• Journal of Korean Society of Steel Construction
• /
• v.27 no.1
• /
• pp.99-108
• /
• 2015

The partially restrained smart CFT (concrete filled tube) column-to-beam connections with top-seat split T connections show various behavior characteristics according to the changes in the diameter and tightening force of the fastener, the geometric shape of T-stub, and material properties. This paper presents results from a systematic three-dimensional nonlinear finite element study on the structural behavior of the top-seat split T connections subjected to cyclic loadings. This connection includes super-elastic shape memory alloy (SMA) T-stub and rods to obtain the re-centering capabilities as well as great energy dissipation properties of the CFT composite frame. A wide scope of additional structural behaviors explain the influences of the top-seat split T connections parameters, such as the different thickness and gage distances of split T-stub.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.27 no.5
• /
• pp.369-377
• /
• 2014

In this paper, to recognize the collision behavior between a submerged floating tunnel(SFT) and underwater navigation vessel(UNV), both structures are modeled and analyzed. The SFT of collision point is modeled tubular section using concrete with steel lining. The other part of SFT is modeled elastic beam elements. Mooring lines are modeled as cable elements with tension. The under water navigation vessel is assumed 1800DT submarine and its total mass at collision is obtained with hydrodynamic added mass. The buoyancy force on SFT is included in initial condition using dynamic relaxation method. The buoyancy ratio (B/W) and the collision speed are considered as the collision conditions. As results, energy dissipation is concentrated on the SFT and that of the UNV is minor. Additionally, the collision behaviors are greatly affected by B/W and the tension of mooring lines. Especially, the collision forces are shown different tendency compare to vessel collision force of current design code.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.3 no.1
• /
• pp.58-63
• /
• 2015

Several researches on cement zero concrete using alkali-activators have been conducted to investigate its fundamental material properties such as slump, strength and durability, however, research on the structural behavior of relevant members involving the elastic modulus, stress-strain relationship is essential for the application of this cement zero concrete to structural members. In this paper the shear behavior of reinforced concrete beams using 50 MPa-alkali activated slag concrete was experimentally evaluated. To achieve such a goal, six reinforced concrete beam specimens were fabricated and their shear behaviors were observed. The maximum difference between test results and analysis results in crack shear stress for beam specimens without stirrups is 31%, while that for beam specimens with stirrup is 15%. Furthermore, it is also found that the shear strength of alkali activated slag concrete is by 22~57% greater than the nominal shear strength calculated by design code, implying that shear design equations would provide conservative results on the safety side.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.27 no.10
• /
• pp.1630-1635
• /
• 2003

The deformation and fracture behaviors of a bulk amorphous metal, Zr-based one (Zr$\_$41.2/Ti$\_$13.8/Cu$\_$12.5/Ni$\_$10/Be$\_$22.5/: Vitreloy), were investigated over a strain rate range (7x10$\^$-4/～4 s$\^$-1/). The uniaxial compression test and the indentation test using 3mm-diameter WC balls were carried out under quasi-static loading conditions. As a result, at the uniaxial compressive state, the fracture stress of the material was very high (～1,700MPa) and the elastic strain limit was about 2%. The fracture strength showed a strain rate independent behavior up to 4 s$\^$-1/. Using indentation tests, the plastic deformation behavior of the Zr-based BAM up to a large strain value of 15% could be achieved, even though it was the deformation under locally constrained condition. The Meyer hardness of the Zr-based BAM measured by static indentation tests was about 5 GPa and it revealed negligible strain hardening behavior. At indented sites, the plastic indentation occurred forming a crater and well-developed multiple shear bands were generated around it along the direction of 45 degree when the indentation load exceeded 7kN. With increasing indentation load, shear bands became dense. The fracture surface of the specimen after uniaxial compressive tests showed vein-like pattern, typical morphology of many BAMs.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.3 s.174
• /
• pp.777-785
• /
• 2000

The low-cycle fatigue behaviors of cast AI-Si alloy and composite with reinforcement of SIC particles were compared with those of extruded unreinforced matrix alloy and composite in order to investigate the influence of cast and extrusion processes on the cyclic deformation and fatigue life. Generally, both cast and extruded composites including the unreinforced alloy exhibited cyclic hardening behaviour, with more pronounced strain-hardening for the composites with a higher volume fraction of the SiC particles. However, cast composite under a low applied cyclic strain showing no observable plastic strain exhibited cyclic softening behavior due to the cast porosities. The elastic modulus and yield strength of the cast composite were found to be quite comparable to those of the extruded composite, however, the extrusion process considerably improved the ductility and fracture strength of the composite by effectively eliminating the cast porosities. Low-cycle fatigue lives of the cast alloy and composite were shorter than those of the extruded counterparts. Large difference in life between cast and extruded composites was attributed to the higher influence of the cast porosities on the fatigue life of the composite than that of the unreinforced alloy material. A fatigue damage parameter using strain energy density effectively represented the inferior life in the low-cycle regime and superior life in the high-cycle regime for the composite, compared to the unreinforced alloy.

• Journal of Adhesion and Interface
• /
• v.14 no.4
• /
• pp.183-191
• /
• 2013

In order to elucidate the granular heaping phenomenon, the movement behaviors of 3 different types of granule (millet, sand and thin foil disc) have been investigated by applying the vertical or the rotational vibration to each of the 3 vessels, respectively containing one of the 3 types of granule. In case of vertical vibrations, all of them showed the heaping phenomenon like Gerner's simulation, and that in the order of the millet, sand and thin foil disc, regardlessly of weight. Especially, a heaping of disc granules was proven to be relatively delayed, and that with several small complex clutters. For rotational vibration, the central area of vessel turned out to rise up due to the repulsive force by vessel wall as well as the collision between elastic granules, right after the turning point of vibration. Even spiral pattern was made when the rotational vibration amplitude got higher. From these facts, one can see that the heaping be characterized by the inclusion of attractive granules as well as the vibrational type applied to granule vessel.

• Ocean Systems Engineering
• /
• v.3 no.1
• /
• pp.35-53
• /
• 2013

In this study, a hybrid floating structure with cylinder was introduced to reduce the hydrodynamic motions of the pontoon type. The hybrid floating structure is composed of cylinders and semi-opened side sections to penetrate the wave impact energy. In order to exactly investigate the hydrodynamic motions and structural behavior of the hybrid floating structure under the wave loadings, integrated analysis of hydrodynamic and structural behavior were carried out on the hybrid floating structure. Firstly, the hydrodynamic analyses were performed on the hybrid and pontoon models. Then, the wave-induced hydrodynamic pressures resulting from hydrodynamic analysis were directly mapped to the structural analysis model. And, finally, the structural analyses were carried out on the hybrid and pontoon models. As a result of this study, it was learned that the hybrid model of this study was showed to have more favorable hydrodynamic motions than the pontoon model. The surge motion was indicated even smaller motion at all over wave periods from 4.0 to 10.0 sec, and the heave and pitch motions indicated smaller motions beyond its wave period of 6.5 sec. However, the hybrid model was shown more unfavorable structural behavior than the pontoon model. High concentrated stress occurred at the bottom slab of the bow and stern part where the cylinder wall was connected to the bottom slab. Also, the hybrid model behaved with the elastic body motion due to weak stiffness of floating body and caused a large stress variation at the pure slab section between the cylinder walls. Hence, in order to overcome these problems, some alternatives which could be easily obtained from the simple modification of structural details were proposed.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.12
• /
• pp.1345-1350
• /
• 2014

This paper presented analysis methods for adapting E-glass fiber/epoxy composite (GFRP) materials to an automotive leaf spring. It focused on the static behaviors of the leaf spring due to the material composition and its fiber orientation. The material properties of the GFRP composite were directly measured based on the ASTM standard test. A reverse implementation was performed to obtain the complete set of in-situ fiber and matrix properties from the ply test results. Next, the spring rates of the composite leaf spring were examined according to the variation of material parameters such as the fiber angles and resin contents of the composite material. Finally, progressive failure analysis was conducted to identify the initial failure load by means of an elastic stress analysis and specific damage criteria. As a result, it was found that damage first occurred along the edge of the leaf spring owing to the shear stresses.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.2 no.2
• /
• pp.72-85
• /
• 2000

Rock is a very complex and heterogeneous material, containing structural flaws due to geologic generation process. Because of those structural flaws, deformation and failure of rock when subjected to differential compressive stresses is non-linear. To simulate the non-linear behavior of rock, mechanical crack models, that is, sliding and shear crack models have been used in several studies. In those studies, non-linear stress-strain curves and various behaviors of rock including the changes of effective elastic moduli ($E_1$, $E_2$, ${\nu}_1$, ${\nu}_2$, $G_2$) due to crack growth were simulated (Kemeny, 1993; Jeon, 1996, 1998). Most of the studies have mainly focused on the verification of the mechanical crack model with relatively less attempt to apply it to practical purposes such as numerical analysis for underground and/or slope design. In this study, the validity of mechanical crack model was checked out by simulating the non-linear behavior of rock and consequently it was applied to a practical numerical analysis, finite element analysis commonly used.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.3
• /
• pp.1764-1769
• /
• 2014

Numerical investigations have been conducted on the junction that connect the multi-tubular section and the single shell section in order to evaluate applicability of hybrid sections in wind turbine towers instead of conventional single shell towers. Major characteristics in structural details include extension of multi-tubular member into shell end section, installation of wing stiffeners, and different layout of floor beams. Elastic and nonlinear incremental analyses were conducted to examine stress concentration patterns and ultimate behaviors, respectively. Based on evaluation of structural performance due to vertical and horizontal forces, it has been confirmed that installation of floor beams and wing stiffeners sensitively affect ultimate strength of global wind tower.