• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.323-328
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• 2001

The behavior of bridge column under multi-directional loading as well as uni-directional loading need to be studied because bridge columns will be subjected to the multi-directional cyclic loading during a strong earthquake. To evaluate the capacity of columns, uni-axial cyclic loading tests and bi-axial alternate cyclic loading tests were carried out. The number of cycles of alternate bi-axial loading were determined considering the ratio of natural frequencies in two orthogonal directions. From the test results, strength degradation and ductility reduction were observed in biaxial loading conditions. Their rates were found to be more rapid in the loading pattern that was determined considering the different natural frequencies.

• Journal of Environmental Science International
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• v.17 no.3
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• pp.343-350
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• 2008

The fate of two cyclic ethers, THF(Tetrahydrofuran) and 1,4-Dioxane, in conventional biological wastewater treatment plants was investigated using sequential activated sludge process. Removal efficiency of THF were about 86% in average, which was greater than that of 1,4-Dioxane, 30%. However, it was not clear whether the removal of cyclic ethers in biological system was caused by microbial activity or not. Thus treatability tests were conducted by batch experiments. The effects of mixing, aeration and the addition of activated sludge on the removal of cyclic ethers were investigated in batch experiments. THF was totally removed by mixing and aeration in 24 hours while removal ratio of 1,4-Dioxane was at most 30% for the same period. This results could be ascribed to the differences in Henry's law constants between the two chemicals. In addition, biological degradation including biosorption was not obviously observed in these batch tests.

• Corrosion Science and Technology
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• v.9 no.1
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• pp.34-38
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• 2010

Electrochemical study on cut edge corrosion of prepainted Zn coated (GI) and 55%Al-Zn coated (GL) steels has been performed in wet-dry cyclic conditions. Maximum width of delaminated polymer coating from the cut edge for GI and GL specimens was evaluated under wet-dry cyclic conditions. The cyclic tests were carried out for 1000 h by changing of relative humidity, where the salt of NaCl was deposited on the specimen every 48 h. The cut edge corrosion test under NaCl deposit indicated that the delamination of the GL specimen progresses at a higher rate than the GI. The electrochemical corrosion monitoring was also performed under condition of alternate exposure to immersion in NaCl solution and drying at 60%RH and $25^{\circ}C$. On the basis of the results of the delamination tests and electrochemical measurements, the mechanism of cut edge corrosion for GI and GL were discussed.

• Structural Engineering and Mechanics
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• v.23 no.2
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• pp.129-145
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• 2006

This paper provides an insight into the response of non-seismic reinforced concrete (RC) building frames to excitations of different frequencies through experimental investigation. The results of cyclic loading tests of six full-scale RC beam-column sub-assemblies are presented. The tested specimens did not have any transverse reinforcement inside the joint core, and they were subjected to quasi-static and dynamic loading with frequencies as high as 20 Hz. Some important differences between the cyclic responses of non-seismic and ductile RC frames are highlighted. The effect of excitation frequency on the behavior of non-seismic joints is also discussed. In the quasi-static tests, shear deformation of the joint panel accounted for more than 50% of the applied story drift. The test results also showed that higher-frequency excitations are less detrimental than quasi-static cyclic loads, and non-seismic frames can withstand a higher load and a larger deformation when they are applied faster.

• Journal of Korean Association for Spatial Structures
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• v.19 no.3
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• pp.101-109
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• 2019

In order to develop the compatible damping device in various vibration source, a hybrid wall-type damper combining slit and friction damper in parallel was developed. Cyclic loading tests and two-story RC reinforced frame tests were performed for structural performance verification. As a result of the 5-cyclic loading test according to KBC-2016 and low displacement cyclic fatigue test, The hybrid wall type damper increased its strength and the ductility was the same as that of the slit damper. In addition, As a result of the two-layer frame test, the reinforced frame had about twice the strength of the unreinforced frame, and the story drift ratio was satisfied to Life Safety Level.

• Structural Engineering and Mechanics
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• v.78 no.5
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• pp.545-556
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• 2021

The present experimental study evaluated the seismic performance of six engineered cementitious composite (ECC) columns strengthened with carbon fiber reinforced polymer (CFRP) laminates under cyclic lateral loading. The ECC columns damaged and crushed in the first stage of cyclic tests were repaired using the ECC with a certain polyvinyl alcohol (PVA) fiber and strengthened with flexural and sheer CFRP laminates and then re-assessed under the cyclic loading. The effects of some variables were examined on lateral displacement, energy absorption and dissipation, failure modes, crack patterns, load bearing capacity and plasticity, and the obtained results were compared with those of the first stage of cyclic tests. The results showed that retrofitting the ECC columns can improve their performance, plasticity and load-bearing threshold, delayed the concrete failure, changed the failure modes and increased the energy absorbed by the strengthened columns element by over 50%.

• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.57-64
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• 2003

The liquefaction potential of saturated sands under seismic loading conditions has been carefully considered by many investigations. Typical of these investigations is the laboratory determination of cyclic strength of sands by means of cyclic triaxial tests. This study was conducted to investigate the effects of the method of sample preparation on the liquefaction characteristics of remolded samples of saturated uniform sands. Cyclic triaxial tests were performed on saturated uniform sand compacted to the same density by 3 different procedures of pluvial compaction through air, pluvial compaction through water and vibratory compaction. It was validated that the cyclic stress ratio of remolded saturated uniform sands by different compaction procedures at the same density was very different.

• Geomechanics and Engineering
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• v.14 no.2
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• pp.203-209
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• 2018

Reliable estimation of compressive as well as tensile in-situ stresses is critical in the design and analysis of underground structures and openings in rocks. Kaiser effect technique, which uses acoustic emission from rock specimens under cyclic load, is well established for the estimation of in-situ compressive stresses. This paper investigates the Kaiser effect on marble specimens under cyclic uniaxial compressive as well as cyclic uniaxial tensile conditions. The tensile behavior was studied by means of Brazilian tests. Each specimen was tested by applying the load in four loading cycles having magnitudes of 40%, 60%, 80% and 100% of the peak stress. The experimental results confirm the presence of Kaiser effect in marble specimens under both compressive and tensile loading conditions. Kaiser effect was found to be more dominant in the first two loading cycles and started disappearing as the applied stress approached the peak stress, where felicity effect became dominant instead. This behavior was observed to be consistent under both compressive and tensile loading conditions and can be applied for the estimation of in-situ rock stresses as a function of peak rock stress. At a micromechanical level, Kaiser effect is evident when the pre-existing stress is smaller than the crack damage stress and ambiguous when pre-existing stress exceeds the crack damage stress. Upon reaching the crack damage stress, the cracks begin to propagate and coalesce in an unstable manner. Hence acoustic emission observations through Kaiser effect analysis can help to estimate the crack damage stresses reliably thereby improving the efficiency of design parameters.

• Geomechanics and Engineering
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• v.25 no.2
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• pp.89-98
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• 2021

The paper presents an experimental study on the strength behaviour of a coral gravelly sand from Vietnam subjected to monotonic and cyclic loading. A series of direct shear tests were carried out to investigate the shear strength behaviour and the factors affecting the shear strength of the sand such as relative density, cyclic load, amplitude of the cyclic load and loading rate. The study results indicate that the shear strength parameters of the coral gravelly sand include not only internal friction angle but also apparent cohesion. These parameters vary with the relative density, cyclic load, the amplitude of the cyclic load and loading rate. The shear strength increases with the increase of the relative density. The shear strength increases after subjecting to cyclic loading. The amplitude of the cyclic load affects the shear strength of coral gravelly sand, the shear strength increases as the amplitude of the cyclic load increases. The loading rate has insignificantly effect on the shear strength of the coral gravelly sand.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.7 s.124
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• pp.649-661
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• 2007

Friction-type reinforcing members(FRM) to enhance the resistance to wind loads of a transmission tower through both stiffness strengthening and damping increase are energy dissipation devices that utilize bending deflection of a tower leg. In this paper, the hysteretic behavior of the transmission tower structure with FRMs was experimentally investigated through cyclic loading tests on a half scale substructure model. Firstly, the variation of friction forces and durability of the FRM depending on the type of friction-inducing materials used in the FRM were examined by performing the cyclic loading tests on the FRM. Secondly, cyclic loading tests of a half-scale two-dimensional substructure model of a transmission tower with FRMs were conducted. Test results show that the FRM, of which desired maximum friction force is easily regulated by adjusting the amplitude of the torque applied to the bolts, have stable hysteretic behaviors and it is found that there exists the optimum torque depending on a design load by investigating the amount of energy dissipation of the FRMs according to the increase of torque.