• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.1
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• pp.55-66
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• 1999

This paper presents an analytical prediction of the hysteresis behavior of reinforced concrete long column with rectangular section under the cyclic loading state. The mechanical characteristic of cracked concrete and reinforcing bar in concrete has been modeled, considering the bond effect between reinforcing bar and concrete, the effect of aggregate interlocking at crack surface and the stiffness degradation after the crack has taken place. The strength increase of concrete due to the lateral confining reinforcement has been also taken into account to model the confined concrete. The formulation of these models for concrete and reinforcing bar has been based on the smeared crack concept that the stress-strain relationship of reinforced concrete element would be defined using the average values. In addition to the material nonlinear properties, the algorithm for large displacement problem that may give an additional deformation has been formulated using total Lagrangian formulation. The analytically predicted behavior was compared with test result and they showed good agreement in overall behavior.

• Journal of the Korean Society for Railway
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• v.15 no.6
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• pp.616-622
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• 2012

Earthquake damage of viaduct bridge of railroad may give rise to social loss due to transport restrictions greater than cost of structural recovery. Therefore, viaduct bridge of railroad should have ensure adequate seismic performance. But, results of seismic performance evaluation, many of seismic retrofit was required. In this study, five scale models of columns were made and four of them were reinforced by HT-A(HyperTex & perforate Aluminum) which is improved than existing method. Testing the columns by constant axial load and cyclic lateral displacements, seismic performance of columns has been verified from the result of evaluating the stiffness, ductility and energy dissipation capacity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.1-8
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• 2017

Three small scale hollow circular reinforced concrete columns with aspect ratio 4.5 were tested under cyclic lateral load with constant axial load. Diameter of section is 400 mm, hollow diameter is 200 mm. The selected test variable is transverse steel ratio. Volumetric ratios of spirals of all the columns are 0.302~0.604% in the plastic hinge region. It corresponds to 45.9~91.8% of the minimum requirement of confining steel by Korean Bridge Design Specifications, which represent existing columns not designed by the current seismic design specifications or designed by seismic concept. The longitudinal steel ratio is 2.017%. The axial load ratio is 7%. This paper describes mainly crack behavior, load-displacement hysteresis loop, seismic performance such as equivalent damping ratio, residual displacement and effective stiffness and flexural over-strength of circular reinforced concrete bridge columns with respect to test variable. The regulation of flexural over-strength is adopted by Korea Bridge Design Specifications (Limited state design, 2012). The test results are compared with nominal strength, result of nonlinear moment-curvature analysis and the design specifications such as AASHTO LRFD and Korea Bridge Design Specifications(Limited state design).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.2
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• pp.149-156
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• 2023

Recently, concerns about natural disasters such as earthquakes, tsunamis and typhoons have increased. As the magnitude and frequency of earthquakes increase, research is needed to prevent structures from collapsing due to earthquake loads. Research is needed to increase the ductility of columns to prevent the collapse of structures. In this study, the ductility improvement of square columns achieved by applying spiral stirrups to square columns. Square columns reinforced with spiral stirrups are more resistant to repetitive loads such as seismic loads than columns reinforced with tie stirrups. Also, the spiral stirrups can apply better confinement to the concrete. In this study, an uniaxial compression test was conducted to evaluate the performance of columns reinforced with spiral stirrups. The results showed that the columns reinforced with spiral stirrups in both the circular and square columns showed higher compressive strength than the columns reinforced with the tie stirrups. In addition, the columns reinforced with spiral stirrups for both the square and circle columns, showed a tendency to endure the load even after the initial cracking and rebar yielding.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.491-497
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• 2014

The corrosion of steel reinforcement in reinforced concrete bridge decks significantly affects the degradation of the capacity. Due to the advantageous characteristics such as high tensile strength and non-corrosive property, fiber reinforced polymer (FRP) has been gathering much interest from designers and engineers for possible usage as a alternative reinforcement for a steel reinforcing bar. However, its application has not been widespread, because there data for short- and long-term performance data of FRP reinforced concrete members are insufficient. In this paper, seven full-scale decks with dimensions of $4000{\times}3000{\times}240mm$ were prepared and tested to failure in the laboratory. The test parameter was the bottom reinforcement ratio in transverse direction. The decks were subjected to various levels of concentrated cyclic load with a contact area of $577{\times}231mm$ to simulate the vehicle loading of DB-24 truck wheel loads acting on the center span of the deck. It was observed that the glass FRP (GFRP) reinforced deck on a restraint girder is strongly effected to the level of the applied load rather than the bottom reinforcement ratio. The study results showed that the maximum load less than 58% of the maximum static load can be applied to the deck to resist a fatigue load of 2 million cycles. The fatigue life of the GFRP decks from this study showed the lower and higher fatigue performance than that of ordinary steel and CFRP rebar reinforced concrete deck. respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.102-111
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• 2022

The aim of this study is to assess the seismic performance of octagonal hollow cross section reinforced concrete bridge pier, and to investigate the effect of longitudinal reinforcement ratios on the failure behavior. Four octagonal hollow section RC bridge columns of small scale model were tested under a quasi-static cyclically reversed horizontal load with constant axial load. The volumetric ratio of transverse spiral hoop of all specimens was maintained constant(0.206%), the ratios of longitudinal reinforcement were varied(2.36 ~ 4.71%). Failure behavior and seismic performance were investigated. Three specimens with the exception of lap spliced specimen showed flexure-shear failure at final stage. The test results with the exception of lap spliced specimen showed that the displacement ductility factor and accumulated energy dissipation decreased in inverse proportion to the ratio of longitudinal steel.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.4
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• pp.94-103
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• 2016

For elevated railway station on which track is connected with superstructure of station, structural vibration level and structure-borne-noise level has exceeded the reference level due to structural characteristics which transmits vibration directly. Therefore, existing elevated railway station is in need of economical and effective vibration reduction method which enable train service without interruption. In this study, structural vibration non-transmissible system which is applied to vibroisolating material for column member is developed to reduce vibration. That system is cut covering material of the column section using water-jet method and is installed with vibroisolating material on cut section. To verify vibration reduction effect and structural performance for structural vibration non-transmissible system, impact hammer test and cyclic lateral load test are performed for 1/4 scale test specimens. It is observed that natural period which means vibration response characteristics is shifted, and damping ratio is increased about 15~30% which means that system is effective to reduce structural vibration through vibration test. Also load-displacement relation and stiffness change rate of the columns are examined, and it is shown that ductility and energy dissipation capacity is increased. From test results, it is found that vibration non-transmissible system which is applied to column member enable to maintains structural function.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.1
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• pp.49-56
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• 2011

The strengthening effect of CFRP sheet and AFRP sheet with buckling-restrained brace for Beam-Column joints under constant axial and cyclic lateral loading is evaluated experimentally in this paper. Six test specimens were constructed. The main test parameters included the FRP Sheet and Buckling-restrained braces. The results of the tests were analyzed by focusing on their mode of failure, maximum load, ductility indexes, and energy dissipation capacity. Test results indicated that CFRP Sheet with the buckling-restrained brace system significantly increased the strength and stiffness of the specimen and that it was the most adequate retrofitting method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.199-206
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• 2005

In many other countries framed structures with inadequate lateral strength and stiffness have been strengthened by providing reinforced concrete infilled wall. There is a general agreement among researchers those infilled walls have 3-5times greater lateral strength compared with bare frame. The main objective of this research is to investigate the behavior and strength of reinforced concrete frames infilled with concrete block and cast-in-place reinforced concrete panels used for strengthening the structure against seismic action. For this purpose three 1/3 scale, one-bay, one-story reinforced concrete infilled frames were tested under reversed cyclic loading simulating the seismic effect. The results indicate that infilled walls increase both strength and stiffness significantly under lateral loads. Especially Strength capacity and initial stiffness of CIP infilled wall increased 3.8 times and 6.6 times higher than lightly reinforced concrete frame.

• Journal of the Korea Concrete Institute
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• v.27 no.4
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• pp.451-458
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• 2015

The infill-wall strengthening method has been widely used for the seismic performance enhancement of the conventional reinforced concrete (RC) frame structures with non-seismic detail, which is one of the promising techniques to secure the high resisting capacity against lateral forces induced by earthquake. During the application of the infill-wall strengthening method, however, it often restricts the use of the structure. In addition, it is difficult to cast the connection part between the wall and the frame, and also difficult to ensure the shear resistance performances along the connection. In this study, an advanced strengthening method using the externally-anchored precast wall-panel (EPCW) was proposed to overcome the disadvantages of the conventional infill-wall strengthening method. The one-third scaled four RC frame specimens were fabricated, and the cyclic loading tests were conducted to verify the EPCW strengthening method. The test results showed that the strength, lateral stiffness, energy dissipation capacity of the RC frame structures strengthened by the proposed EPCW method were significantly improved compared to the control test specimen.