• Journal of Korean Society of Steel Construction
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• v.25 no.2
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• pp.187-196
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• 2013

CFT structures require a diaphragm to prevent buckling of steel at connections. An outer diaphragm has better concrete filling than a through diaphragm due to a large bore, but due to the larger size than the through diaphragm, it has poorer constructability and cooperation with building equipment. The building structure has a floor slab that was unified with the upper diaphragm, so the outer diaphragm was placed at the upper bound. Moreover, the through diaphragmwas placed at the lower connection to avoid obstruction of the building equipment. The CFT structure with the improved concrete filling showed the same structural behavior as the CFT structure with the use of the same type of diaphragms at the upper and lower connections.

• Journal of Korean Society of Steel Construction
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• v.23 no.6
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• pp.737-745
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• 2011

A concrete-filled tube is a concrete-filled steel tube structure. The steel tube confines the concrete to increase the compressive strength, and the concrete contains the buckling of the tube. CFT structures require a diaphragm to prevent buckling of steel at connections. An outer diaphragm has better concrete filling than a through diaphragm due to a large bore, but being larger than the through diagram, it has poorer constructability and cooperation with building equipment. In this study, a CFT structure that uses different types of diaphragms in its upper and lower connections to improve the concrete filling was tested and analyzed via the FEM program. The building structure had a floor slab that was unified with the upper diaphragm, so the outer diaphragm was placed at the upper bound. Moreover, the through diaphragm was placed at the lower connection to avoid obstruction from building equipment. The CFT structure with the improved concrete filling showed the same structural behavior as the CFT structure with the use of the same type of diaphragms at the upper and lower connections.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.1
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• pp.205-215
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• 2006

In this study 3-D shell FEM model was applied to analyze the behavior of curved steel box girders stiffened by diaphragms. The reliability of the analytical method has been proved by comparing with the existing results. It was also found from this analysis that main factors affecting a distortional stress are length of a girder, curvature of the girder, and spacing of diaphragms. A modelled bridge with 30m of span length and 40m of radius was analyzed to find an optimum spacing of diaphragm, and as a result of applying different spacings, 5m was found to be most appropriate to control the stress ratio regulated by specifications. In the effect of diaphragm shape, the rhamen-typed diaphragm is found to be more effective than the fully filled-up one in the range of opening ratio of 0.4 to 0.6. But, the fully filled-up diaphragm had more efficiency in terms of reducing the distortional stress than X-truss typed diaphragm.

• Journal of Korean Society of Steel Construction
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• v.18 no.2
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• pp.123-135
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• 2006

This paper investigates the design equations and the strength behavior of the diaphragm for steel box beams and circular-column connections. The strength of the connection is decided by the strength of the diaphragm and the strength of the beam and the column, because the connection diaphragm supports the concentration forces from the box beam's lower flange. In previous researches, however, the calculation procedure of the diaphragm stress from the indeterminate curved-beam model is to complicated to apply in process of the equation. Moreover, no reasonable design has yet ben made because the diaphragm's effect on the strength of the connection has not ben considered. Therefore, through nonlinear FEM analysis of the connection diaphragm, this study examines the strength behavior of a connection with diaphragm details. In addition, a great difference is confirmed between the theoretical and analytic behaviors. Fi naly, considering the strength of the connection and the rigidity capacity of the diaphragm, the diaphragm design method is proposed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.67-75
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• 2019

The diaphragm used for CFT columns has a small amount of steel to be used, but has a disadvantage that welding is difficult and openings are required because the steel tube and four sides must be welded. The improved diaphragm to be examined in this study was cut into four corners by cutting the center hole for concrete filling. In the improved diaphragm, the width of the center hole is the same as that of the previous diaphragm, but the width of the diaphragm contacting the steel tube is reduced, thereby reducing the welding length by about 70% compared to the previous diaphragm. The in-plane strain of each specimen was analyzed when the same load was applied to the interior diaphragm through a simple tensile test. Using the general FEM program(ANSYS 19.2), the analysis was performed under the same conditions as the actual simple tensile test, and the load transfer between the improved diaphragm and the previous diaphragm was compared. When the width of the diaphragm is equal to or smaller than the flange width, stress is concentrated from the end of the diaphragm, and when the flange width is larger, stress is concentrated at the center.

• Journal of Korean Society of Steel Construction
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• v.17 no.6 s.79
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• pp.649-660
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• 2005

Since the diaphragm manhole of steel box girder bridges is designed generally from experience, it has become the primary factor in the excessive cost of steel bridge construction. For the economical and efficient manufacture of diaphragm manholes, it is necessary to study the exact behavior of the diaphragm manhole in a steel box girder bridge. In this study, both an experimental test and a structural analysis are performed to verify the behavior of the diaphragm manhole in a steel box girder bridge. A detailed structural analysis was performed according to various diaphragm manhole shapes, and in conclusion, the suitable reinforcement method for the support of diaphragm manholes in steel box bridges is presented.

• Journal of Korean Society of Steel Construction
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• v.15 no.3
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• pp.231-239
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• 2003

Many box girder bridges have been constructed during the past several decades due to their large bending and torsional rigidities as well as aesthetic considerations. However, box girders have shortcoming in that the cross section distorts under an eccentric loading and warps out of the section plane. Therefore, in order to reduce distortional stresses such as distortional warping and transverse bending normal stresses, diaphragms were generally installed in the box girders. Shapes of the diaphragms in steel-box-girder bridges constructed up to date were solid-plate, frame, and truss types. The objectives of this study using parametric study were to evaluate the appropriate stiffness ratio of intermediate diaphragms and then to propose the effective spacing and numbers of intermediate diaphragms based on the evaluated stiffness ratio. Target bridges for this study were straight continuous span bridges with a single-cell steel box section. The parameters for the parametric study were the shape of box section, the span numbers, the equivalent span length, the stiffness of intermediate diaphragms, and the spacing of intermediate diaphragms. From the results of the parametric study, the effective spacing and numbers as well as the stiffness ratio of the intermediate diaphragms will be presented.

• Journal of Korean Society of Steel Construction
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• v.26 no.4
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• pp.311-322
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• 2014

Concrete filled tubular structure should be installed diaphragms for moment connection. However internal and through diaphragm should be special welded when connected to column tube. The other hand, that has become increase of stress concentration and extend of construction error. Therefore, In this study the seismic performance of beam to column connections with External Diaphragms and implement cycle loading experiment. we had evaluated seismic performance with mentioned experiment which is concrete filled or not, variable shapes, to be welded or not of diaphragm. Also, formula of strength of external diaphragm was analyzed and looked into adequacy with regard to formula of tension strength.

• Elastomers and Composites
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• v.35 no.1
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• pp.4-11
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• 2000

A rubber diaphragm is a critical element of accumulators. The material of a diaphragm is nitrile rubber so as to recover and adjust the large deformation under external pressure fluctuation. The performance of accumulators is influenced by the deformation behaviors of the diaphragm. A large deformation behavior of the diaphragm has been investigated using the commercial finite element program MARC K7.1. The several elastic moduli have been used in linear analysis and Ogden's coefficients have been used in non-linear analysis. As a result, it has been shown that the deformation behavior with a elastic modulus of $0.3 kg/mm^2$ is similar to the behavior of non-linear analysis. And, the modified diaphragm shape to reduce the stress concentration has been proposed.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.6
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• pp.1-10
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• 2013

In this paper, the main cause on excitation of the combustion instability which may occur in the hybrid rocket motor with a diaphragm was studied. Hybrid rocket motor propulsion tests considering various experimental conditions such as with a diaphragm or not, a diameter of diaphragm, oxidizer mass flow rate, fuel length, etc were performed, and the combustion visualization for the inside of a hybrid rocket motor with a diaphragm was performed. With these experimental results, it was confirmed that the main cause of a large excitation was the hole-tone, and it was shown that the hole-tone model can be predicted experimental primary pressure oscillation frequency quite well.