• Steel and Composite Structures
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• v.26 no.4
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• pp.485-499
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• 2018

In this paper, a hollow steel tube (HST) shear connector is proposed for use in a slim-floor system. The HST welded to a perforated steel beam web and embedded in concrete slab. A total of 10 push-out tests were conducted under static loading to investigate the mechanical behavior of the proposed HST connector. The variables were the shapes (circular, square and rectangular) and sizes of hollow steel tubes, and the compressive strength of the concrete. The failure mode was recorded as: concrete slab compressive failure under the steel tube and concrete tensile splitting failure, where no failure occurred in the HST. Test results show that the square shape HST in filled via concrete strength 40 MPa carried the highest shear load value, showing three times more than the reference specimens. It also recorded less slip behavior, and less compressive failure mode in concrete underneath the square hollow connector in comparison with the circular and rectangular HST connectors in both concrete strengths. The rectangular HST shows a 20% higher shear resistance with a longer width in the load direction in comparison with that in the smaller dimension. The energy absorption capacity values showed 23% and 18% improvements with the square HST rather than a headed shear stud when embedded in concrete strengths of 25 MPa and 40 MPa, respectively. Moreover, an analytical method was proposed and predicts the shear resistance of the HST shear connectors with a standard deviation of 0.14 considering the shape and size of the connectors.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.52-62
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• 2015

This study aims at developing a new seismic resistant method by using precast concrete wall panels for existing low-rise, reinforced concrete beam-column buildings such as school buildings. Three quasi-static hysteresis loading tests were performed on one unreinforced beam-column specimen and two reinforced specimens with U-type precast wall panels. Top shear connection of the PC panel was required to show the composite strength of RC column and PC wall panel. However, the strength of the connection did not influence directly on the ultimate loading capacities of the specimens in the positive loading because the loaded RC column push the side of PC wall panel and it moved horizontally before the shear connector receive the concentrated shear force in the positive loading process. Under the positive loading sequence(push loading), the reinforced concrete column and PC panel showed flexural strength which is larger than 97% of the composite section because of the rigid binding at the top of precast panel. Similar load-deformation relationship and ultimated horizontal load capacities were shown in the test of PR1-LA and PR1-LP specimens because they have same section dimension and detail at the flexural critical section. An average of 4.7 times increase in the positive maximum loading(average 967kN) and 2.7 times increase in the negative maximum loading(average 592.5kN) had resulted from the test of seismic resistant specimens with anchored and welded steel plate connections than that of unreinforced beam-column specimen. The maximum drift ratios were also shown between 1.0% and 1.4%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.4
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• pp.525-530
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• 2006

Recently companies which do not use the heavy metals such as lead, chrome, mercury to the electronic goods and alternate the materials environment-friendly are increasing. In advanced country, lead-free solder without lead is developed and soldering process almost disappeared. The lead-free solder is environment-friendly but is expensive and lack of tack and durability than lead, the improvement is necessary. To solve this problem, the welding process that uses TIG welding and the welding technology between different kind metals for lead-in wire of room lamp and base department was developed. To do this, previous room lamp manufacturing process was analysed and which process can be alternate was proposed. And the test for selection of optimal value of TIG welding parameter was done. Finally the lamp aging test and earthquake resistant test was done to check the reliability of welded room lamp.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.1 no.2
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• pp.1-8
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• 2000

An attempt was made to develop commercially pure titanium frames of glasses with a high-precision laser beam welding machine, in which a resonator with 12kw of the peak power and 200 W of maximum mean power has the capacity of variable in the range of 0.08~10 ms pulse width. In addition the optical fiber beam transmission with 400 ${\mu}{\textrm}{m}$ of the core diameter and a weld chamber to contain specimens in the inert gas atmosphere were also designed and used. In the present study. titanium frames of glasses parts such as temple plus spring hinge. bridge and top bar were experimentally manufactured by utilizing the optimum welding parameters with the optical fiber of GI 400 ${\mu}{\textrm}{m}$, 2.9J energy per pulse, and focussing position for Tee and butt joints. The titanium welded joints with laser beam welding did not reveal any severe weld defects or weld bead appearance except some pores in the weld section.

• Journal of Welding and Joining
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• v.13 no.4
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• pp.55-64
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• 1995

A study was made to examine the effects of postweld heat treatment(PWHT) on the toughness and microstructures in the weld heat affected zone(HAZ) of Cu-bearing HSLA-100 steel. The Gleeble thermal/mechanical simulator was used to simulate the weld HAZ. The details between toughness and PWHT of HAZ were studied by impact test, optical microscopy(O.M.), scanning electron microscopy (SEM), transmission electron microscopy(TEM) and differential scanning calorimetry(DSC). The decrease of HAZ toughness in single thermal cycle comparing to base plate is ascribed to the coarsed-grain formed by heating to 1350.deg.C. The increase of HAZ toughness in double thermal cycle comparine to single thermal cycle is due to the fine ferrite(.alpha.) grain transformed from austenite(.gamma.)formed by heating to .alpha./.gamma. two phase region. Cu precipitated during aging for increasing the strength of base metal is dissolved during single thermal cycle to 1350.deg.C and is precipitated little on cooling and heating during subsequent weld thermal cycle. It precipitates by introducing PWHT. Thus, the decrease of toughness in triple thermal cycle of $T_{p1}$ = 1350.deg.C, $T_{p2}$ = 800.deg.C and $T_{p3}$ = 500.deg.C does not occur owing to the precipitation of Cu. The behaviors of Cu=precipitates in HAZ is similar to that in base plate. PWHT at 550.deg.C shows highest hardness and lowest toughness, whereas PWHT at 650.deg.C shows reasonable toughness, which improves the toughness of as-welded state.state.

• Journal of Welding and Joining
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• v.33 no.6
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• pp.6-12
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• 2015

Thermal fatigue life of the automobile exhaust manifold is directly affected by the restraint force according to the structure of exhaust system and bead shape of the welded joints. In the present study, the microstructural changes and precipitation behavior during thermal fatigue cycle of the 18wt% Cr ferritic stainless steel weld heat affected zone (HAZ) considering restraint stress were investigated. The simulation of weld HAZ and thermal fatigue test were carried out using a metal thermal cycle simulator under complete constraint force in the static jig. The change of the restraint stress on the weld HAZ was simulated by changing the shape of notch in the specimen considering the stress concentration factor. Thermal fatigue properties of the weld HAZ were deteriorated during cyclic heating and cooling in the temperature range of $200^{\circ}C$ to $900^{\circ}C$ due to the decrease of Nb content in solid solution and coarsening of MX type precipitates, laves phase, $M_6C$ with coarsening of grain and softening of the matrix. As the restraint stress on the specimen increased, the thermal fatigue life was decreased by dynamic precipitation and rapid coarsening of the precipitates.

• Journal of Korean Society of Steel Construction
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• v.23 no.3
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• pp.377-384
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• 2011

Recently, for the purpose of reducing work terms and improving performance for construction work, various methods in structure field were developed. This included the HRC system which is applicable to a typical structure (e.g., parking and office building). The HRC system introduced the Gerber Joint to raise structural efficiency and used connection plate to bolt HRC composite beam to H beam in the construction field. In this research, the experimental tests for six specimens, which were in the same field conditions, were conducted with several parameters such as the length and height of the connection plate and the number of stub bolts. The test result was compared with those made by current design codes for the deflection and strains of the main bar. Within the given load, the integration of concrete in beam and connection plate, welded with stud bolts, was verified.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.8
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• pp.1374-1380
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• 2002

Recently, the use of Robot increase little by little for the purpose of developing a welding quality and productivity in the welding part. It is more important to contact the seam for arc welding before moving a welding robot. There are two types of method to contact the seam namely contact and non-contact type largely. In this paper, image processing sensor(a kind of non-contact sensor) is concerned to track the seam by using laser diode and CCD camera. A structured laser diode's light illuminated on the weld groove and the reflected shape is introduced by CCD camera. The image board captures this image and software analyzes this image. The robot is moved and welded exactly as acquired image X-Y data is changed with robot's X-Y value. Also, most of seam tracking are considered by changing the program simply in case of the different weld groove of plane surface.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.227-243
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• 2003

To find the structural characteristics of non-slip device in connecting method B between steel pipe pile and concrete footing, compression and uplift test was performed for full sized specimens not having non-slip device, those having non-slip device with two curved steel plate bars welded inside the steel pipe pile(standard method), and those having non-slip device with serveral curved steel plate bars bolted inside the steel pipe pile(new method). As a result, specimens not having non-slip device had chemical debonding failure at 15.6tonf of peak uplift load and 27.57tonf of peak compression load. And the standard method and the new method showed about 8.9 times of peak uplift load and 6.2 times of peak compression load higher than specimens not having non-slip device. The load transfers of lower non-slip devices of the standard method and the new method were similar in behavior, while the higher non-slip device of the new method showed higher ratio of load transfer than that of the standard method. And these two methods had nearly the same composite action and structural capacity caused by non-slip devices.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.4
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• pp.61-70
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• 1999

Cracking was observed in beam-to-column connections of many steel building frames during the 1994 Northridge and 1995 Kobe earthquakes. Thus extensive experimental researches are currently being conducted to improve the seismic performance of steel frames. A value of 0.015 radian was considered as a reasonable estimate of beam plastic rotation demand in steel moment-resisting frames subjected to severe earthquakes. The objective of this research is to develop a type of connection detail which moves the plastic hinge region in the beam away from the face of the column and can prevent cracking at the welded flange of the beam-to-column connection under seismic loading. An experimental investigation was undertaken on five beam-to-column connection specimens to study the performance of the connections with proposed details. The experiemental results showed that the flexural strength and rotational ductility of the beam connections were adequate for the seismic resistance steel frames to prevent possible cracks at the connections.