• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4A
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• pp.383-389
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• 2010

The concrete structural design provisions in Korea are based on ultimate strength design. Up to service load stage, it is assumed a linear stress-strain relation, but there is no stress-strain relationship for a concrete material from service load stage to limat state. According to the current provisions, an independent method is provided for the each calculation of deflection and crack width. In EC2 provisions based on limit state design, however, a stress-strain relationship of concrete is provided. Thereby, it is able to calculate a strength as well as a deflection directly from concrete stress-strain relationship. In this paper the moment-curvature relationship is directly calculated from a material law using equilibrium and compatibility conditions. Then strength and deflection are formulated. These results are compared with the values from the current provisions in Korea. From the results, the deflection based on a moment-curvature relationship is well agreed with experimental results and it is appeared that the deflection after the yielding of steel is also possible.

• Journal of Korean Society of Steel Construction
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• v.23 no.3
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• pp.385-395
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• 2011

The flexural strength of composite HSB hybrid I-girders under positive moment is investigated by the moment-curvature analysis method to evaluate the applicability of the current AASHTO LRFD design specification to such girders. The hybrid girders are assumed to have the top flange and the web fabricated from HSB600 steel and the bottom flange made of HSB800 steel. More than 6,200-composite I-girder sections that satisfy the section proportion limits of AASHTOL RFD specifications are generatedby the random sampling technique to consider a statistically meaningful wide range of section properties. The flexural capacities of the sections are calculated by the nonlinear moment-curvature analysis in which the HSB600 and HSB800 steels are modeled as an elastoplastic, strain-hardening material and the concrete as CEB-FIP model. The effects of ductility ratio and compressive strength of concrete slab on the flexural strength of composite hybrid girders make of HSB steels are analyzed. Numerical results indicated that the current AASHTO-LRFD equation can be used to calculate the flexural strength of composite hybrid girders fabricated from HSB steel.

• Journal of Navigation and Port Research
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• v.36 no.3
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• pp.215-223
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• 2012

To examine the interaction of the floating pontoon with a steel moment resisting frame, the static structural analysis is carried out, in which the pressure load are calculated from the forgoing fluid dynamic analysis, varying the period of wave from 3 to 15 second and for 3 cases of depth of pontoon, 1.5, 2.0, 2.5m. As results, it has shown that RAO-pitch has the linear relationship with the increase of moment of the frame and the curvature of pontoon is reversely proportional to the stiffness of pontoon. By synthesizing these results, an estimation method is proposed, which predicts the moment of frame of the different depth of pontoon based on the analysis result of an arbitrary depth of a floating pontoon. The estimation result shows considerably good agreement, compared with the analysis result.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.663-667
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• 2000

The equivalent load method has been widely used in the design and analysis of prestressed concrete structures. The purpose of this paper is to explore several important method of obtaining equivalent loads and to clarify the advantages and limitations of each method. The methods devised in this study include the use of curvature of tendon, characteristics of primary moment, self-equilibrium conditions, and linear segments approximation of tendon. It is shown that equivalent lading system is not uniquely determined in some cases and careful engineering judgement is required from the view point of accuracy and practical convenience.

• Steel and Composite Structures
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• v.8 no.5
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• pp.361-388
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• 2008

The Eurocode 4 presents some negative aspects in the design of composite slabs by the m-k Method or the Partial Connection Method. On one hand, the component chemical adherence is not accounted for in the connection between the profiled steel sheet and the concrete. On the other hand, the application of these methods requires some fitting parameters that must be determined by full scale tests. In this paper, the Eurocode 4 methods are compared with a method developed at the Federal Polytechnic School of Lausanne, based on pullout tests, which can be a valid alternative. Hence, in order to calculate the necessary parameters for the three methods, several tests have been performed such as the full scale test described in Eurocode 4 and pull-out tests. This last type of tests is of small dimensions and implicates lower costs. Finally, a full-scale test of a steel-concrete composite slab with a generic loading is presented, with the goal of verifying the analytical formulation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.206-213
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• 1999

The behavior of composite beams, which are composed of cold-formed steel sheeting and normal strength concrete, have been studied. An analytical method has been developed to trace the nonlinear behavior of composite beams. The nonlinear material properties of steel sheeting, reinforcing steel bar and concrete have been included in the analysis. The nonlinear moment-curvature relation of the composite beam has been described using a cross section analysis method and a simple power model, separately. The load-deflection behavior of the beams has been simulated by step-by-step numerical integration method and is compared with test results.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.9
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• pp.62-69
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• 2000

Uneven clearances in the left and right sides of a press die cause deformation of the punch in precision shearing process. This deformation results from the compression stress and bending moment from shearing force in vertical direction and from the side force in horizontal direction acting to the punch, In this study the behavior of punch deformation is investigated in order to clarify the deformation state of the punch by using strain gauge deformation to shearing force side force bending moment radius of curvature and shear plane of the punch. Also we presented the calculation method of deformation size for the punch.

• Steel and Composite Structures
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• v.37 no.3
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• pp.371-390
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• 2020

One of the most common strategies for retrofitting as-built reinforced concrete (RC) columns is to enlarge the existing section through the application of a new concrete layer reinforced by both steel transverse and longitudinal reinforcements. The present study was dedicated to developing a comprehensive model to predict the seismic behavior of as-built RC jacketed columns. For this purpose, a new sectional model was developed to perform moment-curvature analysis coupled by the plastic hinge method. In this analysis-oriented model, new methodologies were suggested to address the impacts of axial, flexural and shear mechanisms, variable confining pressure, eccentric loading, longitudinal bar buckling, and varying axial load. To consider the effective interaction between core and jacket, the monolithic factor approach was adopted to extent the response of the monolithic columns to that of a respective RC jacket strengthened column. Next, parametric studies were implemented to examine the effectiveness of the main parameters of the RC jacket strategy in retrofitting as-built RC columns. Ultimately, the reliability of the developed analytical model was validated against a series of experimental results of as-built and retrofitted RC columns.

• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.147-156
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• 1999

Current design code states that the strength reduction factor shall be permitted to be increased linearly from that for axial compression to that for flexure as the design axial load strength $\Phi$cPn decrease from 0.1fckAg to zero. Since this empirically adopted axial load level of $\Phi$cPn=0.1fckAg considers only sectional area and concrete strength, the other variables such as steel ratio, steel yielding strength, and steel arrangement can not be considered. This research is performed to investigate the consistency and the rationality of the code requirement for determination of column design strength. A nonlinear axial force-moment-curvature analysis was conducted in order to investigate the ductility of reinforced concrete column sections. As the result of ductility analysis, it was found that the ductility at the axial force of $\Phi$cPn=0.1fckAg represented a lock of consistency for the various variable contained sections. Therefore, a more reasonable application method of strength reduction factor is proposed, that is based on the strain ductility index.

• Computers and Concrete
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• v.13 no.6
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• pp.799-827
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• 2014

In this paper, a theoretical and experimental study of the sectional behaviour of reinforced concrete beams subjected to short-term loads is carried out. The pure bending behaviour is analysed with moment-curvature diagrams. Thus, the experimental results obtained from 24 beams tested by the authors and reported in literature are compared with theoretical results obtained from a layered model, which combines the material parameters defined in Model Code 2010 with some of the most recognized tensions-tiffening models. Although the tests were carried out for short-term loads, the analysis demonstrates that rheological effects can be important and must be accounted to understand the experimental results. Another important conclusion for the beams tested in this work is that the method proposed by EC-2 tends to underestimate the tension-stiffening effects, leading to inaccuracies in the estimations of deflections. Thus, the actual formulation is analysed and a simple modification is proposed. The idea is the separation of the deflection prediction in two parts: one for short-term loads and other for rheological effects (shrinkage). The results obtained are in fairly good agreement with the experimental results, showing the feasibility of the proposed modification.