• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.8
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• pp.856-863
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• 2008

High-rise apartments of shear wall system are governed by flexural behavior like a cantilever beam. Installation of the damper-brace system in a structure governed by flexural behavior is not suitable. Because of relatively high lateral stiffness of the shear wall, a load is not concentrate on the brace and the brace cannot perform a role as a damping device. In this paper, a friction damper applying flexibility of shear wall is proposed in order to reduce the deformation of a structure. To evaluate performance of the proposed friction damper, nonlinear time history analysis is executed by SeismoStruct analysis program and MVLEM(multi vertical linear element model) be used for simulating flexural behavior of the shear wall. It is found that control performance of the proposed friction damper is superior to one of a coupled wall with rigid beam. In conclusion, this study verified that the optimal control performance of the proposed friction damper is equal to 45 % of the maximum shear force inducing in middle-floor beam with rigid beam.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.3
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• pp.267-279
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• 2004

A modelling scheme for the stress analysis taking into account load transfer characteristics of the osseointegrated interfaces between dental implant and surrounding alveolar bone was investigated. Main aim was to develop a more realistic simulation methodology for the load transfer at the interfaces than the prefect bonding assumption at the interfaces which might end up the reduced level in the stress result. In the present study, characteristics of osseointegrated bone/implant interfaces was modelled with material nonlinearity assumption. Bones at the interface were given different stiffness properties as functions of stresses. Six different models, i.e. tens0, tens20, tens40, tens60, tens80, and tens100 of which the tensile moduli of the bones forming the bone/implant interfaces were specified from 0, 20, 40, 60, 80, and 100 percents, respectively, of the compressive modulus were analysed. Comparisons between each model were made to study the effect of the tensile load carrying abilities, i.e. the effectivity of load transfer, of interfacial bones on the stress distribution. Results of the present study showed significant differences in the bone stresses across the interfaces. The peak stresses, however, were virtually the same regardless of the difference in the effectivity of load transfer, indicating the conventional linear modelling scheme which assumes perfect bonding at the bone/implant interface can be used without causing significant errors in the stress levels.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.353-356
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• 1997

Hydraulically driven manipulators are superior to electrically driven ones in the power density and electrical insulation. But an electro-hydraulic manipulator using hydraulic actuators has many nonlinear elements, and this parameter fluctuations are greater than those of electrically driven manipulator. So this is relatively difficult to realize not only stable contact work but also accurate force control for the autonomous field task such as the maintenance task of high voltage active electric line or the automatic excavation task by hydraulic excavator. In this report, we propose robust force control algorithm, which can be applied to there real field task such as the construction field, nuclear plant and so on. Proposed force controller has the same structure as that of disturbance observe for position control. The difference between force and position disturbance observer is that the input and output of disturbance observer are forces in the case force disturbance observer and the plant varies much compared to the case of position control. In the design of force disturbance observer, generalized plant is derived and the stabilized filter is designed by H infinity control theory to ensure the robuts t stability even though the stiffness of environment changes from sponge to steel, and the contact surface also changes from flat to round shape. Experimental results show that highly robust force tracking by a 6-link electro-hydraulic manipulator could be achieved under various environment conditions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.661-666
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• 2000

Optimization of the elastic joint of train is performed according to the minimization of ten responses which represent driving safety and ride comfort of train and analyzed by using the each response se surface model from stochastic design of experiments. After the each response surface model is constructed, the main effect and sensitivity analyses are successfully performed by 2nd order approximated regression model as described in this paper. We can get the optimal solutions using by nonlinear programming method such as simplex or interval optimization algorithms. The response surface models and the optimization algorithms are used together to obtain the optimal design of the elastic joint of train. the ten 2nd order polynomial response surface models of the three translational stiffness of the elastic joint (design factors) are constructed by using CCD(Central Composite Design) and the multi-objective optimization is also performed by applying min-max and distance minimization techniques of relative target deviation.

• Steel and Composite Structures
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• v.6 no.1
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• pp.33-53
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• 2006

The rotational behaviour of bolted extended end plate beam-to-column connections is evaluated in the context of the component method. The full moment-rotation response is characterized from the force-deformation curve of the individual joint components. The deformability of end plate connections is mostly governed by the bending of the column flange and/or end plate and tension elongation of the bolts. These components form the tension zone of the joint that can be modelled by means of "equivalent T-stubs". A systematic analytical procedure for characterization of the monotonic force-deformation behaviour of individual T-stub connections is proposed. In the framework of the component method, the T-stub is then inserted in the joint spring model to generate the moment-rotation response of the joint. The procedures are validated with the results from an experimental investigation of eight statically loaded extended end plate bolted moment connections carried out at the Delft University of Technology. Because ductility is such an important property in terms of joint performance, particularly in the partial strength joint scenario, special attention is given to this issue.

• Structural Engineering and Mechanics
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• v.58 no.6
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• pp.949-966
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• 2016

The second order analysis taking place due to non-linear behavior of the structures under the mechanical and geometric factors through implementing exact and approximate methods is an indispensible issue in the analysis of such structures. Among the exact methods is the slope-deflection method that due to its simplicity and efficiency of its relationships has always been in consideration. By solving the differential equations of the modified slope-deflection method in which the effect of axial compressive force is considered, the stiffness matrix including trigonometric entries would be obtained. The complexity of computations with trigonometric functions causes replacement with their Maclaurin expansion. In most cases only the first two terms of this expansion are used but to obtain more accurate results, more elements are needed. In this paper, the effect of utilizing higher order terms of Maclaurin expansion on reducing the number of required elements and attaining more rapid convergence with less error is investigated for the Bernoulli beam with various boundary conditions. The results indicate that when using only one element along the beam length, utilizing higher order terms in Maclaurin expansion would reduce the relative error in determining the critical buckling load and kinematic parameters in the second order analysis.

• Structural Engineering and Mechanics
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• v.57 no.4
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• pp.617-639
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• 2016

In this work, an analytical formulation based on both hyperbolic shear deformation theory and stress function, is presented to study the nonlinear post-buckling response of symmetric functionally graded plates supported by elastic foundations and subjected to in-plane compressive, thermal and thermo-mechanical loads. Elastic properties of material are based on sigmoid power law and varying across the thickness of the plate (S-FGM). In the present formulation, Von Karman nonlinearity and initial geometrical imperfection of plate are also taken into account. By utilizing Galerkin procedure, closed-form expressions of buckling loads and post-buckling equilibrium paths for simply supported plates are obtained. The effects of different parameters such as material and geometrical characteristics, temperature, boundary conditions, foundation stiffness and imperfection on the mechanical and thermal buckling and post-buckling loading capacity of the S-FGM plates are investigated.

• Steel and Composite Structures
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• v.21 no.3
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• pp.479-500
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• 2016

Seismic design criteria allow enhancing the structural ductility and controlling the damage distribution. Therefore, detailing rules and design requirements given by current seismic codes might be also beneficial to improve the structural robustness. In this paper a comprehensive parametric study devoted to quantifying the effectiveness of seismic detailing for steel Moment Resisting Frames (MRF) in limiting the progressive collapse under column loss scenarios is presented and discussed. The overall structural performance was analysed through nonlinear static and dynamic analyses. With this regard the following cases were examined: (i) MRF structures designed for wind actions according to Eurocode 1; (ii) MRF structures designed for seismic actions according to Eurocode 8. The investigated parameters were (i) the number of storeys; (ii) the interstorey height; (iii) the span length; (iv) the building plan layout; and (v) the column loss scenario. Results show that structures designed according to capacity design principles are less robust than wind designed ones, provided that the connections have the same capacity threshold in both cases. In addition, the numerical outcomes show that both the number of elements above the removed column and stiffness of beams are the key parameters in arresting progressive collapse.

• Steel and Composite Structures
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• v.9 no.6
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• pp.569-584
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• 2009

Corrosion of steel rebars in bridge decks which are faced to harsh conditions, is a common problem in construction industries due to the porosity of concrete. In this research, the behavior of one-way concrete slabs reinforced with Glass fiber reinforced polymer (GFRP) molded grating is investigated both theoretically and experimentally. In the analytical method, a closed-form solution for load-deflection behavior of a slab under four-point bending condition is developed by considering a concrete slab as an orthotropic plate and defining stiffness coefficients in principal directions. The available formulation for concrete reinforced with steel is expanded for concrete reinforced with GFRP molded grating to predict ultimate failure load. In finite element modeling, an exact nonlinear behavior of concrete along with a 3-D failure criterion for cracking and crushing are considered in order to estimate the ultimate failure load and the initial cracking load. Eight concrete slabs reinforced with steel and GFRP grating in various thicknesses are also tested to verify the results. The obtained results from the models and experiments are relatively satisfactory.

• Steel and Composite Structures
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• v.7 no.3
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• pp.219-240
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• 2007

An analytical-numerical procedure has been presented in this paper to take into account the nonlinear effects of concrete cracking and time-dependent effects of creep and shrinkage in the concrete portion of the continuous composite beams under service load. The procedure is analytical at the element level and numerical at the structural level. The cracked span length beam element consisting of uncracked zone in middle and cracked zones near the ends has been proposed to reduce the computational effort. The progressive nature of cracking of concrete has been taken into account by division of the time into a number of time intervals. Closed form expressions for stiffness matrix, load vector, crack lengths and mid-span deflection of the beam element have been presented in order to reduce the computational effort and bookkeeping. The procedure has been validated by comparison with the experimental and analytical results reported elsewhere and with FEM. The procedure can be readily extended for the analysis of composite building frames where saving in computational effort would be very considerable.