• Journal of the Korean Geotechnical Society
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• v.21 no.10
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• pp.85-97
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• 2005

Despite a number of advantages of reinforced earth walls over conventional concrete retaining walls, there exist concerns over long-term residual deformation when subjected to repeated and/or cyclic loads, especially when used as part of permanent structures. In view of these concerns, in this paper time-dependent deformation characteristics of geosynthetic reinforced soil under sustained and/or repeated loads were investigated using a series of plane strain compression tests on geogrid reinforced weathered granite soil specimens. The results indicate that sustained or repeated loads can yield appreciable magnitudes of residual deformations, and that the residual deformations are influenced not only by the loading characteristics but by the mechanical properties of geogrid. It is also found that the preloading technique can be effectively used in controlling residual deformations of reinforced soils subjected to sustained and/or repeated loads.

• Computers and Concrete
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• v.12 no.2
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• pp.131-149
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• 2013

Various types of reinforcement splicing methods have been developed and implemented in reinforced concrete construction projects for achieving the continuity of reinforcements. Due to the complicated reinforcement arrangements and the difficulties in securing bar spacing, the traditional lap splicing method, which has been widely used in reinforced concrete constructions, often shows low constructability and difficulties in quality control. Also, lap spliced regions are likely to be over-reinforced, which may not be desirable in seismic design. On the other hand, mechanical splicing methods can offer simple and clear arrangements of reinforcement. In order to utilize the couplers for the ribbed-deformed bars, however, additional screw processing at the ends of reinforcing bars is typically required, which often lead to performance degradations of reinforced concrete members due to the lack of workmanship in screw processing or in adjusting the length of reinforcing bars. On the contrary, the use of screw-ribbed reinforcements can easily solve these issues on the mechanical splicing methods, because it does not require the screw process on the bar. In this study, the mechanical coupler suitable for the screw-ribbed reinforcements has been developed, in which any gap between the reinforcements and sleeve device can be removed by grouting high-flow inorganic mortar. This study presents the uniaxial tension tests on the screw-ribbed reinforcement with the mechanical sleeve devices and the cyclic loading tests on RC columns with the developed coupler. The test results show that the mechanical sleeve connection developed in this study has an excellent splicing performance, and that it is applicable to reinforced concrete columns with a proper confinement by hoop reinforcement.

• Structural Engineering and Mechanics
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• v.18 no.5
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• pp.645-669
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• 2004

In seismic analysis of moment-resisting frames, beam-column connections are often modeled with rigid joint zones. However, it has been demonstrated that, in ductile reinforced concrete (RC) moment-resisting frames designed based on current codes (to say nothing of older non-ductile frames), the joint zones are in fact not rigid, but rather undergo significant shear deformations that contribute greatly to global drift. Therefore, the "rigid joint" assumption may result in misinterpretation of the global performance characteristics of frames and could consequently lead to miscalculation of strength and ductility demands on constituent frame members. The primary objective of this paper is to propose a rational method for estimating the hysteretic joint shear behavior of RC connections and for incorporating this behavior into frame analysis. The authors tested four RC edge beam-column-slab connection subassemblies subjected to earthquake-type lateral loading; hysteretic joint shear behavior is investigated based on these tests and other laboratory tests reported in the literature. An analytical scheme employing the modified compression field theory (MCFT) is developed to approximate joint shear stress vs. joint shear strain response. A connection model capable of explicitly considering hysteretic joint shear behavior is then formulated for nonlinear structural analysis. In the model, a joint is represented by rigid elements located along the joint edges and nonlinear rotational springs embedded in one of the four hinges linking adjacent rigid elements. The connection model is able to well represent the experimental hysteretic joint shear behavior and overall load-displacement response of connection subassemblies.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.3
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• pp.307-312
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• 2012

This study aims to investigate the effect of the post weld treatments on the fatigue life of T-type welded structure made by a SM50A steel material, generally used for excavators, because changes in the geometry, material and surface properties of welded regions affect the fatigue life of welded structures. T-type test specimens were prepared by the CO2 welding of rolled steel plates (SM50A steel) with a thickness of 10 mm at a welding speed of 30 cm/min and these Ttype welded specimens were further treated by UIT (Ultrasonic Impact Treatment) and/or toegrinding post welding treatment methods. In order to investigate improvements on the fatigue life of the samples. 3-point bending fatigue tests were conducted with a stress ratio of R=0.1 under a cyclic loading environment at a frequency of 5 Hz, via a hydraulic fatigue testing machine (${\pm}100\;kN$, MTS 809). The tests were performed at room temperature. The fatigue life of UIT specimens was approximately 25 times longer than that of as-welded specimens at a stress amplitude of 281 MPa, while toe-grinding specimens exhibited 4.15 times longer fatigue life. The current results could provide important guidelines to determine the proper post weld treatment methodologies of T-type welded parts for excavators with a satisfactory fatigue life although under severe operating conditions.

• Journal of the Korea Concrete Institute
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• v.24 no.3
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• pp.323-331
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• 2012

This paper presents a new strengthening method on concrete column against seismic loads for structural performance tests. An X-bracing using high performance carbon fiber threads called the "Carbon fiber anchor X-bracing system" is used to connect RC frames internally. The carbon fiber sheet is wrapped around the column to fix the top and bottom of the column after Super anchor was installed by drilling hole on the column. The structural performance was evaluated experimentally and analytically. Two types of columns specimens were made; flexure fracture scaled model and shear fracture scaled model. For the performance evaluation, cyclic loading tests were conducted on moment and shear resisting columns with and without X bracing. Test results confirmed that the bracing system installed on RC columns enhanced the strength capacity and provided adequate ductility.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.333-336
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• 2008

CFRP tendons have been attempted in concrete structures as a substitute for steel tendons considering their many advantages such as the corrosion-resistance, light weight etc. However, the elastic behavior up to failure is likely to result in ductility problems. To overcome such problems, prestress concrete beams with partially bonded tendons have been developed and suggested. In this new system, the un-bonded part near the mid-span contributes to the improvement of ductility. And the bonded parts at both ends play a role as a safe anchorage. According to the previous research on the static behavior, the suggested method has demonstrated enough ductility and strength. However it is essential to verify the long-term safety for repetitive fatigue loads under service states. For this purpose, flexural fatigue loading tests were carried out in this research. This paper includes an experimental investigation on the static load-carrying capacities of the beams with or without fatigue tests. The results showed that the beams prestressed with partially bonded CFRP tendons possessed good fatigue capacity under the constant cyclic loads.

• Magazine of the Korea Concrete Institute
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• v.11 no.1
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• pp.109-118
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• 1999

Seismic design code has been performed since 1988 in Korea, so it has not been applied to low-rise reinforced concrete buildings which had been built before 1988. Those building have been designed only for gravity loads based on non-seismic code, Therefore, even minor earthquake occurred, those buildings might have serious damages. In this paper, to investigate the behavior of low-rise reinforced concrete moment resisting frame which had been built in according to the building code of Korea that had been published before 1988, two type of 1/2 scaled exterior beam-column subassemblies which have non-seismic detailing based on the building code of Korea were constructed and tested with reversed cycling loading under the displacement control method. The special features of joint with non-seismic detailing is that there is no transverse reinforcement in the joint. In tests, cracks pattern, strength degradation, loss of stiffness, energy dissipation and the slippage of beam and column bars were investigated. Cracks did not occurred in the joint even seismic loading of 0.12g which is considered as peak ground acceleration in Korea was applied. And increasing seismic loading above 0.12g shear crack happened in the joint which have not transverse beam.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3548-3556
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• 2015

In order to fulfill the needs of reliable and economically feasible foundation, engineers should consider not only the working load that can endure extreme conditions but also apprehending precise behavior of continuous dynamic load while designing the foundation of offshore wind power generators. To actualize the foundation, a model pile was made in miniature. Also, calibration chamber was made and a 500mm height of sand-bed was made to perform "static lateral load experiment" and "repetitive loading experiment", total of two Lateral load tests. As a result, in Static Lateral load test, the bigger length/diameter of model pile led an increase in load displacement. However, when performing "Cyclic Lateral load test", the increase in number of under loading led the decrease in horizontal displacement from each repeated lateral load. While performing Static Lateral load test and repeated loading experiment, we could observe the decreasing in the rate of ultimate lateral load capacity increase of the pile. Also, it turned out that the higher relative density of the ground, the lower ultimate lateral load capacity by repeated horizontal loading.

• Journal of Korean Society of Steel Construction
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• v.28 no.6
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• pp.467-476
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• 2016

For the connections between modular units in modular buildings, the bolted joints with connector plates are used commonly. The strength of structure is determined by the weakest part of structure and the connections may be weaker than the members being joined. Therefore, to check the safety of modular building, the structural performance of connections between modular units as well as that of beam-to-column connections should be evaluated. In this study, the behavior of module to module connection with straight and cross shaped connector plates is investigated by lateral cyclic tests according to KBC2009 0722.2.4 which shall be conducted by controlling the story drift angle in the width and the longitudinal direction respectively. All of test results generally show the stable ductile behavior up to 0.04rad drift levels and the tests in longitudinal direction show a superior energy dissipation per cycle in each of the load steps. However, the straight shaped connector plates have the degradation of stiffness with cyclic loading and the larger drift angle of column than the cross shaped connector plates.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.440-447
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• 2020

Masonry structures are used as bearing walls in small buildings, but they are generally considered non-bearing walls. They are used as partition walls that divide the interior spaces of the frame structures of buildings. In addition, wetting techniques that use mortar as an adhesive between blocks or bricks in construction are vulnerable to climatic conditions, especially cracks in mortar, which can cause conduction collapse of the walls in seismic loading. The purpose of this research was to propose a dry concrete block construction method that complements the weak axial shear stiffness and improves the weakness of the wet construction method as well as to investigate its structural behavior. In this study, the material properties of concrete blocks were examined, and the seismic performance of the proposed dry assembly structure was verified by structural behavior tests on horizontal cyclic loads. First, in these study results, concrete blocks can be applied to the dry block construction method instead of wet construction methods because they secure more than C-type blocks in KS regulations. Second, the structural performance of the wall against a horizontal cyclic load indicates that the resisting force of the assembly block wall is increased by increasing the horizontal length of the wall, forming several diagonal cracks. Finally, the proposed dry block wall structure requires a seismic performance assessment considering that the ratio of the shape of the wall by height and length is considered a major influence variable on the structural behavior under a horizontal load.