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This article aims to provide an overview of the fire resistance of concrete‐filled steel tube beam columns and the importance of fire resistance in building design and construction. Ten experimental models were developed to predict the behavior of different types of concrete‐filled steel tubes and beams‐columns under Fire resistance conditions (ISO‐834) under cyclic loading in two groups. The results show the type of concrete effect on moment‐rotation characteristics. Also, increasing the length of the stiffener on the column increases the load and moment capacity, but also affects the failure mode. Moreover, the ideal situation is to use PP fiber concrete in concrete‐filled steel tube structural elements where displacement and rotation capacity are prominent. Withal, the recycling of fire‐exposed steel beam‐to‐column tube element is available by filling the inner space with C50 and/or polypropylene fiber reinforced concrete, also as a fireproof member. [ABSTRACT FROM AUTHOR]

This study builds on existing researches to further investigates cyclic responses of the steel tube-confined reinforced concrete (RC) columns, with a primary focus on those subjected to high-axial load. A total of eleven column specimens were tested under lateral displacement reversal and axial load of either 0.3Ag fcm,c or 0.5Ag fcm,c , where Ag and fcm,c refers to concrete cross section area and tested concrete strength of the column, respectively. Three specimens represented the conventional reinforced concrete (RC) columns while the rest were the steel tube-confined circular RC columns. The key test parameters included (1) amount of longitudinal reinforcement, (2) axial load level, (3) continuity of the confining steel tube, and (4) clear cover of the longitudinal reinforcement. Test results showed that all the steel tube-confined RC specimens sustained the target axial load and maximum lateral strength up to around 10% drift ratio. A simple strength model was proposed to reasonably estimate the maximum strength of the steel tube-confined RC columns. The flexural rigidity ratio, (EI)test/Ecm,cIg , for RC specimens and specimens confined by continuous steel tube ranged between 0.6 and 0.8, approximately. Specimens confined by the cutoff steel tube showed lower (EI)test/Ecm,cIg ratio between approximately 0.3 and 0.6. [ABSTRACT FROM AUTHOR]

Circular steel pipe concrete can give full play to the combination of steel pipes and concrete, resulting in an improvement in the steel pipe's concrete bearing capacity and ductility. In this study, the axial compression load capacities of nine steel pipe concrete columns, including one traditional steel pipe concrete column and eight steel pipe self-stressed concrete columns, were analyzed using an axial pressure test. The damage patterns and stress–strain curves of all the specimens under axial compression load were analyzed, and a comparison analysis was made between the test results of the different specimens. The test results show that the longitudinal expansion displacement of concrete increases with the increase in the expansion agent content. The greater the self-stress, the higher the bearing capacity of steel-tube concrete columns under axial compressive load within a certain range of the expansion agent, indicating that self-stress can increase the bearing capacity of steel-tube concrete columns under axial compressive load, but the effect of the magnitude of the self-stress on the damage pattern of the specimens is limited. The damage patterns of all the specimens were bulging in the center and concave at both ends. In addition, the existing theoretical calculation method of the bearing capacity of steel pipe concrete columns is modified, and a theoretical calculation method applicable to steel pipe self-stressed concrete columns is proposed to simplify the calculation method of the bearing capacity of steel pipe self-stressed concrete columns, which provides a basis for decision-making in practical engineering. [ABSTRACT FROM AUTHOR]

The importance of establishing a proper method for calculating newly studied structural elements and primarily translating the results of experimental and numerical analyses into practical standards poses a significant challenge for structural researchers. In this study, which focuses on the importance of previously studied connections for the precast industry as a case study, two approaches are proposed for calculating the capacity of elements connected by rectangular steel tubes. The first approach involves a step-by-step calculation for analyzing the forces and capacities of different steel tube or concrete section parts under bending and shear, aiming to establish a standard calculation approach. Despite its complexity, the standard calculation approach has proven its accuracy by successfully solving examples with features similar to those of the experimental tests describing the process. The second approach relies on a look-up table generated from experimental data, developing an Adaptive Neuro-Fuzzy Inference System (ANFIS) for interpreting the data. ANFIS not only facilitates the evaluation of the capacity of non-experimentally tested elements but also resembles the calculation process. Evaluating ANFIS's performance concerning the original results underscores its remarkable capacity to analyze experimental data. With a maximum calculation error of only 13% when compared to the experimental tests, ANFIS demonstrates considerable accuracy and user-friendliness. Following the initial internal force evaluations, the proposed standard calculation method requires eight specific control inputs, and comparing these inputs with experimental tests further confirms the effectiveness and safety of this approach for connection design. [ABSTRACT FROM AUTHOR]

The structural response of simply supported Reinforced Concrete (RC) beams with square vertical openings is investigated in this work. Studies were conducted using seven specimens of RC beams, with the aim of comparing beams with vertical openings to those without. Meanwhile, the other beams featured carefully positioned square openings. Note that one of these beams served as the control and had no openings. Each beam was the same length (1400 mm) with a 180×120 mm cross-section. Two-point loads were applied over a span of 1200 mm throughout the testing method, with a central load placed 300 mm from the ends. The openings were positioned in the middle of the span and came in three different widths: 20, 40, and 60 mm. Openings were made using either 1.5 mm thick square steel tubing or none at all. The major goal of this study was to determine whether the steel tube could compensate for the decrease in beam strength and the impact of decreasing beam cross-section (producing opening). Correspondingly, the beam ultimate load was found to decrease by 15.75%, 24.2%, and 32.5% for opening widths of 20 mm, 40 mm, and 60 mm, respectively, as the opening width increased. On the other hand, the performance gain for beams strengthened with steel plates when steel tubes were used was 11.78%, 12.14%, and 13.28% for the respective opening widths. [ABSTRACT FROM AUTHOR]

Summary: This study aims to develop an algorithmic approach to obtain optimum designs for tall buildings having composite columns and investigate the material cost advantages of these buildings over steel structures. The social spider optimization (SSO) algorithm, a new meta‐heuristic optimization method that has shown promising results in optimizing frame structures, was used to obtain the optimum designs. Concrete‐filled steel tube sections were chosen for composite columns. To define the optimization problem, we considered the material cost of the structure as the objective function, the size of columns (strength, deflection, drift, and geometric limitations) as the constraint functions, and ready steel sections as the design variables. We tested eight different frame structures of varying heights and irregularities to analyze how cost varied according to these parameters. Our results demonstrate that composite columns are a more cost‐effective option than steel structures, even for buildings that are not considered high rises. We found that the difference in cost between the two types of structures increases with building height and irregularity. Additionally, our optimization algorithm was unable to find feasible designs for steel structures taller than 180 m using ready steel profiles. [ABSTRACT FROM AUTHOR]

Hybrid double-skin tubular columns (DSTCs) are a promising form of composite columns in which the concrete is sandwiched between inner steel and outer fiber-reinforced polymer (FRP) tubes. A modified form of DSTC incorporating stiffened steel tubes demonstrates more potential benefits than the standard unstiffened design. The inclusion of stiffeners in the steel tube enhances composite interaction among column components, effectively delaying local buckling deformations and potentially improving the behavior of confined concrete. The present study performs both experimental and analytical investigations to measure the impact of stiffeners on the confined concrete behavior of square-circle (SC) configured specimens, considering various column slenderness ratios. Thirty DSTC specimens were experimentally tested with variations in steel stiffener properties, including number, configuration (maintaining a similar combined area), thickness, and width; and unconfined concrete strength. The test results showed a substantial improvement in axial load capacity in the stiffened SC-shaped specimens, reaching up to approximately 37% in this study. Subsequently, the test data were utilized to propose a stress–strain confined concrete model specific to SC-shaped specimens with varying slenderness ratios. This proposed model was employed for calibration study using detailed finite-element (FE) analysis, demonstrating excellent agreement with the test data. A parametric investigation was then conducted through FE analysis to optimize the rib-stiffener properties. Finally, the findings from both the experiments and the FE analysis were utilized to develop a simplified equation that predicts the axial load capacity of stiffened SC-DSTCs. [ABSTRACT FROM AUTHOR]

This study aimed to experimentally compare the bending behavior of reinforced concrete beams in the midspan zone of the maximum bending region with and without vertically perforated openings. Five rectangular cross-section beams were produced for this purpose: one solid specimen, one with an opening without reinforcing steel, and the remaining three had openings reinforced with steel tubes of thickness 1, 1.5, and 2 mm. The square opening width was 40 mm. All specimens were tested under a symmetric fourpoint loading until failure. The test results showed that all specimens failed in bending. The presence of an opening negatively affects the ultimate load-bearing capacity and bending. However, the bending behavior of the reinforced concrete beams exhibited superior performance as the thickness of the steel tube increased. Additionally, the maximum load-bearing capacity increased with increasing tube thickness. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The punching shear problem in composite T-joints with doubler plates has been evaluated in various design codes of practice. However, code provisions do not address the behavior of concrete-filled double steel tubular T-joints filled with concrete, in which concrete contributes to a portion of the shear force to resist punching. The present study presents a finite element modeling analysis to investigate the ultimate load-bearing capacity of circular and square concrete-filled double steel tubular T-joints. A set of 24 double-skin concentric tubular joint specimens were modeled in ABAQUS. A subsequent parametric study was carried out to examine the influence of infill concrete compressive strength, steel tube cross section shape, and section width-to-thickness ratio. Accordingly, stress evolution pattern, buckling mode, stress-strain response, and load–displacement curve of the entire T-joints were investigated. Based on the results obtained, it was revealed that recession in the flange of the primary component, as well as the heaving of the primary component web, are the main reasons for the higher stress levels. It was also seen that when the compressive strength of the infill concrete is 45 MPa, the maximum stress level in circular concrete-filled double steel tubular joint is 2.6 × 102 MPa, while that in the square joint is 2.566 × 102 MPa. The corresponding values for concrete with a compressive strength of 30 MPa are 2.58 × 102 MPa and 0.455 × 102 MPa, respectively. It was also observed that when the width-to-thickness ratio is increased from 20 to 33.33 in circular T-joints, the ultimate load-bearing capacity is reduced by 15%. [ABSTRACT FROM AUTHOR]

Due to their excellent mechanical features, concrete-filled steel tube (CFST) columns are usually employed in high-rise constructions; it is also significant to consider fire safety while designing buildings. The fire-resistance performance of fibre-reinforced CFST columns is superior to that of unreinforced CFST columns under identical conditions. The post-peak behavior of CFST columns can be enhanced by incorporating fibres to reduce the brittleness of concrete. The research on this topic is limited and considerable research gaps are available in the literature. This research examines the structural performance of steel fibre-reinforced concrete (SFRC) filled steel tubes exposed to ambient and elevated temperatures. For this purpose, fourteen CFST columns were investigated and separated into two groups. The first group of CFST columns was filled with three diverse grades of conventional concrete with and without fibres, which was subjected to ambient temperature. The second group is identical to the first group except all columns are exposed to a temperature of 1050 ℃. The parameters examined were the mechanical properties of concrete, load-carrying capacity, load-deflection response, axial load, and axial strain and ductility ratio. Furthermore, using different codes, a comparison was made for the column's empirically determined load-carrying capacity with the theoretical value. Besides, the morphological characteristics of concrete were examined using energy dispersive spectroscopy (EDS), scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). The findings show that the SFRC-filled column has superior structural qualities when subjected to elevated temperatures. At high temperatures, calcium hydroxide decomposes, and the steel tube yields, causing the column to fail by premature local bucking.

The importance of establishing a proper method for calculating newly studied structural elements and primarily translating the results of experimental and numerical analyses into practical standards poses a significant challenge for structural researchers. In this study, which focuses on the importance of previously studied connections for the precast industry as a case study, two approaches are proposed for calculating the capacity of elements connected by rectangular steel tubes. The first approach involves a step-by-step calculation for analyzing the forces and capacities of different steel tube or concrete section parts under bending and shear, aiming to establish a standard calculation approach. Despite its complexity, the standard calculation approach has proven its accuracy by successfully solving examples with features similar to those of the experimental tests describing the process. The second approach relies on a look-up table generated from experimental data, developing an Adaptive Neuro-Fuzzy Inference System (ANFIS) for interpreting the data. ANFIS not only facilitates the evaluation of the capacity of non-experimentally tested elements but also resembles the calculation process. Evaluating ANFIS’s performance concerning the original results underscores its remarkable capacity to analyze experimental data. With a maximum calculation error of only 13% when compared to the experimental tests, ANFIS demonstrates considerable accuracy and user-friendliness. Following the initial internal force evaluations, the proposed standard calculation method requires eight specific control inputs, and comparing these inputs with experimental tests further confirms the effectiveness and safety of this approach for connection design.

Circular steel pipe concrete can give full play to the combination of steel pipes and concrete, resulting in an improvement in the steel pipe’s concrete bearing capacity and ductility. In this study, the axial compression load capacities of nine steel pipe concrete columns, including one traditional steel pipe concrete column and eight steel pipe self-stressed concrete columns, were analyzed using an axial pressure test. The damage patterns and stress–strain curves of all the specimens under axial compression load were analyzed, and a comparison analysis was made between the test results of the different specimens. The test results show that the longitudinal expansion displacement of concrete increases with the increase in the expansion agent content. The greater the self-stress, the higher the bearing capacity of steel-tube concrete columns under axial compressive load within a certain range of the expansion agent, indicating that self-stress can increase the bearing capacity of steel-tube concrete columns under axial compressive load, but the effect of the magnitude of the self-stress on the damage pattern of the specimens is limited. The damage patterns of all the specimens were bulging in the center and concave at both ends. In addition, the existing theoretical calculation method of the bearing capacity of steel pipe concrete columns is modified, and a theoretical calculation method applicable to steel pipe self-stressed concrete columns is proposed to simplify the calculation method of the bearing capacity of steel pipe self-stressed concrete columns, which provides a basis for decision-making in practical engineering.

This study investigates into the influence of opening size and steel tube thickness on the structural properties of reinforced concrete beams, particularly those with utility ducts and pipes. Four reinforced concrete beams were subjected to comprehensive testing, including a reference beam devoid of openings and three specimens featuring square openings of varying intensities. The evaluation encompassed crucial parameters such as load-deflection response, ultimate failure load, cracking load, cracking pattern, stiffness criteria, and ductility index. Employing the Digital Image Correlation (DIC) method, detailed analyses of cracking behavior were conducted. Unstrengthened beams exhibited a reduction in ultimate load capacity and stiffness, approximately 11.18% and 19.8% lower, respectively, compared to the control beam. Introduction of a steel tube significantly enhanced the performance of opening beams, manifesting in improved cracking load, cracking formation, ultimate capacity, stiffness, and ductility index, thereby promoting more ductile behavior. Strengthened beams with 2 and 3 mm-thick steel tubes demonstrated an approximate 9.27% and 28.47% increase in ultimate load compared to their unstrengthened counterparts. Beams featuring 3 mm-thick steel tubes exhibited behavior akin to the reference beam in terms of load-vertical displacement curves, albeit with a 14.12% disparity in ultimate load capacity. Despite a somewhat identical crack morphology across all tested beams, unstrengthened beams displayed higher crack width and deflection than their strengthened counterparts. [ABSTRACT FROM AUTHOR]

The paper presents a novel method of reinforcing concrete columns using small-diameter steel tubes instead of traditional steel bars. The researchers conducted experimental investigations on twelve mid-scale circular concrete column specimens, which were divided into two groups consisting of six specimens each: short and long columns. Two of the specimens in each group were reinforced with steel bars, while the remaining four were reinforced with steel tubes filled with cementitious grouting material. The study proposed two concepts for cementitious grouted steel-tube reinforcement. The first concept utilized steel tubes with equivalent net areas to the steel bar areas used in the reference column, while the second concept used steel-tube reinforcement with the same diameter as the steel bars in the reference column. Nonlinear Finite Element (FE) analyses were conducted on experimental specimens using ABAQUS software. The results showed that using steel tubes with an area equivalent to that of steel bars instead of conventional columns increased the bearing capacity of reinforced concrete columns by 17%. Moreover, using steel tubes whose area matched 30% of the steel bar area achieved a bearing capacity of about 81% of the conventional concrete columns. The experimental and FE analysis findings indicate that this methodology can increase the bearing capacity of reinforced concrete columns when compared to traditional methods. The axial load-axial displacement curves, axial load-axial strain curves, and failure load of the FE model all demonstrated good convergence with the experimental data. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effectiveness of a novel concrete-encased column (CE) using small circular steel tubes filled with cementitious grouting material (GFST) as the primary reinforcement instead of traditional steel bars. The research involved three different types of reinforcement: conventional steel bars, concrete-filled steel tubes with 30% of the reinforcement ratio of steel bars, and concrete-filled steel tubes with the same reinforcement ratio as steel bars. Twenty-four circular concrete columns were tested and categorized into six groups based on the type of reinforcement employed. Each group comprised four columns, with one subjected to concentric axial load, two subjected to eccentric axial load (with eccentricities of 25 mm and 50 mm, respectively), and one tested under lateral flexural loads. To validate the experimental results, finite element (FE) analysis was conducted using ABAQUS software version 6.14. The experimental findings for concentric load reveal that columns with the second type of reinforcement, concrete-filled steel tubes with 30% of the reinforcement ratio of steel bars exhibited a failure load 19% lower than those with steel bars, while columns with the third type of reinforcement, concrete-filled steel tubes with the same reinforcement ratio as steel bars achieved a failure load 17% greater than the traditional steel bars. The FE analysis demonstrates good agreement with the experimental outcomes in terms of ultimate strength, deformation, and failure modes. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, 32 numerical models of CHST columns were established in the ABAQUS program to evaluate the effect of mid-span local defects on the impact resistance of circular hollow steel tube (CHST) columns. The simulation studies were conducted from three aspects: notch length, notch angle, and impact energy. The results showed that under a lateral impact load, the mid-span of the CHST column presented global bending failure patterns accompanied by local indentation deformation in the impact region and local buckling deformation at the bottom of the fixed end. Compared with the mid-span indentation displacement of the non-notch model, when the impact velocities were 30 km/h and 60 km/h, the horizontal notch model surpassed the maximum by 29.3% and 36.3%, the oblique notch model surpassed the maximum by 47.8% and 115.6%, and the vertical notch model only increased by 9.7% and 1.1%. The local damage area and impact force time-history curves of the vertical notch model agreed well with those of the nonnotch model. Among the three notch angles, the impact plateau values of the vertical notch model and the global bending displacement in the mid-span were least affected by the notch length, notch location, and impact energy. The energy absorption of the CHST column was mainly due to indentation deformation in the mid-span, and the global bending deformation was auxiliary. Compared with the energy absorption ratio (EAR) of the non-notch model, with increased impact energy, the EAR of the vertical notch model increased by 20.2%, 13.5%, and 17.3% on average. The horizontal and oblique notch models decreased by 28.2%, 61.0%, 42.4%, and 29.1%, 62.7%, and 49.3%, respectively. The Rd of all notch models showed an overall upward trend as the impact energy increased, and the Rd of the horizontal notch model increased the most. According to the parametric analysis results, the dynamic flexural capacity prediction formula of the CHST columns section was obtained, considering the influence of notch length, notch angle, and impact energy within the parameter range of this study [ABSTRACT FROM AUTHOR]

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.

Nowadays, due to the structural advantages gained by combining three different materials' properties, columns made of carbon-fiber reinforced polymer (CFRP)-confined concrete with inner steel tube have received researchers' interest. This article presents the nonlinear finite element analysis and multiple machine learning (ML) model-based study on the behavior of round corner rectangular CFRP-confined concrete short columns reinforced by the inner high-strength elliptical steel tube under the axial load. The reliability of the proposed nonlinear finite element model was verified against the existing experimental investigations. The effects of the parameters such as the concrete grade, thickness of reinforcing steel tube, cross-sectional size of inner steel tube, and thickness of CFRP on the behavior of the columns are comprehended in this study. Furthermore, multiple ML models were proposed to predict the ultimate axial load, ultimate axial strain, and lateral strain of the test specimens. The reliability of the proposed ML models was evaluated by six distinct performance metrics. From the parametric investigation, it was found that concrete with lower compressive strength gained more strength enhancement because of confinement between CFRP and the inner steel tube than high-strength concrete relative to its unconfined compressive strength. The proposed ML models of extreme gradient boosting and random forest provided the best-fit results than the artificial neural network and Gaussian process regression models in predicting the axial load and axial and lateral strains of the columns.

The reinforcement of concrete columns with steel tubes is a convenient and economical technique in civil engineering. To investigate the mechanical behavior of short circular concrete columns strengthened with grouting-filled steel tubes under eccentric compressive loads, five specimens with different eccentricities were tested in the present work. Finite element simulations were carried out in ABAQUS software to analyze the mechanical behavior of the reinforced columns. A parametric study was performed to evaluate the influences on the SRF, RCR, P-M, and P/Pu-M/Mu curves of the reinforced columns. The results showed that increasing the yield strength and thickness of the steel tube improved the performance of the reinforced columns. The ultimate load-carrying capacities of the specimens determined by the codes were compared with those determined by the proposed formulas. The results also showed that the ultimate load-carrying capacities of the specimens determined by the proposed formulas were more accurate.

Copyright of Steel Pipe is the property of Steel Pipe Magazine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Steel Pipe is the property of Steel Pipe Magazine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study introduces a new precast concrete (PC) double-wall system designed to simplify the complex fabrication process of existing PC double-wall systems and eliminate laitance and other defects that can occur during the manufacture of concrete panels. An experiment and finite element analysis were conducted on 11 specimens to determine the tensile resistance performance of rectangular steel tubes that maintain spacing to avoid damage to the PC panels during transportation or on-site installation. Specimens varied in terms of the end details of the rectangular steel tubes, such as the presence of welded steel plates or embedded concrete and total length in terms of whether longer or shorter specimens were used. As a result, the specimens showed a 20–30% increase in maximum tensile strength compared to the control specimen according to the end details, except for the case where side steel plates were cut and bent inward. The control specimen filled with concrete was the most suitable for connections when constructing PC double-wall systems. It has significant tensile resistance according to the experiment and finite element analysis and does not require additional construction steps or costs. [ABSTRACT FROM AUTHOR]

Copyright of Steel Pipe is the property of Steel Pipe Magazine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Steel Pipe is the property of Steel Pipe Magazine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Steel Pipe is the property of Steel Pipe Magazine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This article outlines the impact of eddy current non-destructive testing (ECT) on steel pipes, and discusses the importance of utilizing numerical analysis to enhance its accuracy. Our research proposes the use of finite element modeling for eddy current testing of cracked pipes. The paper concludes by presenting the results of our finite element modeling and numerical analysis for eddy current testing of cracked steel pipes, wich closely align with experimental data. Our findings demonstrate that the simulation method is not only effective for this application but also applicable to other related work.

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Briefed here in the article are the outputs, apparent consumptions and the self-supply rate, etc. of the domestic steel tube over the years. And also detailed are the data concerning the import and export quantities and main type quantities of domestic steel tubes, seamless steel tubes and weld tubes as well as the names of the foreign countries to and from which the said steel tube products are exported and imported by China over the years. Since 1955, the steel tube yearly output has exceeded that of the import amount; and since 1982, domestic steel tubes have been exported, and from 2003 China has become a purely steel tube-export country, and in 2015 the total steel tube export amount was up to 8 918 300 tons. Along with the substantial increase of the steel tube export amount and the significant decrease of the steel tube import amount, the steel tube import and export pattern of the country has got remarkably changed, the competitiveness in the world steel tube market has been tremendously enhanced, and the influence has been constantly expanding. [ABSTRACT FROM AUTHOR]

Taking the steel tube bright annealing furnace as the research object, a mathematical model concerning steel tube heating and cooling process is set up. Accordingly the methods like theoretical analysis and numerical simulation are used to study and analyze the heat-transfer mechanism between steel tube heating, cooling process and the furnace hearth. Then the model control system for steel tube bright annealing furnace is developed. Furthermore, the said model is verified with inspection and testing data as got from the workshop. The verification result shows that the said model has high accuracy, and the on-line control system is running stably, which satisfies the requirements for the actual production, and brings about good control effectiveness. Application of the above mentioned math model shall improve the heating quality, and shortening the heating time of the steel tube bright annealing furnace, and increase the steel tube output. [ABSTRACT FROM AUTHOR]

This article describes the effects of non-destructive eddy current testing (ECT) on steel pipes. To improve the accuracy of ECT, it is considered important to use numerical analysis. However, we propose finite element modeling for eddy current testing of cracked pipes. The end of this paper describes the results of finite element modeling and numerical analysis for eddy current testing of cracked steel pipes. The results obtained from this method are very similar and consistent with the experimental data. It is proved that the simulation method is also valid for other work. [ABSTRACT FROM AUTHOR]

Copyright of Steel Pipe is the property of Steel Pipe Magazine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Steel tube struts in braced excavations – Simplified design for cross section class 4 Steel tubes are often used as excavation struts. When designing long struts without intermediate supports, tubes with large diameter and small wall thickness are particularly economical. This may lead to reaching the limit of cross section class 4 requiring a shell buckling analysis according to EN 1993‐1‐6. In this article a simplified design method using section‐related buckling stresses based on EN 1993‐1‐6 Annex D is described. Ready‐to‐use section‐related buckling stresses are given for commonly used steel tubes of cross section class 4. [ABSTRACT FROM AUTHOR]

This study deals with the effect of fly ash and recycled sand on the flexural behavior of SFRCCs (steel fiber-reinforced cementitious composites)-filled steel tubes. As a result of the compressive test, the elastic modulus was reduced by the addition of micro steel fiber, and the fly ash and recycled sand replacement decreased the elastic modulus and increased the Poisson's ratio. As a result of the bending and direct tensile tests, strength enhancement by the incorporation of micro steel fibers was observed, and a smooth descending curve was confirmed after initial cracking. As a result of the flexural test on the FRCC-filled steel tube, the peak load of all specimens was similar, and the applicability of the equation presented by AISC was high. The deformation capacity of the steel tube filled with SFRCCs was slightly improved. As the elastic modulus of the FRCC material lowered and the Poisson's ratio increased, the denting depth of the test specimen deepened. This is believed to be due to the large deformation of the cementitious composite material under local pressure due to the low elastic modulus. From the results of the deformation capacities of the FRCC-filled steel tubes, it was confirmed that the contribution of indentation to the energy dissipation capacity of steel tubes filled with SFRCCs was high. From the comparison of the strain values of the steel tubes, in the steel tube filled with SFRCC incorporating recycled materials, the damage was properly distributed between the loading point and both ends through crack dispersion, and consequently, rapid curvature changes did not occur at both ends. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effectiveness of a novel concrete-encased column (CE) using small circular steel tubes filled with cementitious grouting material (GFST) as the primary reinforcement instead of traditional steel bars. The research involved three different types of reinforcement: conventional steel bars, concrete-filled steel tubes with 30% of the reinforcement ratio of steel bars, and concrete-filled steel tubes with the same reinforcement ratio as steel bars. Twenty-four circular concrete columns were tested and categorized into six groups based on the type of reinforcement employed. Each group comprised four columns, with one subjected to concentric axial load, two subjected to eccentric axial load (with eccentricities of 25 mm and 50 mm, respectively), and one tested under lateral flexural loads. To validate the experimental results, finite element (FE) analysis was conducted using ABAQUS software version 6.14. The experimental findings for concentric load reveal that columns with the second type of reinforcement, concrete-filled steel tubes with 30% of the reinforcement ratio of steel bars exhibited a failure load 19% lower than those with steel bars, while columns with the third type of reinforcement, concrete-filled steel tubes with the same reinforcement ratio as steel bars achieved a failure load 17% greater than the traditional steel bars. The FE analysis demonstrates good agreement with the experimental outcomes in terms of ultimate strength, deformation, and failure modes.

This paper proposes a novel glass fiber‐reinforced polymer (GFRP)‐timber‐steel tube‐concrete composite column (GTSC) that combines an outer steel tube with GFRP fabric reinforcement, an inner timber core, and concrete for the rest of the space. The mechanical behavior of eight specimens of novel composite columns was investigated considering diameters of timber cores, layer numbers, and angles of GFRP laminates. The results showed that as the size of the timber core increased from 0 to 50 mm, the ductility and the energy dissipation capacity of the composite column maximum increased by 61.5% and 63.4%, respectively. Conversely, the ultimate load carrying capacity and stiffness decreased. It was also found that the timber core weakened the strength of the confined concrete. However, timber core reduced the weight of columns, which slowed down the reduction of the ultimate load carrying capacity of per unit GTSCs, with the stiffness remains unchanged. GFRP laminates with an angle of 60° provide the best stiffness and ductility, and the layer numbers of GFRP has a positive effect on GTSC's mechanical performance. In addition, an analytical model was proposed based on the ultimate equilibrium method, which accounts for the ultimate bearing capacity of GTSC based on the influence of timber. Analyses revealed a good correlation between analytical and experimental results. [ABSTRACT FROM AUTHOR]

It is well known that the confinement effect provided by the steel tube significantly increases the strength and ductility of circular Concrete Filled Steel Tube (CFST) columns under concentric loading. The lateral pressure is an important factor to calculate the strength enhancement of CFST columns. To reliably predict the ultimate strength of circular CFST columns, many models have been developed for predicting the lateral pressure due to the confinement effect. This paper aims to evaluate some of these confining pressure models. The values of the compressive strength of confined concrete and lateral confining pressure of circular CFST short columns were calculated using these existing models and were compared with those obtained from previous test results. In addition, a comparison between the ultimate loads predicted by these models and by Eurocode 4 (EC4) was carried out. Based on the comparison results, some suitable models for circular CFST short columns with the use of normal-strength, high-strength, and ultra-high-strength concrete were indicated. [ABSTRACT FROM AUTHOR]

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Copyright of Steel Pipe is the property of Steel Pipe Magazine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to study the effect of steel tube, pre-load and temperature on residual performance of heated ultra-high strength concrete (UHSC), an experimental program was carried out to investigate the physical and mechanical properties of UHSC post-fire in room temperature. With total of 54 standard cylindrical concrete specimens subjected to various temperatures ranging from 62 °C to 496 °C, their residual compressive strength, elastic modulus, peak strain was measured after natural cooling down. By comparing the test results of standard cylindrical concrete specimens with the results of the bare specimens in and after fire, it is known that the residual compressive strength of standard cylindrical concrete specimens decayed more serious after exposing to same temperature. Seen from the results, the temperature which the specimens suffered was found to be responsibility to the reduction of the compressive strength, elastic modulus, peak strain. As the temperature up to 300 °C, the strength reduction coefficient of UHSC was 0.67 ~ 0.68 and the elastic modulus reduction coefficient of UHSC was 0.41 ~ 0.51 with peak strain coefficient εcr(T)/ε0 1.57 ~ 1.67. Finally, based on the analysis of test results, simple formulae were proposed to describe the effect of temperature on residual performance of heated UHSC which infilled the steel tube. [ABSTRACT FROM AUTHOR]

To explore the impact of localized corrosion on the mechanical properties of hollow steel columns under eccentric loads, a specialized localized immersion-accelerated corrosion apparatus was developed. This device facilitated the creation of 17 locally corroded specimens, all subjected to eccentric loading. A systematic examination was conducted on various corrosion parameters including corrosion length, corrosion angle, localized corrosion rate, and corrosion location as well as loading conditions, which encompassed eccentricity and loading angle. Surface corrosion morphology and statistical parameters of the specimens were obtained using a 3D scanner. Subsequently, a nonuniform corrosion model, based on element displacement, was formulated through finite element analysis. Both experimental findings and numerical simulations indicate that localized corrosion does not alter the failure mode of locally corroded circular steel tubes (LCCSTs), which predominantly undergo local buckling in the compressed region. However, it was noted that localized corrosion leads to the elimination of the ascending segment in the load-displacement curve of the LCCSTs, thereby reducing both the ultimate load and ductility. Interestingly, the ultimate load of the LCCSTs was found to be relatively unaffected by variations in corrosion length and location but significantly influenced by factors such as localized corrosion rate, corrosion angle, eccentricity, and loading angle. Furthermore, through a comparative analysis of existing calculation models for the ultimate load of LCCSTs in major specifications, a practical model that accounts for localized corrosion is proposed. This model demonstrates high accuracy and is expected to enhance the understanding and prediction of the ultimate load capacity of LCCSTs in real-world applications. • 17 steel tubes with local corrosion were loaded eccentrically. • Localized corrosion does not impact the failure mode but diminishes N u and DI. • Established validated FE models based on element offset for non-uniform local corrosion. • The N u of LCCSTs is more sensitive to the parameters: corrosion rate, angle, eccentricity, and loading angle. • A method was proposed to determine the ultimate strength of LCCSTs. [ABSTRACT FROM AUTHOR]

To study the behavior of the axial compression circular steel tube reinforced by a sleeved tube, the finite element model of casing tube reinforcement was established based on the existing research results. The mechanical properties and failure mechanism of the reinforced casing tube specimen were systematically studied by finite element parameter analysis. The results show that in the elastic stage, the outer-sleeved tube is less involved in the force. After entering the elastic-plastic stage, the outer-sleeved tube starts to work and is stressed together with the inner steel tube. Slenderness ratio, diameter-thickness ratio, and ferrule spacing are the main factors affecting the ultimate axial compression capacity of casing reinforcement components. When other variables are consistent, the ultimate axial compression capacity of specimens after reinforcement with different initial stress ratios is basically the same. The increase of the ferrule width and thickness has little effect on the improvement of the ultimate axial compression capacity of the reinforcement components. The load value after casing reinforcement calculated by the current standard is much higher than the test load value of the component. According to the results of parameter analysis and the current standard, the design method for the ultimate axial compression capacity of the circular steel tube reinforced by a sleeved tube was put forward. • Based on the existing experiments, a finite element model of the casing reinforcement was established and verified. • The behavior of axial compressive circular steel tubes reinforced by a sleeved tube were systematically studied. • A design method for the ultimate axial compression capacity of the circular steel tube reinforced by a sleeved tube was proposed. [ABSTRACT FROM AUTHOR]

This article aims to investigate the structural response of a novel type of composite concrete columns in which the conventional steel bars are replaced in the main longitudinal direction with small circular-section steel tubes infilled with cementitious grouting material (CGM). In this study, 24 circular cross-sectional reinforced concrete columns with different transverse reinforcement configurations were tested under varied eccentric axial loads (in two series with variable slenderness ratios). The type of columns (short with a height-to-diameter ratio of 4.41 or long with a ratio of 10.29), the type of reinforcement (steel bars of 16 mm diameter, steel tubes of 16 mm outer diameter infilled with CGM or steel tubes of 25.4 mm outer diameter infilled with CGM), the spiral pitch (50 or 75 mm), and the eccentricity of the applied load (25 or 50 mm) are the main test parameters included in the experimental program. The remarkable compression and tension strengths of confined CGM in comparison to concrete inspired the idea of embedding CGM within small steel tubes. Furthermore, economic factors support replacing a portion of the conventional steel material with cementitious grouting material. To evaluate the impact of the steel reduction resulting from CGM embedment within the steel tubes, the specimens' load capacity, strain, and deformation were investigated. The outcomes demonstrated that CGM-filled steel tubes are a promising and economically feasible solution for lowering the amount of steel used in column members. The findings demonstrated that the load-carrying capability of both the short and long-tested columns reinforced with 25.4 mm diameter CGM-infilled steel tubes was marginally greater than that of the columns reinforced with 16 mm diameter steel bars by 7%. Furthermore, specimens reinforced with 16 mm outer diameter steel tubes, where the wall area of the steel tube is only 30% of the area of a steel bar with the same diameter, provide an ultimate capacity ranging from 62% to 77% of the columns reinforced with steel bars with a 16 mm diameter. The capacity of the specimens decreased as the slenderness ratio and the eccentricity of the applied load increased, while the tested column's lateral deformation increased. In the meantime, a notable enhancement in the specimen's load capacity was seen with the reduction of the spiral pitch from 75 to 50 mm. • Cementitious grouting material-filled steel tubes were proposed as an alternative to traditional steel bars in composite concrete columns. • The advantage of steel tubes is demonstrated by the higher strength gain for concrete within tubes as opposed to concrete with steel spirals alone. • The axial and lateral stiffness of all tested columns showed a considerable decrease as the eccentricity and slenderness ratio increased. [ABSTRACT FROM AUTHOR]

This study introduces a new precast concrete (PC) double-wall system designed to simplify the complex fabrication process of existing PC double-wall systems and eliminate laitance and other defects that can occur during the manufacture of concrete panels. An experiment and finite element analysis were conducted on 11 specimens to determine the tensile resistance performance of rectangular steel tubes that maintain spacing to avoid damage to the PC panels during transportation or on-site installation. Specimens varied in terms of the end details of the rectangular steel tubes, such as the presence of welded steel plates or embedded concrete and total length in terms of whether longer or shorter specimens were used. As a result, the specimens showed a 20–30% increase in maximum tensile strength compared to the control specimen according to the end details, except for the case where side steel plates were cut and bent inward. The control specimen filled with concrete was the most suitable for connections when constructing PC double-wall systems. It has significant tensile resistance according to the experiment and finite element analysis and does not require additional construction steps or costs.