-nested tube configuration in terms of energy absorption capacity was the sample that contains 6 tubes with 1767 J. While this sample absorbed 5% higher energy than the sample with 5 tubes, the specific energy absorption value was calculated to be 10% lower. Additionally, the sample with 6 tubes has a value of 43% in terms of energy efficiency which is 7% lower compared to that of the sample with 5 tubes. It was determined that the sample with 5 tubes yielded the most efficient design when specific energy absorption capability, work effectiveness, and energy efficiency parameters were considered.

The punching shear failure of reinforced concrete (RC) flat slabs is an undesirable type of failure, as it is sudden and brittle. This paper presents an experimental and numerical study to explore the behavior of flat slabs made of different types of concrete under the influence of punching shear. Experimental tests were carried out on four groups of flat slabs, each group representing a different type of concrete: ordinary normal concrete (NC), high-strength concrete (HSC), strain-hardening cementitious composite concrete (SHCC), and ultra-high-performance fiber concrete (UHPFC). Each group consisted of six slabs, one representing an unreinforced control slab other than the reinforcement of the bottom mesh, and the others representing slabs internally reinforced with SHCC-filled steel tubes and high-strength bolts. An analytical equation was used to predict the punching shear capacity of slabs internally reinforced using steel assemblies. A numerical model was proposed using the ABAQUS program, and was validated by comparing its results with our experimental results. Finally, a case study was performed on large-scale slabs. The results showed that using steel assemblies inside NC slabs increased the slab’s punching shear capacity but does not completely prevent punching shear failure. Internally unreinforced slabs made of UHPFC and SHCC were able to avoid punching shear failure and collapse in a ductile bending pattern due to the high compressive and tensile strength of these types of concrete. The proposed analytical method succeeded in predicting the collapse load of slabs reinforced with steel assemblies with a difference not exceeding 9%.

This paper deals with the comparison of the seamless pulling process of precision seamless tubes using two different reductions from the viewpoint of geometrical stability using computerized tomography, from the point of view of mechanical properties, from the point of view of the surface temperature in the arrangement of the tribological tube-tool pair. Validation of the pipe drawing process also took place based on the finite element method in the simulation program DEFORM 3D. From the point of view of production rationalization, it is necessary to analyze stress and deformation states at different input dimensions for a particular final dimension for a given drawing method, in this case, a drawing whiteout plug method was used.

The present study aimed at evaluating the mechanical performance under bending loads of circular hollow sections of steel. Different bending tests have been carried out by applying two-point loads, to determine and examine the effects of the diameter, the thickness of the section, and the span of the beam on the performance of the steel tube. The effects of square opening and variation in the number of openings on the performance of these sections have also been examined. Ten samples of hollow circular beams of varying thickness (2 mm, 3 mm, and 6 mm), varying diameter (76.2 mm, 101.6 mm, and 219 mm), and varying span (1000 mm, 1500 mm, and 2000 mm) were fabricated and tested for pre-failure and post-failure stages. The dimensions of the reference specimen considered were 3 mm in thickness, 101.6 mm in diameter, and 1500 mm in span. The results have shown that on increasing the section thickness by 200%, ductility and bearing strength were enhanced by 58.04% and 81.75%, respectively. Meanwhile, decreasing the section thickness by 67%, ductility and bearing strength were reduced by 64.86% and 38.87%, respectively. Moreover, on increasing the specimen diameter and on decreasing span, a significant increase in bearing strength and stiffness was observed; however, ductility was reduced. Meanwhile, on increasing the span of the specimen, all the parameters observed, i.e., bearing strength, stiffness, and ductility, decreased. On observing the ultimate strength of each specimen with square opening, the ultimate strength was reduced by 17.88%, 19.71%, and 14.23% for one, two-, and three-square openings, respectively. Moreover, the ductility was significantly reduced by 72.40%, 67.71%, and 60.88% for one, two-, and three-square openings/apertures, respectively, and led to the sudden failure of these specimens. The local buckling failure dominated for specimens having a D/t ratio more than 50 and showed very negligible levels of ovalization of the cross-section. Local buckling failure was observed to be prevented after providing the circular rings in the specimen, since bearing strength increased compared with the specimen without rings.

Circular hollow steel tube columns are widely used in high-rise buildings and bridges due to their ductility and lower weight compared to reinforced concrete. The use of this type of steel section has several advantages over using reinforced concrete members. The present study investigates the bending behavior of steel circular hollow sections when subjected to bending loads. The variations in material characteristics with regard to position along the cross-section of a steel tube member is first considered in this experimental study, providing for a more accurate definition of the material behavior in the model. A supported beam tested by two-point loads is the loading type that is used to study the bending performance of steel tubes. Ten circular hollow beam specimens were prepared and tested up to and post the failure stage with the following dimensions: thickness (2, 3, and 6 mm), diameter (76.2, 101.6, and 219 mm), and span (1000, 1500, and 2000 mm). A finite element analysis has been conducted for these ten specimens using the ANSYS program. The finite element model is compared to experimentally obtained data to verify that both local and global behaviors are correctly considered. The load-deflection results of this analysis showed a good agreement with the experimental results. A parametric study also was performed that considered two variables, which were the effect of the presence of circular rings and the change of opening location in the length direction on the specimens’ behavior. This study showed that the presence of the circular rings in the specimen led to an increase in its ultimate strength (of 53.24%) compared with the non-presence of these rings. In contrast, the presence of openings at 30, 40, and 50% from the specimen length reduced the strength capacity by 8.76, 14.23, and 17.88%, respectively.

Corrosion protection is one of the most frequently addressed issues in metallurgic and engineering applications. Oil film coating of inaccessible areas such as interior of a steel pipe is technically complicated. Because of that, the choice of the interior pipe film coating via oil mist is a viable solution. However, it is necessary to establish what will be the composition of the oil layer and what distance the required oil thickness will span. These are the aspects dealt with in the present paper.

Multi-rifled tubes, i.e. tubes with multiple inner grooving are used in heat exchangers and boilers, providing favourable heat transfer conditions due to turbulent flow of cooling medium. Therefore, strict requirements are placed on the geometry of inner rifling. In production of such tubes, cold drawing with free-to-rotate rifled plug is the final drawing operation to achieve required dimensions. A Finite Element Method (FEM) based numerical model of the process was prepared in order to optimize the geometry of the die. The results of numerical simulations for two different die geometries show the difference in material flow and corresponding drawing force. The final dimensions of the tubes after drawing were compared with the customer`s requirements and a good agreement was found.

This experimental study presents concrete-filled double-skin tubular columns and demonstrates their expected advantages. These columns consist of an outer steel tube, an inner steel tube, and concrete sandwiched between two tubes. The influence of the outer-to-inner tube dimension ratio, outer tube to thickness ratio, and type of inner tube material (steel, PVC pipe) on the ultimate axial capacity of concrete-filled double-skin tubular columns is studied. It is found that the yield strength of the inner tube does not significantly affect the ultimate axial capacity of concrete-filled double-skin tubular composites. With the replacement of the inner tube of steel with a PVC pipe, on average, less than 10% strength is reduced, irrespective of size and dimensions of the steel tube. Hence, the cost of a project can be reduced by replacing inner steel tubes with a PVC pipes. Finally, the experimental results are compared with the existing design methods presented in AISC 360-16 (2016), GB51367 (2019), and EC4 (2004). It is found from the comparison that GB51367 (2019) gives better results, followed by AISC (2016) and EC4 (2004).

This paper presents chosen results of experimental and numerical research of ballizing process of the steel tubes. Ballizing process is a method of burnishing technology of an internal diameter by precisely forcing a ball through a slightly undersized pre-machined tubes. Ballizing process is a fast, low-cost process for sizing and finishing tubes. It consists of pressing a slightly oversized ball through an unfinished tube to quickly bring the hole to desired size. The ball is typically made from a very hard material such as tungsten carbide or bearing steel. Ballizing process is by cold surface plastic forming of the surface structure, thereby leaving a layer of harder material and reducing its roughness. After theoretical and experimental analysis it was determined that the smaller the diameter of the balls, the bigger intensity of stress and strain and strain rate. The paper presents influence of ballizing process on the strain and stress state and on the surface roughness reduction rate of the steel tubes.

A numerical approach has been developed for the analysis of composite joints of steel tubes embedded in reinforced concrete. This kind of joint is typically found at the foundation of composite columns and in open pile supported wharves. The performance of such joints is thought to have a considerable effect on the overall behaviour and ductility of the structures containing them as indicated by previous experimental and analytical work. The developed approach was based on a two-stage two dimensional analysis to account for the three dimensional nature of the joint behaviour. The validity of the new approach was proven by applying it to previously experimentally tested composite joints. Good agreement was observed between the joint behaviour as produced by the numerical analysis using the new approach and the experimental measurements. Considerable saving in computer run time was also achieved compared to the case of using three dimensional analysis.

One simple, efficient, reliable, and inexpensive method to protect the inner surface of slim tubes prior to exposure to corrosion is to apply a dispersed oil fraction through a nozzle and a mixing valve to prepare a mixture of air and oil applied on the texture in a suitable form. The problem, in particular, is in transporting the oil micro particles to the distal end of the lean tube. The method also has an ecological effect, since other known “soaking” methods of oil application onto the inner surface of slim tubes require long and laborious cleaning methods with higher oil consumption. This method was experimentally verified by measurement and modal simulation in Ansys CFX 19.1 software. The results indicate the possibilities of using the method in practice. However, there are a few rules and recommendations to follow when applying this solution strategy.

The main objective of this investigation is to assess the feasibility of strengthening square hollow steel tubular sections subjected to compression and to develop or predict the suitable wrapping scheme of fibre reinforced polymer (FRP) to enhance the structural behaviour of it. For this study, compact mild steel tubes were used with the main variable being FRP characteristics. Carbon fibre has been considered and used as strips with several other parameters such as the number of layers, width and spacing of strips, the sectional area of strips, and wrapping scheme. Experiments were undertaken until column failure to fully understand the influence of FRP characteristics on the compressive behaviour of square hollow steel tubes including their failure modes, stress-strain behaviour, enhancement in load carrying capacity and effect of distribution of CFRP layers. The behaviour of externally bonded hollow steel tubular sections was compared with one another and also with the control specimen. From the test results, it was found that CFRP strengthening significantly increases the load carrying capacity and ductility of the hollow steel tubular members further.

Abstract This paper presents an exact model for studying the global buckling of concrete-filled steel tubular (CFST) columns with compliant interfaces between the concrete core and steel tube. This model is then used to evaluate exact critical buckling loads and modes of CFST columns. The results prove that interface compliance can considerably reduce the critical buckling loads of CFST columns. A good agreement between analytical and experimental buckling loads is obtained if at least one among longitudinal and radial interfacial stiffnesses is high. The parametric study reveals that buckling loads of CFST columns are very much affected by the interfacial stiffness and boundary conditions.