• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.443-449
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• 2022

When fiber reinforced concrete is manufactured, it is useful to utilize lathe scrap as an aiternative material of steel fiber, because it is not only economical as an by-product of steel manufactures, but also has a very similar composition to that of steel fiber. The purpose of this experimental research is to evaluate the compressive strength and tensile behavior and then propose a material model of lathe scrap reinforced mortar. For this purpose, the lathe scrap reinforced mortars were ma de a ccording to their tota l volume fra ction of 1.5 % for wa ter-binder ra tio of 30 % a nd 40 %, respectively, a nd then the mechanical properties such as compressive strength, direct tensile strength, and stress-strain curve of those were evaluated. Also, based on the experimental results of lathe scrap reinforced mortar the material model for tensile behavior was suggested. It was revealed that the experimental results and the proposed material model corresponded relatively well.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.581-586
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• 2005

High-performance concrete (HPC), which is particularly sensitive to self-desiccation, is required to be durable even in severe environmental conditions, i.e. costal area, cold district, etc. However, in recent years, some attention was particularly given to cracking sensitivity of high performance concrete at early age. It has been argued and demonstrated experimentally that such concrete undergoes autogenous shrinkage due to self-desiccation at early age under restrained condition, nd, as a result, internal tensile stress may develop, leading to micro cracking and macro cracking. This shrinkage-introduced crack produces a major serviceability problem for concrete structures. One possible method to reduce cracking due to autogenous shrinkage is the addition of expansive additive. Tests conducted by many researches have shown the beneficial effects of addition of expansive additive for reducing the risk of autogenous shrinkage-introduced cracking. However, the research on hydration model of expansion additive has been hardly researched up to now. This paper presents a study of the hydration model of Ettringite-Gypsum type expansive additive. As a result of comparing forecast values with experiment value, proposed model is shown to expressible of hydration of expansive additive.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.4
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• pp.449-455
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• 2011

Recently, international collaborative research which was organized at Bhabha Atomic Research Centre in India, was conducted to develop for pressure capacity and nonlinear behavior of PHWR 1/4 scale nuclear containment building between experimental test and numerical code. In this paper, a nonlinear finite element analysis was carried out in order to predict ultimate pressure capacity and nonlinear behavior of the 1/4 scale containment building. The 1/4 scale containment building is consisted of basemat, cylinder wall, dome and 4-buttress. For the finite element analysis, commercial program ABAQUS was used. Finite element models including concrete, rebar and tendon have been developed for assessment of ultimate pressure capacity and failure mode for nuclear containment building. From the analysis results, first crack of the concrete, the yielding of the rebar and ultimate capacity pressure occurred at $1.6P_d$(design pressure), $3.36P_d$ and $4.0P_d$, respectively.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.3
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• pp.199-209
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• 2009

This paper deals with the three-dimensional finite element analysis of failure behavior of UHPFRC I-beam under monotonic load. Different from the constitutive law of normal and high strength concrete, an elastic-plastic fracture model that considers the tensile strain hardening is proposed to describe the material properties of UHPFRC. A multi-directional fixed crack criterion with tensile strain hardening is defined in the tensile region, and Drucker-Prager criterion with an associated flow rule is adopted in the compressive region. The influence of span, prestressing force and section on the behavior of UHPFRC I-beam are investigated. The comparison of the numerical results with the test results indicates a good agreement.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.361-364
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• 2008

To design structures with Ultra High Performance Concrete (UHPC), it is necessary to estimate the mechanical properties first of all. The most attractive characteristics of UHPC are the considerable tensile strength and behavior. Therefore the most important thing in order to properly design UHPC structures is to establish the constitutive model to represent the tensile behavior of UHPC. In this study, it was tried to find out the tensile behavior of UHPC by experiments and analyses. Through comparisons with the French SETRA/AFGC recommendations and the Japanese recommendations for the Ultra High-Strength Fiber-Reinforced Concrete Structures, a reasonable model which could represent the tensile stress-strain relationship in the structural design was proposed

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.3
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• pp.531-539
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• 2017

The strut-tie model approach has been recognized as an efficient methodology for the design of all types of concrete members with D-regions, and the approach has been accepted in design codes globally. However, the design of concrete members with the approach requires many iterative numerical structural analyses, numerous graphical calculations, enormous times and efforts, and designer's subjective decisions in terms of the development of appropriate strut-tie model, determination of required areas of struts and ties, and verification of strength conditions of struts and nodal zones. In this study, a computer graphics program, that enables the design of concrete members efficiently and professionally by overcoming the forementioned limitations of the strut-tie model approach, is developed. In the computer graphics program, the numerical programs that are essential in the strut-tie model analysis and design of concrete members including finite element analysis programs for the plane truss and solid problems with all kinds of boundary conditions, a program for automatic determination of effective strengths of struts and nodal zones, and a program for graphical verification of developed strut-tie model's appropriateness by displaying various geometrical shapes of struts and nodal zones, are loaded. Great efficiency and convenience during the application of the strut-tie model approach may be provided by the various graphics environment-based functions of the proposed program.

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.91-100
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• 2006

This paper presents an analytical model for evaluation of crack widths in structural concrete members. The model is mathematically derived from the actual bond stress-slip relationships between the reinforcement and the surrounding concrete, and the relationships summarized in CEB-FIP Model Code 1990 are employed in this study together with the assumption of a linear slip distribution along the interface at the stabilized cracking stage. With these, the actual strains of the steel and the concrete are integrated respectively along the embedment length between the adjacent cracks so as to obtain the difference in the axial elongation. The model is applied to the test specimens available in literatures, and the predicted values are shown to be in good agreement with the experimentally measured data.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.397-400
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• 2008

To carry out this study efficiently, the material, physical and mechanical properties of the existing high temperature area was identified and the thermal transportation of structural elements was carried out through the finite element analysis method(ABAQUS) for 40 to 100 MPa high strength concrete based on Fiber Cocktail mixing. The results are as follows. First, it was analyzed that 40, 50 and 60 MPa high strength concretes have a thermal transportation properties similar to the analysis model of 30 MPa normal concrete. Second, it was analyzed that the analysis model of 80 and 100 MPa high strength concrete have slightly lower thermal transportation properties compared to normal model. Third, this study didn't consider the explosive spalling by the pore pressure within high strength concrete. If the properties for the pore pressure within high strength concrete is considered and database by strength and by inner temperature of various high strength concrete and steel materials are established in the future, it is interpreted that the technical foundation will be laid for performance-based design of fire-resistant construction.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.175-181
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• 2010

The three truss models(equilibrium truss model, Mohr compatibility truss model, and the soften truss model) based on a rotating angle is called the rotating-angle model. The three rotating-angle models have a common weakness: they are incapable of predicting the so-called "contribution of concrete". To take into account this "contribution of concrete", the modern truss model(MCFT, STM) treats a cracked reinforced concrete element as a continuous material. By combining the equilibrium, compatibility, and the softened stress-strain relationship of concrete in biaxial state, MTM is capable of producing the nonlinear analysis of reinforced concrete structures composed of membrane element. In this paper, an efficient algorithm is proposed for the solution of proposed model incorporated with failure criteria. This algorithm is used to analyze the behavior of reinforced membrane element using the results of Hsu test.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.17-24
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• 2020

In this study, series of nonlinear seismic analysis were performed on a reinforced concrete intake tower surrounded by water. To consider the fluid effect around the structure, analysis models were composed using an added mass and CEL approach. At this time, the implicit method was used for the added mass model, and the explicit method was used for the fluid structure interaction model. The input motions were scaled to correspond to 500, 1000, and 2400 years return period of the same artificial earthquake. To estimate the counteractivity of the fluid coupled model, models without fluid effect were constructed and used as a reference. The material models of concrete and reinforcement were selected to consider the nonlinear behavior after yielding, and analysis were performed by ABAQUS. As results, in the acceleration response spectrum of the structure, it was found that the influence of the surrounding fluid reducing the peak frequency and magnitude corresponding to the fundamental frequency of the structure. However, the added mass model did not affect the peak value corresponding to the higher mode. The sectional moments were increased significantly in the case of the added mass model than those of the reference model. Especially, this amplification occurred largely for a small-sized earthquake response in which linear behavior is dominant. In the fluid structure interaction model, the sectional moment with a low frequency component amplifies compared to that of the reference model, but the sectional moment with a high requency component was not amplified. Based in these results, it was evaluated that the counteractivity of the additive mass model was greater than that of the fluid structure interaction model.