Effect Of Cross-sectional Shape Research Articles

Axial Load Behavior of Stiffened Concrete-Filled Steel Columns

This study investigates the axial load behavior of concrete-filled steel tubular (CFT) columns with the width-to-thickness ratios between 40 and 150, and proposes an effective stiffening scheme to improve the mechanical properties of square cross-sectional CFT columns. Seventeen specimens were tested to examine the effects of cross-sectional shapes, width-to-thickness ratios, and stiffening arrangements on the ultimate strength, stiffness, and ductility of CFT columns. Moreover, nonlinear finite element analysis was also conducted to investigate cross-sectional axial stress distribution at the ultimate strength. Comparing the measured ultimate strength with estimates by using some current specifications suggested that current specifications may considerably underestimate the ultimate strength of circular CFT columns, particularly for columns with a small width-to-thickness ratio. Results in this study demonstrate that the proposed stiffening scheme can significantly enhance the ultimate strength and ducti...

Radiative properties of fibers with non-circular cross sectional shapes

The effects of cross sectional shape of non-circular fibers on the radiative properties, such as extinction and scattering efficiencies, are numerically investigated. A finite element method is developed to solve Maxwell's equations that govern a two-dimensional electric field induced by a single fiber that is normally irradiated by a plane wave. The angular profile of the scattered radiation as well as the scattering and extinction efficiencies are derived from the electric fields. The radiative properties of fibers with equilateral triangular cross sectional areas are compared with those of circular fibers. The results show that the intensity distribution of the scattered radiation are scarcely affected by the cross sectional shape when the size parameter is less than 2, and that the efficiencies of the triangular shaped fibers are equivalent to those of the circular fibers having the same cross sectional area. This study also examines the radiative properties of fibers having silk-like cross sections that are thought to cause the luster of silk cloth. The results show that the fibers scatter the radiation more strongly toward the rear semicircle at a certain incident angle than the circular fibers having similar cross sectional areas.

Numerical Analysis of Models of the Standard TSRH Spinal Instrumentation: Effect of Rod Cross-sectional Shape

A numerical technique, geometric element modeling and analysis, was used to investigate the effect of the cross-sectional shape of the rod (circular versus square) in three-dimensional models of the standard (dual-rod) Texas Scottish Rite Hospital (TSRH) spinal instrumentation on two biomechanical characteristics (namely, stiffness and the von Mises equivalent stress) of the instrumentation under compressive force and torque, applied separately. The model constraints are the same as those acting on the instrumentation clinically, that is, when it is attached to the vertebrae of the human spine. Furthermore, the magnitudes of the compressive and torsional loadings applied on the model are within the range of those experienced by the spine during normal walking. It was found that use of square cross-sectioned rods leads to better biomechanical performance of the model compared to the case when the rods are circular. This finding points the way to the possibility of using square cross-sectioned rods in the TSRH instrumentation.

Open Channel Flow Resistance

In 1965, Rouse critically reviewed hydraulic resistance in open channels on the basis of fluid mechanics. He pointed out the effects of cross-sectional shape, boundary nonuniformity, and flow unsteadiness, in addition to viscosity and wall roughness that are commonly considered. This paper extends that study by discussing the differences between momentum and energy resistances, between point, cross-sectional and reach resistance coefficients, as well as compound/composite channel resistance. Certain resistance phenomena can be explained with the inner and outer laws of boundary layer theory. The issue of linear-separation approach versus nonlinear approach to alluvial channel resistances also is discussed. This review indicates the need for extensive further research on the subject.

123 梁要素を用いたトポロジー最適化 : 断面形状の影響を考慮した場合

123 梁要素を用いたトポロジー最適化 : 断面形状の影響を考慮した場合

Heat Transfer in Rotating Narrow Rectangular Ducts With Heated Sides Parallel to the r-z Plane

In gas turbine blade design, a variety of channel shapes and orientations are used in the cooling circuit. Most of the rotating channel heat transfer research to date has considered channels of square or round cross-sections. This research characterizes the effect of rotation on fully developed turbulent convective heat transfer in ducts of narrow cross-section (height-to-width aspect ratio of 1:10). Experiments were conducted using ducts of narrow cross-section, oriented such that the long sides of the duct cross-section are perpendicular to the direction of blade tangential velocity (parallel to the r-z plane). In the experiment, a high-molecular-weight gas (Refrigerant-134A) at ambient pressure and temperature conditions was used to simulate coolant-to-wall density ratios that match engine conditions. Thin foil heaters were used to produce a uniform heat flux at the long sides of the duct; the narrow sides were unheated. Duct Reynolds numbers were varied up to 31,000; rotation numbers were varied up to 0.11. The test results show the effect of rotation and aspect ratio on duct leading and trailing side heat transfer. The results provide insight into the effect of rotation (Coriolis) in the absence of buoyancy effects. Comparisons with previously reported results are presented to show the effect of cross-section shape on rotating channel heat transfer.

Dam-Break Waves in Power-Law Channel Section

The aim of this work is to highlight the effects of cross-sectional shape on dam-break wave propagation along channels by the solution of 1D conservative equations assuming a power-law variation of the channel width. An exact Riemann solution that allows a second-order accuracy of the solution for the power-law section shape is provided and is applied to the dam-break problem in valleys with different shapes but the same dam area. The streamflow state variables upstream of the bore and the bore speed for some typical sectional shapes (rectangular, triangular, concave, and convex banks) are determined as functions of variable flow depth differences and of the power law index.

Effect of stress on the hydraulic conductivity of rock pores

We have made a detailed study of the effect of cross-sectional shape on the hydraulic conductance of rock pores. We consider laminar flow through a single tube with an irregular cross-section; constriction effects, and interconnectedness of pores, will be studied in a future work. We employ three approximate methods: the hydraulic radius approximation, which attempts to correlate the conductivity with the perimeter/area ratio, the Aissen approximation, which utilises a mean value of the conductance of the largest (smallest) circles that can be inscribed (circumscribed) inside (outside) the pore, and the Saint-Venant approximation, which is based on the polar moment of inertia of the shape. The Boundary Element Method is used to provide nominally “exact” estimates of the conductivity, but at the expense of large amounts of computational time. All four methods have been tested on pore shapes from SEM (Scanning Electron Microscope) images of thin-sections of Berea and Massilon sandstone. Surprisingly, the hydraulic radius approximation is the most accurate of the three approximate methods, giving, on average, less than 1% error. Finally, we combine these methods with previous results on the effect of stress on pore deformation, to study the stress-dependence of pore conductivity.

Buckling Analysis of Elastic Space Rods under Torsional Moment

The buckling behavior of elastic space rods under torsional moment is studied theoretically. A consistent method is developed to identify the buckling torsional moment as well as to trace the postbuckling path. Since this buckling phenomenon accompanies a nonlinear interaction between flexural deformation and torsional deformation, a special consideration has to be made in the treatment of finite rotations in three-dimensional space. First, a buckling analysis based on a rigorous nonlinear beam theory is developed to identify the bifurcation moment. This analysis precisely takes into account the prebuckling torsional deformations as well as the effect of axial compressive force. Next, the postbuckling behavior is analyzed by the transfer matrix technique, which was previously presented by the writers. With this method, the buckling and postbuckling behavior of space rods under torsional moment are examined with an emphasis on the effect of cross-sectional shapes as well as axial compressive force.

Impact energy absorption of 6061 aluminum extruded tubes with different cross-sectional shapes

The present article aims at evaluating experimentally impact absorption energies of an extruded 6061 aluminum tube for space frame and at investigating the effect of cross-sectional shape on the compressive deformation behavior under dynamic loading. The dynamic compressive test was conducted on extruded aluminum tube specimens, whose shape and thickness/width (or diameter) ratio are different, using a high performance servo-hydraulic machine. Asymmetric folds were formed mainly in the rectangular tube specimens, whereas symmetric folds were formed in the circular tube specimens. However, the fold shape tended to become symmetric as the thickness/width ratio increased, and absorption energy increased linearly within the scope of the present study. To improve impact absorption energy and maximum resistive force against compressive load of extruded aluminum tube for space frame, it is recommended to make the thickness/width ratio large enough and to design the circular cross-sectional shape in a way to promote the formation of symmetric folds instead of asymmetric ones.

INFLUENCE OF CROSS-SECTIONAL SHAPE ON THE CONDUCTIVITY OF A WALL APERTURE IN MEAN FLOW

An analysis is made of the effect of cross-sectional shape on the motion induced in a wall aperture by a pressure perturbation in the presence of high Reynolds number tangential flow. Previous studies for circular and rectangular apertures indicate that there is a transfer of energy from the applied perturbation to the mean flow (via the production of vorticity in the aperture) provided the Strouhal number based on aperture diameter and mean velocity is small. In this paper apertures are considered whose cross-sections are symmetrically tapered in a direction parallel to the mean flow. For highly tapered apertures of trapezoidal cross-section, it is found that low Strouhal number damping is confined to a smaller range of frequencies. Self-sustaining oscillations of the shear layers spanning the aperture can occur at certain discrete frequencies, which correspond to the real parts of complex eigenfrequencies of the aperture motion havingpositiveimaginary parts. The eigenfrequencies are poles of the Rayleigh conductivity, and are found to vary in proportion toU/L, whereUis mean flow speed andLis the maximum streamwise length of the aperture, but to be only weakly dependent on aperture shape.

Diffusion of floodwaves

Floodwaves may be approximated as an advection-diffusion process when the typical Froude number is much smaller than one. The study refers to the effect of cross-sectional shape on the propagation of a single-peaked flood in a simple river having constant width, slope and roughness. The results are interesting in terms of how exact a shape geometry should be evaluated before proceeding to a detailed numerical computation of river floodwaves. The problem is generally solved by introducing a number of simplifying assumptions that do not detract from the essence of floodwave diffusion. The main parameters retained are the diffusion coefficient and the shape factor. The formulation of the problem is closed with appropriate boundary and initial conditions. The results of the numerical study are discussed in detail and expressions are presented for the main features of the floodwave, including the arrival of the wave front and the wave peak, as well as the peak discharge in terms of diffusion and crosssectional shape. Using a different set of parameters, it can be demonstrated that the last two effects may be dropped for preliminary computations. Accordingly, the prediction of floodwave propagation can easily be accomplished.

Effect of Cross-Sectional Shape of Specimen on Fatigue Strength under Plane Bending.

Plane bending fatigue tests of an annealed 0.42% carbon steel were carried out on specimens with a small blind hole and smooth specimens, with round or square cross sections, in order to investigate the effect of cross-sectional shape on the fatigue strength. The fatigue strength of a round-sectioned specimen is higher than that of a square one under the same stress. This is mainly caused by the difference in the crack growth rates. The crack growth rate can be expressed by the term σnl (small-crack growth law) in each cross-sectional shape, separately. Moreover, by transforming the nominal stress amplitude σ into the plastic strain amplitude εp using the cyclic stress-strain curve measured at the specimen surface, the crack growth rate can be uniquely determined by the term εn'pl, regardless of the shape of the cross section. Based on these results, a conventional prediction method of fatigue crack growth rate and fatigue life is proposed using the small-crack growth law and the cyclic stress strain curve.

Effect of Cross-Sectional Shape on Free-Surface Instability

Effect of Cross-Sectional Shape on Free-Surface Instability

An end-effect model for the single-filament tensile test

The effect of cross-sectional shape on tensile strength of pitch-based carbon fibres was investigated by extensive single-filament testing. For this study, round and trilobal pitch-based carbon fibres were produced at similar processing conditions. The application of a variety of distributions, including the simple Weibull distribution, to the strength data indicated two sources of failure, one source being the accentuation of end effects at short gauge lengths. A new mixed distribution, the end-effect distribution, was proposed to account for these effects and applied to the experimental data. The end-effect model provided an excellent description of the strength distributions of all fibres studied. The end-effect distribution is not complex and is based on sound physical assumptions. It quantifies a recognized inadequacy of the test method which has not previously been accounted for, and it allows separation of end effects from the true fibre strength distribution. The results indicate that end effects can be an important concern for gauge lengths as long as 40 mm. Use of this model revealed that, in the absence of end effects, all fibres failed due to macroscopic flaws; thus, varying the fibre geometry does not result in an unusual failure mechanism. However, the tensile strengths of the non-circular fibre were found to be less dependent on fibre size. Thus, non-circular fibres can be produced at higher mass flow rates, decreasing filament breakage and increasing process conversions.

Effect of cross-sectional shapes of sealing beads on their fatigue resistance to joint movement: Hirai, T., Hashida, H., Koike, M. and Tanaka, K. Reports on the Research Laboratory of Engineering Materials, Tokyo Institute of Technology (1993) (18), 197–208

Effect of cross-sectional shapes of sealing beads on their fatigue resistance to joint movement: Hirai, T., Hashida, H., Koike, M. and Tanaka, K. Reports on the Research Laboratory of Engineering Materials, Tokyo Institute of Technology (1993) (18), 197–208

Improved prediction model for time-dependent deformations of concrete: Part 1-Shrinkage

This paper is the first in a series of papers that present a new prediction model for creep and shrinkage of concrete, called for brevity the BP−KX model. This model represents an update and improvement of the BP model published in this journal in 1978–79. The improvement is possible because further experimental data became available in the literature and at the same time knowledge of physical concepts and mechanisms has improved. This first paper presents a prediction model for the mean (overall) shrinkage strain in cross-sections of long members, which takes into account the influence of environmental humidity, the effective thickness of the member, the effect of cross-section shape, the effect of age at the start of drying, and the effect of temperature. The proposed basic form of the shrinkage formulae is fustified by nonlinear diffusion theory for the movement of moisture through concrete. Extensive comparisons with important test data from the literature, altogether 23 data sets, reveal that the predictions are better than with the previous models. Statistics of prediction are also given. The main error of prediction arises from the estimation of the shrinkage parameters from concrete strength and composition. If limited short-time shrinkage data are available, the predictions can be greatly improved.

Reliability of Partially Prestressed Beams at Serviceability Limit States

A systematic investigation of the reliability of partially prestressed concrete beams at six serviceability limit states is described. The evaluation of reliability is based on the first order, second moment method. The code calibration method was used to determine the reliability index (or safety index) for 64 different beam designs. The effects of cross-sectional shape, span length, magnitude of live load and degree of partial prestressing were also determined.

New Data On Shape Effects In Smooth Rectangular Channels

A method for dealing with the effects of cross-sectional shape on flow resistance in open channels was developed and presented in a previous paper. The new method, which was referred to as Kazemipour's method, was tested against the experimental data of other investigators available at the time when it was developed and published. Later, it was decided to carry out further experiments to obtain a new and independent set of data in smooth rectangular channels and to test the effectiveness of Kazemipour's method on these new data. In this paper, which is an addendum to the previous paper, the new experiments are described. In these experiments a novel approach was used to measure the normal depth of flow. The results of these tests have value in themselves as a new set of accurate data about the resistance to flow, in addition to their use to verify the effectiveness of Kazemipour's method dealing with shape effects.

SHAP EEFFECTS ON RESISTANCE TO UNIFORM FLOW IN OPEN CHANNELS

The effects of the shape of the cross-section on flow resistance in open channels has received considerable attention from hydraulic engineers for many years. Many investigators have tried to introduce parameters to represent the cross-section shape effect but their results have been inconclusive. Some of the techniques previously used to deal with this problem are reviewed and their shortcomings are discussed. A new method for dealing with shape effect is developed in this paper from considerations of dimensional analysis and using the experimental data of TRACY and LESTER and of SHIH and GRIGG. This method, which is referred to as KAZEMIPOUR'S method, employs new parameters more representative of the effect of cross-sectional shape on flow resistance in open channels than those previously used and offers solutions more rational than those previously proposed. The shape factor developed is ϕ = ϕ 1/ϕ 2, where ϕ 1, equal to , reflects the effects of non-uniform distribution of shear stress on the boundary ...