• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.2
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• pp.95-102
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• 2020

Electrical instruments and devices contained in cabinets for controlling nuclear power plants require seismic qualification; likewise, in-cabinet response spectrum (ICRS) is necessary. Gupta et al. (1999) suggested the Ritz method, where rocking, frame bending, and plate bending behaviors of cabinets are considered, as a method for determining ICRS. This research proposes a method to determine the rocking stiffness of cabinets, which represents its rocking behavior. The cabinet is fixed on mounting frames and is connected to the base concrete by anchors. When horizontal excitation is applied to the cabinet, the mounting frames at anchors are locally deformed, the mounting frames are bent, and then rocking in the cabinet becomes evident. A method to determine equivalent vertical spring stiffness representing the local deformation of the mounting frames at anchors is then proposed. Subsequently, the rocking stiffness of this mounting frame is calculated upon assumption of the mounting frame as an indeterminate beam.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.37-44
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• 2020

This research aimed to propose the more proper equation than the leading and existing equations to predict the optimum location of offset outrigger. In this study, a 79 existing models of offset outrigger system were examined. And the key factors in the existing offset outrigger models were the stiffness of shear wall and offset outrigger system, the stiffness of exterior column connected in offset outrigger, the frame stiffness, the ratios of lateral stiffness of frame in shear wall-frame structures, and all that. This paper proposed the modified equation of predicting the optimal location of offset outrigger system. Additionally, the findings of this study provided the important structure engineering materials of the optimal offset outrigger position in tall building.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.5955-5962
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• 2014

Generally, the frame design of a vehicle is a critical technology that plays an important role in the racing and high performance sports car market. The high performance of race car frame means that it requires high torsional stiffness because it directly affects the cornering behavior of the race car. The optimal design for the frame of a low-cost single seat race car was carried out using the DOE (Design Of Experiments) with Taguchi's orthogonal array and FEM (Finite Element Method) analysis to secure sufficient torsional stiffness in this paper. According to the results by DOE and FEM analysis, the optimal design case produced improved 10.7% and 14.5% improvement in each stiffness-to-weight ratio and frame weight than in the early design step. Therefore, this paper shows that the optimal design with Taguchi's orthogonal array is very useful and effective for designing a tubular space frame of a low-cost single seat race car in the early design step.

• Structural Engineering and Mechanics
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• v.51 no.3
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• pp.471-485
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• 2014

Until now, the finite corner stiffness of the right-angle frames used as horizontal girders in a bonnet, have not been considered during the design process to result in not a precise result. This paper presents a design equation set for right-angle frames used as horizontal girders in a bonnet assuming rigid corner stiffness. By comparing the center stresses of the right-angle frame according to the design equation set with the results of the finite element method, the master curves for the empirical corner stiffness can be determined as a function of slenderness ratio. A second design equation set for a right-angle frame assuming finite corner stiffness was derived and compared with the first equation set. The master curves for the corner stiffness and the second design equation set can be used to determine the design moments at the centers of the girder so that the bending stresses can be analyzed more precisely.

• Journal of the Korean Society of Safety
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• v.15 no.2
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• pp.22-30
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• 2000

The sub-frame of passenger car begins to be used widely for the safety of passengers. Conventional design of the sub-frame comprises 22parts, and it requires quite complicated production processes. In this papers, the sub-frame is designed with TWB(Tailor Welded Blanks) to improve stiffness, to reduce weight and to simplify the manufacturing process. To design the proper structure, structural analysis and crash analysis are executed about the conventional design and TWB applied design. A prototype TWB applied sub-frame is manufactured using mash-seam welded TB(Tailored Blanks). Comparing with the conventional sub-frame, the TWB applied sub-frame has 30% weight reduction and 17% increasement of structural stiffness in average.

• Structural Engineering and Mechanics
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• v.61 no.4
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• pp.511-518
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• 2017

This paper presents an experimental investigation on the contribution of RCC strip in the in-filled RC frames. In this research, two frames were tested to study the behavior of retrofitted RC frame under cyclic loading. In the two frame, one was three bay four storey R.C frame with central bay brick infill with RCC strip in-between brick layers and the other was retrofitted frame with same stiffened brick work. Effective rehabilitation is required some times to strengthened the RC frames. Ferrocement concrete strengthening was used to retrofit the frame after the frame was partially collapsed. The main effects of the frames were investigated in terms of displacement, stiffness, ductility and energy dissipation capacity. Diagonal cracks in the infill bays were entirely eliminated by introducing two monolithic RCC strips. Thus more stability of the frame was obtained by providing RCC strips in the infill bays. Load carrying capacity of the frame was increased by enlarging the section in the retrofitted area.

• Transactions of Materials Processing
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• v.20 no.2
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• pp.104-109
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• 2011

The metal front case of a mobile phone is manufactured by press forming and welding of thin metal sheets. Twisting of the frame after the forming process is one of main obstacle for the assembly with reinforcement by welding. This study introduces a method preventing twisting of the metal front case frame in press forming. The spring-back after forming produces twisting of the frame, which leads to a low structural stiffness. To reduce twisting, connectors are required to reinforce the structural stiffness of the frame. In this study, the twisting profile is evaluated using a finite element(FE) analysis for various connector shapes. The actual connector shape is determined by minimization of the frame twisting within the tolerance of the FE-analysis. To verify the validity of the proposed blank shape, a forming experiment is performed and the twisting profile is measured using a 3D laser scanning method. The dimensional accuracy is found to be within the tolerance and in good agreement with the FE-analysis.

• Structural Engineering and Mechanics
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• v.9 no.3
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• pp.241-256
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• 2000

The major sources of energy dissipation in steel frames with partially restrained (PR) connections are evaluated. Available experimental results are used to verify the mathematical model used in this study. The verified model is then used to quantify the energy dissipation in PR connections due to hysteretic behavior, due to viscous damping and at plastic hinges if they are formed. Observations are made for two load conditions: a sinusoidal load applied at the top of the frame, and a sinusoidal ground acceleration applied at the base of the frame representing a seismic loading condition. This analytical study confirms the general behavior, observed during experimental investigations, that PR connections reduce the overall stiffness of frames, but add a major source of energy dissipation. As the connections become stiffer, the contribution of PR connections in dissipating energy becomes less significant. A connection with a T ratio (representing its stiffness) of at least 0.9 should not be considered as fully restrained as is commonly assumed, since the energy dissipation characteristics are different. The flexibility of PR connections alters the fundamental frequency of the frame. Depending on the situation, it may bring the frame closer to or further from the resonance condition. If the frame approaches the resonance condition, the effect of damping is expected to be very important. However, if the frame moves away from the resonance condition, the energy dissipation at the PR connections is expected to be significant with an increase in the deformation of the frame, particularly for low damping values. For low damping values, the dissipation of energy at plastic hinges is comparable to that due to viscous damping, and increases as the frame approaches failure. For the range of parameters considered in this study, the energy dissipations at the PR connections and at the plastic hinges are of the same order of magnitude. The study quantitatively confirms the general observations made in experimental investigations for steel frames with PR connections; however, proper consideration of the stiffness of PR connections and other dynamic properties is essential in predicting the dynamic behavior.

• Journal of the Earthquake Engineering Society of Korea
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• v.17 no.3
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• pp.127-132
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• 2013

This study proposed proposes a retrofitting method using an H-beam frame to improve the seismic performance of non-seismic designed reinforced concrete frames. To evaluate the seismic performance with the H-beam frames, a cyclic lateral load test was performed and the experimental result was compared with the bared frame, and a masonry infilled RC frame. The results was were analyzed regarding aspects of the load-displacement hysteresis behavior, effective stiffness, displacement ductility, and cumulative energy dissipation. AlsoIn addition, it was possible to prove both an increase of in the maximum load capacity, effective stiffness, and energy dissipation capacity using the H-beam frame.

• Structural Engineering and Mechanics
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• v.70 no.4
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• pp.421-429
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• 2019

This paper presents an analytical model for the estimation of initial lateral stiffness of steel moment resisting frames with masonry infills. However, rather than focusing on the single bay-single storey substructure, the developed model attempts to estimate the global stiffness of multi-storey and multi-bay frames, using an assembly of equivalent springs and taking into account the shape of the lateral loading pattern. The contribution from each infilled frame panel is included as an individual spring, whose properties are determined on the basis of established diagonal strut macro-modeling approaches from the literature. The proposed model is evaluated parametrically against numerical results from frame analyses, with varying number of frame stories, infill openings, masonry thickness and modulus of elasticity. The performance of the model is evaluated and found quite satisfactory.