• Geotechnical Engineering
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• v.13 no.5
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• pp.5-18
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• 1997

Anisotropy in strength and deformation characteristics of isotropically consolidated sande prepared by pluviating through air was studied by plane strain compression tests. Seven types of sand of the world-wide origins were tested, which have been extensively used for research purposes. The strains for direction of bmazimum principal stress and direction of minimum principal strews were measured continuously from $10^{-6}\; to 10^{-2}$. The following results were obtained for all sands. The behaviour at strains leas than about 0.001% was elastic and isotropic regardless of the angle $\delta\; of\; the\;\sigma$ direction relative to the bedding plane. However, the sands became gradually more anisotropic as the strain increased to the extent exceeding the elastic limit. The peak strength was noticeably anisotropic with a similar trend. Thus, the angle of internal friction $\phi\; decreased \;as\;\delta$ decreased from $90^{\circ}$, and the ratio of the smallest to largest values of was between 0.82 and 0.90. The l has a minimum at $\delta=0^{\circ}~30^{\circ}$ depending on the hypes of sand. The residual strength became isotropic again.

• Journal of Navigation and Port Research
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• v.26 no.1
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• pp.50-54
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• 2002

The plate bucking is very important design criteria when the ship is composed of high tensile steel plates. The structures under the action of excessive exhibit local failure associated with bucking until they reach the ultimate limit state as a whole. Precise assessment of the behaviour of plate above primary buckling load is important. In this connection, series of elastic plastic large deflection analyses are performed on rectangular plates with aspect ratio 1.4 applying the finite element method. In this paper, the buckling/plastic collapse behavior of ship plates with secondary buckling is investigated. It has found that the other deflection componentes also increase with the increase of compressive load above the primary buckling load.

• Korean Journal of Materials Research
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• v.10 no.2
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• pp.155-159
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• 2000

Microstructural processes during high cycle fatigue are investigated according to plastic-strain hardening, crack formation, crack propagation and fracture. It is shown that the fatigue test resembles the uniaxial tensile test. The logarithm of the number of cycles to failure is proportional to the elongation in the tensile test. Under high cycle fatigue test, the strain is normally elastic. If the strain is absolutly elastic, fatigue could not result. But this is over simplication. Nearly all metals undergo a minor amount of plastic strain even at low stress. Damage accumulation leadling to crack formation can continue in the persistent slip bands at very low average plastic strain amplitude. In the ten­s sile test the overall specimen follows the failure procedure whilst in the high cycle fatigue test the local persistent slip band follows the failure procedure. However accumulations of strain per unit volume in the deforming region before failure in both cases are equal locally.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.1
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• pp.24-38
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• 1989

In this study, an attempt for formulating a new and simplified rectangular finite element having only four corner nodal points is made to analyze the elastic-plastic large deformation behaviour up to the ultimate limit state of plates with initial imperfections. The present finite element contains the geometric nonlinearity caused by both in-plane and out-of-plane large deformation because for very thin plates the influence of the former may not be negligible. Treatment of expanded plastic zone in the plate thickness direction of the element is simplified based upon the concept of plastic node method so that the elastic-plastic stiffness matrix of the element is derived by the simple matrix operation without performing complicated numerical integration. Thus, a considerable saving of the computational efforts is expected. A computer program is also completed based on the present formulation and numerical calculation for some examples is performed so as to verify the accuracy and validity of the program.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.171-180
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• 2005

In this study the seismic performance of a three-story knee-braced moment-resisting frame (KBMRF), which is typically employed to support pipelines for oil or gas, was investigated. Nonlinear static pushover analyses were performed first to observe the force-displacement relationship of KBMRF under increasing seismic load. The results show that, when the maximum inter-story drift reached 1.5% of the story height, the main structural members, such as beams and columns, still remained elastic. Then nonlinear dynamic time-history analyses were carried out using eight earthquake ground motion time-histories scaled to at the design spectrum of UBC-97. It turned out that the maximum inter-story drift was smaller than the drift limit of 1.5 % of the structure height, and that the columns remained elastic. Based on these analytical results, it can be concluded that the seismic performance of the structure satisfies all the requirements regulated in the seismic code.

• Geomechanics and Engineering
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• v.8 no.2
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• pp.187-220
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• 2015

Soil disturbance induced by installation of mandrel driven vertical drains decreases the in situ horizontal hydraulic conductivity of the soil in the vicinity of the drains, decelerating the consolidation rate. According to available literature, several different profiles for the hydraulic conductivity variation with the radial distance from the vertical drain, influencing the excess pore water pressure dissipation rate, have been identified. In addition, it is well known that the visco-plastic properties of the soil also influence the excess pore water pressure dissipation rate and consequently the settlement rate. In this study, a numerical solution adopting an elastic visco-plastic model with nonlinear creep function incorporated in the consolidation equations has been developed to investigate the effects of disturbed zone properties on the time dependent behaviour of soft soil deposits improved with vertical drains and preloading. The employed elastic visco-plastic model is based on the framework of the modified Cam-Clay model capturing soil creep during excess pore water pressure dissipation. Besides, nonlinear variations of creep coefficient with stress and time and permeability variations during the consolidation process are considered. The predicted results have been compared with V$\ddot{a}$sby test fill measurements. According to the results, different variations of the hydraulic conductivity profile in the disturbed zone result in varying excess pore water pressure dissipation rate and consequently varying the effective vertical stresses in the soil profile. Thus, the creep coefficient and the creep strain limit are notably influenced resulting in significant changes in the predicted settlement rate.

• Structural Engineering and Mechanics
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• v.69 no.6
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• pp.627-635
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• 2019

In order to study the axial compression performance of sand-lightweight concrete-filled steel tube (SLCFST) stub columns, three circular SLCFST (C-SLCFST) stub column specimens and three SLCFST square (S-SLCFST) stub column specimens were fabricated and static monotonic axial compression performance testing was carried out, using the volume ratio between river sand and ceramic sand in sand-lightweight concrete (SLC) as a varying parameter. The stress process and failure mode of the specimens were observed, stress-strain curves were obtained and analysed for the specimens, and the ultimate bearing capacity of SLCFST stub column specimens was calculated based on unified strength theory, limit equilibrium theory and superposition theory. The results show that the outer steel tubes of SLCFST stub columns buckled outward, core SLC was crushed, and the damage to the upper parts of the S-SLCFST stub columns was more serious than for C-SLCFST stub columns. Three stages can be identified in the stress-strain curves of SLCFST stub columns: an elastic stage, an elastic-plastic stage and a plastic stage. It is suggested that AIJ-1997, CECS 159:2004 or AIJ-1997, based on superposition theory, can be used to design the ultimate bearing capacity under axial compression for C-SLCFST and S-SLCFST stub columns; for varying replacement ratios of natural river sand, the calculated stress-strain curves for SLCFST stub columns under axial compression show good fitting to the test measure curves.

• Earthquakes and Structures
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• v.22 no.5
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• pp.461-473
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• 2022

Energy-saving block and invisible multiribbed frame composite wall (EBIMFCW) is an important shear wall, which is composed of energy-saving blocks, steel bars and concrete. This paper conducted seismic performance tests on six 1/2-scale EBIMFCW specimens, analyzed their failure process under horizontal reciprocating load, and studied the effect of axial compression ratio on the wall's hysteresis curve and skeleton curve, ductility, energy dissipation capacity, stiffness degradation, bearing capacity degradation. A formula for calculating the peak bearing capacity of such walls was proposed. Results showed that the EBIMFCW had experienced a long time deformation from cracking to failure and exhibited signs of failure. The three seismic fortification lines of the energy-saving block, internal multiribbed frame, and outer multiribbed frame sequentially played important roles. With the increase in axial compression ratio, the peak bearing capacity and ductility of the wall increased, whereas the initial stiffness decreased. The change in axial compression ratio had a small effect on the energy dissipation capacity of the wall. In the early stage of loading, the influence of axial compression ratio on wall stiffness and strength degradation was unremarkable. In the later stage of loading, the stiffness and strength degradation of walls with high axial compression ratio were low. The displacement ductility coefficients of the wall under vertical pressure were more than 3.0 indicating that this wall type has good deformation ability. The limit values of elastic displacement angle under weak earthquake and elastic-plastic displacement angle under strong earthquake of the EBIMFCW were1/800 and 1/80, respectively.

• Earthquakes and Structures
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• v.5 no.6
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• pp.657-678
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• 2013

For economical earthquake resistant design of cable-stayed bridge tower, the use of energy dissipation systems for the earthquake protection of steel structures represents an alternative seismic design method where the tower structure could be constructed to dissipate a large amount of earthquake input energy through inelastic deformations in certain positions, which could be easily retrofitted after damage. The design of energy dissipation systems for bridges could be achieved as the result of two conflicting requirements: no damage under serviceability limit state load condition and maximum dissipation under ultimate limit state load condition. A new concept for cable-stayed bridge tower seismic design that incorporates sacrificial link scheme of low yield point steel horizontal beam is introduced to enable the tower frame structure to remain elastic under large seismic excitation. A nonlinear dynamic analysis for the tower model with the proposed energy dissipation systems is carried out and compared to the response obtained for the tower with its original configuration. The improvement in seismic performance of the tower with supplemental passive energy dissipation system has been measured in terms of the reduction achieved in different response quantities. Obtained results show that the proposed energy dissipation system of low yield point steel seismic link could strongly enhance the seismic performance of the tower structure where the tower and the overall bridge demands are significantly reduced. Low yield point steel seismic link effectively reduces the damage of main structural members under earthquake loading as seismic link yield level decreases due their exceptional behavior as well as its ability to undergo early plastic deformations achieving the concentration of inelastic deformation at tower horizontal beam.

• Korean Journal of Soil Science and Fertilizer
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• v.8 no.1
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• pp.19-23
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• 1975

In order to find out the effect of long-term annual additions of organic matter on the physico-chemical properties of paddy soil, the soil with and without compost application has been analysed. 1. There was no significant difference in the particle size distribution between compost and uncompost treatment, however, hydraulic conductivity, sedimention volume were remarkedly increased in compost. 2. Bulk density and soil strength were decreased in organic matter additions, but porosity increased. 3. Relative to Atterberg Limits, liquid limit, plastic limit, and elastic index were increased in compost. 4. Aggregate size distribution was slightly increased in additions of organic matter. 5. Regarding to chemical properties, pH, organic matter content, C.E.C. and extractable cation were increased in organic matter additions.