Concrete Steel Tube Research Articles

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

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

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

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

Experimental study on the bond-slip behavior of steel tube-coal gangue concrete

This study investigated the bond-slip behavior at the interface between steel tubes and coal gangue concrete, considering the coal gangue coarse aggregate replacement rate, the strength grade of coal gangue concrete, and the bond length as variable parameters. Eleven groups of push out tests were conducted on steel tube coal gangue concrete specimens. The bond slip curve and the longitudinal strain distribution curve of the steel tubes were obtained, and the effects of these parameters on bond strength were analyzed. The results showed that the load-slip curves at both the loading and free ends of the specimens were similar, with slip occurring earlier at the loading end. The regularity of the test curves in repeated experiments indicated that interfacial bond stress was primarily determined by friction in the later stages. The longitudinal strain of steel tubes was approximately exponentially distributed along their length. The interfacial bond strength increased with the increase of coal gangue aggregate replacement rate and was more pronounced in specimens with higher strength coal gangue concrete. Longer bond lengths resulted in greater bond failure loads, with a lower rate of increase in higher strength coal gangue concrete specimens compared to those with lower strength. Based on the three stage bond stress-slip relationship for steel tube-concrete, a bond-slip constitutive model for steel tube-coal gangue concrete was established. This provided a reference for mechanical analysis and interface performance design of steel tube-coal gangue concrete.

Mechanism of interface debonding in steel-concrete components caused by thermal expansion and contraction

The steel tube concrete structure constrains the core concrete through the inner wall of the steel tube, forming a hoop effect, significantly improving the compressive performance of the core concrete and effectively exerting the tensile performance of the steel tube. Although this structure has been optimized in terms of mechanical properties, its ultra-high bonding performance makes it extremely difficult to disassemble and recycle. To explore ways to solve this challenge, this article selects C40 concrete as the matrix concrete, and designs and produces circular steel tube concrete specimens and square steel tube concrete specimens with a height of 250mm and a steel tube wall thickness of 4mm. The specific research content covers the hoop effect of steel pipes on core concrete, the degradation law of thermal expansion and contraction interface bonding performance of steel pipe concrete components, the coupling effect of cutting joints and thermal expansion and contraction on interface bonding performance of steel pipe concrete components, and the mechanism of interface debonding of steel pipe concrete components. Through systematic experiments and analysis, the influence of different variation parameters on the debonding performance of steel tube concrete was deeply studied, and its debonding mechanism was revealed. This series of studies provides an important scientific basis for the theoretical understanding and application of steel-concrete structures, helping to overcome the problem of dismantling and recycling, and promoting the transformation and development of related equipment.

Overview of the Current Research Status of Concrete-Filled Steel Tube

Steel tube concrete refers to a composite structure formed by filling concrete in a steel tube, and the steel tube and its core concrete can jointly bear external loads. The seismic performance of composite structures largely depends on the strength and ductility of the columns. In the structure, columns are the main vertical load-bearing components due to their high strength and good ductility. However, under seismic action, steel tube concrete columns may experience end steel tube wall buckling, and the concrete inside the pipes may be crushed and lose its load-bearing capacity, causing the overall structure to collapse. In order to better utilize the performance of steel tube concrete, this study analyzes the research of scholars and explores the axial compression performance, failure modes, and local buckling effects of different types of concrete filled in steel tubes on the structural performance of steel tube concrete. Therefore, it is particularly important to study the axial compression performance of steel-concrete columns and explore reasonable design methods to delay the local buckling of steel pipes, and accurately evaluate the seismic performance of steel-concrete columns under large earthquake responses.

Compressive Behaviour of Long Steel Tube Columns Filled with Recycled Large Aggregate Self-Compacting Concrete

One of the important directions for green development in the world today is to expand the application methods of recycled concrete, improve the utilization rate of waste aggregates, and slow down the consumption of natural resources. The column structure with a large length and slenderness ratio is the most widely used compression unit in practical engineering, which conforms to the principle of sustainable development. In this paper, we study the mechanical properties and failure modes of long columns fabricated from steel tubes filled with recycled large aggregate self-compacting concrete (RLASCC-ST-LC) under compression load. Moreover, we examine the influence of steel tube thickness, recycled large-aggregate particle size, the strength of self-compacting concrete, and the length-to-diameter ratio on the performance of the members through finite element modelling. The results indicated that RLASCC-ST-LCs exhibited different degrees of buckling damage, and the damage processes were basically the same as that of steel tube concrete. When the thickness of steel pipe increased from 4 mm to 5 mm, the ultimate bearing capacity of the component increased by 12.1%; when the strength of self-compacting concrete increased from 30 MPa to 40 MPa and 50 MPa, the ultimate loads of the component increased by 6.96% and 12.4%, respectively. However, the increase in the aspect ratio weakened the bearing capacity of the component, and the ultimate bearing capacities reduced by 4.78% and 10.51% when the aspect ratios were 8, 10, and 12. Finally, based on the existing design codes, the theoretical calculation formulas are proposed for the ultimate bearing capacities of RLASCC-ST-LCs. These findings have significant implications for the widespread application of RLASCC-ST-LCs.

An Improved Equation for the Bearing Capacity of Concrete-Filled Steel Tube Concrete Short Columns Based on GPR

The determination of the bearing capacity prediction model of concrete-filled steel tubular columns is a key issue in the structural design of prefabricated buildings, which directly relates to the stability and safety of prefabricated buildings. The purpose of this paper is to study the bearing capacity model of concrete-filled steel tubular columns, and propose an explicit formula based on the Gaussian process regression algorithm to calculate the bearing capacity. In order to solve the problem of low accuracy of the traditional empirical bearing capacity model, this paper first proposes a more accurate bearing capacity prediction model based on Gaussian process regression algorithm to automatically learn and capture the characteristics of 122 groups of test data; the paper then determines the function of high sensitivity parameters and section influence parameters through the established bearing capacity prediction model, and this process gives the display formula. Compared with the implicit formula given by a machine learning model, the explicit formula proposed in this paper is more suitable for practical engineering design. In order to verify the validity of the formula, we generated the bearing capacity data through the proposed formula based on the test data and used the descriptive statistical method to verify. The results show that the proposed formula is superior to other existing methods, the error between the data generated by the proposed formula and the test data is smaller, and its accuracy reaches 93.73%, which is more suitable for calculating the bearing capacity of concrete-filled steel tubes with different cross sections.

Reliability analysis of proposed capacity equation for predicting the behavior of steel-tube concrete columns confined with CFRP sheets

Due to higher stiffness to weight, higher corrosion resistance, higher strength to weight ratios and good durability, concrete composite structures provide many advantages as compared with conventional materials. Thus, they have wide applications in the field of concrete construction. This research focuses on the structural behavior of steel-tube CFRP confined concrete (STCCC) columns under axial concentric loading. A nonlinear finite element analysis (NLFEA) model of STCCC columns was simulated using ABAQUS which was then, calibrated for different material and geometric models of concrete, steel tube and CFRP material using the experimental results from the literature. The comparative study of the NLFEA predictions and the experimental results indicated that the proposed constitutive NLFEA model can accurately predict the structural performance of STCCC columns. After the calibration of NLFEA model, an extensive parametric study was performed to examine the effects of different critical parameters of composite columns such as; (i) unconfined concrete strength, (ii) number of CFRP layers, (iii) thickness of steel tube and (iv) concrete core diameter, on the axial load capacity. Furthermore, a large database of axial strength of 700 confined concrete compression members was developed from the previous researches togive an analytical model that predicts the ultimate axial strength of composite columns accurately. The comparison of the predictions of the proposed analytical model was done with the predictions of 216 NLFEA models from the parametric study. A close agreement was represented by the predictions of the proposed constitutive NLFEA model and the analytical model.

Research on Force Design of Concrete Filled Steel Tube Structure with Open Hole and Stiffener

The built-in open-hole type stiffened rectangular steel tube concrete refers to a new combined structure formed by forming an open-hole steel plate in the longitudinal direction of the inner wall of the steel pipe and then filling the concrete. In order to study the function of the built-in open-hole stiffened joints, the design of the stiffened rectangular steel tube concrete was designed to analyze the influence of the mechanical properties of the steel-mixed interface. The results show that the vertical rib opening is formed, and the bearing capacity of the rectangular steel tube concrete interface is increased by 2.06 times under the limit state. The shear stiffness and shear capacity of the interface are improved by more than 4 times under normal use.

Constitutive model for confined ultra-high strength concrete in steel tube

With the development of material science and production technology, ultra-high strength concrete (UHSC) with uniaxial compressive strength up to 200MPa has been made available commercially and used for concrete filled steel tubular (CFST) columns in high-rise buildings. Finite element analysis is a necessary tool to analyze CFST columns, but its accuracy depends on the generic constitutive model for the confined UHSC in the steel tube. This paper proposes a new constitutive model for confined UHSC based on (1) a yield criterion which is a function of hydrostatic pressure and lode angle, (2) a non-associated flow rule with a dilation angle that is a function of the confining pressure and the equivalent plastic strain, and (3) a hardening/softening rule which is dependent on the confining pressure and the equivalent plastic strain. The parameters of the proposed constitutive model are calibrated by a series of uniaxial compression, biaxial compression and triaxial compression tests of UHSC specimens. The constitutive model is then implemented in ABAQUS and verified by the test results of short CFST columns. Comparison of the test and predicted results in terms of compression load versus axial strain and lateral strain curves demonstrates that the proposed model can predict accurately the maximum resistance of the stub CFST columns as well as the interactive behavior between the steel tube and the confined concrete core.

Combined strength of lightweight aggregate concrete-filled steel tube

The strength characteristics of lightweight aggregate concrete confined by steel tube were studied experimentally. Based on the superposition of two materials, a method was established to calculate the combined strength of lightweight aggregate concrete steel tube: the accuracy of this calculation was verified experimentally. The research indicated that the confining effect of steel tube on lightweight aggregate concrete increased as the steel area ratio is enlarged. The confining effect coefficient of lightweight aggregate concrete can be taken as 3·4, which reflected the stress–performance improvement of lightweight aggregate concrete under trip–direction compression. Comparison between calculation and test results showed that the calculations were precise. The calculated result could be regard as ultimate strength at a coefficient of lateral deformation of 0·5, and as its design strength at a coefficient of lateral deformation of 0·3.

Self-Compacting and Tiny Expanding Steel Tube Concrete Using in Large Span Bridges

The experimental studies on self-compacting and tiny expanding concrete filled in steel tube are introduced, which including the measurement of low ability of mixtures, the proportioning of the concrete filled in steel tube. The self-compacting and tiny expanding steel tube concrete has been applied in a large span bridge structure. The state of construction shows that the concrete have a good pump ability, a small loss of slump, a high strength early strength and a better self-compacting property.

Preparation and Application of High Dropping Non Vibration Self-Compacting Concrete

High dropping non vibration concrete is widely used in high-rise steel tube concrete construction. In this paper, a high dropping non vibration self-compacting concrete with high mobility, low slump loss, and good anti-segregation ability is developed by mixing addition of PCA superplasticizer and SCC composite expansive admixture. The test results showed that the admixture and cement used in the test possess sound compatibility. The slump flow of self-compacting concrete prepared are more than 660mm, T500 of 2.8~7.5s, 1h slump flow loss of less than 10%, and the segregation rate of less than 7.5%. Through strictly control production and dropping construction, supplemented by field ultrasonic detection measures, the high dropping self-compacting concrete in steel tube achieved successful application for a high-rise building.

Summary of Performance and the Application of the Concrete Filled Steel Tubular Structures

Due to the restraint of steel tube concrete of concrete filled steel tubular components，three directions’ compression at the same time， the bearing capacity of concrete is obviously improved.As a result of the existence of steel pipe concrete，can effectively prevent the steel tube of local buckling ，com-plementary advantages and disadvantages of these two kinds of material ， the performance of the material is greatly improved. In this paper, the performance and characteristics of the composite material has carried on the detailed instructions，the ultimate bearing capacity of calculation principle has carried on the detailed analysis and research， the application of this new type of material are summarized.

The Non-Probabilistic Reliability Analysis on Bearing Capacity of Steel Tube Concrete Column

The Non-Probabilistic Reliability Analysis on Bearing Capacity of Steel Tube Concrete Column

Cyclic testing of thin-walled circular steel tubular columns filled with demolished concrete blocks and fresh concrete

To simplify the waste concrete recycling process, the authors have proposed several new kinds of structural members containing demolished concrete with a distinctly larger size than conventional recycled aggregates. Previous researches and applications have preliminarily verified the suitability of these new environment-friendly structural members. The objective of the presented research is to provide new test data to study the seismic performance and to evaluate the strength and ductility of the thin-walled circular steel tubular column filled with demolished concrete blocks (DCBs) and fresh concrete (FC). Fifteen specimens, including 10 columns filled with DCBs and FC and 5 reference columns filled with FC alone, were tested under combined constant axial compression and reversed cyclic lateral loadings. Test variables are: replacement ratio of DCBs, thickness of steel tube, and axial load ratio. Based on the concept of combined strength of new and old concrete in steel tube, some design codes are employed to predict the lateral strength of the specimens. Research findings indicate that: (1) the seismic performance of thin-walled circular steel tubular columns filled with DCBs and FC is similar to that of the reference columns filled with FC alone; (2) the lateral strength of the columns filled with DCBs and FC is slightly lower than that of the reference columns filled with FC alone; and (3) even though the diameter-to-thickness ratio is only 168, the ultimate drift ratio of such a specimen filled with DCBs and FC with an axial load ratio of 0.4 can reach 4%, showing good deformation capacity.

Simulation Analysis of Shrinkage and Creep for Bowstring Arch Bridge Steel Tube Concrete in Different Specification

The actual bowstring arch CFST is taken as the background,the paper using finite element analysis method, researched the shrinkage and creep of combination of steel and concrete structure. Through the use of different countries regulation of shrinkage and creep of concrete, the effects of the structure deflection separately were studied ,then explain the different influence degree of different norms in the calculation of the creep and shrinkage of concrete; The paper also has also put forward the doubt about accurate calculation concrete filled steel tubular structure shrinkage and creep of concrete, it puts forward new requirements for the research and standards about steel tube concrete shrinkage and creep at last.

Study on the Function of Steel Tube Concrete in the Fire Prevention

Using circumferential constraint action of steel tube to concrete, steel tube concrete makes concrete be in the condition of three-dimensional pressure, to increase the strength of concrete and enhance the plastic performance. Due to the existence of the concrete could prevent or delay the steel tube from crippling, it makes steel tube material performance can be fulfilled. Steel tube concrete can not only make up two materials their shortcomings, but also give full play to the advantages of both. With high bearing capacity, good plasticity, convenience to construction and good refractory performance, and many other advantages, steel tube concrete make the loss in the fire reduced, and play a certain role in fire prevention and mitigation

The Application of Steel Tube Concrete Column Prestressed Beam Composite Structure in the Svit Building Project in Nanjing

The Application of Steel Tube Concrete Column Prestressed Beam Composite Structure in the Svit Building Project in Nanjing

Application of Prestressing Technology in Long Span Steel Tube Concrete Tied Arch Bridges

Application of Prestressing Technology in Long Span Steel Tube Concrete Tied Arch Bridges