Diameter Of Steel Tube Research Articles

Retraction Note: Repair of Buckled Concrete Filled Steel Tube Columns Subjected to Axial Compression

Concrete filled steel tube (CFST) columns are the main loaded elements in the structures as they provoke the superior mechanical properties of constituent materials. However, concrete filled double steel tube (CFDST) columns refer to a new type of composite elements which have very high level of fire resistance and the potential to be implemented in high-rise structures. Columns are exposed to high stresses due to the increasing loads of daily life. Therefore, unpredictable deformations may occur and affect the performance and safety of structures. This article first studies the effectiveness of a concrete filled circular steel tube (CFCST)-based technique for repairing buckled and stressed CFST columns, then it studies the advantages of CFDST columns in improving the capability of composite members. The CFCST-based repairing system is to place the deformed CFST column in a larger diameter steel tube, and then the concrete is poured in the gap between the deformed column and the larger tube. Buckled CFST specimens with different tube tkicknesses were repaired and tested to failure under axial compression. The performance of repaired CFST columns was compared with that of undamaged counterpart columns. Based on findings, it can be concluded that the repair technique restored the capacity of the deformed columns from 97% to 100% of the capacity of the undamaged counterpart columns which confirm the effectiveness of repairing using CFCST-based technique. Results of the study provide significant information to the available test data concerning repairing of CFST members.

Practical artificial neural network tool for predicting the axial compression capacity of circular concrete-filled steel tube columns with ultra-high-strength concrete

This paper aims to develop a practical artificial neural network tool for predicting the axial compression capacity of circular concrete-filled steel tube columns with ultra-high-strength concrete. For this purpose, a nonlinear finite element analysis of circular concrete-filled steel tube columns with ultra-high-strength concrete was conducted and verified with experiments in the literature. Accordingly, a database of 768 finite element models was generated to use for developing the artificial neural network models. In this regard, the column length, the diameter of steel tube, the thickness of steel tube, yield and ultimate strength of steel tube, and compressive strength of concrete were considered as the input variables while the axial compression capacity was considered as an output variable. The performance of the proposed artificial neural network model was compared with the current structural design codes including AS/NZS 5100.6, Eurocode 4, AISC, and GB 50936. The comparative study indicated that the proposed artificial neural network model achieved a superior prediction compared to others. Ultimately, a graphical user interface tool was developed based on the proposed artificial neural network model to predict the axial compression capacity of circular concrete-filled steel tube columns with ultra-high-strength concrete for practical engineering design. • The proposed ANN model can accurately predict the axial compression capacity of CCFST columns with UHSC. • The proposed ANN model shows more accuracy than four notable existing design code formulas. • A GUI tool is developed based on the proposed ANN model for practical engineering design.

Experimental and numerical study of GFRP-reinforced circular steel tube under axial compression

The performance of glass fiber-reinforced epoxy resin (GFRP) reinforced circular steel tubes under axial compression was studied using both numerical and experimental methods. Through axial compression tests, the effects of steel tube thickness, GFRP winding angle (the angle between the axis of the tube and the tangential direction of winding fiber) and specimen length on specimens' failure modes and stability carrying capacity were studied; and proved that GFRP can improve the axial compression behavior of steel tube. A UMAT subroutine for GFRP that could consider 6 initial failure modes (fiber tension or compression failure, resin tension or compression failure and stretch or compression in-layer delamination failure) and damage evolution was developed, and then the axial compression processes of specimens were simulated; moreover, a further parametric analysis to examine specimens of different GFRP thickness and winding angle, steel tube diameter and thickness, as well as specimen length was carried out. A predictive formula was introduced to estimate the buckling load of specimen by modifying the Perry-Robertson equation. Finally, based on the simulation and the equivalent concept, the application of GFRP reinforced circular steel tube in the reticulated mega-structure was discussed.

Axial compressive performance of RAC-encased RACFST composite columns

A new type of composite column, recycled aggregate concrete (RAC)-encased recycled aggregate concrete-filled steel tube (RACFST) composite columns, promotes the RAC extensive utilization considering synergistic effect between the RAC and the steel tube, which is an attempt to develop environmentally sustainable concrete in high-rise buildings. In this paper, experimental research investigated the axial compressive behavior of RAC-encased RACFST composite columns. Twenty 1:3-scaled specimens were fabricated to test until failure under axial compressive loading. The main variable parameters affecting the behaviour of specimens were recycled coarse aggregate replacement ratio (range from 0% to 100% with 10% increase), stirrup spacing (s = 50 mm, 70 mm, 100 mm, 120 mm), diameter of steel tube (D = 89 mm, 114 mm), concrete strength grade (RC40, RC60) and longitudinal reinforcement ratio (4▪12, 8▪12). The failure modes, the whole load-deformation curves and the mechanical performance of specimens were also obtained based on static loading experiments and theoretical analysis. It was found that RAC-encased RACFST composite columns, which were subjected to identical axial loads, exhibited more favorable bearing capacity and deformation than those of a comparative reinforced recycled aggregate concrete columns (RACC). The replacement ratio of RCA had a slight effect on the mechanical performance of RAC-encased RACFST composite columns, the optimal substitution ratio of RCA was 50–60%. Based on the previous theory of superposition, the concrete cover is considered, and a calculation formula with double reduction coefficients of the axial load-bearing capacity of composite columns is proposed. Compared to the simplified superimposition method and the Chinese code Technical specification for steel tube-reinforced concrete column structure (CECS188:2005), the calculated results of axial compression bearing capacity by the proposed formula are in more agreement with the experimental values, with errors no greater than 15%.

Nonlinear finite element analysis of double skin composite columns subjected to axial loading

The study aimed to simulate the behavior of the concrete-filled double skin steel tubular (CFDST) composite columns having a circular hollow section using the finite element method (FEM). To indicate the accuracy and the reliability of the model, the proposed FEM model was verified by the experimental test results available in the literature. Moreover, the code-based formulas (ACI, AISC, and Eurocode 4) and some empirical models suggested by the previous researchers for predicting the axial capacity of CFDST columns were used in this study to compare their results with the proposed FEM model. Furthermore, to visualize the effectiveness of sectional properties and infilled concrete compressive strength on the ultimate axial strength of double skin composite columns, a parametric study was conducted. For this, 72 test specimens were modeled considering two outer and inner steel tube diameters, three outer and inner steel tube thicknesses, and two different concrete cylinder strengths. All results were statistically evaluated. It was observed that the proposed FEM model had a good prediction performance. As well, the FEM model results indicated that the sectional properties, in particular, the diameter of the outer steel tube and concrete compressive strength, had remarkable effects on the load-carrying capacity of CFDST columns.

RETRACTED ARTICLE: Repair of Buckled Concrete Filled Steel Tube Columns Subjected to Axial Compression

Concrete filled steel tube (CFST) columns are the main loaded elements in the structures as they provoke the superior mechanical properties of constituent materials. However, concrete filled double steel tube (CFDST) columns refer to a new type of composite elements which have very high level of fire resistance and the potential to be implemented in high-rise structures. Columns are exposed to high stresses due to the increasing loads of daily life. Therefore, unpredictable deformations may occur and affect the performance and safety of structures. This article first studies the effectiveness of a concrete filled circular steel tube (CFCST)-based technique for repairing buckled and stressed CFST columns, then it studies the advantages of CFDST columns in improving the capability of composite members. The CFCST-based repairing system is to place the deformed CFST column in a larger diameter steel tube, and then the concrete is poured in the gap between the deformed column and the larger tube. Buckled CFST specimens with different tube tkicknesses were repaired and tested to failure under axial compression. The performance of repaired CFST columns was compared with that of undamaged counterpart columns. Based on findings, it can be concluded that the repair technique restored the capacity of the deformed columns from 97% to 100% of the capacity of the undamaged counterpart columns which confirm the effectiveness of repairing using CFCST-based technique. Results of the study provide significant information to the available test data concerning repairing of CFST members.

The Study on Early‐Age Expansion and Shrinkage Model of Massive Self‐Compacting Concrete Pumped in Steel Tube Column

Massive self‐compacting concrete pumped in steel tube columns has been used more and more widely in super high‐rise buildings and bridge engineering at present. The early‐age expansion and shrinkage performance of its core mass concrete is an important index to ensure the stress state of triaxial compression and structural safety. However, no relevant reports have been found. In view of the actual building with the height of 265.15 meters, the early‐age expansion and shrinkage tests of the massive self‐compacting concrete pumped in full‐scale columns with the height of 12.54 m and 12.24 m and diameter of 1.3 m and 1.6 m were carried out by means of strain gauges embedded in concrete‐filled steel tubes (CFSTs). The early‐age variation regularity of the vertical and horizontal expansion and shrinkage strains for the core concrete with the diameter of steel tube, development time, temperature, the pouring pressure, expansion stress, and so on is given. The calculation model of its early‐age deformation strains is presented in this paper, which is in good agreement with the experimental results. It provides the basis of experimental and theoretical analyses for shrinkage compensation of massive self‐compacting concrete pumped in steel tube columns.

Application of tuned liquid column ball damper (TLCBD) for improved vibration control performance of multi-storey structure.

Tuned liquid column ball damper (TLCBD) is a passive control device used for controlling the building vibrations induced from wind or earthquakes. TLCBD is a modified form of conventional tuned liquid column damper (TLCD). This paper studies the effect of TLCBD on the four-storey steel frame structure. The performance of the TLCBD is also compared with conventional TLCD. The analytical model of both TLCD and TLCBD is presented here. The effectiveness of these analytical models is examined experimentally by series of shaking table tests under different excitation levels including harmonic loadings and seismic excitations. In TLCBD, the vibration is reduced significantly as compared to TLCD by using steel ball as a moving orifice. The difference in diameter of steel ball and tube, containing the liquid column, acts as an orifice which moves with the movement of the ball. This moving orifice phenomenon enhanced the vibration reduction effect by resisting the water motion in the TLCBD. Root mean square (RMS) and peak values of acceleration were calculated for each loading and each storey of uncontrolled and controlled structures. Comparison of the time histories of controlled and uncontrolled structures for different loadings is also reported. Results indicate that the TLCBD is more effective in the earthquake scenarios as compared to the harmonic excitations. The TLCBD controls the vibration of the primary structure significantly in vibration reduction.

Flexural Performance of High-strength Prestressed Concrete-encased Concrete-filled Steel Tube Sections

The sections composed of concrete and steel, which include concrete-encased concrete-filled tubes, generally have defects due to the low tensile strength of concrete. Therefore, an appropriate method was used for the combination of concrete-filled tubes (CFT) and prestressing strands which is encased in concrete. The conventional design guidelines are commonly developed for materials with normal strength thus further investigation is required to be conducted for sections with high-strength materials. In order to develop the design process, high-strength concrete and steel have been utilized in this study to examine the effects of steel and concrete strengths on the core concrete confinement, sectional size and flexural behavior of high-strength prestressed concrete-encased CFST (HS-PCE-CFST) beams. Hence, a total of thirteen HS-PCE-CFST beams were modeled via ABAQUS finite element software. The main variables include the steel tube yield strength, compressive cylinder strength of the core and outer concrete and the steel tube diameter to section width ratio. Furthermore, experimental results were employed to verify the finite element model. The bending moment, ductility, flexural stiffness and failure mode of beams are also examined. The results confirm that among the compressive strength of the outer and core concrete and the steel tube yield strength, change in the outer concrete compressive strength has a greater effect on the change of flexural parameters, also increasing the ratio of steel tube diameter to section width causes a minor increase in the ultimate bending moment and serviceability level flexural stiffness, but a major escalation in the initial flexural stiffness.

Effect of void Ratio of Inner Steel Tube on Compression Behavior of Double Skin Tubular Column

Hybrid double skin tubular columns (DSTCs) are a composite members that consist of outer FRP tube and inner steel tube and concrete filled in between. These three materials combination in one element have several advantages do not found in common columns. The total 12 circular DSTCs were poured and tested under axial load. Every specimen is average of a pair of samples of the variables, diameter and thickness of steel tube, to investigate effect of inner steel tube void ratio on compression behavior of hybrid DSTC. The void ratio was defined as a ratio between the two inner steel and outer FRP tube diameter. The test results show that the stress-strain behavior of concrete material in the hybrid DSTCs has a better confined by two tubes. While the DSTC with small diameter has similar behavior to concrete filled FRP tube (CFFT). Thickness of inner steel tube is slightly effect on concrete stress inside DSTC.

Prediction model on compressive strength of recycled aggregate concrete filled steel tube columns

The design of composite members consisting of a tubular column and in-filled conventional concrete has been available and well-defined in the provisions. However, for steel tube members filled with recycled aggregate concrete, there aren't any other special requirements in the current provisions. In this study, the experimental test results are used to model and evaluate the ultimate strength of axially loaded recycled aggregate concrete filled steel tube columns. The test specimens has a length to diameter ratio ranging from 2.0 to 3.5, indicating that they are the stub column and not failing in overall buckling. The proposed model was derived based the technique of gene expression programming. The database utilized contains a total of 97 test results. The predictor variable employed to generate the model are outer diameter, thickness and yield strength of steel tube, length of the column, recycled coarse aggregate replacement ratio, and concrete compressive strength. The experimental data and associated analytical model are examined by four widely used design codes of ACI, Eurocode 4, AIJ, and DL/T. A sensitivity statistical analysis is further conducted to assess the contributions of each parameter affecting the axial capacity. The outcome indicates that the developed model gives reasonable predictions of the axial capacity of recycled aggregate concrete filled circular steel tube stub columns compared to the existing expressions.

Experimental investigations of concrete-filled steel tubular columns confined with high-strength steel wire

The use of high-strength steel wires is proposed to provide external confinement for concrete-filled steel tubular columns. This article presents an experimental study on high-strength steel-wire-confined concrete-filled steel tubular columns with various high-strength steel wire spacings and steel tube thicknesses and diameters. As observed from the experimental results, high-strength steel wires can effectively constrain and delay the local buckling of the steel tube in concrete-filled steel tubular columns. As a result, the load-carrying capacity and the post-peak stiffness of concrete-filled steel tubular columns are significantly increased by the high-strength steel wire confinement. When the spacing of the high-strength steel wires decreases, the load–axial strain response can evolve from a softening behavior to a hardening behavior for the concrete-filled steel tubular columns. Moreover, theoretical models were developed to predict the load-carrying capacity of the externally confined concrete-filled steel tubular columns, taking into account the mechanical mechanism and the triaxial stress state of the inner concrete. The analytical results are generally in reasonable agreement with the experimental results.

Axial compression capacity of circular CFST columns transversely strengthened by FRP

Fiber reinforced polymer (FRP) jackets have been recently used for strengthening purpose of concrete filled steel tube (CFST) composite columns and also for the suppression of outward local buckling that CFST columns may suffer. This study intends to investigate the axial compression capacity of circular CFST columns transversely strengthened by FRP. For this, an attempt has been made to implement gene expression programming (GEP) technique for the development of axial capacity of confined CFST prediction model. The database required for the derivation of the GEP model is based on the extensive experimental results of the FRP confined CFST columns tested in compression (92 test specimens). Moreover, these test specimens wrapped with the carbon or glass fiber sheets have different length to diameter ratios of 2.0–4.5. The input predictor variables used in the study are the properties of the FRP (the type, thickness and sheet wrap layers, tensile strength and elastic modulus of FRP), the steel tube (outer diameter, thickness, length and tensile strength of steel tube) and unconfined concrete (compressive strength of in-filled concrete). To verify the effectiveness of the model, the values from GEP were examined statistically against those of existing equations given by various researchers. After analyzing and comparing the proposed model with the existing formulas, it was found that the results obtained by GEP have significantly less errors and far more accurate.

Experimental study on flexural behavior of micro circular steel pipe with grouting

In order to study the bending resistance of grouted micro circular steel tube, pure bending tests on 9 grouted steel tubes were carried out with different grouting materials and three kinds of diameter steel tube. Through the analysis of deflection, surface strain and internal steel bar strain during the test, the deformation characteristics and load-strain relationship of members under load are studied. The ultimate bending capacity and bending stiffness test results are compared with the calculated values of different codes. The results show that the ultimate bearing capacity calculated by different codes is quite different from the test results, and the calculated values of Fujian Provincial Standard DBJ13-51-2010 are in good agreement with the test results and are safe. The bending stiffness at the initial stage calculated by different codes and the bending stiffness at the service stage are also quite different from the test results. The calculation results of AIJ (2002) are in good agreement with the test results and can be used for design calculation after revision.

Experimental assessment of a novel steel tube connector in cross-laminated timber

This paper summarises experimental investigations conducted on a novel connector assembly consisting of hollow steel tubes placed inside cross-laminated timber panels. The criteria that drove the connector development were: (i) easy to manufacture and install; (ii) high capacity, stiffness, and ductility; and (iii) neglectable damage to the timber. A total of 24 test assemblies with varying steel tube diameters (ranging from two to four inch) were tested using quasi-static monotonic and reversed cyclic loading. The results demonstrated that – when using an appropriate connection layout – the desired ductile steel yielding failure mechanism was initiated and wood crushing of any form was avoided. The tested configurations reached load-carrying capacities up to 58 kN, exhibited high stiffness (>15 kN/mm), and were classified as moderately to highly ductile. The research presented herein demonstrated that this novel connection assembly for cross-laminated timber panels can be utilized in seismic regions.

Inorganic scale thickness prediction in oil pipelines by gamma-ray attenuation and artificial neural network

Scale can be defined as chemical compounds that are inorganic, initially insoluble, and precipitate accumulating on the internal walls of pipes, surface equipment, and/or parts of components involved in the production and transport of oil. These compounds, when precipitating, cause problems in the oil industry and consequently result in losses in the optimization of the extraction process. Despite the importance and impact of the precipitation of these compounds in the technological and economic scope, there remains difficulty in determining the methods that enable the identification and quantification of the scale at an initial stage. The use of gamma transmission technique may provide support for a better understanding of the deposition of these compounds, making it a suitable tool for the noninvasive determination of their deposition in oil transport pipelines. The geometry used for the scale detection includes a 280-mm diameter steel tube containing barium sulphate (BaSO4) scale ranging from 0.5 to 6 cm, a gamma radiation source with divergent beam, and a NaI(Tl) 2 × 2″ scintillation detector. The opening size of the collimated beam was also evaluated (2–7 mm) to quantify the associated error in calculating the scale. The study was done with computer simulation, using the MCNP-X code, and the results were validated using analytical equations. Data obtained by the simulation were used to train an artificial neural network (ANN), thereby making the study system more complex and closer to the real one. The input data provided for the training, testing, and validation of the network consisted of pipes with 4 different internal diameters (D1, D2, D3, and D4) and 14 different scale thicknesses (0.5 to 7 cm, with steps of 0.5 cm). The network presented generalization capacity and good convergence, with 70% of cases with less than 10% relative error and a linear correlation coefficient of 0.994, which indicates the possibility of using this study for this purpose.

Experimental study on the hysteretic behavior of ECC-encased CFST columns

Concrete-encased concrete-filled steel tube (concrete-encased CFST) columns, which is a conjunction of normal steel reinforced concrete (RC) and CFST columns, have been widely used in structural engineering. However, the outer RC component tends to crush in the early stage due to the significantly different mechanical performance of outer concrete and inner CFST. In this paper, it is proposed to substitute outer concrete with engineered cementitious composite (ECC) to form ECC-encased CFST columns. This paper presents an experimental study on the hysteretic behavior of ECC-encased CFST columns. Eleven specimens, including seven ECC-encased CFST columns and four concrete-encased CFST columns were tested under cyclic loading. According to the test results, ECC-encased CFST columns exhibited stable ductile behavior and the cumulative energy dissipation is about twice as much as that of concrete-encased CFST columns with same geometry. Also, the increase of steel tube diameter and stirrup ratio have positive effects on the hysteretic behavior of ECC- encased CFST columns.

Double-tube concrete columns with a high-strength internal steel tube: Concept and behaviour under axial compression

This article presents a new form of fibre-reinforced polymer-concrete-steel hybrid columns and demonstrates some of its expected advantages using results from an experimental study. These columns consist of a concrete-filled fibre-reinforced polymer tube that is internally reinforced with a high-strength steel tube and are referred to as hybrid double-tube concrete columns. The three components in hybrid double-tube concrete columns (i.e. the external fibre-reinforced polymer tube, the concrete infill and the internal high-strength steel tube) are combined in an optimal manner to deliver excellent short- and long-term performance. The experimental study included axial compression tests on eight hybrid double-tube concrete columns with a glass fibre–reinforced polymer external tube covering different glass fibre–reinforced polymer tube thicknesses and diameters as well as different high-strength steel tube diameters. The experimental results show that in hybrid double-tube concrete columns, the concrete is well confined by both the fibre-reinforced polymer tube and the high-strength steel tube, and the buckling of the high-strength steel tube is suppressed so that its high material strength can be effectively utilized, leading to excellent column performance. Due to the high yield stress of high-strength steel, the hoop stress developed to confine the core concrete is much higher than can be derived from a normal-strength steel tube, giving the use of high-strength steel in double-tube concrete columns an additional advantage.

Forming limit in burring process of large diameter steel tube

Forming limit in burring process of large diameter steel tube

FEM Analysis and Forming Limit in Burring Process of Large Diameter Steel Tube

FEM Analysis and Forming Limit in Burring Process of Large Diameter Steel Tube