• Journal of Korean Society of Steel Construction
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• v.21 no.6
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• pp.575-583
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• 2009

As the height of buildings rises, new structural systems are being applied other than theexisting S, RC, and SRC to decrease the weight of buildings and to make their construction more efficient, CFT structureshad been applied in many building construction projects due to their superior structural performance and construction efficiency. CFT structures need a diaphragm to harmoniously transmit the beam flange load to the column and the opponent beam in connections. Especially, on the right and left sides of the column other beams are connected, The establishment of a diaphragm for the lower part flange load delivery of the beam and guarantee for concrete filing capacity difficulty have (What does this mean?). In this paper, connection details are proposed in the form of a welded vertical plate with a circular hole on the CFT column's interior to harmoniously transmit the lower-part beam flange load to the column and the opponent beam. Thesediaphragm details use the concrete anchor effect in the beam flange load delivery, with the concrete-filled CFT column interior piercing the hole of the perforated plate, and a perforated board is established vertically to improve the concrete filling capacity. To analyze the structural performance of the proposed connection details, five simple tension specimens were made with the following parameters: with our without vertical and horizontal perforated plates, shear hole number, concrete filled or not, thickness of the perforated plate, etc. Then experimental tests were performed on these specimens.

• Journal of Korean Society of Steel Construction
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• v.21 no.6
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• pp.585-596
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• 2009

In the construction of end-plate connections, the end-plate is welded to the end of the beam in a factory and fastened by bolts in the field. This connection is widely used in advanced countries such as European countries and the U.S. Its design and connection details are prescribed in Eurocode 3, AISC LRFD, and FEMA 350. In Korea, the standards for seismic design in KBC 2005 have been reinforced based on IBC 2000 in the U.S., and it is expected that the connection details in the U.S. will be adopted for the establishment of beam-to-column design standards. In the U.S. thick end-plates are used for the connections to prevent beam rupture. The use of the connections in Korea, however, may lead toover-design. In this experimental study, the design standards for the end-plate connections provided by FEMA-350 were analyzed and structural tests for six specimens were conducted with the variables being the shim plate and the connection shape, to provide the best specifications for connections with plastic deformation in the end-plate for use in Korea.

• Journal of Korean Society of Steel Construction
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• v.26 no.4
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• pp.263-275
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• 2014

In this study, connection of steel reinforced concrete(SRC) column and composite beam which consists of H-section and U-section members were tested under cyclic loading. An essential point of the composite beam is the structural performance of welded joint between the H-section and the U-section members. To improve the structural performance of joint of two beam members, vertical stiffeners, trapezoidal stiffeners, and top bars were used. Five full-scaled specimens were designed to study the effect of a number of parameters on cyclic performance of connections such as H-section beam size($H-500{\times}200{\times}10{\times}16$, $H-600{\times}200{\times}11{\times}17$), the presence of stiffeners and top bars, and the presence of no weld access hole(WAH) method. Based on the test results, deformation capacity of the specimens with H-500 series beam and H-600 series beam were 4% and 3% rotation angle, which is the requirement for the Special Moment Frame and Intermediate Moment Frame(IMF), respectively. Test result showed that deformation capacity of connection with stiffeners and top bars is greater than that of connection without stiffeners and top bars. Finally, energy dissipation capacity and strain profile of specimens were summarized.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.1939-1946
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• 2012

High performance steel for bridges requires higher performance in tensile and yield strength, toughness, weldability, etc. The purpose of this study is to investigate the weldability of HSB 600 steel. The effects of heat input (1.4~3.2kJ/mm) and postweld heat treatment (PWHT, $600^{\circ}C$, 40hr.) on the TMCP HSB600 steel weldments made by GMAW process were investigated. The tensile strength and hardness of as-welded specimens decreased with increasing heat input. Charpy V-notch impact energy did not show any significant difference by postweld heat treatment. The fine-grained acicular ferrite was mainly formed in the 2.1kJ/mm of heat input while polygonal and side plate ferrites were dominated in the high inputs. Meanwhile, tensile strength and hardness of PWHT weldments decreased due to the coarsening and globularization of ferrite microstructure and reduction of residual stresses with increasing heat inputs. However, there was no significant difference in the impact energy absorption.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.2
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• pp.98-106
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• 2011

The deck of steel box girder bridges is composed of deck plate, longitudinal rib, and transverse ribs. The orthotropic steel decks have high possibility to fatigue damage due to numbers of welded connection part, the heavy contact loadings, and the increase of repeated loadings. Generally, the local stress by the repeated loadings of heavy vehicles causes the orthotropic steel deck bridge to fatigue cracks. The increase of traffic volume and heavy vehicle loadings are promoted the possibility of fatigue cracks. Thus, it is important to exactly evaluate the structural behavior of bridge considering the contact loading area of heavy vehicles and real load patterns of heavy trucks which have effects on the bridge. This study estimated the effect of contact area of design loads and real traffic vehicles through the finite element analysis considering the real loading conditions. The finite element analysis carried out 4 cases of loading patterns in the orthotropic steel deck bridge. Also, analysis estimated the influence of contact area of real truck loadings by the existence of diaphragm plate. The result of finite element analysis indicated that single tire loadings of real trucks occurred higher local stress than one of design loadings, and especially the deck plate got the most influence by the single tire loading. It was found that the diaphragm attachment at joint part of longitudinal ribs and transverse ribs had no effects on the improvement of structural performance against fatigue resistance in elastic analysis.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.2
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• pp.108-116
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• 2014

The proper stress history measurement should be conducted in order to examine the accurate cause of fatigue cracks or the fatigue safety in the steel bridge. Only one strain gauge is generally installed in the field for the stress history examination because of the field circumstances, economic feasibility, workability, and so on. However, this method may not consider the actual size of the specific structure, the gauge length, and the affect of stress concentration in the welded joint. In addition, it is difficult to apply for the stress analysis. Therefore, this study suggests improvements that are a great number of gauge installations, the gauge location adjustment, and the use of the minimum length gauge. It is drived the correlative equation of strain for the distance between the welding toe and the strain gauge installation, and compare correlative equation with equation of IIW. Also, this study could estimate the remaining life and fatigue damage of bridge in service by selecting the suitable stress category. In conclusion, it is possible to understand the member which is high in the fatigue cracks, and the quantitative relations between the welding toe and the strain gauge installation distances. The proposed approach in this study can make an more accurate fatigue damage and a remaining life prediction so that the improved method should be applied in measuring the strain of bridges from now on.

• Journal of the Institute of Convergence Signal Processing
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• v.19 no.2
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• pp.61-67
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• 2018

Welding preheating means that the surface of the base material to which the metal is welded before the main welding is heated to a constant temperature. It prevents the cracks of the adjacent influences such as reduction of material hardening degree by controlling the cooling rate, suppression of segregation of impurities, prevention of thermal deformation, and moisture removal. For this reason, it is a necessary operation for high quality welding. Induction heating is an efficient heating method that converts electric energy into heat energy by applying electromagnetic induction phenomenon. Compared with combustion heat generated by gas and liquid, it is clean, stable, and economical as well as rapid heating. It can be heated regardless of the shape, depth and material of the heating body by modifying the shape of the frequency and the coil with a simple structure. In this paper, we implemented a low frequency welding preheating system using induction heating technique and observed the temperature changes of coil resistance, inductance and automotive transmission parts according to the height of each transmission in winding coil for three kinds of automotive transmission parts. We confirmed that the change of current is a very important factor in the low frequency heating.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.1
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• pp.150-168
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• 1991

A practical procedure for the ultimate compressive strength-based safety and reliability assessment of the double skin upper deck structure is described. The external compressive stress acting on the upper deck structure which is due to the still water and wave-induced sagging moment is approximately estimated by using the existing rule of classification society. The ultimate compressive stress of double skin structure under the action of sagging moment is analyzed by using idealized structural unit method. Here an idealized plate element subjected to uniaxial load is formulated by idealizing the nonlinear behaviour of the actual element taking account of the initial imperfections in the form of initial deflection and welding residual stress. The interaction effect between the local and global failure in the structure is also taken into consideration. The accuracy of the present method is verified comparing with the present solution and the existing numerical and experimental results for unit member and welded box columns. The safety of the structure is evaluated using the concept of conventional central safety factor and the reliability assessment is made by using Cornel's MVFOSM method. The present procedure is then applied to upper deck structure of double skin product oil carrier. The influence of the initial imperfections and the yield stress of the material on the safety and reliability of the structure is investigated.

• Journal of the Korean Society for Railway
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• v.20 no.2
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• pp.241-247
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• 2017

Railway bridges with continuously welded rail have a limitation of span length due to track-bridge interaction. In order to overcome this, a sliding slab track system has been developed that comprises with a low-frictional sliding layer between the bridge deck and the track slab to isolate the longitudinal behavior between the bridge and the track. In this study, a real scale track system is prepared to experimentally evaluate the longitudinal frictional behavior. Applied loading rates were 0.2, 1.0, 5.0 and 10mm/min; vertical mass on the track are track slab only, 5,000 and 10,000kg added mass, respectively. Test results showed that the resulting frictional coefficients varied from 0.22 to 0.33. In addition, 10,000 cycle loadings were applied to simulate repetitive sliding to represent 30 years of service life. The frictional coefficient increase was measured and found to be 7% of that of the initial loading stage, which means that the sliding layer is adequate to provide low-frictional behavior for the sliding slab track system. Effects of changes of the frictional coefficient of the sliding layer were analyzed by rail-structure interaction analysis.

• The Journal of the Petrological Society of Korea
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• v.25 no.1
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• pp.1-12
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• 2016

This study reports the results about the petrography of volcanic rocks in Namoo island and Namhyeongje island, off the southern coast of Busan City. The rocks in the Namhyeongje island composed of dacitic crystal-vitric welded tuff, showing phenocrysts of plagioclase, rock fragment with flow structure of elongated and flattened pumice fragments. In thin section it shows pyroclastic texture. The volcanic rocks in Namoo island are mainly dark grey-bluish dacite with phenocrysts of plagioclase and gradually changed to pink-greyish rhyodacite with auto-brecciated. In the northeastern part of the island, the volcanic rocks occurred as aggromerate with a poorly sorted mixture of blocks, lappili and ash and felsic feeder dike intrude the aggromerate. Major element composition of the volcanic rocks in Namhyeongje island and Namoo island are $SiO_2$ 73.6~74.4 wt.% and 65.5~68.3 wt.%, respectively. The volcanic rocks in these island are felsic volcanic rocks.