Small Steel Tubes Research Articles

Experimental investigation of Al-Fe2O3 thermite reactions for thermal plug and abandonment of oil wells

The use of thermite in the plug and abandonment of wellbores is a promising new method for sealing oil wells. However, the reactants for thermite mixtures are usually in a powder state at ambient conditions, making a perfect homogenization for high heat release a challenging task. In this sense, this study aims to investigate the Fe2O3–Al thermite system prepared through a solvent-based method to maximize homogenization of the mixture and enhance energy release during the exothermic reaction. Tests were conducted to compare the burning velocity, ejected mass percentage, and temperature profiles of the reaction through small steel-tubes, comparing a dry-mixed, stoichiometric composition with a solvent-based mixture. The effect of additives such as Al2O3 and Al were also evaluated. Results showed that the solvent-based process led to higher compactness, higher temperatures on the steel tube's exterior, a more stable reaction, and a 40% decrease in ejected material. Also, Al-rich mixtures had faster reactions, lower temperatures, and more ejected material when compared to the stoichiometric system, while Al2O3-diluted mixtures showed a linear decrease in burning velocity and mass ejection at higher dilution levels, with no significant variation in temperature levels. Mixtures with 40% or higher dilution did not self-propagate. Therefore, a thermite mixture prepared using solvent and diluted with Al2O3 at 20–30% is recommended for the thermal plug and abandonment technology.

Bending performance of NSTS members based on steel tube connection

This paper proposes a NSTS (new steel tube slab) structure by connecting the longitudinal steel tubes with small steel tubes in transverse, in order to decrease the construction difficulty and improve the bearing capacity of existing NTR (new tubular roof) or STS (steel tube slab) structures. Experimental study on the bending performance and influences of following parameters are carried out: the connection type of the steel tube, the diameter and eccentricity of the small steel tube, and the thickness of the bottom steel plate. The results show that the NSTS members present progressive ductile flexural failure under concentrated load. The connection type has important effect on the mechanical behavior, and the bolts fixed T-shaped plate (B+T) connection method, which provides much higher bending stiffness, is proved to be the most reliable connection type. The increase of small steel tube diameter enhances the bending performance as expected, which also confirms the effectiveness of the B+T connection, while the tube eccentricity presents little impact on the bearing capacity. The bottom steel plate significantly improves the bearing capacity and stiffness and reduces the mid-span deflection. Furthermore, the bending capacity calculation method is proposed and the calculated values show good agreement with the test results. Also, the effect rules of the diameter-thickness ratio of the small tube, the length-diameter ratio of the member and the thickness variety of the bottom steel plate on the bending capacity of NSTS members are further investigated based on the proposed theoretical method.

Circular fibre-reinforced polymer (FRP)-concrete-steel hybrid multitube concrete columns: Compressive behaviour

This paper presents a study on circular fibre-reinforced polymer (FRP)-concrete-steel hybrid multitube concrete columns (MTCCs), which consists of an outer FRP tube, a number of inner small steel tubes to form a “steel wall” and concrete filled in the remaining spaces. The advantages of MTCCs include excellent axial load and deformation capacities, ease of construction, elimination/mitigation of difficulties in transporting and installing large steel tubes, and possibility of optimising the arrangement of the small steel tubes to improve structural performance. A total of 7 pairs of MTCCs, 4 pairs of concrete-filled FRP tubes (CFFTs), 4 pairs of concrete-filled steel walls (CFSWs) and 3 pairs of concrete-filled steel tubes (CFSTs) were tested in the present study, with the investigated parameters covering the thickness of FRP tube, the number and type of steel inner tubes, the type of concrete and status of the steel inner tubes. The test results lead to an in-depth understanding of the behaviour of MTCCs under axial compression. Furthermore, a comparison between the test results and predictions by a model previously proposed by the authors shows that the model can reasonably well predict the axial load–strain behaviour of MTCCs but largely underestimates the ultimate strain of the specimen. This model may be used for conservative design, while further investigation is needed for the development of a more accurate model.

Karakteristik Torrefaksi dan Densifikasi Limbah Tandan Kosong Kelapa Sawit

Energy demand increases continuously due to the growth of industries. Most industries still rely on fossil fuel that its price commonly increases and the deposit in the universe decreases since it is not renewable resource. Indonesia is the largest palm oil producer in the world that has potential abundance biomass of empty fruit bunch (EFB) of oil palm. It can be alternative energy source. The EFB is commonly used as fuel for heat source of boiler jn the palm oil plant. Most applications were by conventional combustion process that has disadvantage of low energy value. The EFB was only chopped and grinded, and then dried prior to combustion process. This study investigates improvement of energy quality of EFB through torrefaction (or light pyrolysis) and densification process. The EFB was chopped in the small size and grinded in the form of fiber, then dried. The EFB fiber in small slices was pressed in a small steel tube and heated in the range of 200-300°C. The variables of study were duration and temperature of process. The initial heat value of EFB was 18,241 MJ/kg that slightly lower than its of kernel shell heat value 19.955 MJ/kg. The water content were found 6.28% and 4.31% for EFB and kernel shell respectively. Results have shown that torrefaction and densification have improved the calorific value of EFB in the range of 6.58-16.71% of its initial value. On the other hand, the energy yield has decreased to 97.54, 97.26 and 93.76% of its initial energy yield for torrefaction temperature of 200, 250 and 300°C respectively

Experiments on flexural strength on composite modular bridge pier cap for CFT columns

Modular bridge substructures consisting with Concrete-Filled steel Tube (CFT) columns, composite precast segments have been suggested to accelerate bridge construction. The precast segmental pier cap consists of a composite pier table and prestressed precast concrete segments on the table. The pier table has embedded steel sections to mitigate stress concentration at the connection between concrete pier cap and small steel tubes. The shear strength of the pier cap was obtained by extending vertical reinforcing bars from the table to the precast segment. Transverse prestressing was introduced to control tensile stresses of the segments with service loadings. Structural performance of the proposed modular system was evaluated by static tests. Test results showed that the horizontal shear force from the vertical load should be resisted by bond, friction and vertical reinforcements crossing the interface. When the anchorage of vertical reinforcements and preventing of premature fracture of prestressing steels were provided, the flexural strength of the pier cap module at the joint location showed reasonable prediction.

Experimental study on impact performance of steel tube reinforced by small steel tubes

Experimental study on impact performance of steel tube reinforced by small steel tubes

Tests and models for engineered wood product connections using small steel tube fasteners

Laminated Strand Lumber (LSL) is a type of engineered wood product widely used as a substitute for sawn structural lumber. This is because LSL can be manufactured to have superior mechanical and physical performance to competing products, including high resistance to splitting, high strength and dimensional stability. The authors studied connections in LSL with behaviour of similar connections in sawn Spruce lumber as a benchmark. Proneness to splitting is the Achilles heel of most wood-based construction materials and especially products like sawn lumber and glued-laminated-timber. This characteristic makes it especially difficult to make connections that are mechanically efficient. However, when constructing with LSL it is possible to create connections that not only have desirable response characteristics, but also achieve labour efficiencies. The particular type of connection studied by the authors uses small diameter steel tube fasteners inserted in tight-fitting holes in conjunction with steel plate elements located in slots in ends of joined members and links them together. Tube fasteners are driven perpendicular to the axes of wood members and pass through both those members and steel link elements. Tests were conducted under static tensile loads with multiple-fastener arrangements obeying spaced and end distance rules typical for solid bolts in sawn softwood lumber. The response was highly ductile and failure occurred mainly in the fasteners. Consequently the so-called European Yield Model (EYM) for doweled timber connections yields good predictions of connection strengths. A detailed finite element analysis was also performed to assist interpretation of test results and validate predictions from the EYM beyond the range of test data. The finite element model was developed using the ABAQUS software and results from that model agreed closely with experimental findings in both qualitative and quantitative aspects.

Electromagnetic Inspection Method of Outer Side Defect on Small and Thick Steel Tube Using Both AC and DC Magnetic Fields

As thick steel tubes of small diameter are used in heat exchangers in various electric power plants and petrochemical plants, the inspection of these steel tubes is very important. The outer side defects are often observed on these small steel tubes. Moreover, since these steel tubes in heat exchangers are stored as a bundle, it is necessary to inspect the outer side defects of these steel tubes from the inside of the tube. In this paper, the electromagnetic inspection method using a direct current (dc) magnetic field and an alternating current (ac) magnetic field is proposed. The behavior of flux in steel is examined using 3-D finite-element method (FEM) taking account of hysteresis (minor loop) and eddy current. It is shown that the detection of outer side defect is possible by the differential permeability of minor loop of which the position on the hysteresis loop is affected by the existence of the defect.

Wood and Engineered Wood Product Connections Using Small Steel Tube Fasteners: An Experimental Study

AbstractThe work discussed is aimed at identifying combinations of 'wood member' materials and mechanical fasteners capable of creating structural connections that have high initial stiffness, high strength and high ductility. Experimentation shows that the goal can be achieved by joining sawn wood and Engineered Wood Products (EWP) using steel tube fasteners with outside diameters up to 12.7 mm in conjunction with steel plate link elements. Wood members considered are Spruce lumber and Laminated Strand Lumber (LSL), with rectangular cross-sections. In such connections the steel plate link elements are located in slots cut into the ends of wood members so that the plates lie in planes parallel to wide faces of the joined members. Fasteners are placed in tight-fitting pre-drilled holes that penetrate both members and link elements. Connection specimens were axially loaded in tension at a loading rate that caused the maximum capacity to be reached in about 0.1 hours. All test specimens exhibited highly duct...

Pasarela metálica excéntrica suspendida y apoyada en un arco metálico en Orense, España

The article explains the design and project of a steel footbridge, suspended and supported by an eccentric arc, situated in Orense. The footbridge, known as “Bellour”, has a main span of 20 meters, with a leaned steel eccentric arc that supports the deck. The deck was designed with a uniform slope of 8%, due the difference of level between each end. It is suspended from the arc in the Orense side and supported in the other boarder, because of the headway limitations. The deck is 2,80 meters wide. The cross section is composed of a steel eccentric tube with steel cantilever beams, of variable depth, and is joined at the other edge to a small steel tube. The pedestrian zone is narrower than the board, leaving individual empty spaces at both sides, and is constituted by a structural concrete slab of 7 centimeters thick and 2 meters wide, linked to the deck top sheet, with a steel profiles. The board was designed with a structural skeleton, spine shaped, suspended or supported from the arc, and it´s joined to the skin, a rough concrete surface that avoids frost and slides due to the rain.

Wood and Engineered Wood Product Connections Using Small Steel Tube Fasteners: Applicability of European Yield Model

Capacities of wood connections with laterally loaded dowel fasteners by plastic analysis can be predicted using the European yield models (EYM) equation. The underlying concept is that failure occurs due to crushing of wood beneath fasteners and / or formation of plastic hinges in fasteners with a rigid-plastic representation of the materials involved. EYM prediction is now “the” way within design codes to calculate the maximum attainable capacity per fastener. Subsequent adjustments discount those predictions through factors which account for unequal sharing of force between fasteners and premature connection failure by fracturing. In North America the EYM is the basis for lateral load capacities of connections made with bolts, drift-pins, screws, nails, and timber rivets. This paper addresses the capability of the EYM for predicting load carrying capacities of solid wood (sawn softwood lumber) and laminated strand lumber (LSL) connections employing tight-fitting steel tube fasteners with external diamet...