• Korea-Australia Rheology Journal
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• v.11 no.4
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• pp.305-311
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• 1999

The shear behavior of polymers obtained by means of devices such as capillary and cone-and-plate rheo-meters is commonly used to assess their processing performance and as a characterization tool. However, the number of instances when two polymers have the same shear properties but perform differently during certain types of processing operations (e.g. film blowing and sheet extrusion) indicate that shear properties alone may not be sufficient to characterize polymeric fluids. We begin by defining the kinematics of shear-free or extensional flow and the associated material functions. The extensional and shear behavior of three different types of polyethylene (PE) are then compared to illustrate the points that one cannot ascertain the extensional properties of polymer melts from their shear properties and, furthermore, there may not be a simple relation between properties obtained from one type of extensional flow and those of another type. The kinematics of most processing flows are extensional rather than shear in nature, and , hence, the performance of polymers during processes such as fiber spinning, film casting, film blowing, thermoforming, blow molding, and even extrusion is more readily accounted for through extensional viscosity measurements. Methods for carrying out extensional flow measurements are then reviewed including approximate methods. To illustrate the sensitivity of extensional viscosity measurements to subtle changes in the molecular architecture of PEs, results are presented for samples with a narrow molecular weight distribution but with varying numbers of long chain branches. Finally, constitutive equations which allow one to separate shear and extensional flow behavior are discussed as any attempts to simulate the subtle processing differences between two polymers will require constitutive equations of this nature.

• Steel and Composite Structures
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• v.17 no.3
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• pp.237-252
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• 2014

The use of composite structures is increasingly present in civil building works. Composite Box Girder Bridges (CBGB), particularly, are study of effect of shear connector's numbers and distribution on the behavior of CBGBs is submitted. A Predicti structures consisting of two materials, both connected by metal devices known as shear connectors. The main functions of these connectors are to allow for the joint behavior of the girder-deck, to restrict longitudinal slipping and uplifting at the element's interface and to take shear forces. This paper presents 3D numerical models of CBGBs to simulate their actual structural behavior, with emphasis on the girder-deck interface. Additionally, a Prediction of several FE models is assessed against the results acquired from a field test. A number of factors are considered, and confirmed through experiments, especially full shear connections, which are obviously essential in composite box girder. A good representation for shear connectors by suitable element type is considered. Numerical predictions of vertical displacements at critical sections fit fairly well with those evaluated experimentally. The agreement between the FE models and the experimental models show that the FE model can aid engineers in design practices of box girder bridges. Preliminary results indicate that number of shear studs can be significantly reduced to facilitate adoption of a new arrangement in modeling CBGBs with full composition. However, a further feasibility study to investigate the practical and economic aspects of such a remedy is recommended, and it may represent partial composition in such modeling.

• Steel and Composite Structures
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• v.27 no.3
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• pp.311-325
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• 2018

This article presents the bending analysis of FGM rectangular plates resting on non-uniform elastic foundations in thermal environment. Theoretical formulations are based on a recently developed refined shear deformation theory. The displacement field of the present theory is chosen based on nonlinear variations in the in-plane displacements through the thickness of the plate. The present theory satisfies the free transverse shear stress conditions on the top and bottom surfaces of the plate without using shear correction factor. Unlike the conventional trigonometric shear deformation theory, the present refined shear deformation theory contains only four unknowns as against five in case of other shear deformation theories. The material properties of the functionally graded plates are assumed to vary continuously through the thickness, according to a simple power law distribution of the volume fraction of the constituents. The elastic foundation is modeled as non-uniform foundation. The results of the shear deformation theories are compared together. Numerical examples cover the effects of the gradient index, plate aspect ratio, side-to-thickness ratio and elastic foundation parameters on the thermo-mechanical behavior of functionally graded plates. Numerical results show that the present theory can archive accuracy comparable to the existing higher order shear deformation theories that contain more number of unknowns.

• Structural Engineering and Mechanics
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• v.40 no.2
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• pp.191-213
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• 2011

This paper presents an improved 8-node shell element for the analysis of plates and shells. The finite element, based on a refined first-order shear deformation theory, is further improved by the combined use of assumed natural strain method. We analyze the influence of the shell element with the different patterns of sampling points for interpolating different components of strains. Using the assumed natural strain method with proper interpolation functions, the present shell element generates neither membrane nor shear locking behavior even when full integration is used in the formulation. Further, a refined first-order shear deformation theory, which results in parabolic through-thickness distribution of the transverse shear strains from the formulation based on the third-order shear deformation theory, is proposed. This formulation eliminates the need for shear correction factors in the first-order theory. Numerical examples demonstrate that the present element perform better in comparison with other shell elements.

• Steel and Composite Structures
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• v.31 no.1
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• pp.27-41
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• 2019

Shear lag effect can be an important phenomenon to consider in design of the steel-concrete composite beams. Researchers have found that the effect can be strongly related with the moment distribution, the stiffness and the ductility of the composite beams. For continuous composite beams expected to sustain hogging moment, the shear lag effect can be more distinct as cracking of the concrete slab reduces its shear stiffness. Despite its influences on behaviour of the steel-concrete composite beams, a method for calculating the shear lag effect in steel-concrete composite beams sustaining hogging moment is still not available. Shear lag effect in steel-concrete composite beams sustaining hogging moment is investigated in this paper. A method was proposed specifically for predicting the effect in the cracked part of the steel-concrete composite beam. The method is validated against available experimental data. At last, FE studies are conducted for steel-concrete composite beams with different design parameters, loading conditions and boundary conditions to further investigate the shear lag effect and compare with the proposed method.

• Journal of Korean Society of Steel Construction
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• v.23 no.4
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• pp.475-481
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• 2011

In this study, a simplified method of improving not only transverse shear stress but also shear strain based on the first-order shear deformation theory was developed. Unlike many established methods, such as the higher-order shear deformation and layerwise theories, this method can easily apply to finite elements as only $C^0$ continuity is necessary and the formulation of equations is very simple. The basic concept in this method, however, must be corrected:the distribution of the transverse shear stresses and shear strains through the thickness from the formulation based on the higher-order shear deformation theory. Therefore, the shear correction factors are no longer required, based on the first-order shear deformation theory. Numerical analyses were conducted to verify the validity of the proposed formulations. The solutions based on the simplified method were in very good agreement with the results considering the higher-order shear deformation theory.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1587-1592
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• 2010

The effects of specimen geometry and loading conditions on the stress distribution in a sandwich specimen under combined loads are investigated by elastic finite element analysis. A commercial software NASTRAN is used in plain-strain two-dimensional finite element analysis of sandwich specimens; the analysis was performed for three different specimen shape factors and four different combined displacement conditions. The results of computational analysis suggest that the effect of the combined displacement angle, which is defined as the ratio of the shear displacement to the normal displacement, on the size of the non-homogeneous stress distribution is observed only in the case of the shear stress and von Mises stress. Also as the combined displacement angle increases, the size of the nonhomogeneous stress distribution decreases in the case of the shear stress and increases in the case of the von Mises stress. In addition, as the specimen shape factor, which is defined as the ratio of the specimen length to the height, increases, the size of the non-homogeneous stress distribution under combined displacement conditions decreases significantly.

• Structural Engineering and Mechanics
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• v.90 no.6
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• pp.577-590
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• 2024

Considering the Column-Supported Group Silos (CSGSs) often arranged by rows in practical applications, earthquake responses will be affected by group effect. Since group effect presenting uncertainties, establishing the analytic model and evaluating characteristics of CSGSs seems necessary. This study aimed at providing a simplified method to evaluate seismic performances of the CSGSs. Firstly, the CSGSs with different storage granule heights are used as numerical examples to derive the base shear formula for three-particle dynamic analytical model. Then, the base shear distribution coefficient is defined as the group effect index. The simplified calculation method of the group silos based on the distribution coefficients is proposed. Finally, based on the empty, half, and full granular storage conditions, the empirical design parameters for the group silos system are given by combining finite element simulation with shaking table test. The group effect of storage granule heights of group silos on its frequency and base shear are studied by comparative analysis between group silos and independent single silo. The results show that the frequency of CSGSs decreases with the increasing weight of the stored granule. The connection between the column top and silo bottom plate is vulnerable, and structural measures should be strengthened to improve its damage resistance. In case of different storage granule heights, distribution coefficients are effective to reconstruction the group effect. The complex calculations of seismic response for CSGSs can be avoided by adopting the empirical distribution coefficients obtained in this study. The proposed method provides a theoretical reference for evaluation on the seismic performances of the CSGSs.

• Journal of the Korea Concrete Institute
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• v.23 no.1
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• pp.3-12
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• 2011

The structural behavior of continuous reinforced concrete deep beams is mainly controlled by the mechanical relationships associated with the shear span-to-effective depth ratio, flexural reinforcement ratio, load and support conditions, and material properties. In this study, a simple indeterminate strut-tie model which reflects characteristics of the complicated structural behavior of the continuous deep beams is presented. In addition, the reaction and load distribution ratios defined as the fraction of load carried by an exterior support of continuous deep beam and the fraction of load transferred by a vertical truss mechanism, respectively, are proposed to help structural designers for the analysis and design of continuous reinforced concrete deep beams by using the strut-tie model approaches of current design codes. In the determination of the load distribution ratio, a concept of balanced shear reinforcement ratio requiring a simultaneous failure of inclined concrete strut and vertical steel tie is introduced to ensure a ductile shear failure of reinforced concrete deep beams, and the primary design variables including the shear span-to-effective depth ratio, flexural reinforcement ratio, and concrete compressive strength are implemented after thorough parametric numerical analyses. In the companion paper, the validity of the presented model and load distribution ratio was examined by applying them in the evaluation of the ultimate strength of multiple continuous reinforced concrete deep beams, which were tested to failure.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.281-282
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• 2002

To reduce the spin-off of lubricants on a magnetic disk, which is caused by the radial component of shear force between the disk and air, we analyzed the air-velocity distribution and the air-shear force by three-dimensional large-eddy simulation (LES). This sensitivity analysis, on five design parameters, showed that disk/arm clearance and arm thickness have a greater effect on the mean radial air-shear force than the other parameters. The force on a disk optimized according to the optimum parameters is 12% less than the force on a conventional disk.