• Proceedings of the Korean Geotechical Society Conference
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• 1993.10a
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• pp.69-72
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• 1993

In this paper, relatively new slope reinforcing system using an anchored wall is presented. For practical design purposes a method of external and internal stability analyses of an anchored wall installed at the toe of the original unstable or quasi-stable slope is developed. And also Murray's full-scale test results are compared with the passive resistance of an anchor predicted by the present study. Finally a design example of reinforced slope using an anchored wall is analyzed, and the safety as well as benefits is compared with a method of changing the geometry of the original unstable slope.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.113-120
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• 2002

The effect of out-of-plane loads on the fatigue strength of welded steel structures is examined through fatigue tests with weldment of two fillet weld joint types. The results of the fatigue tests are compared with those under axial loads, on the basis of the hot spot stress range at the weld toe. From the result of the comparison, a method on how to incorporate the effect of the out-of-plane bending stress is proposed using design S-N curves derived from fatigue tests under the axial load. The proposed method is useful for rational assessment of the fatigue strength of fillet-welded structures, where combined stresses of the in-plane axial stress and the out-of-plane bending stress are induced simultaneously due to the complexity of applied loads and structural geometry.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.200-205
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• 2000

Fatigue failure modes of load-carrying cruciform weld joints are dependent on the characteristics of the fatigue crack initiation and propagation from the weld toe or the weld root. In this study, constant amplitude fatigue tests on load-carrying fillet welded specimen carried out, and fatigue strengths were evaluated. Also, an attempt is made to develop a new analytical model with more accuracy to predict the fatigue crack propagation life of fillet welded cruciform joints of SWS 490B steels containing lack of penetration defects. From the result of this study, fatigue crack growth characteristics of load-carrying fillet welded cruciform joints, containing lack of penetration defects are found to be affected by the weld geometry, stress range and microstructures of the weld zone.

• International Journal of Korean Welding Society
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• v.2 no.1
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• pp.33-39
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• 2002

The effect of out-of-plane loads on the fatigue strength of welded steel structures is examined through fatigue tests with weldment of two fillet weld joint types. The results of the fatigue tests are compared with those under axial loads, on the basis of the hot spot stress range at the weld toe. From the result of the comparison, a method on how to incorporate the effect of the out-of-plane bending stress is proposed using design S-N curves derived from fatigue tests under the axial load. The proposed method is useful for rational assessment of the fatigue strength of fillet-welded structures, where combined stresses of the in-plane axial stress and the out-of-plane bending stress are induced simultaneously due to the complexity of applied loads and structural geometry.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.3
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• pp.307-312
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• 2012

This study aims to investigate the effect of the post weld treatments on the fatigue life of T-type welded structure made by a SM50A steel material, generally used for excavators, because changes in the geometry, material and surface properties of welded regions affect the fatigue life of welded structures. T-type test specimens were prepared by the CO2 welding of rolled steel plates (SM50A steel) with a thickness of 10 mm at a welding speed of 30 cm/min and these Ttype welded specimens were further treated by UIT (Ultrasonic Impact Treatment) and/or toegrinding post welding treatment methods. In order to investigate improvements on the fatigue life of the samples. 3-point bending fatigue tests were conducted with a stress ratio of R=0.1 under a cyclic loading environment at a frequency of 5 Hz, via a hydraulic fatigue testing machine (${\pm}100\;kN$, MTS 809). The tests were performed at room temperature. The fatigue life of UIT specimens was approximately 25 times longer than that of as-welded specimens at a stress amplitude of 281 MPa, while toe-grinding specimens exhibited 4.15 times longer fatigue life. The current results could provide important guidelines to determine the proper post weld treatment methodologies of T-type welded parts for excavators with a satisfactory fatigue life although under severe operating conditions.

• Journal of Korean Society of Steel Construction
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• v.23 no.2
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• pp.137-146
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• 2011

In the fabrication of steel bridges, blast cleaning prior to painting is carried out on the steel members to clean the forged surface and to increase the adhesive property of the applied painting systems. The effect of blast cleaning on the fatigue strength improvement of the weld joints, however, is not clear. In this study, Almen strips and steel specimens were blast-treated, conforming to ten types of blast-cleaning conditions deducted from the blast-cleaning conditions of seven steel structure fabrication companies. The arc height, roughness, hardness, and compressive residual stress were measured before and after the implementation of the ten blast-cleaning methods, and the relationship between the blast conditions and the measured values was studied. The geometry of the weld toe and the compressive residual stress near the weld toe were also measured before and after the blast cleaning of the butt-welded joints, and fatigue tests were carried out on the butt weld joints. The test results showed that blast cleaning significantly increases the fatigue strength and limit.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.8
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• pp.842-848
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• 2009

Fatigue failures are often occurred at welded joints where stress concentrations are relatively high due to the joint geometry. Although employing good detail design practices by upgrading the welded detail class enables to improve the fatigue performance, in many cases, the modification of the detail may not be practicable. As an alternative, the fatigue life extension techniques that reduce the severity of the stress concentration at the weld toe region, remove imperfections and introduce local compressive welding residual stress, have been applied. These techniques are also used as definite measures to extend the fatigue life of critical welds that have failed prematurely and have been repaired. In this study, a hammer peening procedure for using commercial pneumatic chipping hammer was developed, and the effectiveness is quantitatively evaluated. The pneumatic hammer peening makes it possible to give the weld not only a favorable shape reducing the local stress concentration, but also a beneficial compressive residual stress into material surface. In the fatigue life calculation of non-load carrying cruciform specimen treated by the pneumatic hammer peening, the life was lengthened about ten times at a stress range of 240MPa, and fatigue limit increased over 65% for the as-welded specimen.

• Journal of Korean Society of Steel Construction
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• v.10 no.3 s.36
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• pp.497-508
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• 1998

The objective of this study is to examine fatigue behavior of as-welded butt-welded joints with incomplete penetration from fatigue tests. The test results are the following. In static tests, tensile strength and yield strength of butt-welded joints are constant regardless of incomplete penetration. And in fatigue tests, fatigue strength of fully penetrated butt-welded joints satisfies fatigue limits, prescribed in Korean Specifications and JSSC, respectively. The results show that as the magnitude of incomplete penetration increases, fatigue strength decreases. In fractured surfaces, full and incomplete penetration specimen show different shapes, it is because that stress concentration factor vary with structural geometry in bead toe and root tip, and certify in FEM analysis. This study suggests that defects such as incomplete penetration from welding must be avoided in order to attain the sufficient life of steel structures.

• Magazine of the Korean Society of Agricultural Engineers
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• v.42 no.5
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• pp.151-159
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• 2000

Dynamic loading of structures often causes excursions of stresses will into the inelastic range and the influence of geometry changes on the response is also significant in may cases. In general , the shell structures designed according to quasi-Static analysis may collapse under condition of dynamic loading. Therefore, for a more realistic prediction on the lad carrying capacity of these shell. both material and geometric nonlinear effects should be considered. In this study , the material nonlinearity effect on the dynamic response is formulated by the elasto-viscoplastic model highly corresponding to the real behavior of the material. Also, the geometrically nonlinear behavior is taken into account using a Total Lagrangian formulation. the reinforcing bars are modeled by the equivalent steel layer at the location of reinforcements, and Von Mises yield criteria is adopted for the steel layer behavior. Also, Drucker-Prager yield criteria is applied for the behavior of concrete. the shape imperfection of dome is assumed as 'dimple type' which can be expressed Wd1=Wd0(1-(r-a)m)n while the shape imperfection of wall is assumed as sinusoidal curve which is Wwi =Wwo sin(n $\pi$y/l). In numerical test, three cases of shape imperfection of 0.0 -5.0cm(opposite direction to loading ; inner shape imperfection)and 5cm (direction to loading : outward shape imperfection) and thickness of steel layer determined by steel ratio of 0,3, and 5% were analyzed. The effect of shape imperfection and steel ratio and behavior characteristics of perfect shape shell and imperfect shape shell are identified through analysis of above mentioned numerical test. Dynamic behaviors of dome and wall according toe combination of shape imperfection and steel ratio are also discussed in this paper.

• Journal of Korean Society of Steel Construction
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• v.21 no.1
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• pp.55-62
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• 2009

Blast cleaning has been applied in steel bridges for cleaning forged surface and increasing adhesive property of applied coating systems. Blasting is the operation of cleaning or preparing a surface by forcible propelling a stream of abrasive metals against it. Blast cleaning may improve surface geometry and induce compressive residual stress, and eventually may increase fatigue life of weld joints. In this paper, fatigue tests were carried out on three types of non-load-carrying fillet welded cruciform joints, as-welded joints, blast-treated joints, and stress-relieved joints after blasting, in order to investigate effect of blast cleaning on fatigue behavior of the weld joints. By Blast cleaning, the weld toe radius was increased by 29% and compressive residual stress was induced near weld toes. Blast cleaning increased fatigue life and fatigue endurance limit of the weld joints. When the applied stress ranges decreased, the increment in fatigue life became larger. About a 150% increase in fatigue limit could be realized by using blast cleaning.