• Steel and Composite Structures
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• v.17 no.6
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• pp.929-949
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• 2014

Thirty one push-out tests were carried out in order to investigate the bond behavior between shape steel, steel tube (named steels) and recycled aggregate concrete (RAC), including 11 steel reinforced recycled aggregate concrete (SRRAC) columns, 10 recycled aggregate concrete-filled circular steel tube (RACFCST) columns and 10 recycled aggregate concrete-filled square steel tube (RACFSST) columns. Eleven recycled coarse aggregate (RCA) replacement ratios (i.e., 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100%) were considered for SRRAC specimens, while five RCA replacement ratios (i.e., 0%, 25%, 50%, 75% and 100%), concrete type and length-diameter ratio for recycled aggregate concrete-filled steel tube (RACFST) specimens were designed in this paper. Based on the test results, the influences of all variable parameters on the bond strength between steels and RAC were investigated. It was found that the load-slip curves at the loading end appeared the initial slip earlier than the curves at the free end. In addition, eight practical bond strength models were applied to make checking computations for all the specimens. The theoretical analytical model for interfacial bond shear transmission length in each type of steel-RAC composite columns was established through the mechanical derivation, which can be used to design and evaluate the performance of anchorage zones in steel-RAC composite structures.

• Steel and Composite Structures
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• v.44 no.3
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• pp.339-351
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• 2022

A mortar-filled rectangular hollow structural section (RHS) can increase a structural section property as well as a compressive buckling capacity of a RHS member. In this study, the tensile performance of newly developed mortar-filled RHS members was experimentally evaluated with various connection details. The major test parameters were the type of end connections, the thickness of cap plates and shear plates, the use of stud bolts, and penetrating bars. The test results showed that the welded T-end connection experienced a brittle weld fracture at the welded connection, whereas the tensile performance of the T-end connection was improved by additional stud bolts inserted into the mortar within the RHS tube. For the end connection using shear plates and penetrating stud bolts, ductile behavior of the RHS tube was achieved after yielding. The penetrating bars increased load carrying capacity of the RHS. Based on the analysis of the load transfer mechanism, the current design code and test results were compared to evaluate the tensile capacity of the RHS tube according to the connection details. Design considerations for the connections of the mortar-filled RHS tubes were also recommended.

• Steel and Composite Structures
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• v.50 no.2
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• pp.217-235
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• 2024

Concrete-filled steel tubes (CFSTs) nowadays are widely used as the main parts of momentous structures, and its connection has gained increasing attention as the complexity in configuration and load transfer mechanism. This paper proposes a novel CFST pier-to-footing incorporating tube-confined RC encasement. Such an innovative approach offers several benefits, including expedited on-site assembly, effective confinement, and collision resistance and corrosion resistance. The seismic behavior of such CFST pier-to-footing connection was studied by testing eight specimens under quasi-static cyclic lateral load. In the experimental research, the influences on the seismic behavior and the order of plastic hinge formation were discussed in detail by changing the footing height, axial compression ratio, number and length of anchored bars, and type of confining tube. All the specimens showed sufficient ductility and energy dissipation, without significant strength degradation. There is no obvious failure in the confined footing, while local buckling can be found in the critical section of the pier. It suggests that the footing provides satisfactory strength protection for the connection.

• Journal of the Korean Society for Railway
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• v.14 no.2
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• pp.143-150
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• 2011

This paper presents a preliminary study for air-tightness evaluation of vacuum tube structures for super-speed tube railway systems. The formula for flow rate of the air caused by the pressure difference of the inside and outside of the tube structure is derived based on Darcy's law. A test is then performed to measure the air-permeability of concrete with various compressive strengths, the result of which is used for analytical simulation of the air intrusion for a tube structure with a preliminarily defined section. It has been shown that concrete with the compressive strength of at least more than 50MPa is recommended for effective operation and maintenance of the vacuum pump systems, as the air-permeability of concrete is inversely proportional to the exponent of its compressive strength.

• Steel and Composite Structures
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• v.30 no.3
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• pp.201-215
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• 2019

In this research, the behavior of tube-in-tube BRBs (TiTBRBs) has been investigated. In a typical TiTBRB, the yielding core tube is located inside the outer restraining one to dissipate energy through extensive plastic deformation, while the outer restraining tube remains essentially elastic. With the aid of FE analyses, the monotonic and cyclic behavior of the proposed TiTBRBs have been studied as individual brace elements. Subsequently, a detailed finite element model of a representative single span-single story frame equipped with such a TiTBRB has been constructed and both monotonic and cyclic behavior of the proposed TiTBRBs have been explored under the application of the AISC loading protocol at the braced frame level. With the aid of backbone curves derived from the FE analyses, a simplified frame model has been developed and verified through comparison with the results of the detailed FE model. It has been shown that, the simplified model is capable of predicting closely the cyclic behavior of the TiTBRB frame and hence can be used for design purposes. Considering type of connection detail used in a frame, the TiTBRB member which behave satisfactorily at the brace element level under cyclic loading conditions, may suffer global buckling due to the flexural demand exerted from the frame to the brace member at its ends. The proposed TiTBRB suit tubular members of offshore structures and the application of such TiTBRB in a typical offshore platform has been introduced and studied in a single frame level using detailed FE model.

• KIEAE Journal
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• v.7 no.6
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• pp.119-126
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• 2007

In the field of composite structures, the use of carbon tube for the confinement of concrete has been arisen since 1990's. However, experimental and analytical studies were limited to those of reinforced concrete and concrete filled steel tube. The carbon tube provides excellent confinement capabilities for concrete cores, enhancing compressive strength and ductility of concrete significantly. The carbon tube has high tensile strength, light weight, corrosion immunity and high fatigue strength properties. Since carbon fiber is an anisotropic material, carbon tube could be optimized by adjusting the fiber orientation, thickness and the number of different layers. In this study, both experimental and analytical studies of axial and lateral behavior of full-scale CFCT (Concrete Filled Carbon Tube) columns subjected to monotonic axial load were carried out using Drucker-Prager theory. And, based on comparison results between experiment results and analytical results, k factor estimation was proposed for effective analysis.

• Journal of Korean Association for Spatial Structures
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• v.15 no.3
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• pp.85-93
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• 2015

This paper presents a foundation pile to steel column connection that can resist large magnitude of moment and that can be easy installed. The developed joint has spherical shape and it is given the name HAT joint to mean Hallow half-sphere steel joint. Four types of HAT joints are developed. Namely, H-type, T-type, P-type and K-type. In this paper I will talk about the performance assessment of T-type(Tube Column) and P-type(Pile Column) of HAT joints with finite element analysis and experiment on a full scale model is presented.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.317-322
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• 1995

This study is to examine the usefulness in using precast girder-infilled steel tube column in reinforced concrete structures through the analysis of the test results, in order to develope the new composite structural system using precast girder-Infilled steel tube column, The variables of specimen are strength of concrete, the numble of hoops, the form of beam-column The variables of specimen are strength of concrete, the number of hoops, the form of beam-column joints. By raising strength of concrete and incresing number of hoops in beam-column joint, it becomes clear to take similar structure capacity to monolithic structures.

• Journal of the Korean Society for Advanced Composite Structures
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• v.4 no.3
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• pp.13-21
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• 2013

In this study, uniaxial compression tests were performed to investigates the stress-strain relations of Double Skinned Composite Tubular Columns reinforced with steel tube. The confined concrete has been known as the strength of concrete increases significantly. Specimens reinforced with outer and inner steel tube were tested by uniaxial compression test. To investigate the influence of concrete strength increase by confining conditions in steel tubes, 8 specimens with different thickness of tube, hollowness ratio and concrete strength were tested and compared with other researcher's concrete material model.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.1
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• pp.1-6
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• 2013

Ultrasonic guided wave techniques have been widely used for long range nondestructive detection in tube-like structures. The present paper investigates the ultrasonic linear and nonlinear parameters for evaluating the thermal damage in aluminum pipe. Specimens were subjected to thermal loading. Flexible polyvinylidene fluoride (PVDF) comb transducers were used to generate and receive the ultrasonic waves. The second harmonic wave generation technique was used to check the material nonlinearity change after different heat loadings. The conventional linear ultrasonic approach based on attenuation was also used to evaluate the thermal damages in specimens. The results show that the proposed experimental setup is viable to assess the thermal damage in an aluminum pipe. The ultrasonic nonlinear parameter is a promising candidate for the prediction of micro-damages in a tube-like structure.