• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년도 춘계 학술대회 개요집
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• pp.94-96
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• 2006

Recently, steel structures have been increasing because of its brilliant features. In general, cracks and corrosion are produced due to the numerous environmental factors in steel structures. However, the validity of repair method for the damaged steel structures has not been fully verified because of its lack of safety and reliability after application. Moreover, repair method by welding inevitably involves cutting and welding processes and reliability for the safety during the processes has net been established yet. Therefore, this study carried out experiments on the fatigue strength of repair welded joints of old steel bridge to investigate the fatigue characteristics in the repair welded joints. Fatigue tests were conducted by 250kN capacity MIS with the frequency of 5Hz under amplitude loading. From the results, it is known that fatigue strength grade of the repair welded joints was satisfied with C grade which specification requires.

• Journal of Welding and Joining
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• 제23권6호
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• pp.37-42
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• 2005

Most of the welding steel plate structures have complicated mechanical problems such as rolling directional characteristics and residual stresses caused by manufacturing process. For the enhancement of reliability and safety in those structures, therefore, a systematic investigation is required. SS400 steel plate used for common structures was selected and welded by FCAW butt-welding process for this study, and then it was studied experimently about characteristics of fatigue crack propagations with respect to rolling direction and welding residual stress of welded steel plates. When the angles between rolling direction and tensile loading direction in base material are increased, their ultimate strength not show a significant difference, but yielding strength are increased and elongations are decreased uniformly. It is also shown that fatigue crack growth rate can be increased from those results. When the angles between welding bead direction and loading direction in welded material are increase, fatigue crack growth rate of them are decreased and influenced uniformly according to the conditions of residual stress distribution. In these results, it is shown that the welded steel plate structures are needed to harmonize distributed welding residual stress, rolling direction and loading direction fur the improvement of safety and endurance in manufacture of their structures.

• 한국해양공학회지
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• 제19권4호
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• pp.21-27
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• 2005

Large welded structures, including ships and offshore structures, are normally in operation under cyclic fatigue loadings. These structures include many geometric discontinuities, as well as material discontinuities due to weld joints. The fatigue strength at these hot spots is very important for the structural performance. In the past, various Non Destructive Evaluation (NDE) techniques have been developed to detect fatigue cracks and to estimate their location and size. However, an important limitation of most of the existing NDE methods is that they are off line; the normal operation of the structure has to be interrupted, and the device often has to be disassembled. This study explores the development of a structural health monitoring system, with a special interest in applying the technique to welded structural members in ship and offshore structures. In particular, the impedance based structural health monitoring technique that employs the coupling effect of piezoceramic (PZT) materials and structures is investigated.

• Journal of Welding and Joining
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• 제29권4호
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• pp.61-66
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• 2011

The purpose of this study is to develop improved boom structures with reliable fatigue strength of weldment and lower production cost. For that purpose, multi-body dynamic analysis was performed to evaluate forces acting on arm & boom cylinders and joints of boom structure during operation of an excavator for three working postures, then stress analysis was made to investigate stress distribution around diaphragms at the bottom plate of boom structures which was known to be susceptible to fatigue failures of welded joints, and finally boom structures with optimum arrangement of diaphragms was proposed. This work mainly consists of the following two parts: part 1 focuses on multi-body dynamic analysis of excavators during operation and part 2 includes evaluations of fatigue strength of welded joints for modified boom structures.

• 한국공간구조학회논문집
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• 제11권4호
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• pp.37-47
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• 2011

재하속도에 따른 용접강관의 모멘트-곡률 거동특성에 관한 해석적 연구를 수행하였다. 3차원 열역학해석을 통하여 용접이음부의 잔류응력을 산출하였다. 그리고 동적소성모델이 적용된 탄소성 유한요소해석 프로그램을 이용하여 잔류응력을 고려한 용접강관(Welded pipe)의 동적해석을 수행하였다. 그리고 용접이음부가 없는 일반강관(Seamless pipe)에 대한 동적거동과의 비교를 통하여 해석을 수행하여 용접강관의 해석력과 해석결과는 용접강관의 모멘트가 일반강관의 모멘트에 비해 낮은 응답을 보였으나 재하속도가 증가함에 따라 모멘트 응답의 차이는 점차 감소하는 경향을 보였다.

• 한국공간구조학회논문집
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• 제16권4호
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• pp.75-82
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• 2016

Building hardware joints are welded in most cases, which have risks of fire and explosion. Besides, the secondary damage of the destruction of the welded parts can be caused by the horizontal displacement of the structure due to earthquake or wind load. This paper compared the horizontal displacement following abilities of welded building hardware and non-welded building hardware. To do this, We conducted actual formation shake table test, and checked on the horizontal displacement following ability of structure by comparing their responses to earthquake load. We made the 2m-high framework to examine the responses of the actually constructed building hardwares, and analyzed the displacement responses of the welded-typed, non-welded-typed, and cruciform bracket building hardwares. We conducted the test by increasing acceleration rate until displacement reached 40mm corresponding to allowable relative story displacement II. The result of the test showed that the building hardware using welding work made cracking and breakage on welded connections of welded building hardware, but non-welded building hardware with no use of welding work and cruciform bracket building hardware make no problem, and that non-welded building hardware is superior to that of the welded building hardware in the horizontal displacement following ability due to earthquake or wind load.

• Steel and Composite Structures
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• 제11권3호
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• pp.225-232
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• 2011

In this study, the deflection and deformation behaviours of IPN80 steel beam and column were investigated under the different industrial loads. Single-sided welds were applied to IPN80 steel beams using shielded metal arc (SMAW) and metal inert gas welding (MIG) method in the form of T-type. After that, the performance of SMAW and MIG welded joints were identified using beam bending test under 500 and 3000 N loads. SMAW and MIG methods were compared with each other to understand the deflection and deformation behaviours of the welded steel structures. Lower deformation and deflection were obtained in MIG welded steel beams. The results show that, steel beams welded MIG method has higher load capacity than SMAW welded ones. MIG welding method is more reliable than the SMAW method for the combining performance and load capacity.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2008년도 춘계학술발표대회 개요집
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• pp.31-31
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• 2008

• 대한기계학회논문집A
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• 제28권12호
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• pp.1864-1870
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• 2004

A spot welded structures have an influence on a diverse climatic situation, for instance temperature, humidity and precipitation. In addition factors of environmental pollution such as acid rain, that courses corrosion, have the tendency to increase. But spot welded structures strength is affected by humidity and environment temperature. Therefore, it is important to evaluate effect of temperature and water immersion on strength properties of spot welded part. In this study, the strength distribution of spot welded plates is evaluated the environmental temperature of zinc coated steel plates. Test is conducted with welded part immersed in distilled and synthetic sea water. Specimens are immersed into water for 10, 100, 500 and 1000 hours to evaluate the offsets of water immersion time on tensile-shear strength under the conditions of -40, 0, 20 and 5$0^{\circ}C$. From this result, spot welded specimens with 5 mm clearance have lower tensile-shear strength in the distilled water or synthetic sea water than without clearance. And they have lower tensile-shear strength under -4$0^{\circ}C$ and over 5$0^{\circ}C$.

• 한국공간구조학회:학술대회논문집
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• 한국공간구조학회 2008년도 춘계 학술발표회 논문집
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• pp.161-164
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• 2008

사회가 발전함에 따라 대공간 구조물의 필요성이 증대되고, 더 넓은 공간을 확보하려는 노력이 지속되고 있다. 그러나 기존의 방법으로는 공간의 확보에 있어서 기술적 어려움이 따른다. 본 논문에서는 단층 래티스 돔에 적용 가능한 용접 접합부를 제안함으로써, 기존의 단층 래티스 돔보다 더 넓은 공간과 안정성을 확보할 수 있는 방안을 제시하고자 하였다. 또한, 제안된 용접 접합부를 바탕으로 하여, 유한요소해석과 실험을 통해 제안된 용접 접합부의 구조적 성능을 평가하고자 하였다.