• Computers and Concrete
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• v.30 no.1
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• pp.19-32
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• 2022

This paper presents an investigation into the failure of RC columns under impact loadings. A numerical simulation of 19 identical RC columns subjected to single and repeated impact loadings was performed. A free-falling hammer was dropped at midspan with the same total kinetic energy input but varying mass and momentum. The specimens under the repeated impact test were struck two times at the same location. The colliding index, defined as the impact energy-momentum ratio, was proposed to explain the different impact responses under equal-energy impacts. The increase of colliding index from low to high indicates the transition of the impact response from static to dynamic and failure mode from flexure to shear. This phenomenon was more evident when the column had a greater axial load and was impacted with a high colliding index. The existence of the axial load had an inhibitory effect on the crack development and increased the shear resistance. The second impact changes the failure mode from flexural to brittle shear as found in the specimen with 20% axial load subjected to high a colliding index. Moreover, a deflection prediction equation based on the impact energy and force was limited to the low colliding index impact.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.547-552
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• 1998

The small-scale models have been utilized for the prediction of inelastic behavior of reinforced concrete structures for a long time. The parameters that affect the similitude between the model and the prototype are various. Among them, the effect of bond between the model reinforcement and the model concrete is one of the most important factors. The study reported herein is addressed to verifying this similitude in bond behavior. Another topic is the similitude in shear. The selected scales are 1/1, 1/5, 1/10 and 1/12. Two prototype specimens and three models were tested in addition to the associated material tests. The test results are compared from the viewpoint of similitude.

• International Journal of Concrete Structures and Materials
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• v.10 no.2
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• pp.125-142
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• 2016

An overall review of the structural behaviors of ultra-high-performance fiber-reinforced concrete (UHPFRC) elements subjected to various loading conditions needs to be conducted to prevent duplicate research and to promote its practical applications. Thus, in this study, the behavior of various UHPFRC structures under different loading conditions, such as flexure, shear, torsion, and high-rate loads (impacts and blasts), were synthetically reviewed. In addition, the bond performance between UHPFRC and reinforcements, which is fundamental information for the structural performance of reinforced concrete structures, was investigated. The most widely used international recommendations for structural design with UHPFRC throughout the world (AFGC-SETRA and JSCE) were specifically introduced in terms of material models and flexural and shear design. Lastly, examples of practical applications of UHPFRC for both architectural and civil structures were examined.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.745-750
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• 2000

Steel plate bonding technique is most widely used in strengthening of existing concrete structures, but it has inherently a problem of the premature failure such as interface separation and rip off. So far, many studies have been arid out in the manner of laboratory tests for the reinforced concrete beams to find out he mechanism of the premature failure. However, in order to verify the characteristics of the premature failure, more reasonable local investigations are needed rather than such relatively global experimental works. In this study, therefore, the double lap test which simulate the pure shear loadings and the half beam tests which consider combined flexure-shear force have been done. There are, however, difficulties in getting the normal stress caused to premature failure, so that finite element analysis was performed, too. In numerical study, material nonlinearity was considered, and the interface element was applied to model the interface between steel plate and adhesive. From the results of experimental and numerical studies, a realistic failure criterion on the separation of steel plates has been derived.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.633-638
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• 1997

This study was performed to investigate the fatigue behaviour and fatigue damage process of RC structures under repeated load. Especially, the behavior of RC beams subjected to flexure-shear force has been focused. The test results show that the deflections of beam and the strains of longitudinal steels and stirrups under cyclic loads increase with constant rate, and these increases depend on diagonal crack openings and strain increases. The present study provides useful data for the analysis of damage accumulation of reinforced concrete beams under repeated loadings.

• Journal of the Korean Geophysical Society
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• v.6 no.4
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• pp.213-219
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• 2003

This study in on the development of analytic model that can predict the hysterisis response of steel-concrete under the periodic loads. Analytic value and experimental value including developed model were compared and interpreted. From the comparing interaction between torque and shear was focused on the its importance.

• Structural Engineering and Mechanics
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• v.72 no.6
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• pp.723-736
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• 2019

The efficacy of a technique for the rehabilitation and strengthening of RC beam-column connections damaged due to cyclic loading was investigated. The repair mainly uses epoxy resin infused under pressure into the damaged region to retrieved back the lost capacity and then strengthening using fiber reinforced polymer (FRP) sheets for capacity enhancement. Three common types of reduced scale RC exterior beam-column connections namely (a) beam-column connection with beam weak in flexure (BWF) (b) beam-column connections with beam weak in shear (BWS) and (c) beam-column connections with column weak in shear (CWS) subjected to reversed cyclic loading were considered for the experimental investigation. The rehabilitated and strengthened specimens were also subjected to similar cyclic displacement. Important parameters related to seismic capacity such as strength, stiffness degradation, energy dissipation, and ductility were evaluated. The rehabilitated connections exhibited equal or better performance and hence the adopted rehabilitation strategies could be considered as satisfactory. Confinement of damaged region using FRP sheet significantly enhanced the seismic capacity of the connections.

• Computers and Concrete
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• v.29 no.5
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• pp.285-301
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• 2022

This study aims at developing a torsional strength model based on a nonlinear analysis method presented in the previous studies. To this end, flexural neutral axis depth of a reinforced concrete section and effective thickness of an idealized thin-walled tube were formulated based on reasonable approximations. In addition, various sectional force components, such as shear, flexure, axial compression, and torsional moment, were considered in estimating torsional strength by addressing a simple and linear strain profile. Existing test results were collected from literature for verifications by comparing with those estimated from the proposed model. On this basis, it can be confirmed that the proposed model can evaluate the torsional strength of RC members subjected to combined loads with a good level of accuracy, and it also well captured inter-related mechanisms between shear, bending moment, axial compression, and torsion.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.10a
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• pp.16-23
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• 1993

The new p-version crack model is proposed to estimate the bending stress intensity factors of the thick cracked plate under flexure. The proposed model is based on high order theory and $C^{\circ}$-plate element including shear deformation. The displacements fields are defined by integrals of Legerdre polynomials which can be classified into three groups such as basic mode, side mode and internal mode. The computer implementation allows arbitrary variations of p-level up to a maximum value of 10. The bending stress intensity factors are computed by virtual crack extention approach. The effects of ratios of thickness to crack length(h/a), crack length to width(a/W) and boundary conditions are investigated. Very good agreement with the existing solution in the literature are shown for the uncracked plate as well as the cracked plate.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.6
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• pp.1289-1298
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• 1994

The new p-version crack model is proposed to estimate the stress intensity factors of the thick cracked plate under flexure. The proposed model is based on high order theory and $C^{\circ}$-plate element including shear deformation. The displacements fields are defined by integrals of Legendre polynomials which can be classified into three groups such as basic mode, side mode and internal mode. The computer implementation allows arbitrary variations of p-level Up to a maximum value of 10. The stress intensity factors are computed by virtual crack extention approach. The effects of ratios of thickness to crack length(h/a), crack length to width(a/W) and boundary conditions are investigated. Very good agreement with the existing solution in the literature are shown for the uncracked plate as well as the cracked plate.