• Journal of the Earthquake Engineering Society of Korea
• /
• v.7 no.5
• /
• pp.57-66
• /
• 2003

In order to verify the applicability of the developed modified parallel IWAN model. two types of cyclic torsional shear tests were performed using Kum-Kang and Toyoura sands. One was a symmetric-limit loading test and the other was an irregular loading test. Model parameters were derived from the symmetric limit loading tests at various relative densities and confining pressures. The modified parallel IWAN model can predict the cyclic hardening behavior of sands very well as increasing loading cycles in the symmetric-limit tests. Irregular loading tests were performed using the loading shape suggested by Pyke(1979). Cyclic behaviors under irregular loading were simulated using model parameters derived from symmetric limit loading test results of similar loading conditions. The predicted cyclic hardening behaviors under irregular loading matched well with experimental results and the applicability of the proposed model was verified.

• Journal of the Korean Geotechnical Society
• /
• v.16 no.1
• /
• pp.157-165
• /
• 2000

The applicability and performance of HMS-25 as the railroad roadbed materials were evaluated through the model and laboratory tests. The uniaxial compression test of HMS-25, model soil box test, and combined resonant column and torsional shear test were performed for static and dynamic analysis of railroad roadbed. The uniaxial compression test result of HMS-25 shows steady increase in strength due to hardening chemical reaction between HMS-25 and water. The result of model soil box test reveals that railroad roadbed of HMS-25 is better than that of soil in several aspects such as bearing capacity and settlement. The combined resonant column and torsional that shear test result indicates that shear modulus of HMS-25 increases with the power of 0.5 to the confining pressure and that shear modulus increases with the increase of curing period.

• The Journal of the Acoustical Society of Korea
• /
• v.18 no.5
• /
• pp.28-34
• /
• 1999

The effects of the viscosity of an adjacent viscous fluid on the characteristics of the elastic waves have been studied theoretically and experimentally. Expressions for the wave speed and attenuation of the elastic waves of transverse motion, such as the torsional wave propagating in a circular cylinder and the Love wave in a layered half-space solid, have been obtained as functions of the viscosity and mass density of the fluid by exact and asymptotic analyses. The theoretical results have been compared with experimental observations, and it has been demonstrated that a device described herein can be used as a sensor for measuring the viscosity of a fluid with a known mass density.

• Geotechnical Engineering
• /
• v.11 no.1
• /
• pp.113-126
• /
• 1995

Both resonant column (RC) and torsional shear(TS) tests were performed at small to intermediate strain levels to investigate deformational characteristics of cohesive soils. The effects of variables such as strain amplitude, loading frequency, and number of loading cycles were studied. Plasticity index was found to be an important variables in evaluating these effects. Soils tested include undisturbed silts and clays and compacted subgrade soils. At small strains below the elastic threshold, shear modulus is independent of number of loading cycles and strain amplitude. Small strain material damping exists wi th ranges be tween 1.1% and 1.7% for 75 tests. The elastic threshold strain increases as confining pressure and plasticity index increases. Above the cyclic threshold strain, the modulus of cohesive soil decreases with increasing number of cycles while damping ratio is almost independent of number of load cycles. Moduli and damping ratios of cohesive soils obtanined by RC test are higher than those from 75 test because of the frequency effect. Shear modulus of cohesive soil increases linearly as a function of the logarithm of loading frequency.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.1
• /
• pp.561-568
• /
• 2014

A modular fish-bone girder pier consists of one main girder system named as "Spine Girder". Therefore, this pier can be most affected by torsion as well as flexural bending. The design considerations of the fish-bone girder pier are proposed to assure the reasonable design in this study. In order to investigate the behavior characteristics, structural analysis F.E model is developed, and the verification of the developed model is performed by comparison with experimental data. From the investigation of the structural behavior, the vertical stiffener is required at the bottom of bone-beams to prevent the excessive local stress. Also, it is found that the normal stress of the flange and the shear stress of the web and flange are dominantly affected by the warping torsion and pure torsion, respectively.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.27 no.1
• /
• pp.35-44
• /
• 1990

Most of the medium-size ships are powered by large-bore, long-stroke, slow-speed and two-stroke diesel engines in order to improve the fuel efficiency. Such a propulsion plant develops low-frequency excitation forces/moments of significant magnitude. A RO/RO car/truck carrier is also one of the cases. In this paper, the rational methods for analysis of vertical and coupled horizontal-torsional vibrations are presented. Taking account of unusual characteristics of the hull form and structural systems, the emphasis is put on modelling methods based on beam analogy, calculation of system parameters such as added mass and its center, polar added-mass moment of inertia, shear coefficient of hull sections and coupling degree in antisymmetric modes, and modal analysis of forced vibrations.

• Journal of the Korean Geotechnical Society
• /
• v.34 no.10
• /
• pp.5-16
• /
• 2018

The ever-increasing amount of waste vinyl is causing big environmental problems. In particular, those from farming industry are sometimes left on site or even illegally reclaimed due to the lack of environmental concerns and capacity for collection, which worsens the situation. It is, therefore, believed that the recycling of waste vinyl is the most ideal solution in the viewpoint of environmental preservation. In this context, the potential of vinyl strip as a ground reinforcing material is investigated to expand the application of waste vinyl recycling. In this study, a series of uniaxial compression tests and resonant column tests were performed for sand specimens reinforced with vinyl strips and cement to investigate their reinforcing effects on static and dynamic behaviors. The changes in the uniaxial compressive strength (UCS), the shear modulus and the damping ratio according to the mixing ratio of vinyl strips and cements were analysed for sand specimens, having 40% and 60% relative densities, under various mixing conditions. As a result, both the static and dynamic reinforcing effects of vinyl strip-cement mixture were confirmed and the optimum mixing ratio was proposed.