• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.1
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• pp.63-70
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• 2010

The purpose of this study is to investigate experimentally the behavior of unreinforced masonry RC frames strengthened by CFRP sheet under cyclic lateral loading. Four test specimens were constructed as one-story, one-bay, 1/2 scale unreinforced masonry infilled RC frames and differences in strength and stiffness were evaluated in specimens on which had been applied different retrofitting methods. Test results indicated that the CFRP sheets significantly increased the strength and stiffness of the specimens, and the specimens retrofitted in columns and masonry indicated the most adequate retrofitting methods.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.131-139
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• 2012

The lateral reinforcements of concrete such as hoops and spiral bars are known to confine concrete to compensate the strength loss due to fire by reducing explosive spalling and improving the capacity of ductility. In this context, a study was conducted to investigate the residual mechanical properties of confined and unconfined concrete($f_{ck}$=60MPa) after a single thermal cycle at 300, 600, $800^{\circ}C$. The main parameters required to establish the stress-strain relationship are the peak stress, the elastic modulus, and the strain at peak stress. The knowledge of the residual mechanical properties of concrete is necessary whenever the thermally damaged structure is required to bear a significant share of the loads, even after a severe thermal accident. Based on the results obtained in this study, the residual stress of confined concrete under thermal damage is higher according to the level of confinement and the larger strain made it to have better ductility. The decreasing ratio of elastic modulus from the relationship of stress and strain was also smaller than that of unconfined concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.175-182
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• 2006

In the design of composite structures, shear connectors such as headed stud, channel, perforated plate, etc, are commonly used to transfer longitudinal shear forces across the steel-concrete interface. Many researches have been conducted to improve the characteristics of different types of shear connector. This paper presents the results of 11 push-out tests performed on the new perforated rib connectors with shearing bars embedded in concrete slab under static loads. The results obtained from these tests are as following : 1) The bearing plate welded on both sides of perforated rib plate improves the stiffness and strength. 2) The capacity of perforated connectors is influenced primarily by the transverse reinforcements and shearing bars.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.5
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• pp.1-10
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• 2012

This paper presents an experimental result and suggests the confinement effect of headed cross tie in reinforced concrete(RC) columns subjected to cycling horizontal loads under constant axial load. Five RC columns specimens were manufactured, taking confined type of transverse reinforcement, whether or not using cross tie, end detail of cross tie (hooked or headed), and axial stress in column as major variables, Cyclic horizontal load applied to the columns under constant axial stress and the effect of cross tie to structural capacity of column was evaluated from the test. The column without cross tie failed showing bending deformation of hoop with crack in core concrete at low horizontal load while the column with cross tie showed quite improved strength and ductility by suppressing bending deformation of hoop as well as buckling of longitudinal bar at once even after crack in core concrete. At high lateral displacement, the column with hooked cross tie showed the failure pattern loosing the confining force of cross tie since the $90^{\circ}$ hooked part of cross tie was stretched out and the cracked core concrete lumps were came off. However, the column with headed cross tie showed very stable behavior since the head of cross tie effectively confined the hoop and longitudinal bars even at high lateral displacement.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.75-82
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• 2015

In this study, experimental research was carried out to evaluate steel reinforced ECC (Engineered Cementitious Composites) column, which exhibits excellent crack control property and highly ductile behavior. Ordinary portland cement and high volume fly ash were used as binding materials in the mixture proportions for the purpose of achieving a high level of multiple cracking property with the tightly controlled crack width. To compare with the cyclic behavior of steel reinforced ECC column specimen, a conventional reinforced concrete column was prepared and tested under reversed cyclic loading condition. Based on the cyclic load test, ECC column exhibited higher cyclic behavior, compared to the conventional RC column, in terms of load carrying capacity and energy dissipation capacity.

• Journal of Korean Society of Steel Construction
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• v.17 no.1 s.74
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• pp.45-52
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• 2005

The object of this study was a cold-formed steel wall stud panel sheathed by gypsum boards. In the beam-analysis, the panel was treated as a simple beam with a uniform lateral loading. The deflections were calculated by considering the primary factors that reduced the stiffness of the panel. In the column-analysis, the panel was treated as a bearing wall with an axial load. By using an energy method, nominal axial strength could be evaluated by considering both flexural buckling and torsional-flexural buckling. All calculations were programmed and compared with the results of the experiment. In the beam-analysis, experimental deflections were close to theoretical deflections. In the column-analysis, the experimental values were also close to theoretical values in axial strength.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.365-372
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• 2002

This experimental investigation was conducted to examine the behavior of eight a third scale columns made of high-strength concrete(HSC). The columns were subjected to constant axial load corresponding to target value of 30 percent of the column axial load capacity and a cyclic horizontal load-inducing reversed bending moment. The variables studied in this research are the volumetric ratio of transverse reinforcement(Ps=1.58, 2.25 ％), tie configuration(hoop-type, cross-type, diagonal-type) and tie yield strength(fy=5,600, 7,950 kgf/$\textrm{cm}^2$). Test results indicated that the flexural strength of all the columns did not exceed calculated flexural capacities based on the equivalent concrete stress block used in current design code. Columns with 42 percent higher amounts of transverse reinforcement than that required by seismic provisions of ACI 318-99 were shown ductile behavior. With axial load of 30 percent of the axial load capacity, the use of high-strength steel as transverse reinforcement may lead to equal or higher ductility than would be achieved with low-strength steel.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.311-318
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• 2018

When reinforced concrete structures are exposed to fire, their mechanical properties such as compressive strength, elasticity coefficient and rebar yield strength, are degraded. Therefore, the structure's damage assessment is essential in determining whether to dismantle or augment the structure after a fire. In this study, the confinement effect of lateral reinforcement of RC column according to the numbers of fire exposure face and stirrup was verified by fire resistant test with the heating temperatures of $400^{\circ}C$, $600^{\circ}C$ and $800^{\circ}C$. The test results showed that the peak stress decreases and peak strain increases as the temperature is getting higher, also transverse ties are helpful in improving the compressive resistance of concrete subjected to high temperature. Based on the results of this study, the residual stress of confined concrete under thermal damage is higher at the condition of more lateral reinforcement ratio and less fire exposure faces. The decreasing ratio of elastic modulus of more confined and less exposure faces from the relationship of load and displacement was also smaller than that of opposite conditions.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.3
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• pp.149-154
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• 2019

The structural system of domestic high-rise apartments can be divided into two parts; the core wall system, which is composed of walls concentrated in the center and the shear wall system, which comprises a great number of walls distributed in the plan. In order to analyze the lateral behavior of each system, buildings with typical domestic high-rise apartment plans were selected and nonlinear static analysis was performed to investigate the their collapse mechanism. From the force-displacement relation derived from nonlinear static analysis, response modification factor was evaluated by calculating the overstrengh and ductility factor, which are important in the seismic response. The ductility of core wall system is small, but as it is governed by wind load, its overstrength is greatly estimated, and its response modification factor is calculated by the overstrengh factor. Due to a large number of walls, shear wall system has a large ductility, making the response modification factor considerably large.

• Journal of the Korea Concrete Institute
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• v.24 no.3
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• pp.241-248
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• 2012

This paper presents a reinforced concrete composite column method in order to improve seismic performance of reinforced concrete column specimens by selectively applying steel fiber-reinforced mortars at the column plastic hinge region. In order to evaluate seismic improvement of the newly developed column method, a series of cyclic load test of column specimens under a constant axial load was investigated by manufacturing three specimens, two reinforced concrete composite columns by applying steel fiber-reinforced mortars at the column plastic hinge region and one conventional reinforced concrete column. Both concrete and steel fiber-reinforced mortar was cast-in placed type. From cyclic load test, it was found that the newly developed steel fiber-reinforced columns showed improved seismic performances than conventional reinforced concrete column in controlling bending and shear cracks as well as improving seismic lateral load-carrying capacities and lateral deformation capacities.