• Journal of Korean Society of Steel Construction
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• v.20 no.2
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• pp.289-301
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• 2008

Double skin composite (DSC) wall is a structural wall that is filed with concrete between two steel plate skins connected by tie bars. This type of wall was developed to enhance the structural performance of wall, to reduce wall thickness, and to enhance constructibility, eliminating the use of formwork and re-bars. In this study, cyclic tests were performed to investigate the inelastic behavior and earthquake resistance of isolated and coupled DSC walls with rectangular and T-shapedcross-sections. The DSC walls showed stable cyclic behaviors, exhibiting excellent energy dissipation capacity. The te st specimens failed by the tensile fracture of welded joints at the wall base and coupling beam and by the severe local buckling of the steel plate. The deformation capacity of the walls varied with the connection details at the wall base and their cross-sectional shapes. The specimens with well-detailed connections at the wall base showed relatively god deformation capacity ranging from 2.0% to 3.7% drift ratio. The load-carrying capacities of the isolated and coupled wall specimens were evaluated considering their inelastic behavior. The results were compared with the test results.

• Journal of Korean Society of Steel Construction
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• v.27 no.2
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• pp.219-229
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• 2015

An experimental study was performed for thin-walled rectangular concrete-filled tubular (CFT) columns. The present study mainly focused on evaluation of the axial load-carrying capacity of concrete-filled tubular columns using high-strength steel and slender section. The test parameters were width-to-thickness ratio, concrete strength, steel yield strength, and the use of stiffeners. Five specimens were tested under monotonic axial loading. Although elastic local buckling occurred in the slender-section specimens with high-strength steel, the specimens exhibited considerable post-buckling reserve. The test results also satisfied the predictions of a current design code. The specimens strengthened with vertical stiffeners exhibited improved strength and ductility when compared with the un-stiffened specimens.

• Journal of Korean Association for Spatial Structures
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• v.8 no.1
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• pp.89-97
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• 2008

The object of this paper is to evaluate on behavior the experimentally of beam-to-column joints for modular steel frame with the hollow structural steel section to LEB C-shape. Beam-to-column joints carried out test on the joint shape bracket-type and welded-type to consideration which the joints for modular steel frame was capacity, deformation and failure mode. Test of results, the beam-column joints decided to the lateral buckling strength in LEB C-shape regardless of joint-shape and joint failure. The strength & stiffness for joints increase as the bracket-thickness. The results from theory of lateral buckling are compared to the experimental results. The ratio of experimental results to theory value is $0.83{\sim}0.95$ in the case of bracket-type and welded-type of $0.87{\sim}0.9$, indicating an accurate and safe estimation.

• Composites Research
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• v.22 no.6
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• pp.23-31
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• 2009

This paper investigated acoustic emission (AE) characteristics in association with various fracture processes of glass fiber reinforced plastic skin/ aluminum honeycomb core (GF-AH) hybrid composites under compressive and bending loads. Various failure modes such as skin layer fracture, skin/core interfacial fracture, and local plastic yield buckling and cell wall adhesive fracture occurring in the honeycomb cell wall were classified through the fracture identification in association with the AE frequency and amplitude analysis. The distribution of the event-rate in which it has a high amplitude showed a procedure of cell wall adhesive fracture, skin/core interfacial debonding and fiber breakage, whereas distribution of different peak frequencies indicated the plastic deformation of aluminum cell wall and the friction between honeycomb walls. Consequently, the fracture behaviors of GF-AH hybrid composites could be characterized through a nondestructive evaluation employing the AE technique.

• Journal of Korean Society of Steel Construction
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• v.23 no.4
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• pp.503-514
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• 2011

In this research, the seismic connection details for two concrete-filled U-shape steel beam-to-H columns were proposed and cyclically tested under a full-scale cruciform configuration. The key connecting components included the U-shape steel section (450 and 550 mm deep for specimens A and B, respectively), a concrete floor slab with a ribbed deck (165 mm deep for both specimens), welded couplers and rebars for negative moment transfer, and shear studs for full composite action and strengthening plates. Considering the unique constructional nature of the proposed connection, the critical limit states, such as the weld fracture, anchorage failure of the welded coupler, local buckling, concrete crushing, and rebar buckling, were carefully addressed in the specimen design. The test results showed that the connection details and design methods proposed in this study can well control the critical limit states mentioned above. Especially, the proposed connection according to the strengthening strategy successfully pushed the plastic hinge to the tip of the strengthened zone, as intended in the design, and was very effective in protecting the more vulnerable beam-to-column welded joint. The maximum story drift capacities of 6.0 and 6.8% radians were achieved in specimens A and B, respectively, thus far exceeding the minimumlimit of 4% radians required of special moment frames. Low-cycle fatigue fracture across the beam bottom flange at a 6% drift level was the final failure mode of specimen A. Specimen B failed through the fracture of the top splice plate of the bolted splice at a very high drift ratio of 8.0% radian.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.93-101
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• 1987

Residual stresses have remained around welding areas of a steel structure member after welding operation. The major causes to occur these residual stresses are the local heat due to a welding, the heat stresses due to a irregular and rapid cooling condition, the material and rigidity of a steel structure. Ultimatly, these residual stresses have been known to decrease a brittle fracture strength, a fatigue strength, a buckling strength, dynamic properties, and the corrosion resistance of the material. This paper deals with the residual stresses on a steel structure member through experimental studies. SWS 58 plates were welded by the method of X-groove type. These plates were layed on the heat treatment at four different temperatures; $350^{\circ}C$, $500^{\circ}C$, $650^{\circ}C$ and $800^{\circ}C$. The resulting residual Stresses were measured by hole drilling method, and the followings were obtained. The residual stresses on the vicinity of a welding point were relieved most effectively at the temperature of $650^{\circ}C$, and these stresses relieved completly when the ratio of a hole diamerter to a hole depth became unity. Hardness test shows that the higher value of hardness at the heat affected zone dropped to belower as the temperature went up from $350^{\circ}C$ to $800^{\circ}C$. The Welding input heats have not influenced the magnitude of residual stresses at the input heat range between above and below one forth than standard.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.4
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• pp.351-359
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• 2011

In a structure, damage can occur at several scales from micro-cracking to corrosion or loose bolts. This makes the identification of damage difficult with one mode of sensing. Hence, a multi-mode actuated sensing system is proposed based on a self-sensing circuit using a piezoelectric sensor. In the self sensing-based multi-mode actuated sensing, one mode provides a wide frequency-band structural response from the self-sensed impedance measurement and the other mode provides a specific frequency-induced structural wavelet response from the self-sensed guided wave measurement. In this study, an experimental study on the pipeline system is carried out to verify the effectiveness and the robustness of the proposed structural health monitoring approach. Different types of structural damage are artificially inflicted on the pipeline system. To classify the multiple types of structural damage, a supervised learning-based statistical pattern recognition is implemented by composing a two-dimensional space using the damage indices extracted from the impedance and guided wave features. For more systematic damage classification, several control parameters to determine an optimal decision boundary for the supervised learning-based pattern recognition are optimized. Finally, further research issues will be discussed for real-world implementation of the proposed approach.

• Journal of Korean Society of Steel Construction
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• v.27 no.2
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• pp.155-167
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• 2015

If of application of the deep deckting floor in long span more than 6m, the deflection caused by the construction load occurred high. Because the constructing-works and safety by this deflection, take actually supports to laborers working on the deck. However, installed supports are having difficultly such as the restricted passage, deficiency of working space, and lowering of efficiency. And toward-opening deck is seen as local buckling of web plate, flexural-torsional buckling, and gradually opening of corrugated decking. In this study, we will suggest a deep decking floor system that reinforced with both ends cap plates for toward-opneing decking change from opening to closing. The constructing deflection of a deep decking more than 6m must be satified 30mm and L/180 as proposed. Full-scale field tests loading by sand conducted a deep decking reinforced with and without cap plate. In conclusion, the specimen reinforced with cap plates have shown that to ensure the negative moment $wl^2/18$. And constructing-deflection of deep decking shown that to satisfy the evaluation value (L/180 or 30mm).

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.3
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• pp.134-141
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• 2011

There have been increased economic and societal demands to continuously monitor the integrity and long-term deterioration of civil infrastructures to ensure their safety and adequate performance throughout their life span. However, it is very difficult to continuously monitor the structural condition of the pipeline structures because those are placed underground and connected each other complexly, although pipeline structures are core underground infrastructures which transport primary sources. Moreover, damage can occur at several scales from micro-cracking to buckling or loose bolts in the pipeline structures. In this study, guided wave measurement can be achieved with a self-sensing circuit using a piezoelectric active sensor. In this self sensing system, a specific frequency-induced structural wavelet response is obtained from the self-sensed guided wave measurement. To classify the multiple types of structural damage, supervised learning-based statistical pattern recognition was implemented using the damage indices extracted from the guided wave features. Different types of structural damage artificially inflicted on a pipeline system were investigated to verify the effectiveness of the proposed SHM approach.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.5
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• pp.488-496
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• 2023

Ship and bridge structures are a type of long box-shaped structure, and resistance to vertical bending moment is a key factor in their structural design. In particular, because box girders are repeatedly exposed to irregular wave loads for a long time, the continuous collapse behavior of structural members must be accurately predicted. In this study, plastic collapse behavior, including buckling according to load changes of the box girder receiving pure bending moments, was analyzed using a numerical analysis method. The analysis targets were selected as three box girders used in the Gordo experiment. The cause of the difference was considered by comparing the results of the structural strength experiment with those of non-linear finite element analysis. This study proposed a combination of the entire and local sagging shape to reflect the effect of the initial sagging caused by welding heat that is inevitably used to manufacture carbon steel materials. The procedures reviewed in the study and the contents of the initial sagging configuration can be used as a good guide for analyzing the final strength of similar structures in the future.