• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.789-799
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• 1998

The purpose of this study is to propose the prototypes of bolted end plate moment connection between CFT column and H-beam sections. Nine different types of bolt are designed in this study. The shapes of those bolt are straight. bent, hooked or stud-type. The end plate moment connection between CFT column and H-beam sections which are jointed by those bolts are studied experimentally to compare their performances. The simple beam bending tests are carried out to investigate the structural behavior of beam-to-column connections. The experimental results show that some of the bolted end plate connection types have quite good performance in the structural behavior but still have a lot of week points to be solved for the efficiency of construction.

• Structural Engineering and Mechanics
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• v.76 no.2
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• pp.175-191
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• 2020

In this study, the effect of Nano silica (SiO2) on the buckling strength of the glass fiber reinforced laminates containing the machining process causes holes were investigated. The tests have been applied on two status milled and non-milled. To promote the mechanical behavior of the fiber-reinforced glass epoxy-based composites, Nano sio2 was added to the matrix to improve and gradation. Nano sio2 is chosen because of flexibility and high mechanical features; the effect of Nanoparticles on surface serenity has been studied. Thus the effect of Nanoparticles on crack growth and machining process and delamination caused by machining has been studied. We can also imply that many machining factors are essential: feed rate, thrust force, and spindle speed. Also, feed rate and spindle speed were studied in constant values, that the thrust forces were studied as the main factor caused residual stress. Moreover, entrance forces were measured by local calibrated load cells on machining devices. The results showed that the buckling load of milled laminates had been increased by about 50% with adding 2 wt% of silica in comparison with the neat damaged laminates while adding more contents caused adverse effects. Also, with a comparison of two milling tools, the cylindrical radius-end tool had less destructive effects on specimens.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.5
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• pp.100-112
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• 2011

This paper studied on a theoretical approach to predict structural performances and weight -reduction rates of hybrid bodyshells in case that the material of underframe structure is substituted. To choose other light-weight materials to be substituted for the original underframe material, compressive, bending and twisting deformations are considered under constant stiffness and strength conditions, which derive some new weight-reduction indices from a structural performance point of view. Next, these weight-reduction indices were verified using the finite element analyses of some simplified examples. It is shown that the derived indices to estimate the weight-reduction can be utilized as a good criterion for material substitution of the underframe at a basic design stage.

• Journal of the Korea Institute of Building Construction
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• v.11 no.2
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• pp.162-170
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• 2011

As the result of implementing a treated material test and durability test after quickly drying S.P.F. species, a type of softwood structural material, within a short period time, soaking it in liquid phosphate flame proof agent for an hour, microwave heating it, and compressing it from 3.8cm to 1cm, when setting the appropriate heating time of microwave heating at 7 minutes at 5kW, it is observed that it satisfies the target water content (4~5%). It is shown that in a water content measurement of the wood that is compressed after being softened by soaking in the flame proof agent, drying and heating at 3kW for 9 minutes, all specimens satisfied 12~14%, the appropriate water content for exterior wood. Also, it is shown that in terms of the flame performance obtained through a flame resistance treatment of the compressed wood and a treated material test, the specimen soaked in flame proof agent for 30 minutes was the most excellent, and that the performance test result of the compressed wood in all areas, such as nail withdrawal resistance, compression, bending strength, and shearing strength, were all improved in their mechanical features to twice to three times better performances.

• Journal of the Korean Wood Science and Technology
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• v.26 no.1
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• pp.97-105
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• 1998

This study examined the combined using effects of urea-formaldehyde (UF) resin and emulsifiable methylene diphyenyl diisocyanate (EMDI) resin to overcome performance limit of three-layer particleboards commonly made by UF resin. Two adhesive adding methods were applied with three types of resin combination system to each layer of particleboards. The one was simultaneously spreading method with emulsified compound resin (UF and EMDI) while the other was separately spreading method with unemulsified EMDI resin after UF resin spreading. The performance of particleboards bonded with 2% EMDI resin to the inner layers(IL) were similar to that of controls bonded with 8% UF resin. In the case of the emulsified compound resin application to the all layers of particleboards, there were marked reinforcing effects of EMDI resin, although a small amount of EMDI resin was mixed with UF resin. Especially bending MOR after 24 hours cold water-immersion and thickness swelling after 2 hours hot water-immersion of compound resin-bonded particleboards were remarkably different from those of pure UF resin-bonded particleboards. It was found that separately spreading method with unemulsified EMDI resin was more effective than simultaneously spreading method with emulsified compound resin to sustain the internal bond strength of particleboards after 24 hours cold water-immersion. In the resin combination systems to outer layers/inner layers of particleboards, water resistance and strength properties were superior in order of UF+EMDI/UF+EMDI > UF/UF+EMDI > UF/UF. And water resistance of particleboards was greatly dependent upon EMDI resin level in any adhesive adding method.

• Journal of the Korea Concrete Institute
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• v.19 no.5
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• pp.569-575
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• 2007

The repair of concrete surfaces does not normally take into account structural tolerance for longer service lift and better capabilities of concrete structures. In particular, the repair of surface spelling completes as mortar is applied, which does not display additional structural performances. The use of crimped wire mesh for better construction and fracture resistance, however, expects to have some reinforcement effects. Particularly, it is also expected that the repair of bottom part in structures built between bridges like irrigation structures results in the increase of flexural resistance. Therefore, this study is intended to perform the repair using crimp wire mesh and examine strength depending on the repair section and depth. For this, a slab with 150 mm in depth, 3,000 mm in length and 600 mm in width and total 8 objects to experiment such as upper part, upper whole, bottom part, bottom whole and crimp wire mesh reinforced are manufactured to perform flexural performance. The results of the analysis show that yield strength and failure load increase as the depth of repair materials in the experiment reinforced with crimp wire mesh get bigger. In the same condition, repair of bottom part is able to increase internal force of bending force. Besides, the results show that partial repair of structures under bending force cannot produce flexural performance. Consequently, the repair method with crimp wire mesh results in the increase of flexural resistance.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.1
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• pp.25-34
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• 2009

RC flat plate, which has no large flexural stiffness by boundary beams, may be governed by serviceability as well as strength condition. A construction sequence and its impact on distributions of construction loads among slabs tied by shores are decisive factors on immediate and long term performances of flat plate. The over-loading and tensile cracking in early-aged slabs significantly increase the deflection of flat plate system. In this study, for slab deflections, the practical analysis scheme using a linear analysis program is formulated with considering construction sequence and concrete cracking effects. The concept of the effective moment of inertia in calculating deflections of one-way bending member, that is presented in structural design codes, is extended to the finite element analysis of the two-way slab system of flat plates. Effects of over-loads during construction on deflections of flat plate system are analyzed by applying the proposed practical analysis scheme into the critical construction load conditions calculated from the simplified method.

• Journal of Korean Society of Steel Construction
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• v.24 no.1
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• pp.59-71
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• 2012

Results of the analysis of the structural behavior of axially loaded nodes in freeform structure were not fully understood due to certain difficulties, including the application of various welding and bolting types. In this study, a node of single layered freeform structure was tested to determine its structural behavior when subjected to axial loads. The tests were classified into node ball tests to evaluate the center of the node subjected to cyclic and monotonic loading. The node part tests were also conducted to evaluate the whole node subjected to monotonic loading. The test showed that the node ball is safe with the tensile force, but the node ball needs to increase its strength with the node loaded compressive force due to the additional bending moment of the node ball's asymmetric form.

• Journal of the Korean Wood Science and Technology
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• v.38 no.1
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• pp.1-10
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• 2010

In this study, to study an effective use and improve strength performances of woods and wood-based materials, three-ply hybrid laminated woods which are composed of spruce in the face and three kinds of wood-based boards (MDF, PB, OSB) in the core were manufactured, and the effect of constitution elements used for the core laminae on bending creep performances was investigated. The shape of creep curves showed exponential function plots which the upper right side was increased, and differed among the kinds of wood-based boards used for the core laminae of hybrid laminated wood. The creep deformation perpendicular to the grain of faces of hybrid laminated woods was in order $C_{\perp}$(P) > $C_{\perp}$(M) > $C_{\perp}$(O) with PB, MDF and OSB in the core, respectively. It was found that the creep deformation arranged with OSB in the core had 2 times smaller than those arranged with MDF and PB in the core. By hybrid laminating, the creep deformation of spruce perpendicular to the grain was markedly decreased. On the other hand, the creep deformation parallel to the grain of the faces ($C_{\parallel}$ type) of hybrid laminated woods was in order $C_{\parallel}$(P) > $C_{\parallel}$(O) > $C_{\parallel}$(M) with PB, OSB and MDF in the core. The ratios among three hybrid laminated woods were considerably decreased, especially the difference between $C_{\parallel}$(P) and $C_{\parallel}$(O) hybrid laminated woods arranged with PB and OSB in the core was very small. These values showed 0.108~0.464 times smaller than creep deformation of three wood-based boards and it was found that creep deformation of three wood-based boards was considerably decreased by hybrid laminating. Creep anisotropy of hybrid laminated woods was greater in creep deformation than in initial deformation, whereas it was found that the values was much smaller than that of spruce parallel laminated woods.

• Journal of the Korean Geotechnical Society
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• v.34 no.3
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• pp.43-56
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• 2018

Vertical cutoff walls such as steel pipe sheet piles (SPSPs) have been commonly applied for the construction of the offshore waste landfill site. Because the SPSPs are sequentially installed by connecting their joints to those of adjacent piles, their mechanical stability should be ensured against the inherent external forces on the sea. The objective of this study is to evaluate the structural performances of the newly developed types of SPSP joint compared with those of other joint types. The problems of the traditional SPSP joints are investigated, and an advanced joint shape of SPSP, which is named double H with L-T (DHLT) joint, are designed for improving the constructability and maintenance. Full-scale models of the DHLT joint are manufactured, and then its joint areas are filled with grout material. After 28 days of curing time, compressive and tensile strength tests were performed on the joint models and the test results were compared with those of the traditional joints. Experimental results show that the structural capacities of the DHLT joint models are lower than those of traditional joints due to the influence of grout and steel members. In the cases of the compressive strength test, especially, bending occurs on steel H-beam with no distinct cracks in grout due to the asymmetrical structure of joint which has no reaction force. This study shows that the performance of the SPSP joint can be improved by considering the influence factors on the structural capacities estimated by the experimental tests.