• Geomechanics and Engineering
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• v.17 no.6
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• pp.553-564
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• 2019

This paper presents experimental results of rock-concrete bi-material discs under cyclically diametrical compression. It was found that both specimens under cyclical and static loading failed in three typical modes: shear crack, tensile crack and a combined mode of shear and wing crack. The failure modes transited gradually from the shear crack to the tensile one by increasing the interface angle between the interface and the loading direction. The cycle number and peak load increased by increasing the interface angle. The number of cycles and peak load increased with the interface groove depth and groove width, however, decreased with increase in interface groove spacing. The concrete strength can contribute more to the cycle number and peak load for specimens with a higher interface angle. Compared with the discs under static loading, the cyclically loaded discs had a lower peak load but a larger deformation. Finally, the effects of interface angle, interface asperity and concrete strength on the fatigue strength were also discussed.

• Steel and Composite Structures
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• v.31 no.2
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• pp.159-172
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• 2019

Strengthening of civil infrastructure with advanced composites have recently become one of the most popular methods. The use of Fiber Reinforced Polymer (FRP) strips plates and fabric for strengthening of reinforced concrete structures has well established design guidelines and standards. Research on the application of FRP composites to steel structures compared to concrete structures is limited, especially for shear strengthening applications. Whereas, there is a need for cost-effective system that could be used to strengthen steel high-way bridge girders to cope with losses due to corrosion in addition to continuous demands for increasing traffic loads. In this study, a parametric finite element study is performed to investigate the effect of applying thick CFRP strips diagonally on webs of plate girders on the shear strength of end-web panels. The study focuses on illustrating the effect of several geometric parameters on nominal shear strength. Hence, a formula is developed to determine the enhancement of shear strength gained upon the application of CFRP strips.

• Journal of Korean Association for Spatial Structures
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• v.22 no.3
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• pp.65-72
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• 2022

A typical low and medium-sized neighborhood living facility in reinforced concrete building secures a high floor and pursues an efficient module plan(long span). Accordingly, research on the development of new hybrid beams that can innovatively reduce labor costs such as on-site installation and assembly while securing strength and rigidity is ongoing. In order to verify the structural performance of the U-flanged truss composite beam with newly developed shape, Experiments with various variables are required. Based on the results, this study is to evaluate the strength of U-flanged truss hybrid beam through the flexural strength of the Korea Design Code and experimental values. It was evaluated that nominal flexural strength was 110% to 135% higher than the experimental value.

• Journal of Korean Society of Steel Construction
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• v.22 no.6
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• pp.609-616
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• 2010

The objective of this study is to investigate the structural character of the buckling strength of 600MPa-class high-strength steel compression members. The buckling strength of circular hollow-section columns is evaluated by a numerical analysis of the stress-strain curves of the tension test results. The numerical analysis was based on the beam-column theory and the tangent modulus theory. It was considered possible to enlarge the nominal yield strength of the 600MPa-class steel.

• Journal of Korean Society of Steel Construction
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• v.17 no.3 s.76
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• pp.271-283
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• 2005

This paper concerns the prediction of shear capacity, as governed by steel failure and concrete breakout failure, of set anchors installed in plain concrete. For this purpose, the methods to evaluate the shear capacity of the set anchors in concrete are summarized and the experimental data are compared with capacities by the two present methods : the method of ACI349-90 and the Concrete Capacity Design (CCD) method. (1) The constant-0.684 in the steel strength equation of set anchor was determined from shear test data at the 5 percent fractile probability. Consequently, it was concluded that the constant-0.6 and 0.5 in the steel strength equation for steel failure of ACI318-02 and EOTA were safe. The nominal shear strength of set anchor was proposed as following. $V_s=0.684 A_{se}f_{ut}$. (2) The CCD method was considered reasonable in estimating the concrete breakout strength of set anchors. In terms of the CCD method, the nominal concrete breakout strength of set anchor in shear was provided as follows; $V_b=0.609(\frac{\iota}{d_o})^{0.2}\sqrt{d_0}\sqrt{f_c}(c_1)^{1.5}$(N). (3) The CCD method was considered reasonable in estimating the concrete breakout strength for spacing of set anchors. The proposed equation was considered safe in estimating the concrete breakout strength for spacing of set anchors.

• Composites Research
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• v.31 no.5
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• pp.177-185
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• 2018

Fiber metal laminate (FML) is a type of hybrid composites which consist of metallic and fiber-reinforced plastic sheets. As the FML has a drawback of the delamination that is a failure of the interfacial adhesive layer, the nominal stresses and the energy release rates should be determined to identify the delamination behavior. However, it is difficult to derive the nominal stresses and the energy release rates since the operating temperature of the equipment is restricted. For this reason, the objective of this paper is to predict the mode-I nominal stress and the mode-I energy release rate of the adhesive layer using the inverse analysis based on the Levenberg-Marquardt method. First, the mode-I nominal stress was assumed as the tensile strength of the adhesive layer, and the mode-I energy release rate was obtained from the double cantilever beam test. Next, the finite element method was applied to predict the mode-I delamination behavior. Finally, the mode-I nominal stress and the mode-I energy release rate were predicted by the inverse analysis. In addition, the convergence of the parameters was validated by trying to input two cases of the initial parameters. Consequently, it is noted that the inverse analysis can predict the mode-I delamination behavior, and the two input parameters were converged to similar values.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.993-996
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• 2008

Compression stress block used to concrete structure design substitutes equivalent triangle, rectangle, trapezoid and parabola-rectangle stress block for actual concrete stress distribution. Its shape is different in design code of the major advanced countries. It reflects the material feature of each of country. Presently, compression stress block of korea concrete design code is equal to it of ACI code that doesn't reflect the material feature of the high strength concrete. So, many research conclusions showed that it is not reasonable. The study compares concrete stress blocks of the major advanced countries and does an experiment on concrete compression stress block to know the material feature of the concrete in korea. It obtains the operating load and the concrete strain in experiment and draw stress block parameters. It compares stress block parameters applied to design code with those by the experiment conclusion. In addition, It compares and analyses nominal axial force-moment diagram by the stress block of the major advanced countries.

• Journal of Korean Society of Steel Construction
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• v.13 no.1
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• pp.19-28
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• 2001

The strength and ductility of steel flexural members are investigated experimentally in this study. As for the performance evaluation of flexural members. experimental studies on the 9 test specimens were carried out. Four specimens were fabricated from SM490 and five specimens were fabricated from SM570. The experimental results of the specimens were analyzed with focus on the flexural strength and ductility. The experimental results exhibited that all the specimens provided sufficient flexural strengthes which exceeded the nominal flexural strengthes specified in the current Limit State Design Specification by average ratio of 1.22. However. the experimental results showed that the compact-section specimens fabricated from SM570 did not provide the required rotational ductility. The yield-to-tensile strength ratio(YR) of SM570 of about 0.9 might be the causes of such insufficient capacities.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.469-474
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• 2002

Recently fiber sheets are used for strengthening the damaged concrete structures due to its many advantages such as its durability, non-corrosive nature, low weight, ease of application, cost saving, control of crack propagation, strength to thickness ratio, high tensile strength, serviceability and aesthetic. However, the lack of analytical procedures for predicting the nominal moment capacity by the fiber sheet reinforcement leads to difficulties in the effective process of decisions of the factors in the strengthening procedure. In this work, flexural strengthening effects by fiber sheets bonded on soffit and web of the member are theoretically studied for the reinforced concrete T beam. The analytical solutions are compared with experimental results of several references to verify the proposed approach.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.144-147
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• 2004

In this paper, field application of mass concreting using super retarding agent(SRA) are discussed based on setting. time difference with SRA in big discount market in Chongju. Mechanical and physical properties of .concrete are investigated. Temperature history of concrete is also measured. Slump and air content meet the requirement of target value. Compressive strength of concrete exceeded the nominal strength with 24MPa. Compressive strength of SRA concrete is higher than that of plain concrete by about $3\~4\%$. For temperature history, peak temperature of concrete at middle section at top concrete layer reached $49.6^{\circ}C$ within 24hours, and at bottom concrete layer, $54.6^{\circ}C$ within 42hours. Based on the naked eye's observation, no crack was found at mass concrete.