• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.5 s.51
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• pp.25-33
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• 2006

This paper provides a method to predict the ductile capacity of reinforced concrete beam-column joints that fail in shear after the plastic hinges occur at both ends of the adjacent beams. After the plastic hinges occur at both ends of the beams, the longitudinal axial strain at the center of the beam section in the plastic hinge region abruptly increases because the neutral axis continues to move upward toward the extreme compressive fiber and the residual strain of the longitudinal bars continues to increase with each cycle of inelastic loading. An increase in the axial strain of the beam section after flexural yielding widens the cracks in the beam-column joints, thus leading to an decrease of the shear strength of the beam-column joints. The proposed method takes into account shear strength deterioration in the beam-column joints. In order to verify the shear strength and the corresponding ductility of the proposed method, test results of 52 RC beam-column assembles were compared. Comparisons between the observed and calculated shear strengths and their corresponding ductilities of the tested assembles, showed reasonable agreement.

• Steel and Composite Structures
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• v.36 no.4
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• pp.399-415
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• 2020

Responses of semi-rigid frames having different degrees of semi-rigidity obtained by the nonlinear static analysis (NSA) are evaluated at specific target displacements by comparing them with those obtained by the nonlinear time-history analysis (NTHA) for scaled earthquakes. The peak ground accelerations (PGA) of the earthquakes are scaled such that the obtained peak top story displacements match with the target displacements. Three different types of earthquakes are considered, namely, far-field and near-field earthquakes with directivity and fling-step effects. In order to make the study a comprehensive one, three degrees of semi-rigidity (one fully rigid and the other two semi-rigid), and two frames having different heights are considered. An ensemble of five-time histories of ground motion is included in each type of earthquake. A large number of responses are considered in the study. They include the peak top-story displacement, maximum inter-story drift ratio, peak base shear, total number of plastic hinges, and square root of sum of the squares (SRSS) of the maximum plastic hinge rotations. Results of the study indicate that the nonlinear static analysis provides a fairly good estimate of the peak values of top-story displacements, inter-story drift ratio (for shorter frame), peak base shear and number of plastic hinges; however, the SRSS of maximum plastic hinge rotations in semi-rigid frames are considerably more in the nonlinear static analysis as compared to the nonlinear time history analysis.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.4
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• pp.476-490
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• 2016

This paper defines mode shape function of a composite solar panel assumed as Kirchhoff-Love plate for considering a torsional mode of composite solar panel. It then goes on to define dynamic model of a high-agility satellite considering the flexibility of composite solar panel as well as stiffness of a solar panel's hinge using Lagrange's theorem, Ritz method and the mode shape function. Furthermore, this paper verifies the validity of dynamic model by comparing numerical results from the finite element analysis. In addition, this paper performs a dynamic response analysis of a rigid satellite which includes only natural modes for solar panel's hinges and a flexible satellite which includes not only natural modes of solar panel's hinges, but also structural modes of composite solar panels. According to the results, we confirm that the torsional mode of solar panel should be considered for the structural design of high-agility satellite. Finally, we performed optimization of high-agility satellite for minimizing mass with solar panel's area limit using the defined dynamic model. Consequently, we observed that the defined dynamic model for a high-agility satellite and result of the optimal design are very useful not only because of their optimal structural design but also because of the dynamic analysis of the satellite.

• Structural Engineering and Mechanics
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• v.39 no.3
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• pp.427-447
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• 2011

The progressive collapse phenomenon is generally regarded as dynamic. Due to the impracticality of nonlinear dynamic computations for practitioners, an interest arises for the development of equivalent static pushover procedures. The present paper proposes a methodology to identify such a procedure for sudden column removals, using energetic evaluations to determine the pushover loads to apply. In a dynamic context, equality between the cumulated external and internal works indicates a vanishing kinetic energy. If such a state is reached, the structure is sometimes assumed able to withstand the column removal. Approximations of these works can be estimated using a static computation, leading to an estimate of the displacements at the zero kinetic energy configuration. In comparison with other available procedures based on such criteria, the present contribution identifies loading patterns to associate with the zero-kinetic energy criterion to avoid a single-degree-of-freedom idealisation. A parametric study over a family of regular steel structures of varying sizes uses non-linear dynamic computations to assess the proposed pushover loading pattern for the cases of central and lateral ground floor column failure. The identified quasi-static loading schemes are shown to allow detecting nearly all dynamically detected plastic hinges, so that the various beams are provided with sufficient resistance during the design process. A proper accuracy is obtained for the plastic rotations of the most plastified hinges almost independently of the design parameters (loads, geometry, robustness), indicating that the methodology could be extended to provide estimates of the required ductility for the beams, columns, and beam-column connections.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.2 s.48
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• pp.11-19
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• 2006

In this paper the seismic performances of 4, 10, and 30-story staggered truss systems (STS) were evaluated by observing the force-displacement relationship up io failure. The results were compared with the seismic performance of conventional moment resisting frames and braced frames. According to the analysis results, the STS showed relatively satisfactory lateral load resisting capability. However, in the mid- to high-rise STS, plastic hinges formed first at the chords were transferred to vertical members of the vierendeel panels, which formed a week link and subsequently leaded to brittle collapse of the structure. Therefore to enhance the ductility of STS it would be necessary to reinforce the vertical bracing members of the virendeel panels so that the plastic hinges, once toned in cord members of a virendeel panel, spread out to virendeel panels of neighboring stories.

• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.441-448
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• 2007

The beam-column assembly in a ductile reinforced concrete (RC) frames subjected to seismic loading are generally controlled by shear and bond mechanisms, both of which exhibit poor hysteretic properties. Hence the response of joints is restricted essentially to the elastic domain. The usual earthquake resistant design philosophy of ductile frame buildings allows the beams to form plastic hinges adjacent to beam-column assembly. Increased strain in these plastic hinge regions affect on joint strain to be increased. Thus bond and shear joint strength are decreased. The research reported in this paper presents the test results of five RC beam-column assembly after developing plastic hinges in beams. Main parameter of the test Joints was the amount of the longitudinal tensile reinforcement of the beams. Test results indicted that the ductile capacity of joints increased as the longitudinal tensile reinforcement of the beams decreased. In addition, both the tensile strain of the longitudinal reinforcement bars in the joint and the ductile ratio of the beam-column assemblages increased due to the yielding of steel bars in the plastic hinge regions.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.2
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• pp.89-96
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• 2020

In this study, we developed a finite element model for the built-in bottom-freezer type refrigerator and then used the structural analysis method to analyze and evaluate the deflection of the doors. We tested the validity of the developed analytical model by measuring the deflection of the hinge when loads were applied to the upper and lower hinges of the refrigerating compartment and compared these with the analysis results. The comparison of the vertical displacement of the measured result and the analysis result showed an error ratio of up to 12.8%, which indicates that the analytical model is consistent. Using the analytical model composed of the cabinet, hinges and doors, we performed analyses for two cases: both doors closed, and the refrigerating door open. Since the maximum vertical displacement of the refrigerating compartment door (R-door) with the food load is smaller than the gap between the lower surface of the R-door and the upper surface of the freezer compartment door (F-door), it is judged that the R-door and the F-door do not contact when the doors are opened or closed. In addition, the analysis result showed that the difference between the vertical displacement at the hinge on the opposite side and the hinge side of the R-door is favorably smaller than the management criterion of the refrigerator manufacturer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.1
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• pp.71-78
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• 2014

Door hinges of large refrigerators are required to ensure that the doors open and close smoothly in addition to supporting door weights and enduring the impact loads due to door opening and closing. However, door hinge design is difficult because of complex hinge mechanisms and sensitive structural safety. In this study, the mechanism satisfying the required spring response, space constraints, and structural strength is optimized, and the volume of the outer frame covering the hinge mechanism is minimized for reducing production costs. The entire design process is automated using the PIDO(Progress Integration and Design Optimization) technique, which achieves an efficient design process. Therefore, the frame mass is reduced to 24%, and the mechanism performance and structural stability are improved.

• Structural Engineering and Mechanics
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• v.66 no.2
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• pp.217-227
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• 2018

In the last decades, valuable results have been reported regarding conventional passive, active, semi-active, and hybrid structural control systems on two-dimensional and a few three-dimensional shear buildings. In this research, using a three-dimensional finite element model of high-rise concrete structures, designed by performance based plastic design method, it was attempted to construct a relatively close to reality model of concrete structures equipped with Tuned Mass Damper (TMD) by considering the effect of soil-structure interaction (SSI), torsion effect, hysteresis behavior and cracking effect of concrete. In contrast to previous studies which have focused mainly on linearly designed structures, in this study, using performance-based plastic design (PBPD) design approach, nonlinear behavior of the structures was considered from the beginning of the design stage. Inelastic time history analysis on a detailed model of twenty-story concrete structure was performed under a far-field ground motion record set. The seismic responses of the structure by considering SSI effect are studied by eight main objective functions that are related to the performance of the structure, containing: lateral displacement, acceleration, inter-story drift, plastic energy dissipation, shear force, number of plastic hinges, local plastic energy and rotation of plastic hinges. The tuning problem of TMD based on tuned mass spectra is set by considering five of the eight previously described functions. Results reveal that the structural damage distribution range is retracted and inter-story drift distribution in height of the structure is more uniform. It is strongly suggested to consider the effect of SSI in structural design and analysis.

• Structural Engineering and Mechanics
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• v.38 no.6
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• pp.697-714
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• 2011

Assessing the ductility of reinforced concrete sections and members has been a complex and intractable problem for many years. Given the complexity in estimating ductility, members are often designed specifically for strength whilst ductility is provided implicitly through the use of ductile steel reinforcing bars and by ensuring that concrete crushing provides the ultimate limit state. As such, the empirical hinge length and neutral axis depth approaches have been sufficient to estimate ductility and moment redistribution within the bounds of the test regimes from which they were derived. However, being empirical, these methods do not have a sound structural mechanics background and consequently have severe limitations when brittle materials are used and when concrete crushing may not occur. Structural mechanics based approaches to estimating rotational capacities and rotation requirements for given amounts of moment redistribution have shown that FRP plated reinforced concrete (RC) sections can have significant moment redistribution capacities. In this paper, the concept of moment redistribution in beams is explained and it is shown specifically how an existing RC member can be retrofitted with FRP plates for both strength and ductility requirements. Furthermore, it is also shown how ductility through moment redistribution can be used to maximise the increase in strength of a member. The concept of primary and secondary hinges is also introduced and it is shown how the response of the non-hinge region influences the redistribution capacity of the primary hinges, and that for maximum moment redistribution to occur the non-hinge region needs to remain elastic.