• Tunnel and Underground Space
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• v.19 no.5
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• pp.397-406
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• 2009

Recently, the number of industrial structures that must be demolished due to structural deterioration and unsatisfactory functional conditions has been increased. To minimize environmental hazardous factors created during the process of demolition, the explosive demolition method has been applied increasingly. This execution case was intended to describe an application of the explosive demolition method to the demolition of a Crusher & Screen structure, which was a large-section reinforced concrete special structure. It was deemed necessary due to its structural deterioration and unsatisfactory functional condition. Various pre-weakening processes and blasting patterns were applied to the large-section reinforced concrete members, and to reduce blasting vibration and impact vibration, time intervals were established for blasting in the same column and for blasting between blasting blocks. By applying the explosive demolition method to the demolition of a large-section reinforced concrete special structure, the explosive demolition was completed safely and efficiently, without causing any damage to surrounding facilities.

• Explosives and Blasting
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• v.34 no.1
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• pp.19-28
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• 2016

The number of industrial structures that must be demolished due to functional and structural deterioration has been increased. There is an increasing application of explosive demolition or explosive demolition combined with mechanical demolition to minimize temporal and spatial environmental hazardous factors created during the process of demolition. In this case study, to demolish the turbine foundation structure, which is a large-section reinforced concrete structure, the parital explosive demolition thchnique was conducted. As a result of the partial explosive demolition, the overall crushing of the blasting sections of beam-column joints structure with haunched beams and second-floor columns about the turbine foundation was satifactory, and the explosive demolition was completed without causing any damage to surrounding facilities.

• Explosives and Blasting
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• v.40 no.3
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• pp.54-65
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• 2022

Recently, the demand for the dismantling of large-scale industrial structures is increasing, and the construction of restoring the dismantled industrial to their original natural environment is underway. This case was an application of the explosive demolition method to the demolition of a large section turbine foundation structure which structural obsolescence and failure to meet functional requirements. As a result of the explosive demolition, the fracture condition of the turbine foundation was satisfactory, and the explosive demolition was completed without causing any damage to the surrounding facilities.

• Earthquakes and Structures
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• v.11 no.5
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• pp.823-840
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• 2016

The plastic hinge lengths of beams and columns are a critical demand parameter in the nonlinear analysis of structures using the finite element method. The numerical model of a plastic hinge plays an important role in evaluating the response and damage of a structure to earthquakes or other loads causing the formation of plastic hinges. Previous research demonstrates that the plastic hinge length of reinforced concrete (RC) columns is closely related to section size, reinforcement ratio, reinforcement strength, concrete strength, axial compression ratio, and so on. However, because of the limitations of testing facilities, there is a lack of experimental data on columns with large section sizes and high axial compression ratios. In this work, we conducted a series of quasi-static tests for columns with large section sizes (up to 700 mm) and high axial compression ratios (up to 0.6) to explore the propagation of plastic hinge length during the whole loading process. The experimental results show that besides these parameters mentioned in previous work, the plastic hinge of RC columns is also affected by loading amplitude and size effect. Therefore, an approach toward considering the effect of these two parameters is discussed in this work.

• Journal of Korean Association for Spatial Structures
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• v.22 no.2
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• pp.29-37
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• 2022

The collapse of reinforced concrete (RC) frame buildings is mainly caused by the failure of columns. To prevent brittle failure of RC column, numerous studies have been conducted on the seismic performance of strengthened RC columns. Concrete jacketing method, which is one of the retrofitting method of RC members, can enhance strength and stiffness of original RC column with enlarged section and provide uniformly distributed lateral load capacity throughout the structure. The experimental studies have been conducted by many researchers to analyze seismic performance of seismic strengthened RC column. However, structures which have plan and vertical irregularities shows torsional behavior, and therefore it causes large deformation on RC column when subjected to seismic load. Thus, test results from concentric cyclic loading can be overestimated comparing to eccentric cyclic test results, In this paper, two kinds of eccentric loading pattern was suggested to analyze structural performance of RC columns, which are strengthened by concrete jacketing method with new details in jacketed section. Based on the results, it is concluded that specimens strengthened with new concrete jacketing method increased 830% of maximum load, 150% of maximum displacement and changed the failure modes of non-strengthened RC columns.

• International Journal of High-Rise Buildings
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• v.3 no.3
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• pp.167-171
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• 2014

TORANOMON HILLS is the main building of a large-scale re-development project located in the center of Tokyo. This high-rise building has a height of 247 m and 52 floors above ground, 5 floors below ground, and $62m{\times}80m$ in plan. It is used as hotel, residential facilities, offices, shops and conference facilities. The super structure is mainly a rigid steel frame with response-control devices, using concrete-filled steel tube columns. The underground section is a mixed structure composed of steel, steel-reinforced concrete and reinforced concrete framings. The piled-raft foundation type is used. The remarkable feature of this high-rise building is that the motorway runs through the basements of the building, which makes it stand just above the motorway. This condition is an important factor of the building design. The plan shape is designed to fit along the curve of the motorway. Special columns at the corners are required to avoid placing columns in the motorway. This special column is a single inclined column in the lower floors that branches into two columns in the mid-floors to suit the column location in the upper floors. The cast steel joint is used for the branching point of each special column to securely transfer the stress.

• Structural Engineering and Mechanics
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• v.73 no.1
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• pp.17-25
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• 2020

A finite element (FE) model for analyzing slender reinforced high-strength concrete (HSC) columns under biaxial eccentric loading is formulated in terms of the Euler-Bernoulli theory. The cross section of columns is divided into discrete concrete and reinforcing steel fibers so as to account for varied material properties over the section. The interaction between axial and bending fields is introduced in the FE formulation so as to take the large-displacement or P-delta effects into consideration. The proposed model aims to be simple, user-friendly, and capable of simulating the full-range inelastic behavior of reinforced HSC slender columns. The nonlinear model is calibrated against the experimental data for slender column specimens available in the technical literature. By using the proposed model, a numerical study is carried out on pin-ended slender HSC square columns under axial compression and biaxial bending, with investigation variables including the load eccentricity and eccentricity angle. The calibrated model is expected to provide a valuable tool for more efficiently designing HSC columns.

• Journal of Korean Association for Spatial Structures
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• v.22 no.1
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• pp.41-49
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• 2022

In the case of columns in buildings with soft story, the concentration of stress due to the difference in stiffness can damage the columns. The irregularity of buildings including soft story requires retrofit because combined load of compression, bending, shear, and torsion acts on the structure. Concrete jacketing is advantageous in securing the strength and stiffness of existing members. However, the brittleness of concrete make it difficult to secure ductility to resist the large deformation, and the complicated construction process for integrity between the existing member and extended section reduces the constructability. In this study, two types of Steel Grid Reinforcement (SGR), which are Steel Wire Mesh (SWM) for integrity and Steel Fiber Non-Shrinkage Mortar (SFNM) for crack resistance are proposed. One reinforced concrete (RC) column with non-seismic details and two columns retrofitted with each different types of proposed method were manufactured. Seismic performance was analyzed for cyclic loading test in which a combined load of compression, bending, shear, and torsion was applied. As a result of the experiment, specimens retrofitted with proposed concrete jacketing method showed 862% of maximum load, 188% of maximum displacement and 1,324% of stiffness compared to non-retrofitted specimen.

• Journal of the Korea Concrete Institute
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• v.20 no.1
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• pp.59-66
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• 2008

This study is about manufacturing and producing girder, which is an essential component of bridge structure, in a composite of FRP + concrete. This has a higher competitive power in price than steel girder. The girder used in this study is made of glass fiber which has a lower elastic modulus than steel and thus has some technical limitations such as excessive deflection compared to steel girder and lack of production facilities in FRP production companies to make a large-section component material. Thus, this study suggested a section of a new module that will allow for applying a large section in order to solve the technical difficulties mentioned above and to secure low stiffness of FRP, developed a new FRP+concrete composite girder that is filled with the appropriate amount of concrete. To identify the structural behavior of this FRP+concrete composite girder, experiments were conducted to measure its flexural strength according to the difference in the strength of confined concrete and the existence of stud. The results of the flexural strength test confirmed the composite effect from confining concrete and the effect of increase in strength proportional to the strength of concrete. In developing FRP+concrete composite girder, NDT study was also conducted to analyze the interface characteristics of concrete and FRP.

• Advances in concrete construction
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• v.2 no.3
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• pp.163-176
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• 2014

Essentially, when electrical current flows easily in concrete that has large pores filled with highly connective pore water, this is an indication of a low resistivity concrete. In concrete, the flow of current between anodic and cathodic sites on a steel reinforcing bar surface is regulated by the concrete electrical resistance. Therefore, deterioration of any existing reinforced concrete structure due to corrosion of reinforcement steel bar is governed, to some extent, by resistivity of concrete. Resistivity of concrete can be improved by using SCMs and thus increases the concrete electrical resistance and the ability of concrete to resist chloride ingress and/or oxygen penetration resulting in prolonging the onset of corrosion. After depassivation it may slow down the corrosion rate of the steel bar. This indicates the need for further study of the effect of electric arc furnace dust (EAFD) addition on the concrete resistivity. In this study, concrete specimens rather than mortars were cast with different additions of EAFD to verify the electrochemical results obtained and to try to understand the role of EAFD addition in influencing the corrosion behaviour of reinforcing steel bar embedded in concrete and its relation to the resistivity of concrete. The results of these investigations indicated that the corrosion resistance of steel bars embedded in concrete containing EAFD was improved, which may link to the high resistivity found in EAFD-concrete. In this paper, potential measurements, corrosion rates, gravimetric corrosion weight results and resistivity measurements will be presented and their relationships will also be discussed in details.