• Earthquakes and Structures
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• v.13 no.5
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• pp.473-484
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• 2017

The objective of this paper is to report on a study of the use of unstiffened thin steel plate shear walls (SPSWs) for the seismic performance improvement of reinforced concrete frames with deficient lateral rigidity. The behaviour of reinforced concrete frames during seismic activities was rehabilitated with an alternative and occupant-friendly retrofitting scheme. The study involved tests of eight 1/3 scale, one bay, two storey test specimens under cyclic quasi-static lateral loadings. The first specimen, tested in previous test program, was a reference specimen, and in seven other specimens, steel infill plates were used to replace the conventional infill brick or the concrete panels. The identification of the load-deformation characteristics, the determination of the level of improvement in the overall strength, and the elastic post-buckling stiffness were the main issues investigated during the quasi-static test program. With the introduction of the SPSWs, it was observed that the strength, stiffness and energy absorption capacities were significantly improved. It was also observed that the experimental hysteresis curves were stable, and the composite systems showed excellent energy dissipation capacities due to the formation of a diagonal tension field action along with a diagonal compression buckling of the infill plates.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1603-1610
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• 2006

In this paper compressive characteristics of composite egg-box panels were investigated and energy absorption was calculated from the nominal stress-strain relations obtained by the compressive tests. Several different stacking sequences and number of plies were introduced for investigation of static compression characteristics and the energy absorption rates of composite egg-box panels. The compressive stress-strain relation and energy absorption of various composite egg-box panels were compared with those of aluminium egg-box panels. From the test results it was found that the fracture behavior of composite egg-box panel was affected by stacking angle causing different local deformation, during lay-up and draping processes and types of prepreg; that is, plain weave carbon/epoxy and 4-harness satin glass/epoxy. The energy absorption capacity of composite egg-box panels were proved to be higher than that of aluminium egg-box panels with low mass.

• Journal of the Korean Geotechnical Society
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• v.29 no.8
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• pp.15-25
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• 2013

In order to examine the unsaturated shear strength characteristics of compacted weathered gneiss soils, the constant water content compression (CWCC) test was carried out. Specimens were made by static compaction under two densities conditions. The shear behavior in accordance with an initial suction obtained by varying initial degrees of saturation was evaluated. The suction could be directly measured by the use of the ceramic disk and the pore-water pressure transducer. The results of the peak shear strength from the CWCC test were examined using the relationship with Mp line from triaxial test under the saturated state, that is, by means of the suction stress which was calculated using the measured suction. In addition, the applicability of the suctions stress to the unsaturated shear behaviour of compacted weathered gneiss soils was discussed by applying Suction stress-SWCC Method (SSM).

• Journal of the Society of Naval Architects of Korea
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• v.57 no.4
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• pp.182-190
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• 2020

This study reports a series of drop impact tests performed to generate denting damages on stiffened plates and their residual ultimate strength tests under axial compression. The models were fabricated of general structural steel, and each model has six longitudinal stiffeners and two transverse frames. Among six fabricated models, four were damaged, and two were left intact for reference. To investigate the effects of collision velocity and impact location on the extent of damage, the drop height and the impact location were changed in each impact test. After performing the collision tests, the ultimate axial compression tests were conducted to investigate the residual strengths of the damaged stiffened plates. Finite element analyses were also carried out using a commercial package Abaqus/Explicit. The material properties obtained from a quasi-static tensile tests were used, and the strain-rate sensitivity was considered. After importing the collision simulation results, the ultimate strength calculations were carried out and their results were compared with the test data for the validation of the finite element analysis method.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.100-109
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• 2004

Is this study, results of static pile load tests of in-situ cast piles in weak or uncemented sedimentary rock layers have been analyzed and presented. Consdierations on the characteristics of soils sedimentary rocks have been made. From the measurements of strain gauges and extensometers the relationship of unit skim friction versus displacement and that of unit end bearing versus displacement have been obatined to verity the characteristics of bearing capacity of this uncemented sedimentary rock layers. Also, a comparison has been made between ultimate skin friction in compression and tension.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.4
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• pp.354-359
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• 2014

The objective of this study is to examine the fatigue behavior in compression of normal-weight and lightweight concrete mixtures with high volume supplementary cementitious material(SCM). The selected binder composition was 30% ordinary portland cement, 20% fly-ash, and 50% ground granulated blast-furnace slag. The targeted compressive strength of concrete was 40 MPa. For the cyclic loading, the constant maximum stress level varied to be 75%, 80%, and 90% of the static uniaxial compressive strength, whereas the constant minimum stress level was fixed at 10% of the static strength. The test results showed that fatigue life of high volume SCM lightweight concrete was lower than the companion normalweight concrete. The value of the fatigue strain at the maximum stress level intersected the descending branch of the monotonic stress-strain curve after approximately 90% of the fatigue life.

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

• Journal of the Korean GEO-environmental Society
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• v.16 no.7
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• pp.5-13
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• 2015

The pressure penetrating steel pipe pile method which can be constructed in a narrow space using the hydraulic jack is used on the foundation reinforcement, extension of the structure and basement, restoration of the differential settlement etc.. This method is possible to construct in narrow areas and low story height, the non-noise and non-vibration works, and it is possible for the construction site to be clean without slime. And it is possible to confirm the bearing capacity of pile due to penetrating the pile with the compression load of hydraulic jack. In this study, the static load test with the load-transfer test was carried out to investigate the bearing behavior characteristics of the pressure penetrating steel pipe pile. Four series of static load test were executed to investigate the variation of bearing behavior of the pressure penetrating steel pipe pile. As a result of these tests, the allowable load of the pressure penetrating steel pipe was evaluated more than 637 kN, and the shaft resistance corresponding to 81~86% of each applied load was mobilized with only a small portion of the base resistance acting. And it was also evaluated that the unit skin friction was mobilized to maximum value after two months.

• Earthquakes and Structures
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• v.20 no.4
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• pp.431-444
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• 2021

T-shaped column is usually used as side column in buildings, which is one of the weak members in structural system. This paper presented a quasi-static cyclic loading experiment of six specimens of reinforced concrete (RC) T-shaped columns under compression-flexure-shear-torsion combined loadings to investigate the effect in the ratio of torsion to moment (T/M) and axial compression ratio (n) and height-thickness ratio of flange plate (φ) on their seismic performance. Based on the test results, the failure characteristics, hysteretic curves, ductility, energy dissipation, stiffness degradation and strength degradation were analyzed. The results show that the failure characteristics of RC T-shaped columns mainly depend on the ratio of torsion to moment, which can be divided into bending failure, bending-torsion failure and shear-torsion failure. With the increase of T/M ratio, the torsion ductility coefficient increased, and in a suitable range, the torsion and horizontal displacement ductility coefficient of RC T-shaped columns could be effectively improved with the increase of axial compression ratio and the decrease of height-thickness ratio of flange plate. Besides, the energy dissipation capacity of the specimens mainly depended on the bending and shear energy dissipation capacity. On the other hand, the increase of axial compression ratio and the ratio of torsion to moment could accelerate the torsional and bending stiffness degradation of RC T-shaped columns. Moreover, the degradation coefficient of torsion strength was between 0.80 and 0.98, and that of bending strength was between 0.75 and 1.00.

• 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.