• Journal of Korean Society of Steel Construction
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• v.15 no.6 s.67
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• pp.701-709
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• 2003

The paper presented the seismic performance of T-stiffener moment connections for use in steel moment-resisting frames. The connections were strengthened by welding the vertical and horizontal clement of the T-stiffener to the beam flange and column f1ange. Finite clement analysis and experiments were conducted to determine the behavior of T-stiffener-reinforced connections. The results of the finite element analysis confirmed the effectiveness of the T-stiffener, whose horizontal element lengthened to mitigate local stress concentrations of the beam flange on the horizontal stiffener. Full-scale specimens were also tested cyclically to study hysteresis behavior. The main parameters used were the ratio of the T-stiffener to beam strength and the shape of the horizontal element. As the length of the horizontal element increased, the deformation capacity of the connections enhanced. Likewise, all specimens behaved according to the Ramberg-Osgood curve and showed stable hysteresis behavior.

• Journal of Korean Association for Spatial Structures
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• v.23 no.1
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• pp.15-23
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• 2023

In this work, we deal with the feasibility of structural topology optimization for beam designs using retrofits that optimally allocates the reinforcement to the web under the condition that designers set bolt regions for H-beams of different dimensions. Mean compliance or minimal strain energy is considered for the optimization. Volume fraction is given to the design space to assign appropriate steel material quantities. The purpose of this study is to evaluate optimal shapes of stiffeners with the maximum rigidity that improves the axial and shear performance of the H-beam and to satisfy a given safety design standard of H-beam and stiffeners in case arbitrary load effect and resistances. Finally, the effectiveness of stiffness-based topology optimization on stiffeners is verified with several practical applicable examples.

• Journal of Korean Society of Steel Construction
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• v.16 no.6 s.73
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• pp.781-792
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• 2004

Experiments were performed to study the cyclic behavior of framed steel walls with thin web plates. Five specimens of single-bay and three-story steel plate walls were tested for cyclic lateral load. The parameters for the test specimens included the plate thickness and the column strength. Based on the test results, the strength, deformability, and energy dissipation capacity of the framed steel walls were studied. The test results showed that the behavioral characteristics of the framed steel walls with thin web plates were different in many aspects from those of the conventional braced frame, and the steel wall with a stiffened web plate exhibited cantilever action, high strength, and low ductility. With the framed steel plate walls, local plate buckling and tension-field action developed in the thin web plates, and plastic deformation was uniformly distributed along the wall's height. As a result, the framed steel plate walls exhibited combined flexural and shear deformation, but they also showed high strength and energy dissipation capacity. Moreover, such walls have high deformability, which was equivalent to that of the conventional moment frame. Frame members such as columns and beams, however, must be designed to resist the tension-field action of the thin web plates. If the column does not have sufficient strength, and if its sections are not compact enough, the overall strength of the framed steel wall might be significantly decreased by the development of the soft-story mechanism. The framed steel walls with thin web plates have advantages, such as high deformability and high strength. Therefore, they can be used as ductile elements in earthquake-resistant systems.

• Journal of Korean Society of Steel Construction
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• v.15 no.2
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• pp.167-174
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• 2003

This paper presented the results of cyclic loading tests of 7 full-scale beams to column subassemblages with improved connection detail i.e., fillets of the stiffening plates at the column corners and ends of the stiffener-to-beam flange weld. Major findings from the test results were: (1) Fillets reduced the stress concentrations that may cause early brittle fractures and considerably improved the cyclic performance compared to the detail without fillets. (2) As the width of the stiffening plate increased, the stiffness and peak strength increased and energy dissipation capacity decreased. (3) While all specimens failed by a fracture, they could develop a total rotation of 0.04 radian required for special moment resisting frames.

• Journal of Korean Society of Steel Construction
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• v.14 no.1
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• pp.69-78
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• 2002

This paper describes the analysis results for tensile behavior of tubular column to H-beam connection with T stiffeners. Using the elasto-plastic finite element method, analysis results are compare with experimental results. Parametric analyses with different size of T-stiffener have conducted to understand the stress distribution at the connections. Stress concentration in elastic region and PEEQ distribution in plastic region are plotted for different shape. The results of analysis were applied to design equations and were checked for the applicability of design equations.

• Journal of Korean Society of Steel Construction
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• v.10 no.1 s.34
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• pp.25-35
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• 1998

A moment connection of H beam-to-rectangular tube column with external stiffeners was proposed. A formula to predict the ultimate strength of the connection was derived based on the yield line mechanism. Experimental investigation was performed to determine the applicability of the connection type and the strength formula. The ultimate strengths computed by the formula agreed well with the experimental values.

• Journal of Korean Society of Steel Construction
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• v.27 no.2
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• pp.219-229
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• 2015

An experimental study was performed for thin-walled rectangular concrete-filled tubular (CFT) columns. The present study mainly focused on evaluation of the axial load-carrying capacity of concrete-filled tubular columns using high-strength steel and slender section. The test parameters were width-to-thickness ratio, concrete strength, steel yield strength, and the use of stiffeners. Five specimens were tested under monotonic axial loading. Although elastic local buckling occurred in the slender-section specimens with high-strength steel, the specimens exhibited considerable post-buckling reserve. The test results also satisfied the predictions of a current design code. The specimens strengthened with vertical stiffeners exhibited improved strength and ductility when compared with the un-stiffened specimens.

• Journal of Korean Society of Steel Construction
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• v.21 no.3
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• pp.257-266
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• 2009

The results of the analysis of the structural behavior of diagrid nodes that were subjected to cyclic loads such as wind and earthquakes was not fully understood due to difficulties in considering the welding type. In this study, diagrid nodes were tested to determine their behavior when they are subjected to seismic or wind loads. Five specimens were designed and fabricated. The corresponding test parameters were the welding type for each point and the length of the overlap of the side stiffener and the brace web. Tensile force was applied to one diagrid brace member, and compression force was applied to the other diagrid brace member. Cyclic loading was applied until the failure. The test showed that failures are due to axial stress from axial force and the additional bending moment of the two combined axial forces that have different directions. Tensile failure was observed from the tensile force, and local buckling was observed from the compressive force at the flange of the brace member. In addition, the welding type and the length overlap affected the initial stiffness, the yielding stress, and the energy absorption of the diagrid node.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.1
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• pp.65-72
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• 2013

This case study presents a practical method to reduce resonant vibration of large vertical pumps. The pumps are driven at 400 rpm rated speed by induction motor. The vibration was not significantly large when operated at this rated speed. Large vibration was occurred when the pump was operated below the rated speed for flow control. Due to the large vibration resonance, variable speed operation of the pump was not possible for several months at worst cases. To find an efficient vibration control method, the flexural responses of pumps for both normal and transient operations were measured. The measured modal characteristics were compared with those of finite element analysis. When the pump was operated at a specific rpm, the natural mode whose resonance frequency is twice the rotating angular speed induced the large vibration. The retrofit utilizing stiffeners to reduce this resonant vibration were performed. Effects of designed stiffeners on reducing vibration were validated through tests after actual installation.

• Journal of Korean Society of Steel Construction
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• v.28 no.2
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• pp.75-83
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• 2016

Existing tubes for concrete filled tubular structure are made through welding of four plates irrespective, but the production performance is poor and special welding technique is needed to weld the internal or through diaphragm. Accordingly, We developed a welded built-up square steel tube having a welding lines and a stiffeners at location out of stress concentration. The welded built-up square steel tube occurred a interference with stiffeners at the internal or through diaphragm, therefore researches of a external diaphragm for welded built-up square CFT column connections are needed for the purpose of avoidance of a interfere with stiffeners. In this study we suggest a design formulation for external diaphragm of the welded built-up square CFT external diaphragm connections. Four specimens were manufactured for a experimental test, then we analyzed the behaviors of the specimens.