• Journal of Mechanical Science and Technology
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• v.19 no.9
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• pp.1761-1772
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• 2005

In blood flow passing through the mechanical heart valve (MHV) and elastic blood vessel, hemolysis and platelet activation causing thrombus formation can be seen owing to the shear stress in the blood. Also, fracture and deformation of leaflets can be observed depending on the shape and material properties of the leaflets which is opened and closed in a cycle. Hence, comprehensive study is needed on the hemodynamics which is associated with the motion of leaflet and elastic blood vessel in terms of fluid-structure interaction. In this paper, a numerical analysis has been performed for a three-dimensional pulsatile blood flow associated with the elastic blood vessel and curved bileaflet for multiple cycles in light of fluid-structure interaction. From this analysis fluttering phenomenon and rebound of the leaflet have been observed and recirculation and regurgitation have been found in the flow fields of the blood. Also, the pressure distribution and the radial displacement of the elastic blood vessel have been obtained. The motion of the leaflet and flow fields of the blood have shown similar tendency compared with the previous experiments carried out in other studies. The present study can contribute to the design methodology for the curved bileaflet mechanical heart valve. Furthermore, the proposed fluid-structure interaction method will be effectively used in various fields where the interaction between fluid flow and structure are involved.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.4
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• pp.427-435
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• 2009

This study deals with the analytical solution for soil-lining interaction in a deep and circular tunnel. Simple closed-form analytical solutions for thrust and moment in the circular tunnel lining due to static and seismic loadings are developed by considering the relations between displacement and interaction forces at the soil-lining interface. The interaction effect at the soil-lining interface is considered with new ratios (the normal and shear stiffness ratios). The effects of the ratios on the normalized thrust and the normalized moment are investigated.

• Steel and Composite Structures
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• v.15 no.3
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• pp.323-342
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• 2013

In the case of seismic-resistant composite dual moment resisting and eccentrically braced frames, the current design practice is to avoid the disposition of shear connectors in the expected plastic zones, and consequently to consider a symmetric moment or shear plastic hinges, which occur only in the steel beam or link. Even without connectors, the real behavior of the hinge may be different from the symmetric assumption since the reinforced concrete slab is connected to the steel element close to the hinge locations, and also due to contact friction between the concrete slab and the steel element. At a larger level, the structural response in the case of important seismic motions depends directly on the elasto-plastic behavior of elements and hinges. The numerical investigation presented in this study summarizes the results of elasto-plastic analyses of several steel frames, considering the interaction of the steel beam with the concrete slab. Several parameters, such as the inter-story drift, plastic rotation requirements and behavior factors q were monitored. In order to obtain accurate results, adequate models of plastic hinges are proposed for both the composite short link and composite reduced beam sections.

• Geomechanics and Engineering
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• v.19 no.6
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• pp.533-542
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• 2019

Geosynthetic reinforced soil method in coarse-grained soils has been widely used in last decades. Two effective factors on soil-geosynthetic interaction are confining stresses and loading rate in clay. In terms of methodology, one pull-out test with four different strain rates, namely 0.75, 1.25, 1.75 and 2.25 mm/min, and three different normal stresses equal to 20, 50, and 80 kg have been performed on specimens with dimensions of 30×30×17 cm in the saturated, consolidated condition. The obtained results have demonstrated that activation of geosynthetic strength at contact surface depends on the applied stress. In addition, the increase in normal stress would increase the shear strength at contact surface between clay and geogrid. Moreover, it is concluded that the strain rate increment would increase the shear strength.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.7
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• pp.918-927
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• 1999

In the fully developed internal flow fields, there are complex transition flows caused by interaction of the cross flow and jet when jet is Injected Into the flow. These interactions are studied by means of the flow visualization methods. An instantaneous laser tomographic method is used to reveal the physical mechanism and the structure of vortices formation in the branch pipe flow. The velocity range of cross flow of the pipe is 0.7m/s and the corresponding Reynolds number $R_{cf}$, based on the duct height is $5.6{\times}10^3$, diameter/height ratios(d/H) 0.14 and velocity ratios 3.0. Oil mist with the size of $10{\mu}m$ diameter is used for the scattering particle. The instantaneous topological features of the vortex ring roll-up of the jet shear layer and characteristics of this flow are studied in detail by performing flow visualization in rectangular duct flow. It is found that the formation and roll-up of ring vortices is a periodic phenomenon. The detailed topology of the vortices in the near field of a cross -flow jet and the mechanism associated with them give enforced hints of vortex breakdown within the vortex system due to the interaction of the jet and the cross-flow.

• Membrane Journal
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• v.7 no.3
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• pp.150-156
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• 1997

The particle back transport velocity from the membrane surface were evaluated to determine the critical flux. Four kinds of back transport mechanisms were considered, i.e. back diffusion, shear induced migration, lateral migration, and interaction enhanced migration. The interaction enhanced migration caused by electrostatic repulsion between particles and membrane surface was found to be the most important mechanism of particle back transport for the charged particles of 0.1 ~10${\mu}{\textrm}{m}$ diameter with 20 to 40 mV of zeta potential. Hematite particles with different sizes were synthesized with ferric chloride (FeCl$_3$) and hydrochloric acid (HCl) at high temperature, and subsequently experimental critical fluxes for each sized particle were obtained. The experimental results were well coincident with the calculated critical fluxes based on back transport mechanisms.

• Steel and Composite Structures
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• v.38 no.4
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• pp.463-476
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• 2021

The concept of using Steel-concrete (SC) composite walls as retaining walls has recently been introduced by the authors and their effectiveness of resisting out-of-plane loads has also been demonstrated. In this paper, an improved analytical formulation based on partial interaction theory, which has previously been developed by the authors, is presented. The improved formulation considers a new loading condition and also accounts for cracking in concrete to simulate the real conditions. Due to a limited number of test specimens, further finite element (FE)simulations are performed in order to verify the analytical procedure in more detail. It is observed that the results from the improved analytical procedure are in excellent agreement with both experimental and numerical results. Moreover, a detailed parametric study is conducted using the developed FE model to investigate effects of different parameters, such as distance between shear connectors, shear connector length, concrete strength, steel plate thickness, concrete cover thickness, wall's width to thickness ratio, and wall's height to thickness ratio, on the behavior of SC composite walls subjected to out-of-plane loads.

• Steel and Composite Structures
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• v.42 no.2
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• pp.191-207
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• 2022

Undoubtedly, the employment of direct bond interaction between steel and concrete is preceding the other mechanisms because of its ease of construction. However, the large scatter in the experimental data about the issue has hindered the efforts to characterize bond strength. In the following research, the direct bond interaction and bond-slip behavior of CFTs with circular cross-section were examined through repeated load-reversed push-out tests until four cycles of loading. The influence of different parameters including the diameter of the tube and the use of shear tabs were assessed. Moreover, the utilization of expansive concrete and external spirals was proposed and tested as ways of improving bond strength. According to the results section dimensions, tube slenderness, shrinkage potential of concrete, interface roughness and confinement are key factors in a natural bond. Larger diameters will lead to a considerable drop in bond strength. The use of shear tabs by their associated bending moments increases the bond stress up to eight times. Furthermore, employment of external spirals and expansive concrete have a sensible effect on enhancing bonds. Macro-locking was also found to be the main component in achieving bond strength.

• Geomechanics and Engineering
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• v.34 no.5
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• pp.529-545
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• 2023

The coupled soil-pile-structure seismic response is recently in the spotlight of researchers because of its extensive applications in the different fields of engineering such as bridges, offshore platforms, wind turbines, and buildings. In this paper, a simple analytical model is developed to evaluate the dynamic performance of seismically isolated bridges considering triple interactions of soil, piles, and bridges simultaneously. Novel expressions are proposed to present the dynamic behavior of pile groups in inhomogeneous soils with various shear modulus along with depth. Both cohesive and cohesionless soil deposits can be simulated by this analytical model with a generalized function of varied shear modulus along the soil depth belonging to an inhomogeneous stratum. The methodology is discussed in detail and validated by rigorous dynamic solution of 3D continuum modeling, and time history analysis of centrifuge tests. The proposed analytical model accuracy is guaranteed by the acceptable agreement between the experimental/numerical and analytical results. A comparison of the proposed linear model results with nonlinear centrifuge tests showed that during moderate (frequent) earthquakes the relative differences in responses of the superstructure and the pile cap can be ignored. However, during strong excitations, the response calculated in the linear time history analysis is always lower than the real conditions with the nonlinear behavior of the soil-pile-bridge system. The current simple and efficient method provides the accuracy and the least computational costs in comparison to the full three-dimensional analyses.

• Steel and Composite Structures
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• v.49 no.1
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• pp.19-30
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• 2023

Steel-concrete composite slabs represent a very efficient floor solution combining the key performance of two different materials: the steel and the concrete. Composite slab response is governed by the degree of the interaction between these two materials, mainly depending by chemical and mechanical bond. The latter is characterized by a limited degree of confinement if compared with the one of the rebars in reinforced concrete members while the former is remarkably influenced by the type of concrete and the roughness of the profiled surface, frequently lubricated during the cold-forming manufacturing processes. Indeed, owing to the impossibility to guarantee a full interaction between the two materials, a key parameter governing slab design is represented by the horizontal shear-bond strength, which should be always experimentally estimated. According to EC4, the design of the slab bending resistance, is based on the simplified assumption that the decking sheet is totally yielded, i.e., always in plastic range, despite experimental and numerical researches demonstrate that a large part of the steel deck resists in elastic range when longitudinal shear collapse is achieved. In the paper, the limit strain for composite slab, which corresponds to the slip, i.e., the debonding between the two materials, has been appraised by means of a refined numerical method used for the simulation of experimental results obtained on 8 different composite slab types. In total, 71 specimens have been considered, differing for the properties of the materials, cross-section of the trapezoidal profiled metal sheets and specimen lengths.