Steel Tube Research Articles

Hysteretic behavior optimization of hollow laminated viscoelastomer-filled steel tube damper

This study proposes a shape optimization approach for designing hollow laminated viscoelastomer-filled steel tube dampers (HLVSTDs), aiming to reduce stress concentration, enhance energy dissipation capacity, and improve low-cycle fatigue performance. The shape optimization curve is obtained based on the definition of stress contours for HLVSTD bending moments and shear forces, with the assumption that points on the same contour yield simultaneously. Cyclic loading experiments were conducted on four HLVSTDs. Numerical models were established and validated to further investigate the mechanical properties, energy dissipation capacity, and seismic performance of the shape-optimized HLVSTDs. The results demonstrate that the shape-optimized HLVSTDs specimen exhibits excellent energy dissipation capacity and improved low-cycle fatigue performance. The calculated initial stiffness and yield force closely align with experimental values. Compared to non-optimized HLVSTDs, the shape-optimized HLVSTDs exhibit more uniform stress and equivalent plastic strain distributions, effectively reducing the concentration of plastic strains. Additionally, structures equipped with shape-optimized HLVSTDs demonstrate superior seismic performance.

Axial compression performance of concrete-filled steel tubular columns with damaged BFRP jackets

Concrete-filled basalt fiber reinforced polymer (BFRP) -steel composite tube (CFBCT) columns have become a highly anticipated composite structure. The lateral confinement provided by BFRP can effectively suppress the possible local buckling of the steel tube, thereby achieving the goal of optimizing axial compression performance. With the widespread application of CFBCT in engineering practice, the BFRP outer layer is likely to be affected by factors such as construction accidents or connection design, resulting in slotting and drilling damage to the BFRP outer layer. Therefore, the mechanical properties of CFBCT subjected to local damage are critical. This article examined the effects of slotting and drilling the BFRP outer layer on the axial compression performance. The non-uniform strain distribution at the damaged site was analyzed using digital image correlation (DIC) testing technology. The results show that the local damage can lead to a decrease in the bearing capacity and ductility. Compared with drilling damage, slotting has a more significant impact on axial behavior. Due to the local damage, the ultimate stress decrease by 8.1 % and 12.4 % respectively. A new computational method was introduced to predict the quantitative impact of local damage on CFBCT.

Post-fire bond-slip performance of concrete-filled stainless steel tube columns

Concrete-filled stainless steel tube (CFSST) structures exhibit superior strength, durability, and fire resistance. These attributes, coupled with their aesthetic appeal and corrosion resistance, make them highly suitable for a broad range of civil engineering applications, ensuring long-term performance and safety across diverse environments. This study investigates the post-fire bond-slip performance of CFSST structures to facilitate the strengthening and retrofitting of fire-damaged CFSST structures. The paper reviews the bond-slip performance and fire resistance of CFSST. A series of fire tests and push-out tests were conducted on 99 circular CFSST stub columns, considering variables such as fire duration, wall thickness of the stainless steel tube, and concrete strength. The analysis covers the slip mechanism, load-slip relationship, sliding load, ultimate displacement, and ultimate bond strength of specimens post-fire. The bonding force between interfaces transitions from cementation to mechanical interlock and ultimately to friction, with some overlap among these mechanisms. A positive correlation exists between sliding load and wall thickness when fire duration is short. For shorter fire durations, fire exposure reduces the ultimate displacement while increasing bond-slip stiffness. Finally, a formula is proposed to predict the ultimate bond strength of CFSST stub columns following exposure to ISO 834 standard fire conditions.

Numerical Modeling of Steel Fiber Reinforced Recycled Concrete Filled Steel Tube Column Under Cyclic Loading

A finite element model (FEM) was created with the aim of analyzing the behavior of steel fiber reinforced recycled concrete (SFRRC)-filled steel tube columns under combined cyclic loading and monotonic axial load. The FEM considered the effect of steel tube confinement on the inner concrete behavior under cyclic loading. The numerical model was described in detail, with a focus on modeling the materials involved (normal concrete, SFRRC, and steel) under cyclic loading. A constitutive concrete model - with and without considering confinement - was based on utilizing a concrete damaged plasticity (CDP) model. The steel tube - concrete core interface was modeled by a surface-to-surface contact. A stress-strain constitutive concrete model, confined by circular steel tubes, was implemented, and validated using experimental results from the literature. The developed FEM considered various parameters: steel tube thickness, volume ratios of steel fibers, besides strengths of both concrete core and the steel tube. The FEM results showed great similarity to the under- cyclic- loading tested columns. The results indicated that the concrete confining pressure must be considered in CDP model. A good correlation between numerical and experimental findings was obvious, including failure modes, and hysteretic curves of load-displacement.

Axial compressive performance of CFRP-steel composite tube confined seawater sea-sand concrete intermediate slender columns

To alleviate the scarcity of river sand resources and fully utilize the advantages of Carbon Fiber Reinforced Polymer (CFRP), a new type of CFRP-steel composite tube was developed to confine seawater-sea sand concrete (FCTSSC) column structures. This study conducted experimental research on FCTSSC intermediate slender columns for the first time, analyzing their failure modes and working mechanisms. The investigation explored the effects of outer CFRP layers and slenderness ratios on the mechanical performance. The results indicate that the FCTSSC intermediate slender column specimens exhibited global buckling accompanied by local bulging of steel tubes as their failure mode. The load-displacement curves can be divided into strong confinement and weak confinement models. Specimens confined by CFRP exhibited a 12.51–31 % increase in ultimate bearing capacity. The ultimate bearing capacity and its enhancement rate were positively correlated with the outer CFRP layers and negatively correlated with the slenderness ratio. Peak lateral displacements were positively correlated with both parameters. Finally, the model for calculating the axial compression ultimate bearing capacity of FCTSSC intermediate slender columns was proposed, providing a reference for future practical applications in offshore engineering.

Analytical model of an I-core coil inside a metal tube of finite length

An analytical solution is presented for the interaction of an I-core coil with a metal tube of finite length. Using the Truncated Region Eigenfunction Expansion (TREE) method, the impedance variation of the I-core coil is expressed in a closed form. Notably, the 1D finite element method (1D FEM) is adopted to calculate the complex eigenvalues and eigenfunctions of the steel tube, by which the overflow issue of complex eigenfunctions has been surmounted. And the 1D FEM also simplifies the calculation in the ferrite core region immensely. A performant algorithm is obtained due to the matrix formalization and the high speed of the sparse eigenvalue solver. The tubes made of aluminum alloy and stainless steel are investigated by the proposed method and tested in the experiment. The high reliability and efficiency of the proposed method are proved, and the results are also validated by the comparison with simulation and measurement data.

3D numerical study of axial compression behavior of concrete-filled steel tubular columns from mesoscopic perspective

This study investigates the axial compression behavior of Concrete-Filled Steel Tubular (CFST) short columns from a mesoscopic perspective. Concrete is regarded as a three-phase composite material consisting of aggregates, mortar, and interfacial transition zones (ITZs). The Concrete Damaged Plasticity (CDP) model was employed to simulate the nonlinear mechanical response and fracture characteristics of concrete. Verified against experimental results, the numerical model excels in realistically simulating the uniaxial compression behavior of CFST short columns. Subsequently, factors influencing the macroscopic behavior of CFST short columns were investigated. Results indicate that the random aggregate model adopted for concrete enables a more realistic prediction of the behavior of CFST short columns. Additionally, circular section steel tubes demonstrate a stronger confinement effect compared to square ones. With increasing lateral confinement, the properties of CFST short columns, such as bearing capacity and ductility, are significantly enhanced.

Experimental Study on Mechanic Behavior of Flange Joint for Steel Tube Under Axial Tension

The flange joint is an important connection in steel tube structures. In this paper, 11 groups of flange joint tests were conducted to investigate the influences of tube diameter, flange plate thickness, the distance from the bolt to the tube centroid, bolt numbers and material strength on the mechanical behavior. One of two failure modes in tests is that the excessive plastic deformation on the flange plate makes the flange plate lose the bearing capacity; the other is that the steel tube yield makes the joints fail. The results show that the calculating method for flange joint in Chinese design code is so safe that amplifying the calculating results of the code by 1.2 times would be closer to the bearing capacity of specimens. For a flange joint with different tube diameters, thickening the flange plate of thinner tube or thinning the flange plate of another tube are effective to ensure the deformations on both sides of the flange plates are equivalent. The ratio of the bearing capacity of the steel tube to that of flange plate should be greater than 1.7. And the thickness of the flange plate should be thicker than 14mm to reduce the deformation caused by cutting, drilling and welding during manufacturing.

Mechanism and bearing load-capacity of compound stirrup UHPC-encased CFST columns under axial compression

To augment the synergistic performance between the outer reinforced concrete and the core concrete-filled steel tube (CFST) in standard reinforced concrete encased CFST columns, 14 columns underwent axial compression testing. Of these, 12 columns were encased with compound stirrup Ultra-High Performance Concrete (UHPC), one with compound stirrup high-strength cement-based material, and one with ordinary reinforced concrete. The experiment investigated the effects of compound stirrup forms, stirrup spacing, steel fiber content, steel tube wall thickness, outer concrete types, and core concrete strength on the final failure mode, load-displacement curve, strain characteristics, and development pattern of the specimens. Results indicated improved deformation coordination between the outer compound stirrup UHPC and the core CFST in compound stirrup UHPC encased CFST columns. The yield strength of both the compound stirrup and the steel tube was fully developed within the tested parameter range. A calculation method considering the compound stirrups, fiber constrained outer concrete, and the CFST’s contribution ratio was used to predict the ultimate bearing capacity of reinforced concrete encased CFST columns.

Damage detection method for square steel tube based on CS-NME algorithm via ultrasonic guided waves

The utilization of ultrasonic guided wave (UGW) technology has garnered considerable attention in non-destructive testing field, particularly for steel components. However, for square steel tubes with noncircular cross sections, this method encounters severer frequency dispersion, which hampers the accuracy of damage identification. To address this issue, the approach utilizing the normal mode expansion (NME) method combined with cuckoo search (CS) algorithm to develop a layout strategy for ultrasonic transducer position and length is proposed, which enables single mode excitation of UGW while reducing the interference from redundant clutter signals, thereby enhancing the accuracy of damage detection. The efficacy of the proposed approach is evaluated via numerical simulations and laboratory experiments. The results show that this method can significantly reduce the interference of other modes by optimizing the location and length of ultrasonic transducers, and successfully detect the hole and crack damage on the square steel tube.

Axial compression behaviour of square concrete-filled stainless-clad bimetallic steel tubular stub columns

Concrete-filled stainless-clad bimetallic steel tube (CFSCBST) members combines the advantages of excellent corrosion-resistance and good economy compared with conventional concrete-filled steel tube (CFST) members, which has great prospects in engineering application. This paper presents a comprehensive experimental and numerical investigation into the axial compression behaviour of CFSCBST stub columns with square sections. A total of eight specimens was conducted on CFSCBST specimens, incorporating varying width-to-thickness ratios, clad ratios and steel strengths, The experimental investigation provided a detailed report on failure modes, load versus displacement and strain response. The experimental results were utilized in a parallel numerical simulation to validate the finite element (FE) model. Subsequently, an extended parametric analysis was conducted to investigate the influence of the strength of the concrete, the substrate steel grade, the clad ratio, and the width-to-thickness ratio were carried out. The data obtained from tests and numerical studies were used to evaluate the applicability of existing design codes AISC/ANSI 360-22, EN 1994–1-1, GB 50936–2014 and DBJ/T 13-51-2020 for predicting the compressive capacity of square CFSCBST stub columns. Overall, a modified design method was proposed, adapted from DBJ/T 13-51-2020, was proposed for CFSCBST stub columns, demonstrating enhanced accuracy in predictions.

Corrosion Evaluation and Mechanical Life Prediction of J55 Tubing Steel under Air-Foam Flooding Oil Well Conditions

Corrosion Evaluation and Mechanical Life Prediction of J55 Tubing Steel under Air-Foam Flooding Oil Well Conditions

Seismic Response and Collapse Analysis of a Transmission Tower Structure: Assessing the Impact of the Damage Accumulation Effect

This paper delves into the impact of the damage accumulation effect, which leads to the degradation of material strength and stiffness, on the seismic resistance of transmission towers. Building upon the elastic–plastic finite element theory, a mixed hardening constitutive model is derived for circular steel tubes, standard elements in transmission towers, incorporating the damage accumulation effect. A user material subroutine, UMAT, is created within the LS–DYNA framework. The program’s validity and reliability are established through axial constant–amplitude loading tests on single steel tubes. The subroutine is employed to conduct the incremental dynamic analysis (IDA) of an individual transmission tower and to contrast it with the structure utilizing the Plastic Kinematic material model, assessing the discrepancies in tower top displacements and segment damage indices (SDIs) at both macroscopic and microscopic scales. The results shows that the Plastic Kinematic model inflates the seismic performance of the transmission tower. When considering the damage accumulation effect in structural failure, the damage index of the members increases, leading to a reduction in both the structural strength and stiffness. The dynamic response in the plastic phase becomes more pronounced, and the onset of structural failure is accelerated. Consequently, structural analysis under seismic conditions should account for the damage accumulation process. Through the delineation of member and segment damage, the extent of damage to transmission tower segments can be quantitatively assessed. Subsequently, the ultimate load–bearing capacity and the most vulnerable location of the transmission tower can be ascertained. Finally, this paper provides a detailed analysis of the transmission tower collapse process under seismic action and summarizes the mechanism of collapse for the structure.

A Study on the Problem of AC Corrosion of Power Umbilical Cables Caused by Electromagnetic Induction Phenomena

During the normal laying and operation of a three-core umbilical cable, AC current can easily lead to AC electrochemical corrosion on the outer surface of the steel tube. To explore the electrochemical corrosion mechanism and the factors affecting the three-core umbilical cable, this paper optimizes the internal induced potential calculation method for three-core umbilical cables. It analyzes the changes in the characteristics of the induced potential and explores the variations in the density of induced current under different conditions. The research results show that by optimizing the calculation method for the induction potential of the umbilical cable’s steel pipe, for the electromagnetic significance of the smallest repeating unit, the induction potential on the steel pipe’s surface exhibited a cyclic change. The peak part of the induction potential is most likely to experience electrochemical corrosion. Additionally, reducing the radius of the outer insulation aperture of the steel pipe and improving the conductivity of seawater will increase the density of the induced current in the insulation aperture, thereby increasing the risk of electrochemical corrosion. As the cable pitch and AC frequency increase, the current density in the steel pipe pores will also rise.

Comparative study on the impact behaviors of CFWST columns reinforced with steel spiral and tube

To obtain superior corrosion resistance and impact resistance, as well as good economic benefits, two new types of composite structure called as steel tube internally-reinforced concrete-filled weathering steel tube (STRCFWST) and steel spiral internally-reinforced concrete-filled weathering steel (SSRCFWST) columns are proposed and compared in terms of their impact resistance in this paper. Eleven impact tests were conducted and three parameters comprising steel spiral diameter, wall thicknesses of outer and inner steel tube were considered to evaluate their influences on the lateral impact behaviors. Results show the presence of inner steel tube and reinforcement cage significantly enhances the impact resistance while slightly decreases the energy absorption capacity. Increasing inner steel tube wall thickness helps to improve the impact resistance, however the contribution is not so good as that produced by increasing the outer steel tube wall thickness, whilst varying steel spiral diameter almost has no impact. Numerical models were developed by ABAQUS/Explicit and verified via the test, based on which the full-range behaviors of STRCFWST, SSRCFWST and unreinforced concrete-filled weathering steel tube (CFWST) columns under impact loading were compared and discussed. It is demonstrated that steel tube and reinforcement cage provide little confinement on concrete infill under impact. With the same internal steel ratio, inner steel tube makes a greater contribution to sectional bending moment resistance and energy absorption as compared to the reinforcement cage.

Behavior of UHPC filled high-strength square steel tubular stub columns under combined flexural and axial loads

This study experimentally and numerically investigated the behaviors of UHPC-filled high-strength square steel tube stub columns with compact, noncompact and slender sections under combined flexural and axial loads. Eighteen tests were conducted, addressing the gap of limited tests on concrete-filled square steel tubular stub columns with noncompact or slender sections. Additionally, finite element analyses were developed and benchmarked for parametric studies. The results of tests and parametric studies show that (1) steel tube outward buckling and concrete crushing occurred at 1/4–1/2L of the compression zone; (2) the load-axial displacement curves organized into three phases: elastic, elastic-plastic, and recession phase; (3) the compressive strength increased with increasing tube thickness, concrete strength, and steel yield strength. The compressive strength decreased with increasing eccentric ratio and slenderness coefficient. Test and numerical results are utilized to assess the suitability of current design specifications for predicting compressive strength. The evaluation showed that neither GB 50936–2014 nor Eurocode 4 provided reasonable predictions of strength, while AISC 360–16 provided conservative predictions.

Compressive behavior of sustainable rubberized concrete‐filled steel tube columns having various recycled tire rubber aggregate contents and developing a predictive design model

AbstractAs a sustainable solution, employing recycled tire rubber aggregates in the production of concrete is of considerable interest. However, the applicability of rubberized concretes in construction is restricted due to their relatively low mechanical performance. Using rubberized concrete as a filling material in a steel tube provides a suitable solution for overcoming this issue and for using it effectively as a load‐bearing element. The objective of this study is to examine the impact of the material characteristics of the sustainable rubberized concrete‐filled steel tube (Ru‐CFST) and develop a design model based on ultimate strength prediction for the axially loaded Ru‐CFST stub columns with varying contents of tire rubber aggregate. The model was developed through the gene expression programming (GEP) technique by employing the experimental test results to determine the ultimate compressive strength of Ru‐CFST columns. Based on the principal component analysis, the sectional properties of the load‐bearing element (such as outer diameter, thickness, and length), material strengths (such as rubberized concrete and steel tube strengths), and rubber content were determined as statistically significant parameters affecting the ultimate axial strength of Ru‐CFST stub columns and thus, they were considered in the stage of the model generation. Furthermore, the proposed model's performance was compared to that of available models suggested for traditional CFST columns by commonly employed design codes, namely, ACI, AIJ, AISC, CSA, EC4, and GB. Based on the statistical analysis of the results, it can be concluded that the existing formulations have a relatively acceptable randomness and scatter of observations within the distribution, while the proposed design model gives a more accurate prediction for the ultimate bearing capacity of axially loaded Ru‐CFST columns with the highest R‐squared value of about 0.99 and the comparatively lowest mean absolute percent error of 7.54. It can be stated that the proposed GEP‐based design model will encourage engineers to use such sustainable structural members in their designs and constructions.

Corrosion behavior of SMSS 13Cr and SS 316L under chloride solution and H2S/CO2 environments

Abstract Corrosion resistant alloys (CRAs) include a range of different stainless steels and nickel alloys that are used in corrosion-aggressive environments encountered in oil and gas operations. Supermartensitic stainless steel (SMSS 13Cr) has been used in the manufacture of steel tubes for use in oil drilling due a more financially viable option to replace the austenitic stainless steel (SS 316L) in the oil and gas market. This present work estimate the effect of the hydrogen sulphide (H2S) on SMSS 13Cr and SS 316L, in saline solution, simulating the operating conditions in the oil and gas industry. Corrosion behavior was monitored using Potentiodynamic-Potentiostatic-Potentiodynamic (PD-PS-PD) technique in order to obtain pitting potential (Ep) or crevice potential (Ecrev)) and repassivation potential (Erp) while the long-term Open Circuit Potential (OCP) technique was applied to estimate the stable corrosion potential (Ecorr*). A Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-ray Spectroscopy (EDS) and Optical Microscopy were used for surface characterization. With all analysis carried out was possible to propose a trend regarding the pitting probability. The pitting increases with increasing H2S concentration on SSSM 13Cr, consequently, large, and deeper pits were observed, making possible to develop into cracks if there are mechanical stresses. On the contrary, the pitting probability for the SS 316L is low (compared with SMSS 13Cr) for all environments reproduced here in this research.

Experimental and theoretical studies on lateral behavior of prefabricated composite concrete-filled steel tubes truss column

Enhancing the lateral force resistance of residential structures through innovative prefabricated designs is crucial for improving structural resilience and safety. This study presents an innovative design for prefabricated concrete-filled steel tube (CFT) column trusses with V-shaped or Z-shaped configurations to enhance the lateral displacement and ductility of residential buildings under lateral forces. The CFT-column truss is a prefabricated system featuring two square CFT columns connected to H-section beams using fish plates. Additionally, the beams and columns are linked to a web truss component made of double-angle sections. To assess their failure patterns and characteristic capacities, two large-scale specimens were subjected to lateral monotonic loads. The test results indicated that both V-shaped and Z-shaped trusses exhibited exceptional performance. The V-shaped trusses demonstrated significant improvements in yield stiffness and ductility, increasing by approximately 22 % and 31 %, respectively. However, the yield and peak bearing capacities of these trusses were reduced by about 10 % and 6.75 %, respectively. Furthermore, a theoretical model was developed based on the observed test failure modes and verified through finite element (FE) analyses. The predictive results of the theoretical model were compared to a group of FE models, demonstrating their suitability for accurately estimating bearing capacities and yield stiffness with a high level of agreement.

Simplified finite-element analysis method for local and global prediction on axial compression behavior of square spiral-confined reinforced concrete-filled steel tubular columns

Square spiral-confined reinforced concrete-filled steel tubular (SSCRCFST) columns have recently been proposed as an advanced form of composite columns. However, there is still a lack of an efficient approach that can accurately predict both their section-average behavior and local concrete behavior. This paper presented a novel simplified method combining elastic finite element analysis with accurate material laws of concrete, steel tube and longitudinal bar to analyze the axially compressive behavior of SSCRCFST columns. The proposed method utilized elastic finite-element analysis to approximate the distribution and ultimate state of confining stress within each core concrete element, which was then substituted into the Mander confined concrete model to obtain the strength enhancement in each core concrete element subjected to different level of lateral confinement. Finally, the integrated compressive curve of a column can be derived by summarizing the strength of all elements. Verification of the proposed method against a large test database confirmed its capability to accurately capture the results of existing compression tests of SSCRCFST columns. The proposed computationally efficient method was then used to investigate both the section-average and local behavior of SSCRCFST column under monotonic compression for an improved understanding of the confinement mechanism. Finally, a reasonably modified design method for the axial strength of SSCRCFST column was proposed based on research findings in this study, which led to the continuity in the axial strength predictions of SSCRCFST columns with various corner radius ratio and showed good agreement with the test results.