• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.292-299
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• 2006

The purpose of this study is to investigate the inelastic behavior of precast segmental prestressed concrete bridge columns. A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. An unbonded tendon element based on the finite element method, that can represent the interaction between tendon and concrete of prestressed concrete member, is used. A joint element is newly developed to predict the inelastic behaviors of segmental joints. The proposed numerical method for the inelastic behavior of precast segmental prestressed concrete bridge columns is verified by comparison with reliable experimental results.

• Earthquakes and Structures
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• v.8 no.1
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• pp.1-18
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• 2015

A simple method of assessing the risk of overturning of precast reinforced concrete columns is presented in this paper. The displacement-based methodology introduced herein is distinguished from conventional force-based codified methods of aseismic design of structures. As evidenced by results from field tests precast reinforced concrete columns can be displaced to a generous limit without sustaining damage and then fully recover from most of the displacement afterwards. Realistic predictions of the displacement demand of such (rocking) system in conjunction with the displacement capacity estimates enable fragility curves for overturning to be constructed. The interesting observation from the developed fragility curves is that the probability of failure of the precast soft-storey column decreases with increasing size of the column importantly illustrating the "size effect" phenomenon.

• Structural Engineering and Mechanics
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• v.78 no.1
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• pp.77-86
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• 2021

Local school buildings are critical facilities that can provide shelter in disasters such as earthquakes, so they must be more resistant to seismic forces than other structures. In this study, a sensitivity analysis was conducted to determine which columns-as the most critical members in a reinforced concrete building-most urgently require seismic retrofitting. The sensitivity analysis was conducted using an optimization technique with the location of each column as a parameter. A numerical model was developed to simulate a realistic collapse mode through a three-dimensional dynamic analysis. Based on numerical analysis results, it was found that the columns positioned in the lower floors, such as the first floor and in the outer part of a building, urgently require retrofitting. For reinforcement of the RC columns, which has been proven for its performance in previous research, was applied. Through this study, the importance of appropriate retrofitting is demonstrated. Further, a method for determining the appropriate location for retrofitting-when retrofitting is not possible on the entire structure-is presented.

• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.6
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• pp.247-253
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• 2022

The columns of older reinforced concrete (RC) buildings generally have limited reinforcement details. Thus, they could be vulnerable to earthquake ground motions, leading to partial or complete building collapse. In this study, high-performance fiber-reinforced cementitious composite (HPFRCC) was applied to RC columns to improve their seismic behavior. Experimental tests were conducted with two full-sized specimens with limited reinforcement details, including short lap splices, while unidirectional loadings were applied to the specimens. The seismic behavior of RC columns was substantially improved by using HPFRCC.

• Earthquakes and Structures
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• v.24 no.3
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• pp.193-204
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• 2023

The concept of meta-material-based isolation systems (MMIS) for structural columns has been revisited in the present study in order to enhance the stability of rubber pads by using steel shim reinforced rubber (SSRR) layers. Analytical calculations have shown a significant improvement in the stability of MMIS with SSRR pads. Finite element analysis has also been conducted to further show the reduced response of a bridge with the modified MMIS under excitations having frequencies within the corresponding attenuation zone (AZ) as compared to the response of a conventional bridge without MMIS. FE analysis further shows the stress generated on the bridge with MMIS systems are within safe limits. Finally, a generalized procedure has been developed to design bridge columns with the proposed modified MMIS.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.237-238
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• 2022

The seismic performance of existing reinforced concrete (RC) elements to which seismic design was not applied is questionable. To evaluate the behavior of existing RC columns, column specimens with widely spaced transverse reinforcement and 90-degree hoop anchor hooks as variables were designed. Experimental tests were performed by applying a fixed low axial load and increasing lateral cyclic loads to the specimens. As a result, the hoop spacing and anchor hook angle did not significantly affect the load-displacement relationship and the dissipated energy before failure.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.97-100
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• 2004

Steel encased composite columns are widely used due to their excellent structural performance in terms of stiffness, strength, and ductility. However, experimental studies were usually for the columns having higher steel ratio $(3-4\%)$. There are two different design concepts for SRC columns. ACI-318 specifies the design strength of the column using the same concept of reinforced concrete columns. AISC-LRFD specifies the P-M diagram using the concept of steel column. In this paper, SRC columns have the steel ratio of $0.53\%\;and\;1.06\%$. From the test results, ACI-318 specifications showed better evaluation of SRC columns having low steel ratio. H beam and steel tube partially filled with concrete were embedded in concrete. Flexural tests showed considerably high ductility.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.978-982
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• 2009

In recent years, due to some excellent properties of fiber reinforced polymer (FRP) composites, the use of FRP sheets for strengthening the weak concrete columns have become increasingly popular. Axial loading is the basic assumption in most of the models that are presented for estimating the compression strength of confined concrete columns. However a large number of weak concrete columns in the bending frames are under the combination of both axial and flexural loads. This paper presents the results of an experimental study on the effects of eccentricity of load on the compressive strength of concrete columns confined by FRP sheets. This research shows that the eccentricity of compression load affects decreasingly the performance of confining FRP jacket in confined columns.

• Steel and Composite Structures
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• v.51 no.6
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• pp.619-645
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• 2024

In the construction industry, composite structures have revolutionized traditional design principles, opening innovative possibilities. The Concrete Encased - Concrete Filled Steel Tubular (CE-CFST) column stands out as a distinctive composite structure, offering structural stability and resilience for various engineering applications. Comprising Reinforced Concrete (RC) and Concrete Filled Steel Tubular (CFST) components, CE-CFST columns are valued for their inherent properties, including ductility and rigidity, CE-CFST is commonly used in the construction of bridges, high-rise buildings, and more. This article aims to provide a concise overview of the evolutionary development of CE-CFST columns and their performance in structural applications. Through a comprehensive review, the study delves into the behaviour of CE-CFST columns under different scenarios. It examines the influences of key parameters such as size, infills, cross section, failure causes, and design codes on the performance of CE-CFST columns, highlighting their enhanced functionality and future potential. Moreover, the review meticulously examines previous applications of CE-CFST columns, offering insights into their practical implementation.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.2
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• pp.15-27
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• 2009

The purpose of this study is to investigate the seismic behavior of precast segmental PSC bridge columns. For the analysis of reinforced concrete structures, a computer program named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology) is used. To represent the interaction between tendon and concrete of a prestressed concrete member, a bonded or unbonded tendon element based on the finite element method is used. A joint element is modified to predict the inelastic behaviors of segmental joints. The solution of the equations of motion is obtained by numerical integration using Hilber-Hughes-Taylor (HHT) algorithm. The proposed numerical method gives a realistic prediction of seismic behavior throughout the input ground motions for numerical examples.