• Proceedings of the KSME Conference
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• 2007.05a
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• pp.796-801
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• 2007

The optical performance of the mirror for satellite camera is highly dependent on the adhesive properties between the mirror and its support. In order to design a mirror with high optical performance, the mechanical properties of adhesives should be well defined. In this research, the mechanical properties of three kinds of space adhesives are studied. In case of the materials which show nearly incompressible behavior such as space adhesives, it is important to measure shear modulus which governs deviatoric stress components. Shear moduli of the adhesives are determined by using single lap adhesively bonded joint. For the shear tests, several points have been selected from $-20^{\circ}C$ to $50^{\circ}C$ which is operating temperature range of the adhesive. The shear modulus of each adhesive is expressed as a function of temperature. Characteristics of the adhesives are discussed regarding their temperature sensitivity. The analysis results of RMS wavefront error w.r.t shear modulus are presented.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.577-581
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• 1998

Recent trends in the construction of building frame feature the increase use of composite steel concrete members functioning together in what terms of mixed structural systems. One of such systems, RCS(reinforced concrete column and steel beam) system, is known to make use of type of member in the most efficient manner to maximize the structural and economic benifits. Based on the results, joint behavior and design were described in terms of two primary modes of failure ; joint panel shear and vertical bearing. In test specimen, joint deformation is observed at internal region greater than at external region.

• Earthquakes and Structures
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• v.12 no.2
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• pp.237-250
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• 2017

There has been increasing attention in many countries on seismic retrofit of old fashioned RC structures in recent years. In such buildings, the joints lack transverse reinforcement and suffer inadequate seismic dimensional requirements and the reinforcement is plain bar. The behavior of the joints is governed by sliding of steel bars and diagonal shear failure is less influential. Different methods to retrofit beam-column joints have been proposed in the literature such as wrapping the joint by FRP sheets, enlargement of the beam-column joint, and strengthening the joint by steel sheets. In this study, an enlargement technique that uses external prestressed cross ties with steel angles is examined. The technique has already been used for substructures reinforced by deformed bars and has advantages such as efficient enhancement of seismic capacity and lack of damage to the joint. Three reference specimens and two retrofitted units are tested under increasing lateral cyclic load in combination with two levels of axial load. The reference specimens showed relatively low shear strength of 0.150${\surd}$($f_c$) and 0.30${\surd}$($f_c$) for the exterior and interior joints, respectively. In addition, relatively brittle behavior was observed and large deformations extended into the panel zone of the joints. The retrofit method has increased ductility ratio of the interior beam-column joints by 63%, and energy dissipation capacity by 77%, relative to the control specimen; For external joints, these values were 11%, and 94%. The retrofit method has successfully relocated the plastic joints far from the column face. The retrofit method has improved shear strength of the joints by less than 10%.

• Journal of Korean Society of Steel Construction
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• v.21 no.6
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• pp.647-657
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• 2009

This paper studies the behavior of joints in steel-PSC (prestressed concrete) hybrid beams, which is necessary for the application of hybrid beams to spliced girder bridges, and proposes a new type of joint with improved construction convenience and structural behavior. In the proposed joint, perfobond rib shear connectors are attached to the upper and lower plates, which are expanded from the steel girders and located between the steel girder and the PSC girder. The experimental tests were performed on hybrid beams with the suggested joint. The results showed that all the beams had similar ultimate strengths and failure modes, due to the failure of their PSC parts. The composite action of the perfobond ribs was verified by examining the initial stiffness and cracks of the test beams. In addition, the test beams showed a higher degree of ultimate strength than the beams with stud shear connectors in the joints that had been previously studied. Thus, the proposed joint is effective for the steel-PSC hybrid beam.

• Earthquakes and Structures
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• v.9 no.1
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• pp.233-256
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• 2015

This paper presents an experimental study to assess the effectiveness of using ferrocement to strengthen deficient beam-column joints. Ferrocement is proposed to protect the joint region through replacing concrete cover. Six exterior beam-column joints, including two control specimens and four strengthened specimens, are prepared and tested under constant axial load and quasi-static cyclic loading. Two levels of axial load on column (0.2fc'Ag and 0.4fc'Ag) and two types of skeletal reinforcements in ferrocement (grid reinforcements and diagonal reinforcements) are considered as test variables. Experimental results have indicated that ferrocement as a composite material can enhance the seismic performance of deficient beam-column joints in terms of peak horizontal load, energy dissipation, stiffness and joint shear strength. Shear distortions within the joints are significantly reduced for the strengthened specimens. High axial load (0.4fc'Ag) has a detrimental effect on peak horizontal load for both control and ferrocement-strengthened specimens. Specimens strengthened by ferrocement with two types of skeletal reinforcements perform similarly. Finally, a method is proposed to predict shear strength of beam-column joints strengthened by ferrocement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.8 s.227
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• pp.1174-1182
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• 2004

Recently, Self Piercing Rivet(SPR) has been spotlighted in the automotive industry as a substitutive resort of spot welding and has also been watched by the designer as lightening a car body due to their superior assembly processes. Fatigue behavior of SPR joint needs to be investigated experimentally and numerically to predict its structural stiffness and fatigue life. Testing of lap-shear specimens with various material combinations is performed to obtain the joining strength and the fatigue life of SPR connections. The simulation of SPR lap-shear specimens is also conducted to obtain the structural stiffness of SPR connections under different material combinations. A Finite element model of the SPR lap-shear specimen is developed using a FEMFAT SPR pre-processor. The fatigue lift of SPR specimen is predicted using a FEMFAT 4.4e based on the liner finite element analysis.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.105-108
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• 2006

Current ACI and AIJ guidelines only address the importance of the concrete strength and geometry of the joint. There are no significant attention paid to other variables. In addition, the current design code doesn't predict the ductility of the beam-column assemblies. The former researcher proposed the analytical model to predict the shear strength of the joint panel as well as the ductility of the beam-column assemblies in year 2004. In this study, the experiments to investigate shear behavior of reinforced concrete beam-column joints and to verify proposed model were carried out, based on the experimental results. As the formal researcher proposed, the factor K (K=0.5), the ductility of BJ-failure was predicted reasonably when the transverse reinforcement ratio exceeded 0.0186. However, the proposed equation showed a large discrepancies in the ductility estimating when transverse reinforcement ratio was below 0.0186.

• Journal of Korean Society of Steel Construction
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• v.20 no.2
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• pp.347-354
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• 2008

Steel plate-concrete (SC) structure has recently been used in nuclear power structure because of its construction efficiency. In this study, experimental and analytical study to investigate the behavior of the SC structure's wall slab connection was carried out. Experiments were performed for typical SC and RC connections in order to examine the basic difference between each structure. Finite element analysis was performed and the result of the analysis was found to closely reflect the experimental result. By varying the thickness of the shear plate and friction coefficients and the distance of applied load from the wall, the influence of the parameters on the joint strength and failure modes were examined. Finally, it was confirmed that the joint strength formula proposed in th this research gives conservative results.

• Journal of Welding and Joining
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• v.35 no.3
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• pp.1-6
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• 2017

The effect of metal turnover (MTO) of electroless Ni plating bath on the brittle fracture behavior of electroless nickel electroless palladium immersion gold (ENEPIG)/Sn-3.0wt%Ag-0.5wt%Cu(SAC305) solder joint was evaluated in this study. The MTOs of the electroless Ni for the ENEPIG surface finish were 0 and 3. As the MTO increased, the interfacial IMC thickness increased. The brittle fracture behavior of the ENEPIG/SAC305 solder joint was evaluated with high speed shear (HSS) test. The HSS strength decreased with increasing the MTO of the electroless Ni bath. The brittle fracture increased with increasing the shear speed of the HSS test. The percentage of the brittle fracture for the 3 MTO sample was much higher than that for the 0 MTO sample.

• Steel and Composite Structures
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• v.29 no.6
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• pp.735-748
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• 2018

In this paper, the cyclic behavior of steel beam-concrete encased steel (CES) column joints was investigated experimentally and numerically. Three frame middle joint samples with varying concrete slab widths were constructed. Anti-symmetrical low-frequency cyclic load was applied at two beam ends to simulate the earthquake action. The failure modes, hysteretic behavior, ultimate load, stiffness degradation, load carrying capacity degradation, displacement ductility and strain response were investigated in details. The three composite joints exhibited excellent seismic performance in experimental tests, showing high load-carrying capacity, good ductility and superior energy dissipation ability. All three joint samples reached their ultimate loads due to shear failure. Numerical results from ABAQUS modelling agreed well with the test results. Finally, the effect of the concrete slab on ultimate load was analyzed through a parametric study on concrete strength, slab thickness, as well as slab width. Numerical simulation showed that slab width and thickness played an important role in the load-carrying capacity of such joints. As a comparison, the influence of concrete grade was not significant.