• Journal of Mechanical Science and Technology
• /
• v.17 no.1
• /
• pp.48-56
• /
• 2003

This paper investigates the collapse characteristics of CF/Epoxy composite tubes subjected to axial loads as changing interlaminar number and outer ply orientation angle. The tubes are aften used for automobiles, aerospace vehicles, trains, ships, and elevators. We have performed static and dynamic impact collapse tests by a way of building impact test machine with vertical air compression. It is fanad that CF/Epoxy tube of the 6 interlaminar number (C-type) with 90$^{\circ}$ outer orientation angle and trigger absorbed more energy than the other tubes (A. B and D-types). Also collapse mode depended upon outer orientation angle of CF/Epoxy tubes and loading type as well； typical collapse modes of CF/Epoxy tubes are wedged, splayed and fragmentcl.

• Structural Engineering and Mechanics
• /
• v.57 no.3
• /
• pp.403-423
• /
• 2016

The challenges involved with fatigue damage assessment of steel catenary riser (SCR) in the touchdown zone (TDZ) are primarily due to the non-linear behaviour of the SCR-seabed interaction, considerable uncertainty in SCR-seabed interaction modelling and geotechnical parameters. The issue of fatigue damage induced by the cyclic movements of the SCR with the seabed has acquired prominence with the touch down point (TDP) interaction in the TDZ. Therefore, the SCR-seabed response is critical for reliable estimation of fatigue life in the TDZ. Various design approaches pertaining to the lateral pipe-soil resistance model are discussed. These techniques have been applied in the finite element model that can be used to analyse the lateral SCR-seabed interaction under hydrodynamic loading. This study investigates the sensitivity of fatigue performance to geotechnical parameters through a parametric study. In this study, global analyses are performed to assess the influence of vertical linear seabed springs, the lateral seabed model and the non-linear seabed model, including trench evolution into seabed, seabed normalised stiffness, re-penetration offset parameter and soil suction resistance ratio, on the fatigue life of SCRs in the TDZ.

• Coupled systems mechanics
• /
• v.3 no.3
• /
• pp.267-289
• /
• 2014

A proper physical modeling of infilled building frame-foundation beam-soil mass interaction system is needed to predict more realistic and accurate structural behavior under static vertical loading. This is achieved via finite element method considering the superstructure, foundation and soil mass as a single integral compatible structural unit. The physical modelling is achieved via use of finite element method, which requires the use of variety of isoparametric elements with different degrees of freedom. The unbounded domain of the soil mass has been discretized with coupled finite-infinite elements to achieve computational economy. The nonlinearity of soil mass plays an important role in the redistribution of forces in the superstructure. The nonlinear behaviour of the soil mass is modeled using hyperbolic model. The incremental-iterative nonlinear solution algorithm has been adopted for carrying out the nonlinear elastic interaction analysis of a two-bay two-storey infilled building frame. The frame and the infill have been considered to behave in linear elastic manner, whereas the subsoil in nonlinear elastic manner. In this paper, the computational methodology adopted for nonlinear soil-structure interaction analysis of infilled frame-foundation-soil system has been presented.

• International Journal of High-Rise Buildings
• /
• v.7 no.3
• /
• pp.255-264
• /
• 2018

This paper introduces three distinctive means for the use of a 189-meter high damped structure ensuring safety against earthquake: 1. Realization of L-shaped elevational structural planning: The bottom and top of the tower have belt trusses and hat trusses respectively to restrain the bending deformation. Furthermore, large-capacity oil dampers (damping force 6,000 kN) are installed in the middle part of the tower to restrain the higher-mode deformation. 2. Realization of L-shaped planar structural planning: We devised a means of matching the centers of gravity and rigidity by adjusting planar rigidity. Moreover, viscous damping devices are located at the edges of the L-shaped plan, where torsional deformation tends to be amplified. We call this the "Damping Tail" system. 3. Composite foundation to equalize deformations under different loading conditions: We studied the vertical and horizontal deformations using sway-rocking and 3D FEM models including the ground, and applied multi-stage diameter-enlarged piles to the tower and a mat foundation to the podium to keep the foundations from torsional deformations and ensure structural safety.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2001.09a
• /
• pp.107-114
• /
• 2001

When group pile supporting structures are to be subjected to large lateral loads, generally, hatter piles are used in group pile with vertical piles. It is well known that batter piles resist lateral static loads which are acted upon the piles as axial farces quite well but, they show a poor performance under seismic loads. However, it is not yet known how the batter piles behave under dynamic loading and how to strengthen the batter piles to improve the seismic performance. Shaking table tests were performed to investigate the seismic behavior of the batter pile and to bring up the countermeasures to improve the seismic performance. As the result of the shaking table tests, batter piles failed due to not only the excessive increase of compressive force near the pile head but also that of tensile force. In case that the pile head was connected with pile cap by rubber joint, the max. acceleration at the pile cap was reduced due to the high damping ratio of rubber and the max. moment and max. axial farce at the pile head was decreased remarkably. When the inclinations(V:H) of the batter pile were 8:3 and 8:4, max. moment, max. shear force, and max. axial farce were reduced notably and max. acceleration and max. displacement at the pile cap was diminished, too.

• Proceedings of the KSR Conference
• /
• 2007.05a
• /
• pp.340-350
• /
• 2007

The major objective of this study is to investigate the fatigue effects of rail pad on High Speed Railway with concrete slab track system. It analyzed the mechanical behaviors of HSR concrete slab track with applying rail pad stiffness based on fatigue effect(hardening and increasing stiffness) on the 3-dimensional FE analysis and laboratory test for static & dynamic characteristics. As a result, the hardening of rail pad due to fatigue loading condition are negative effect for the static & dynamic response of concrete slab track which is before act on fatigue effect. The analytical and experimental study are carried out to investigate rail pad on fatigue effected increase vertical acceleration and stress and decrease suitable deflection on slab track. And rail pad based on fatigue effect induced dynamic maximum stresses, the increase of damage of slab track is predicted by adopting fatigue effected rail pad. after due consideration The servicing HSR concrete slab track with resilient track system has need of the reasonable determination after due consideration fatigue effect of rail pad stiffness which could be reducing the effect of static and dynamic behavior that degradation phenomenon of structure by an unusual response characteristic and a drop durability.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.19 no.12
• /
• pp.1410-1415
• /
• 2008

This paper proposes an small electronically steerable parasitic array radiator composed of a uniplanar dipole as a feeding element and two dipoles as parasitic elements. The fabricated antenna shows by measurement the $3.3{\sim}4.3\;dB$ gain between $-100{\sim}1000$ azimuth range in the dipole vertical plane and -10 dB return loss within $5.4{\sim}5.9\;GHz$, which includes $5.725{\sim}5.825\;GHz$ UNII band.

• Ocean Systems Engineering
• /
• v.8 no.3
• /
• pp.345-360
• /
• 2018

Increasing demand for large-sized Floating, Storage and Regasification Units (FSRUs) for oil and gas industries led to the development of novel geometric form of Buoyant Leg Storage and Regasification Platform (BLSRP). Six buoyant legs support the deck and are placed symmetric with respect to wave direction. Circular deck is connected to buoyant legs using hinged joints, which restrain transfer of rotation from the legs to deck and vice-versa. Buoyant legs are connected to seabed using taut-moored system with high initial pretension, enabling rigid body motion in vertical plane. Encountered environmental loads induce dynamic tether tension variations, which in turn affect stability of the platform. Postulated failure cases, created by placing eccentric loads at different locations resulted in dynamic tether tension variation; chaotic nature of tension variation is also observed in few cases. A detailed numerical analysis is carried out for BLSRP using Mathieu equation of stability. Increase in the magnitude of eccentric load and its position influences fatigue life of tethers significantly. Fatigue life decreases with the increase in the amplitude of tension variation in tethers. Very low fatigue life of tethers under Mathieu instability proves the severity of instability.

• Computers and Concrete
• /
• v.22 no.5
• /
• pp.493-500
• /
• 2018

Due to the fact that the ratio of their height to their openings is very large compared to normal beams, there are difficulties in the design and analysis of deep beams, which differ in behavior. In this study, the optimum horizontal and vertical reinforcement diameters of 5 different beams were determined by using genetic algorithms (GA) due to the openness/height ratio (L/h), loading condition and the presence of spaces in the body. In this study, the effect of different mutation operators and improved double times sensitive mutation (DTM) operator on GA's performance was investigated. In the study following random mutation (RM), boundary mutation (BM), non-uniform random mutation (NRM), Makinen, Periaux and Toivanen (MPT) mutation, power mutation (PM), polynomial mutation (PNM), and developed DTM mutation operators were applied to five deep beam problems were used to determine the minimum reinforcement diameter. The fitness values obtained using developed DTM mutation operator was higher than obtained from existing mutation operators. Moreover; obtained reinforcement weight of the deep beams using the developed DTM mutation operator lower than obtained from the existing mutation operators. As a result of the analyzes, the highest fitness value was obtained from the applied double times sensitive mutation (DTM) operator. In addition, it was found that this study, which was carried out using GAs, contributed to the solution of the problems experienced in the design of deep beams.

• Ocean and Polar Research
• /
• v.25 no.spc3
• /
• pp.385-392
• /
• 2003

A new type of soft ground breakwater was recently developed, which does not need ground improvement because of light weight and structural characteristics. The various studies about consolidation settlements and lateral behavior of proposed soft ground breakwater have been conducted. But, the systematic investigations on the construction performance and long-term settlements of new type breakwater has not been accomplished. In this study, construction simulation of soft ground breakwater with soil box model test and experiments of the long-term wave loaded breakwater were performed. The results of test shows that it is possible to compensate differential settlements by dead loading and/or suction pressure, and to reduce the consolidation settlements by preloading method. It was also found that the vertical and lateral displacements of long-term wave loaded breakwater were negligible.