Steel Tube Research Articles

Tests on Mechanical Properties of Concrete-Filled Double-Skin Circular Steel Tubes Connected by Thread Under Axial Compression

Tests on Mechanical Properties of Concrete-Filled Double-Skin Circular Steel Tubes Connected by Thread Under Axial Compression

Mechanical properties of geopolymer recycled concrete infilled steel tubes with three sectional types

The steel tubes with geopolymer recycled concrete (GRC) infill are actively seeking environmentally friendly and low-carbon building materials as alternatives in the process of promoting sustainable development, maximizing the use of waste materials and resources, and reducing consumption of natural resources and environmental pollution. In this paper, three types of steel tube specimens with GRC infill were proposed, i.e., the geopolymer recycled concrete-filled steel tube (GRCFST), geopolymer recycled concrete-filled double skin steel tube (GRCFDST), and geopolymer recycled concrete-filled double section steel tubes (GRCFDSST). These GRC-steel tube structures were tested under axial compressive loading, and the influence of some crucial factors on bearing capacity, ductility and strain distribution of specimens was considered, such as the slag content, and the types of steel tube section and the replacement rate of recycled aggregate. The experimental results show that the steel tube can provide effective confinement for geopolymer recycled concrete and thus compensate for the adverse effect induced by recycled aggregate. The slag content has less effect on the bearing capacities of the GRCFDSST specimen compared with the GRCFST and GRCFDST specimens due to the stronger confinement effect of the former. The ductility of GRCFDSST specimens is better than the other steel tube specimens under the same parameter conditions. This study, building on existing literature, provides new insights and design recommendations for the mechanical performance of concrete-filled steel tube structures by using geopolymer recycled concrete as a filling material.

Shaking table test-based numerical study on post-buckling ULCF fracture behavior of partially concrete filled steel tubular piers

Steel structures may undergo local buckling deformation or ultra-low cycle fatigue (ULCF) fracture due to stress concentration under earthquake excitations, and the stress concentration may further develop after buckling deformation, thus leading to ULCF fracture. To investigate the post-buckling fracture behavior of partially concrete-filled steel tube (PCFST) piers under earthquake exactions, a new ULCF analysis method that integrates three fracture indexes of cyclic void growth model (CVGM) was proposed in this study based on a shaking table test of PCFST piers, and then the index for quantifying the buckling deformation of PCFST piers was developed to study the post-buckling ULCF mechanism. Finally, the effect of each design parameter on the ULCF fracture index was analyzed. The results indicate that all three indexes of CVGM can accurately predict the triggering time, crack location, and crack propagation of ULCF fracture after buckling. The failure mechanism of PCFST bridge piers experiencing post-buckling fracture is also revealed, i.e., under repeated lateral loads, the plastic hinge region at the pier bottom bulges, causing an expansion of the plastic region. Meanwhile, the cumulative rate of ULCF damage rapidly increases during the expansion process and slows down after the bulge reaches the maximum stable value until the cumulative damage value meets the fracture condition. In addition, the results of the parametric analyses indicate that the model with high ductility can undergo a greater number of cycles before localized instability failure, and thus is more likely to suffer ULCF fracture first.

Experimental Study on the Detection of the Existence and Location of Mimicked and Unexpected Interface Debonding Defects in an Existing Rectangular CFST Column with PZT Materials.

Interface bonding conditions between concrete and steel materials play key roles in ensuring the composite effect and load-carrying capacity of concrete-steel composite structures such as concrete-filled steel tube (CFST) members in practice. A method using both surface wave and electromechanical impedance (EMI) measurement for detecting the existence and the location of inaccessible interface debonding defects between the concrete core and steel tube in CFST members using piezoelectric lead zirconate titanate (PZT) patches as actuators and sensors is proposed. A rectangular CFST specimen with two artificially mimicked interface debonding defects was experimentally verified using PZT patches as the actuator and sensor. By comparing the surface wave measurement of PZT sensors at different surface wave travelling paths under both a continuous sinusoidal signal and a 10-period sinusoidal windowed signal, three potential interface debonding defects are quickly identified. Furthermore, the accurate locations of the three detected potential interface debonding defects are determined with the help of EMI measurements from a number of additional PZT sensors around the three potential interface debonding defects. Finally, the accuracy of the proposed interface debonding detection method is verified with a destructive observation by removing the local steel tube at the three detected interface debonding locations. The observation results show that the three detected interface debonding defects are two mimicked interface debonding defects, and an unexpected debonding defect occurred spontaneously due to concrete shrinkage in the past one and a half years before conducting the test. Results in this study indicate that the proposed method can be an efficient and accurate approach for the detection of unknown interface debonding defects in existing CFST members.

Study of the UHPC–NC Interfacial Bonding Properties of Steel Tubes with Internally Welded Reinforcement Rings

Ultra-high-performance concrete (UHPC) has the advantages of high strength, excellent durability performance, etc., and its compressive strength is several times that of normal concrete (NC). Due to the role of materials such as steel fibers, the tensile strength of UHPC is higher than that of NC. For steel-tube concrete columns in corrosive seawater environments, UHPC–NC columns with welded ring reinforcement inside the steel tube are proposed to strengthen the interfacial bonding performance, and the effects of seawater corrosion of steel-tube concrete are studied. Eight steel-tube UHPC–NC specimens were designed for push-out tests. The steel tubes were internally constructed with glossy unconstructed and reinforcing rings, with the core concrete with UHPC used below and the C40 plain concrete used above. By examining push-out load, slip displacements, and steel-tube wall strains, this study analyzed the influence of different factors on the bond behavior and failure mechanism of bond-slip in shear-resistant reinforcing ring connectors. The push-out simulation of the steel-tube concrete was carried out using ABAQUS 2021 software, and the simulation results were compared with the experimental results, which showed good agreement. The results show that the bond strength of the steel tube–concrete column interface can be significantly improved by using the construction measures of internally welded reinforcement rings; for specimens with the same percentage of core concrete UHPC and C40 thickness, the bond strength of the two rings was significantly improved by approximately 33% over that of the one-ring reinforcement ring; corrosive environments will degrade the bond strength of the steel tube–concrete column interface.

Behaviour of high-performance alkali-activated slag concrete-filled double-skin steel tubes under compression loading

Behaviour of high-performance alkali-activated slag concrete-filled double-skin steel tubes under compression loading

Mechanical response of long-span CFST arch bridges based on the hydration heat temperature effect

As the span of concrete-filled steel tube (CFST) arch bridges increases, the hydration heat temperature effect of concrete inside steel tube becomes more severe, which increases the safety risk during the construction process. Therefore, a numerical simulation of the mechanical response of a long-span CFST arch bridge under the influence of hydration heat was carried out. First, based on the hydration heat conduction theory, a finite element model of the transient temperature field of a CFST arch rib was established. The temperature distribution of the CFST arch rib and its variation with time were revealed, and an approximate formula for the distribution of the hydration heat temperature along the radial direction of the CFST was provided. Subsequently, the variation law of the thermal stress of a CFST during hydration heat release was investigated. Finally, based on the principle of temperature equivalence, a finite element model of the overall CFST arch rib was established to examine the effect of hydration heat on the deformation of the arch rib. The results reveal that the hydration heat temperature field of the CFST arch rib exhibits nonlinear and axisymmetric characteristics. The maximum temperature of the section and the maximum temperature difference can reach 73.5 °C and 33.2 °C, respectively. Because of the influence of the hydration heat, there is a significant stress gradient in the cross section of the arch rib. A maximum radial stress of 2.08 MPa is attained, indicating a risk of concrete cracking. Additionally, the displacement along the transverse and vertical directions of the chord tube exhibits an initial increase, followed by a decrease over time. The maximum transverse displacement of the chord tube reaches 70.6 mm, while the vertical displacement reaches 117.8 mm.

Joining of Al-Alloy Tubes by Carbon Steel Tubes using MPW Technique

Background/ Objectives: Joining aluminum alloys with low carbon steel (DC01) through fusion welding is a challenging task due to the occurrence of solidification defects like porosity, alloy segregation, and hot cracking. However, these issues can be addressed by employing solid-state welding techniques like explosive welding and MPW (magnetic pulse welding). MPW is a cost-effective and high-speed solid state welding method that involves creating joints in an overlap configuration. Methods: The MPW technique was employed to join dissimilar aluminum alloy AL 7075T6 hollow tube and DC01 steel rod in this study. A central composite design model was created to analyze the relationship between key MPW process parameters, including stand-off distance (SoD), overlap length, and discharge energy, and the bonding strength of the joints. Experimental setups were established and correlate with tensile-shear fracture load and interface hardness of the joints with the MPW process parameters. Findings: It is understood that the maximum TSFL of 2.404 kN was obtained under the welding condition of 23kJ discharge energy, 2.25 mm Stand-off distance, 8.5 mm overlap length, which is the optimum MP welding state for AA 7075 T6 with DC01 and confirmed by RSM. In addition, the cultivated connection can be aptly leveraged to anticipate the TSFL of MPW joints with a 95% confidence level. Novelty: The parametric mathematic samples were developed for forecasting TSFL of joints. The MPW parameters were optimized to enhance TSFL of joints. Aluminium alloys with low carbon steel joints were developed using MPW for cars and ships applications without fusion welding defects. Keywords: Magnetic Pulse Welding, Dissimilar Joint, (RSM) Response Surface Methodology, Tensile Shear-Fracture Load

Designing prepacked aggregate concrete for improved mechanical properties and its field application in constructing steel tube concrete

Prepacked aggregate concrete (PAC) is made by placing coarse aggregates of various sizes into a formwork and then filling the voids between coarse aggregate and grout. The mechanical performance of PAC is dominated by the compactness due to grout filling, but few study considered the pouring methods and grout performance synchronously. The coupled effect of pouring methods and grout performance on the compactness of PAC is investigated in this study. The results show that the gravity pouring method is only suitable for grouts with good flowability. The pump pouring method is more widely used. It can be adapted to grout with poorer fluidity and coarse aggregate with greater apparent density. The ultrasonic pulse velocity test method provides a relatively accurate evaluation of the compactness of PAC. Furthermore, due to the enhanced mechanical properties of PAC, the filed application potential in the preparation of steel tube concrete columns has also been confirmed, where the results exhibited that PAC based steel tube concrete contributed to an enhanced ductility and autogenous shrinkage.

A Critical Review of Cold-Formed Steel Built-Up Composite Columns with Geopolymer Concrete Infill

Concrete-filled built-up cold-formed steel (CFS) columns offer enhanced load-carrying capacity, improved strength-to-weight ratios, and delayed buckling through providing internal resistance and stiffness due to the concrete infill. Integrating sustainable alternatives like self-compacting geopolymer concrete (SCGC) with low carbon emissions is increasingly favoured for addressing environmental concerns in construction. This review aims to explore the current knowledge regarding CFS built-up composite columns and the performance of SCGC within them. While research on geopolymer concrete-filled steel tubes (GPCFSTs) under various loads has demonstrated high strength and ductility, investigations into built-up sections remain limited. The literature suggests that geopolymer concrete’s superior compressive strength, fire resistance, and minimal shrinkage render it highly compatible with steel tubular columns, providing robust load-bearing capacity and gradual post-ultimate strength, attributed to the confinement effect of the outer steel tubes, thereby preventing brittle failure. Additionally, in built-up sections, connector penetration depth and spacing, particularly at the ends, enhances structural performance through composite action in CFS structures. Consequently, understanding the importance of using a sustainable and superior infill like SCGC, the cross-sectional efficiency of CFS sections, and optimal shear connections in built-up CFS columns is crucial. Moreover, there is a potential for developing environmentally sustainable built-up CFS composite columns using SCGC cured at ambient temperatures as infill.

Axial compressive behavior of reinforced hollow circular high strength concrete filled steel tubular short columns

This study aims to investigate the mechanical behavior of reinforced hollow circular high-strength concrete-filled steel tubular (RHCFST) short columns under axial compression. The axial compression test of 6 RHCFST short columns was carried out, and the bearing capacity, ductility and failure modes of the columns were analyzed. The results revealed that the failure modes of RHCFST short columns primarily included mixed failure, shear failure, and crushing failure. Comparatively, the failure modes of specimens with ordinary reinforcement exhibited a shift towards mixed failure, significant improvement in ductility, and a decrease in the increase trend of ultimate bearing capacity with the growth of steel tube thickness. Based on the test results, finite element models were developed using ABAQUS software for parameter analysis. The results demonstrated a positive correlation between the short column’s bearing capacity and parameters such as steel strength, sandwich concrete strength, steel tube thickness, and ordinary reinforcement diameter. Additionally, the initial stiffness of the short column increased with the increase of steel tube thickness. Considering the mechanical properties and engineering applicability of the member, the recommended design of steel tube yield strength, sandwich concrete strength, steel tube thickness and ordinary reinforcement diameter were given. Furthermore, the axial bearing capacity calculation formulae for RHCFST short columns were proposed. The calculated values were found to closely match both experimental and simulated values, with errors falling within 10 %. Consequently, the formulae can offer a reliable prediction of the member’s axial bearing capacity.

Cyclic performance of precast steel beam-to-CECFST column exterior sub-assemblages with dry connections: Experimental studies and mechanism analyses

Combining advantages of both reinforced concrete (RC) and concrete-filled steel tube (CFST), concrete-encased concrete-filled steel tube (CECFST) members demonstrate superior structural performance over pure RC or CFST counterparts. Nevertheless, current research in this domain has primarily focused on member and connection behaviour of CECFST columns, with no attention given to frame-level performance. This significantly impedes applications of this form of high-performance composite members into actual engineering practice. To bridge this research gap, a novel precast steel beam-to-CECFST column composite system is proposed in this study. This is followed by a comprehensive experimental programme, where seven precast steel beam-to-CECFST column exterior sub-assemblages were tested under cyclic loads. In the test specimens, three types of connections, including beam-to-beam (B-B), column-to-column (C-C) and beam-to-column (B-C), were incorporated to establish a precast steel beam-to-CECFST column sub-assemblage. Horizontal displacement versus shear force relationship and failure mode of the test specimens are reported, followed by a detailed analysis of test results and findings. Furthermore, a comprehensive mechanism analysis is presented, with emphasis on energy dissipation behaviour and deformation mechanism of the proposed precast composite system. The test results show that the proposed precast composite system has comparable load-carrying capacity and energy dissipation capacity in comparison with conventional cast-in-place counterparts. This indicates that despite using precast beam-to-beam and column-to-column connections, structural performance of the composite frame system would not be significantly affected, showing that this form of precast steel beam-to-CECFST column composite system has considerable potential to be adopted in actual engineering practice.

Stability Investigation of Fully Recycled Support System of Steel-Pipe-Anchored Sheet Pile in Soft Soil Excavation

As a temporary project, the supporting system of excavation often encounters issues such as the waste of support components, environmental pollution, and high carbon emissions. This article presents a foundation pit support technology that utilizes steel tube anchorage sheet piles, which can be assembled and fully recycled. The composition of the support system is also introduced. Furthermore, a large-scale model test of steel-pipe-anchored sheet piles was designed and implemented. The displacement of each component of system and stability during excavation were investigated using 3D finite element modeling and analysis. The study results indicate that the deformation and failure mode of the model foundation under the steel-pipe-anchored sheet pile support system are closely related to the distance between the pipe pile and the sheet pile. When the distance is 10 cm, both the pipe pile and the sheet pile tilt simultaneously. When the distance is approximately 30–50 cm, the sliding surface becomes exposed from the position of the pipe pile. At distances up to 100 cm, the sliding surface is exposed between the pipe pile and the sheet pile. The anchoring effect of pipe piles and tie rods can effectively reduce the horizontal displacement of the sheet pile itself. The horizontal displacement at the top of both the pipe pile and sheet pile remains consistent throughout the excavation period of this model foundation. During excavation, measured earth pressure on the sheet pile is less with theoretical active earth pressure. After excavation, the maximum horizontal displacement of the top of the pipe pile exhibits a hyperbolic relationship with excavation depth.

Stabilizacja zboczy podatnych na osuwiska za pomocą kotew rurowych

This paper presents an anchor of a new design, whose properties have been selected to retain the advantages of a tubular anchor over the other anchor types and at the same time, ensure its adaptation to specific conditions associated with slope stabilization. The proposed anchor consists of a steel tube filled with expanding cement mortar. The outer diameter of the tube is 2-3 mm less than the diameter of the borehole, a groove is cut on the outer surface of the tube. A metal rod is placed in the center of the tube at the outer end of which a support plate is installed, and a tie wrench is fixed. The length of the metal rod is equal to the depth of the bore hole, while the length of the steel tube is at least half the length of the borehole. In the process of solidification and expansion of the solution, pressure is created on the walls of the bore hole. Under the influence of pressure, the pipe is opened around the groove and close contact is achieved between the pipe and the borehole surfaces. As soon as the solution hardens, the steel tube is firmly embedded in the concrete, after which the anchor reaches operational capacity. Preliminary tests of the proposed anchor showed that it has a high clamping force (for hard rock conditions - 46-75 kN/m and for soft rock conditions 32-36 kN/m). He has other advantages, namely it does not require special equipment for installation, the inside of a tube is filled with hard concrete-like mass, which hampers the process of corrosion and increases shear strength.

PEMBUATAN PADUAN INTERMETALIK Mg2Si DENGAN DOPING BISMUTH SEBAGAI MATERIAL TERMOELEKTRIK

Increasing efficiency in gasoline fuel consumption in motorized vehicles is currently continuing. One way this is done is by making use of the energy that is lost during the combustion of a motorcycle engine. About half of the energy produced during burning will be lost due to heat energy and exhaust gases. This waste heat can be utilized by converting it into another form of energy. Thermoelectric materials are those that can convert heat energy into electricity directly. Thus, in this work, we synthesized the bismuth-doped Mg2Si thermoelectric material using a solid-state reaction method using a powder in a sealed tube technique. The initial step in the production process involves measuring the raw materials bismuth, silicon, and magnesium using the Mg2Si1-xBix formula (x = 0.00, 0.025, and 0.045). The raw material powder is grinded in a shaker mill before being sealed in a stainless steel tube. The powder is sealed in a tube and heated to 800 °C for 6 hours. According to XRD test results, the Mg2Si phase and Si and MgO phases have formed. The lattice constant of the cubic Mg2Si phase was found at ~0.636 nm. A SEM investigations of surface morphology suggest that bi-doping on Si sites influences grain size refinement. Therefore, it can be concluded that the Mg2Si intermetallic alloy production process was successfully completed.

Machine learning and nonlinear finite element analysis of fiber‐reinforced polymer‐confined concrete‐steel double‐skin tubular columns under axial compression

AbstractFiber‐reinforced polymer (FRP)‐confined double‐skin tubular columns (DSTCs) are an innovative type of hybrid columns that consist of an outer tube made of FRP, an inner circular steel tube, and a concrete core sandwiched between them. Available literature focuses on hollow DSTCs with limited research on DSTCs made with inner steel tubes filled with concrete. Overall, DSTCs have many applications, highlighting the importance of studying the effects of concrete filling and strength on the composite system. To address this gap, finite element models (FEMs) and both traditional and innovative machine learning (ML) techniques were used to develop accurate models for predicting load‐bearing capacity and confined ultimate strain under axial loads. A comprehensive database of 60 experimental tests and 45 FEMs simulations of columns was analyzed, with five parameters selected as input variables for ML‐based models. New techniques like gradient boosting (GB), random forest (RF), convolutional neural networks, and long short‐term memory are compared with established algorithms like multiple linear regression, support vector regression (SVR), and empirical mode decomposition (EMD)‐SVR. Regression error characteristics curve, Shapley Additive Explanation analysis, and statistical metrics are used to assess the performance of these models using a database containing 105 FEMs test results that cover a range of input variables. While EMD‐SVR and GB perform well for confined ultimate strain, the suggested EMD‐SVR, GB, and RF models show superior predictive accuracy for confined ultimate load. To be more precise, for confined ultimate load prediction, EMD‐SVR, GB, and RF obtain values of 0.99, 0.989, and 0.960, respectively. The values for GB and EMD‐SVR at confined ultimate strain are 0.690 and 0.99, respectively. However, design engineers are limited by the “black‐box” nature of ML. In order to solve this, the study presents an open‐source GUI based on GB, which gives engineers the ability to precisely estimate confined ultimate load and strain under various test conditions, enabling them to make well‐informed decisions about mix proportion.

Experimental response characterization and comparative seismic performance assessment of a long-stroke shape memory alloy bridge restrainer

In this study, a long-stroke SMA Restrainer (LSR) device was fabricated and its response was characterized through experimental testing. The LSR consists of a long SMA bar encased in a steel tube to prevent its buckling. First, an optimal heat treatment procedure was identified to obtain superelastic response for SMA bars. Subsequently, the LSR underwent testing using an increasing amplitude tension-compression loading protocol and its mechanical properties such as equivalent stiffness and equivalent viscous damping ratio were computed. Based on the experimental findings, a high-fidelity 3D finite element model of LSRs was developed, which then used to design a full-scale LSR and verify its performance. Nonlinear time history analyses were conducted to assess the seismic performance of the proposed restrainers when used in a four-span simply supported bridge structure. The response of a case-study bridge equipped with steel cable restrainers, SMA bar restrainers, or LSRs were comparatively evaluated using a set of 40 near-fault ground motion records. Both SMA bar restrainers and LSRs were able to effectively limit the displacement response and provide the re-centering capabilities, while LSRs producing similar moments on piers compared to steel cable restrainers. In addition, compared to tension-only SMA bar restrainers, the LSRs require about only a quarter of SMA materials used in SMA bar restrainers.

Axial Compressive Performance of L-Shaped Columns Composed of RAC-Filled Steel Tubes

Axial Compressive Performance of L-Shaped Columns Composed of RAC-Filled Steel Tubes

Hybrid particle swarm optimization and group method of data handling for the prediction of ultimate strength of concrete-filled steel tube columns

This study presents a hybrid model coupling particle swarm optimization (PSO) with group method of data handling (GMDH) for predicting the ultimate strength of rectangular concrete-filled steel tube (RCFST) columns. A large database of 490 data samples collected from the existing literature was used to construct the model. Compared with the optimal model among the nine existing models, the coefficient of variation (COV), mean absolute percentage error (MAPE) and root relative squared error (RRSE) values of all datasets of the PSO-GMDH model were decreased by 58.38 %, 69.22 % and 64.27 %, respectively; while the coefficient of determination (R2) and a20-index values were increased by 34.32 % and 8.65 %, respectively. The results show that the predicted results of PSO-GMDH model are in good agreement with the experimental results and can accurately predict the ultimate strength of rectangular RCFST columns. In addition, a graphical user interface (GUI) has been developed to facilitate the application of the PSO-GMDH model.

Enhancing thermal performance of heat exchanger by using different 4-lobed swirl tube arrangements

This study numerically and experimentally investigated the thermal performance of a 4-lobed swirl tube. A double-pipe heat exchanger was built using 3D-printed steel tubes with PD ratios ranging from 4, 6 to 8. In addition, a 3D-printed circular pipe was also manufactured to investigate the influence of the 3D-printing method. In the experimental results, the PD4 decaying swirl tube had the highest performance for all PD ratios. The effects of different pitch-to-diameter (PD) ratios and tube arrangements on the swirl pipe were also investigated during simulations. The results reveal that the tube with a smaller PD ratio and crossover arrangement has a larger thermal enhancement and pressure drop. However, in comparison, the decaying arrangement has a relatively higher overall performance since it has a lower pressure drop. The PD6 decaying tube arrangement is the highest, especially at higher Reynolds numbers. Moreover, by showing the streamline within the swirl tube, small-scale vortices are found within the swirl tube, especially in the crossover arrangement. These vortices are formed due to the swirl motion and can enhance mixing and the heat transfer rate. Based on these simulation results, a regular-spaced swirl tube arrangement is proposed and its thermal performance is evaluated. In the experimental results, the PD4 decaying swirl tube gave the highest overall performance from 1.12 to 1.09 across all configurations. In the numerical results, the regularly-spaced swirl tube can further improve the overall performance with moderate pressure drop. Type 2 PD4 has the highest performance value at 1.06.