• Steel and Composite Structures
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• v.15 no.2
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• pp.163-173
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• 2013

The thermal creep is one of the major factors causing the buckle of steel columns in the fire events. But, few related studies have been reported to evaluate the factors affecting the thermal creep of steel column experimentally or numerically. In this study a series of Fire-resistant steel columns with three different slenderness ratios under a sustained load are tested under a uniform temperature up to six hours in order to evaluate the creep upon three selected factors, temperature, applied load, and column slenderness. Based on experimental results, a proposed creep strain rate model is established as the function of a single parameter of the load ratio of temperature LR(T) to determine the buckling time of steel column due to creep. Furthermore it is found that the creep can be neglected when LR(T) is smaller than 0.77.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.9
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• pp.1674-1680
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• 2008

The objective of this study is to compare age-related differences of 15 characteristic variables estimated from SEMG signals, which were obtained from the old group(62 subjects) and young group(72 subjects). The SEMG signals were recorded from biceps brachii muscle under sustained isometric elbow flexion contraction with constant load(4kg dumbbell) during 30 seconds. Ten time domain (ARV, RMS, MSA, MTA, ZC, MSF, MTF, MSD, MTD, MSS) and five frequency domain(MNF, MDF, $f_{max}$, $P_{max}$, $P_{to}$) variables were extracted from the SEMG signals and then statistically analyzed, respectively. The findings of the analysis indicate significant age-related differences in the SEMG signal during constant load contraction.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.765-772
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• 2008

For RC structures, long-term deformation occurs due to the inherent characteristics, which are creep and shrinkage. In terms of serviceability, it is important to limit deflection caused by the deformation to the allowable deflection. In the recent years, various repair and strengthening methods have been used to improve performance of the existing RC structures. One of the typical methods is FRP externally bonded method (EBR). Fiber reinforced polymer (FRP) has been used worldwide as repair and strengthening materials due to its superior properties. Besides, it has to offer improved strengthening performance not only under instantaneous load but sustained load. Therefore, accurate prediction method of deflection for the RC members externally bonded with FRP under sustained load is required. In this paper, three beams were fabricated. Two beams were externally strengthened with one of CFRP plate and GFRP plate respectively. Total three beams were superimposed under sustained load of 25 kN. During 470 days, deflections at midspan were obtained. Moreover, creep coefficients and shrinkage strains were calculated by using ACI-209 code and CEB-FIP code. In order to predict the deflection of the beams, EMM, AEMM, Branson's method and Mayer's method were used. Through the experiment, it was found that the specimen with CFRP plate has the most flexural capacity and Mayer's method is the most precise method to predict total long-term deflections.

• Journal of the Korean Geotechnical Society
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• v.24 no.1
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• pp.71-80
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• 2008

This paper presents the reusults of wide width tensile tests under sustained and cyclic loads with vairous loading rate on geogrids. A seires of modified wide width tensile tests were conducted to investigate the effect of tensile strain rate on the deformation behavior of the geogrids. In addition, residual deformation characteristics of a geogrid under sustained or cyclic tests were also investigated. The results indicated that the residual deformation of a geogrid is strongly related to the viscous behavior of the geogrid, and the residual deformation can be well described by a hyperbolic curve. Also revealed was that residual deformation of a geogrid when subject to sustained or cyclic load should be described with the framework of viscous behavior.

• Geotechnical Engineering
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• v.12 no.6
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• pp.51-64
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• 1996

After the model open-ended pile attached with strain gages was driven into a pressure chamber, in which the saturated microfine sand was contained, the static compression loading test was performed for that pile. Based on the test results, ultimate pile capacity was determined. Then, either simulated earthquake shaking or sinusoidal shaking was applied to the pile with the sustained certain level OP ultimate pile load. Then, pile capacity degradations characteristics during shaking were studied. Pile capacity degradation during two different shakings were greatly different. During the simulated earthquake shaking, capacity degradation depended upon the magnitude of applied load. When the load applied to the pile top was less than 70% of ultimate pile capacidy, pile capacity degradation rate was less than 8%, and pile with the sustained ultimate pile load had the degradation rate of 90%. Also, most of pile capacity degradation was reduced in outer skin friction and degradation rate was about 80% of ultimate pile capacity reduction. During sinusoidal shaking, pile capacity degradation did not depend on the magnitude of applied load. It depended on the amplitude and the frequency , the larger the amplitude and the fewer the frequency was, the higher the degradation rate was. Reduction pattern of unit soil plugging (once depended on the mode of shaking. Unit soil plugging force by the simulated earthquake shaking was reduced in the bottom 3.0 D, of the toe irrespective of the applied load, while reduction of unit soil plugging force by sinusoidal shaking was occurred in the bottom 1.0-3.0D, of the toe. Also, the soil plugging force was reduced more than that during simulated earthquake shaking and degradation rate of the pile capacity depended on the magnitude of the applied load.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.1
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• pp.9-16
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• 1991

The concept of damage is all-pervasive in structural engineering. It can be considered a state variable and defined to vary from 0(no damage) to 1(failure). Thus, the factor of safety against failure, the most important aspect of a structure, cannot be assessed without evaluating the damageability of a structure under load. It is the objective of the research reported herein to study the behavior of concrete under repeated load applications. Concrete is known to deteriorate under such loading, i.e., it suffers damage of increasing degree. Its response to future loading is a function of the amount of damage sustained during previous load exposures. The same can be said about reinforced concrete members and entire structures, but here we wish to consider only plain concrete and express some of its material properties as functions of the degree of sustained damage. The work described herein is based on the stipulation that the energy dissipation capacity of plain concrete is a material property and the damage accumulates in direct proportion to the degree to which the energy dissipation capacity is being exhausted, in some analogy to both high- and low-cycle failure behavior of materials.

• The Journal of Engineering Research
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• v.2 no.1
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• pp.125-131
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• 1997

The regenerator is important part of the glass melting furnace to increase the temperature of the intake air through the combustion flame. The insulation, checker brick, prevention of the air leak has been studied to decrease the fuel consumption in glass melting industries. Thus the new types of checker brick and the design of the rider arch has been studied to prolong the life of the glass melting furnace. The height of the regenerator increased from 5.64 m to 7.89 m in the reforming of the glass melting furnace. Thus the stability of the rider arch is studied under the condition of increased load of checker brick in this research. The rider arch was estimated to be stable inspite of the increase of load according to the calculation. The max. sustained compressive stress of the rider arch is 163 kg/$cm^2$ and the max. sustained shear stress is 6.37 kg/$cm^2$.

• Journal of the Korean Society of Safety
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• v.14 no.2
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• pp.116-121
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• 1999

When plate anchors are embedded in soft clay, they may undergo a deformation under the pressure of sustained load. The critical depth at which the transition from a shallow to a deep anchor takes place depends on the properties of soil. Laboratory model tests were performed for the short-term net ultimate uplift capacity of a circular anchors with respect to various embedment depths and moisture content in saturated kaolinite. The tests have been conducted with the anchor at two different moisture contents. Based on the model test results, empirical relationships between the net load, rate of strain, and time have been developed. In creep tests of kaolinite for load versus ultimate uplift capacity, the displacement of plate anchors rapidly increases during the primary stage but thereafter becomes constant over a period of time.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.8
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• pp.1062-1066
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• 2001

Studies were carried out on forty young bulls of the Hariana breed (around 18 months of age) selected on the basis of their dam's milk yield at the animal farm of CCS HAU, Hisar during the period 1993-1999. Since animals showed variation in capacity to work over prolonged periods, they were subjected to regimes of carting without load and with 8 qtls. of load for three hours. The study revealed that maximum change took place in the pulse rate, followed by respiration rate and rectal temperature. The mean fatigue score for pulling an empty cart ranged between 1.66 to 2.20 after two hours work, and 2.36 to 2.73 after three hours work. For a cart loaded with 8 qtls., the corresponding ranges were 2.90 to 3.36 and 3.40 to 4.10, respectively. These results indicated that the animals under experiment had the capacity to pull moderate load (8 qtls.) for about two hours without showing any serious effect on the ability to recover and soon to work again.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.12
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• pp.18-29
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• 2014

This paper proposes the integration of photovoltaic (PV) and energy storage systems for sustained power generation. In this proposed system, whenever the PV system cannot completely meet load demands, the super capacitor provides power to meet the remaining load. A power management strategy is designed for the proposed system to manage power flows between PV array systems and supercapacitors (SC). The main task of this study was to design PV systems with storage strategies including MPPT with direct control and an advanced DC-link controller and to analyze dynamic model proposed for a PV-SC hybrid power generation system. In this paper, the simulation models for the hybrid energy system are developed using Matlab/Simulink, SimPowerSystems and Matlab/Stateflow tool. This is the key innovative contribution of the research paper. The system performances are verified by carrying out simulation studies using practical load demand profile and real weather data.