• Earthquakes and Structures
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• v.8 no.3
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• pp.699-712
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• 2015

Bracing structures with off-centre bracing system is one of the new resistant systems that frequently used in the frame with pin connections. High ductility, high-energy dissipation and decrease of base shear are advantages of this bracing system. However, beside these advantages, reconstruction and hard repair of off-centre bracing system cause inappropriate performance in the earthquake. Therefore, in this paper, the goal is investigating the behavior of this type of bracing system with ductile element (circular dissipater), in order to providing replacement of damaged member without needing repair or reconstruction of the general system. To achieve this purpose, some numerical studies have been performed using ANSYS software, a frame with off-centre bracing system and optimum eccentricity (OBS-C-O) and another frame with the same identifications without ductile element (OBS) has been created. In order to investigate precisely on the optimum placement of circular elements under monotonic load again three steal frames were modeled. Furthermore, the behavior of this general system investigated for the first time, linear and nonlinear behavior of these two steel frames compared to each other, to achieve the benefit of using the circular element in an off-centre bracing system. Eventually, the analytical results revealed that the performance of steel ring at the end of off-centre braces system illustrating as a first defensive line and buckling fuse in the off-centre bracing system.

• Journal of the Korean Society of Safety
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• v.33 no.2
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• pp.86-93
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• 2018

Recently, the use of composite steel plate concrete structural modules filled with concrete between steel plates of complex internal structure, in which a large amount of studs are installed, is increasing in order to reduce the weight and to increase workability of structures such as LNG storage tanks. However, in Korea, there is no systematic criterion for evaluating the construction performance of composite steel plate concrete structural modules. Therefore, in this study, we propose a filling guideline of concrete for composite steel plate structural module. For this purpose, high filling performance concrete with general strength range was formulated and tested for filling ability and permeability for each formulation. Rheology analysis was performed to quantitatively evaluate the flow characteristics of concrete. The reliability of $T_{500}$ and plastic viscosity was evaluated to reflect the results of each test, and a guideline for high filling concrete satisfying the reliability of 0.9 or more was derived by reflecting the results of the study on the relationship between the $T_{500}$ and plastic viscosity. Through final fill-box test, filling performance was verified and guidelines were suggested.

• International Journal of Concrete Structures and Materials
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• v.10 no.3
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• pp.325-335
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• 2016

This paper studies the effects of steel fibre geometry and architecture on the cracking behaviour of steel fibre reinforced concrete (SFRC), with the reinforcements being four types, namely 5DH ($Dramix^{(R)}$ hooked-end), 4DH, 3DH-60 and 3DH-35, of various hooked-end steel fibres at the fibre dosage of 40 and $80kg/m^3$. The test results show that the addition of steel fibres have little effect on the workability and compressive strength of SFRC, but the ultimate tensile loads, post-cracking behaviour, residual strength and the fracture energy of SFRC are closely related to the shapes of fibres which all increased with increasing fibre content. Results also revealed that the residual tensile strength is significantly influenced by the anchorage strength rather than the number of the fibres counted on the fracture surface. The 5DH steel fibre reinforced concretes have behaved in a manner of multiple crackings and more ductile compared to 3DH and 4DH ones, and the end-hooks of 4DH and 5DH fibres partially deformed in steel fibre reinforced self-compacting concrete (SFR-SCC). In practice, 5DH fibres should be used for reinforcing high or ultra-high performance matrixes to fully utilize their high mechanical anchorage.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.79-81
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• 2005

Bridges constructed recently are preferred to have long spans and simple structure details considering not only the function as bridge but scenic beauty, maintenance, construction term and life cycle cost, etc. Therefore, they require high performance steels like extra-thick plate steels and TMCP steels. A TMCP steel produced by themo-mechanical control process is now spot lighted due to the weldability for less carbon equivalent. It improved at strength and toughness in microstructure. Recently, the SM570-TMC steel which is a high strength TMCP steel whose tensile strength is 600MPa has been developed and applied to steel structures. But, for the application of this steel to steel structures, it is necessary to elucidate not only the material characteristics but also the mechanical characteristic of welded joints. In this study, the characteristics of residual stresses in welded joints of SM570-TMC steel were studied through the three-dimensional thermal elastic-plastic analyses on the basis of mechanical properties at high temperatures obtained from the elevated temperature tensile test.

• Steel and Composite Structures
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• v.42 no.6
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• pp.765-777
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• 2022

Ultra high performance concrete (UHPC) can be used in the UHPC-steel composite structures especially for bridge structures to achieve high stiffness and high fatigue resistance with low self-weight. The structural performances of UHPC-steel composite slabs subjected to hogging moment have a significant influence on the global stiffness and durability of UHPC-steel composite structures. In order to study the structural behaviors of non-steam-cured UHPC-steel composite slabs subjected to negative moment, five composite slabs combined the thin UHPC layers to steel plates via shear stud connecters with the diameter of 16mm were fabricated and tested under negative moment. The test program aimed to investigate the effect of stud spacing and longitudinal reinforcement ratios on the failure mode, load-deflection behaviors, cracking patterns, bond-slips, and carrying capacities of composite slabs subjected to negative moment. In addition, direct tensile tests for the dog-bone UHPC specimens with longitudinal reinforcement bars were carried out to study the effect of reinforcement bars on the tensile strength of UHPC in the thin structure members. Based on the experimental results, analytical models were also developed to predict the cracking load and ultimate load of UHPC-steel composite slabs subjected to negative moment.

• Journal of Korean Society of Steel Construction
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• v.18 no.3
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• pp.395-403
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• 2006

Recently constructed bridges often have long spans and simple structure details considering not only the function but other important factors such as aesthetics, maintenance, construction duration and life cycle cost. Therefore, bridges require high-performance steels like extra-thick plate steels and thermo-mechanical control process (TMCP) steels. TMCP stels are now gaining wide attention due to their weldability improved strength and toughness. Recently, SM570-TMC steel, which is a high-strength TMCP steel with a tensile strength of 600 MPa, has been developed and applied to steel structures. However, using this steel in building steel structures requires the elucidation of not only material characteristics but also the mechanical characteristic of welded joints. In this study, high-temperature tensile properties of SM570-TMC steel were investigated through the elevated temperature welded joints of SM570-TMC steel were studied through the three-dimensional thermal elasticplastic analyses on the basis of mechanical properties at high temperatures obtained from the experiment.

• Corrosion Science and Technology
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• v.19 no.2
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• pp.57-65
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• 2020

As competition among global automakers intensifies, demand for materials that are better in price and performance is increasing. While steel and plastic materials compete for automotive fuel tanks, plastic materials have advantages such as light weight for automobiles. However, they have high prices. Accordingly, in this paper, four types of Zn-X plated steel sheets, electroplating (X = none, Sn) and galvannealed (X = Fe, Fe-Mg), were manufactured and their applicability as a fuel tank material was evaluated. Nano-composite coating solution with good conductivity was treated on the surface of plated steels using a roll coater and then cured through induction furnace to improve corrosion resistance. Quality characteristics such as corrosion resistance, fuel resistance to diverse gasoline and diesel fuels, and seam weldability were evaluated for the above plated steels. Their properties were compared and analyzed with conventional Zn-Ni electroplating steels. Among the above plated steels, Zn-Fe-Mg galvannealed steels coated with nano-composite coating exhibited better properties than other steels. Detailed experimental results suggest that evenly distributed Mg elements on the coating layer play a key role in the enhanced quality performance.

• Steel and Composite Structures
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• v.44 no.4
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• pp.545-555
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• 2022

Empirical relationships that capture the nonlinear behavior of headed steel shear stud anchors have been derived from standard push out tests, where the specimens are comprised of large wide flanged steel sections attached to flat concrete slabs via the anchors. However, many composite systems used in practice utilize much smaller steel members and/or steel decking as part of the slab system. Composite open web steel joist systems generally include both of these elements and consequently the nonlinear performance ofthe anchor is not accurately represented by existing models. In this paper, a new empirical relation is presented for open web steel joist systems based on experimental results from a modified push out test that more realistically represent a composite open web steel joist system. The methodology for obtaining the proposed nonlinear function where the response of the system is characterized by two parameters(α and β) is presented. The two-step process for obtaining the two parameters is described and the empirical relation is calibrated with the experimental data. In comparison with existing expressions, the new proposal herein more accurately predicts the high initialstiffness of the system and overall nonlinear system performance.

• Journal of Korean Society of Steel Construction
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• v.17 no.3 s.76
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• pp.365-373
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• 2005

There is increasing need for high-strength steel especially for the high-rise steel building structure. High- strength steels, however, may have mechanical properties that are significantly different from those of the conventional steels.The application of high-strength steels to building structures should be reviewed as to whether inelastic behavior equivalent to that of conventional steels can be attained or not. In this study, SM570TMC steel, which was developed recently in Korea, was tested to evaluate mechanical properties and welding characteristics for use as a structural steel. Yield phenomenon of SM570TMC steel, which is continuous yielding, is quite different from that of conventional steel. The distributions of yield strength of SM570TMC steel were uniform regardless of thickness, while the minimum yield strength was 440MPa. Also, the flat distributions of hardness in z-direction were found to comprise one of the important properties. Results of the charpy impact tests at -5oC revealed toughness values of SM570TMC steel, which were higher than those of equivalent as rolled steel. Carbon equivalent(Ceq) values of SM570TMC steel, which were related to welding performance, were lower than those of equivalent as rolled steel.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.240-241
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• 2000

Sapphire fiber has been used to provide an optical path for the total radiation pyrometry. In measuring the temperature, we use the two-color detector, which consists of a high-performance Silicon detector mounted in a "sandwich" configuration over a Germanium detector. Sapphire fiber can withstand high temperature in the molten steel for two and a half hours. The maximum value of the error is the $\pm$2.5$^{\circ}C$ in the range of 152$0^{\circ}C$~1$600^{\circ}C$. This paper presents the simple scheme for measuring the molten steel temperature in the blast furnace of the iron ＆ steel making process.g process.