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Showing papers on "Flexural rigidity published in 2006"


Journal ArticleDOI
TL;DR: In this paper, a modified couple stress theory was used for the bending of a Bernoulli-Euler beam and a variational formulation based on the principle of minimum total potential energy was employed.
Abstract: A new model for the bending of a Bernoulli–Euler beam is developed using a modified couple stress theory. A variational formulation based on the principle of minimum total potential energy is employed. The new model contains an internal material length scale parameter and can capture the size effect, unlike the classical Bernoulli–Euler beam model. The former reduces to the latter in the absence of the material length scale parameter. As a direct application of the new model, a cantilever beam problem is solved. It is found that the bending rigidity of the cantilever beam predicted by the newly developed model is larger than that predicted by the classical beam model. The difference between the deflections predicted by the two models is very significant when the beam thickness is small, but is diminishing with the increase of the beam thickness. A comparison shows that the predicted size effect agrees fairly well with that observed experimentally.

976 citations


Journal ArticleDOI
TL;DR: This work used direct buckling force measurements with optical traps to determine the flexural rigidity of individual microtubules bound to polystyrene beads and applied a new analytical model assuming nonaxial buckling.

210 citations


Journal ArticleDOI
TL;DR: In this paper, a low-speed impact of a one-dimensional sandwich panel by a rigid cylindrical projectile is considered, where the core of the sandwich panel is functionally graded such that the density and hence its stiffness vary through the thickness.

157 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present the results of an experimental study on the flexural behavior of a new type of hybrid FRP-concrete-steel member and a corresponding theoretical model based on the plane section assumption and the fiber element approach.
Abstract: This paper presents the results of an experimental study on the flexural behavior of a new type of hybrid FRP-concrete-steel member as well as results from a corresponding theoretical model based on the plane section assumption and the fiber element approach. This new type of hybrid member is in the form of a double-skin tube, composed of a steel inner tube and an FRP outer tube with a concrete infill between the two tubes, and may be employed as columns or beams. The parameters examined in this study include the section configuration, the concrete strength, and the thicknesses of the steel tube and the FRP tube, respectively. The results presented in this paper show that these hybrid beams have a very ductile response because the compressive concrete is confined by the FRP tube and the steel tube provides ductile longitudinal reinforcement. The beams' flexural response, including the flexural stiffness, ultimate load, and cracking, can be substantially improved by shifting the inner steel tube toward the...

140 citations


Journal ArticleDOI
TL;DR: In this paper, a further study on the flexural behaviour of concrete-filled steel tubes based on the former work presented by Han [Han LH. 2004] is presented, and compared with predicted beam flexural stiffness using different methods, such as AIJ-1997, AISC-LRFD-1999, BS5400-1979, EC4-1994 and the method proposed in this paper.

136 citations


Journal ArticleDOI
TL;DR: Using a coarse-grained bilayer model, bending rigidities are efficiently obtained that compare very well with complementary measurements based on an analysis of thermal undulation modes and it is illustrated that no deviations from simple quadratic continuum theory occur up to a radius of curvature comparable to the bilayer thickness.
Abstract: The tensile force along a cylindrical lipid bilayer tube is proportional to the membrane’s bending modulus and inversely proportional to the tube radius. We show that this relation, which is experimentally exploited to measure bending rigidities, can be applied with even greater ease in computer simulations. Using a coarse-grained bilayer model we efficiently obtain bending rigidities that compare very well with complementary measurements based on an analysis of thermal undulation modes. We furthermore illustrate that no deviations from simple quadratic continuum theory occur up to a radius of curvature comparable to the bilayer thickness.

129 citations


Journal ArticleDOI
TL;DR: Brownian dynamics simulations are employed to demonstrate that the particles self-assemble into a membrane and to study equilibrium properties, such as bending rigidity, surface tension, line tension, and diffusion constant.
Abstract: A meshless particle-based membrane model is proposed. The particles possess no internal degree of freedom and interact via a potential, which has three different contributions: a short-range repulsive pair potential, an attractive multibody potential, and a curvature potential based on the moving least-squares method. Brownian dynamics simulations are employed to demonstrate that the particles self-assemble into a membrane and to study equilibrium properties, such as bending rigidity, surface tension, line tension, and diffusion constant. The bending rigidity and line tension are shown to depend on different potential parameters and can therefore be varied independently. The finite-size effects of nearly planar membranes are investigated. This model is well suited to study the membrane dynamics with topological changes.

111 citations


Journal ArticleDOI
TL;DR: In this paper, the performance of hollow structural steel (HSS) stub columns and beams filled with normal concrete and recycled aggregate concrete (RAC) under instantaneous loading was investigated experimentally.
Abstract: The behaviour of hollow structural steel (HSS) stub columns and beams filled with normal concrete and recycled aggregate concrete (RAC) under instantaneous loading was investigated experimentally. A total of 40 specimens, including 30 stub columns and 10 beams, were tested. The main parameters varied in the tests were: (1) recycled coarse aggregate (RCA) replacement ratio, from 0 to 50%, (2) sectional type, circular and square. The main objectives of these tests were threefold: first, to describe a series of tests on new composite columns; second, to analyze the influence of RCA replacement ratio on the compressive and flexural behaviour of recycled aggregate concrete filled steel tubes (RACFST), and finally, to compare the accuracy of the predicted ultimate strength, bending moment capacity and flexural stiffness of the composite specimens by using the recommendations of ACI318-99 (1999), AIJ (1997), AISC-LRFD (1999), BS5400 (1979), DBJ13-51-2003 (2003) and EC4 (1994).

94 citations


Journal ArticleDOI
TL;DR: In this article, the effects of surrounding members (i.e. beams and columns) on the overall behavior of thin steel plate shear walls are studied, and it is shown that the flexural stiffness of the surrounding members has no significant effect, either on elastic shear buckling or on the post-buckling behaviour of shear wall.

90 citations


Journal ArticleDOI
TL;DR: Atomic force microscope force spectroscopy is presented as a method allowing force-deformation measurements of submicron vesicles and bending rigidities of small unilamellar dipalmitoylphosphatidylcholine (DPPC) liposomes (R<200 nm) can be derived from the force- deformation data using analytical models based on shell theory and are in good agreement with independent measurements.
Abstract: Mechanical properties of lipidic membranes such as their bending rigidity are governing liposome morphology and play an important role in processes like membrane fusion and adhesion. Force versus deformation measurements are the most direct means to determine this, but so far experimental data is scarce and mainly stems from techniques that are limited to giant vesicles. We present atomic force microscope force spectroscopy as a method allowing force-deformation measurements of submicron vesicles. Bending rigidities of small unilamellar dipalmitoylphosphatidylcholine (DPPC) liposomes (R<200 nm) can be derived from the force-deformation data using analytical models based on shell theory and are in good agreement with independent measurements.

89 citations


Journal ArticleDOI
TL;DR: Weinbaum et al. as mentioned in this paper reported additional experiments and apply large deformation theory for elastica to describe the restoration of the fibres in a Brinkman medium which absorbs fluid as the ESL expands.
Abstract: There is wide interest in the role of the endothelial surface layer (ESL) in transmitting blood shear stress to the intracellular cytoskeleton of the endothelial cell. However, very little is known about the mechanical properties of the glycocalyx or the flexural rigidity of the core proteins that comprise it. Vink, Duling & Spaan ( FASEB J. , vol. 13, 1999, p. A 11) measured the time-dependent restoration of the ESL after it had been nearly completely compressed by the passage of a white blood cell (WBC) in a tightly fitting capillary. Using this initial experiment, Weinbaum et al. ( Proc. Natl. Acad. Sci. USA , vol. 100, 2003, p. 7988) predicted that the core proteins have a flexural rigidity EI of 700 pN nm $^{2}$ , which is $\sim$ 1/20 the measured value for an actin filament. However, their analysis assumes small deflections and only the fibre motion is considered. In the present paper we report additional experiments and apply large-deformation theory for ‘elastica’ to describe the restoration of the fibres in a Brinkman medium which absorbs fluid as the ESL expands. We find that there are two phases in the fibre recoil: an initial phase for large compressions where the ESL thickness is $ its undisturbed thickness, and the ends of the fibres overlap and are parallel to the capillary wall; and a second phase where the fibres assume a shape that is close to the solutions for an elastic bar with linearly distributed vertical loading. The predicted time-dependent change in thickness of the ESL provides remarkably good agreement with experiment and yields an estimate of 490 pN nm $^{2}$ for the flexural rigidity EI of the core protein fibres, which is unexpectedly close to that predicted by the linear theory in Weinbaum et al. (2003).

Journal ArticleDOI
TL;DR: In this paper, the authors presented accurate numerical calculations of the natural frequencies for elastic rectangular plates of variable thickness with various combinations of boundary conditions The thickness variation in one or two directions of the plate is taken in polynomial form.

Journal ArticleDOI
TL;DR: In this article, the authors focused on the characterization of flexural behaviour of RC members strengthened with NSM glass-FRP bars. But, they did not evaluate the performance of the tested beams including modes of failure, moment-deflection response and ultimate moment capacity.

Journal ArticleDOI
TL;DR: In this article, a method for the identification of prestress force of a prestressed concrete bridge deck is presented using the measured structural dynamic responses, and the prestress forces in each beam element are identified using a sensitivity-based finite element model updating method.

Journal ArticleDOI
TL;DR: In this article, the structural design for enhancing the magnetic controllability of magnetorheological elastomer (MRE)-based sandwich beams is addressed. But the theoretical approach is based on a high-order theory and a non-dimensional analysis.
Abstract: Due to the field-dependent shear modulus of magnetorheological elastomer (MRE), the bulk dynamic flexural rigidity of sandwich beams with MRE cores can be adjusted by applied magnetic fields. The maximum relative change of the flexural rigidity adjusted by applied magnetic fields is referred to as magnetic controllability in this research. This paper will address the structural design for enhancing the magnetic controllability of MRE-based sandwich beams. The theoretical approach is based on a high-order theory and a non-dimensional analysis. Numerical simulations are conducted on a simply supported sandwich beam. This work will benefit the design of MRE-based sandwich beams to yield the maximum magnetic controllability index, and will explore the fundamental understanding of the field-adjustable dynamic flexural rigidity of the MRE-based sandwich beams.

Journal ArticleDOI
TL;DR: Analysis showed that the solutions for multilayered discs subjected to biaxial flexure tests could be obtained from the existing solutions for monolayered systems by replacing the neutral surface position and the flexural rigidity of monolayers with those of multilayers.

Journal ArticleDOI
TL;DR: These results confirm that longitudinal Young's modulus of microtubules is length-independent, and the observed length-dependence of the flexural rigidity and Young’s modulus is a result of strongly anisotropic elastic properties of micro Tubules which have a length-dependent weakening effect on flexural Rigidity of shorter microtubule.

Journal ArticleDOI
TL;DR: In this paper, the influence of low energy impacts on residual strength of carbon-epoxy laminates was studied under 1.5 J, 2 J, 3 J and 3 J impact energies.
Abstract: The aim of present work is to study the influence of low energy impacts on residual strength of carbon-epoxy laminates. Experimental tests were performed on [0,90,0,90]2s and [0,90]8 laminates using a drop weight-testing machine. The influence of the laminate stacking sequence is analysed under 1.5 J, 2 J, 2.5 J and 3 J impact energies, corresponding to a 0.91 ms-1, 1.05 ms-1, 1.18 ms-1 and 1.29 ms-1 of impact velocity, respectively. The impacted plates were inspected by CScan to evaluate the size, shape and position of the delaminations through the thickness of the plate. The same plates were inspected by C-Scan before the impact, to evaluate the eventual presence of defects produced during the manufacturing process. The residual flexural strength showed that the [0,90,0,90]2s laminates have better performance than the [0,90]8 ones. The explanation is related with the lower flexural stiffness of the antisymmetric lay-up relatively to the symmetric one.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the mechanism of reconfiguration of broad leaves subjected to wind loading, and derived scaling laws from the mechanical equilibrium of the sheets, the balance between form drag and elastic forces, and the experimental data collapsed onto master curves.
Abstract: The mechanism of reconfiguration of broad leaves subjected to wind loading is investigated. Circular plastic sheets cut along a radius are immersed in a water flow. They roll up into cones when held at their centres. The opening angle of the cone and the drag force exerted on the sheet are measured as a function of the flow velocity and of the sheet bending rigidity. The cone becomes sharper when the velocity increases or when the sheet stiffness decreases; the reconfiguration leads to a decrease in the drag coefficient. Scaling laws are derived from the mechanical equilibrium of the sheets – the balance between form drag and elastic forces – and the experimental data collapse onto master curves. Two models for the pressure field yield theoretical curves in semi-quantitative agreement with the experiments.

Journal ArticleDOI
01 Dec 2006-EPL
TL;DR: In this paper, the persistence length of semidefinite polymers and one-dimensional fluid membranes is derived from the renormalization of their bending rigidity, which vanishes exponentially at large length scales.
Abstract: The persistence length of semiflexible polymers and one-dimensional fluid membranes is obtained from the renormalization of their bending rigidity. The renormalized bending rigidity is calculated using an exact real-space functional renormalization group transformation based on a mapping to the one-dimensional Heisenberg model. The renormalized bending rigidity vanishes exponentially at large length scales and its asymptotic behaviour is used to define the persistence length. For semiflexible polymers, our result agrees with the persistence length obtained using the asymptotic behaviour of tangent correlation functions. Our definition differs from the one commonly used for fluid membranes, which is based on a perturbative renormalization of the bending rigidity.

Journal ArticleDOI
TL;DR: In this article, a simple and closed form solution for the vibration response of finite ribbed plates to point force/moment excitations is presented, where the input mobilities of the ribbed plate are bounded by the input of the uncoupled plate and beam.
Abstract: A simple and closed form solution for the vibration response of finite ribbed plates to point force/moment excitations is presented in this paper This solution shows that input mobilities of finite ribbed plates are bounded by the input mobilities of the uncoupled plate and beam that form the ribbed plate It is found that point force input mobilities of a finite ribbed plate are controlled by the plate bending stiffness when the excitation force is more than a quarter wavelength away from the beam The input mobilities are mainly dominated by the beam flexural stiffness when the force acts on or very close to the beam, and when the beam flexural stiffness is far greater than the plate bending stiffness A similar result is found in the moment excitation case when the moment axis is perpendicular to the beam neutral axis (bending moment excitation) In contrast, the input mobilities of the ribbed plate do not vary much from that of the corresponding uncoupled plate when the moment axis parallels to the beam’s neutral axis (torsional moment excitation) where the input mobilities are mainly dominated by the plate bending stiffness The reductions in plate kinetic energy due to beam insertions are discussed

01 Feb 2006
TL;DR: In this article, a simple and closed form solution for the vibration response of finite ribbed plates to point force/moment excitations is presented, which shows that the input mobilities of a ribbed plate are bounded by the input stiffness of the uncoupled plate and beam.
Abstract: A simple and closed form solution for the vibration response of finite ribbed plates to point force/moment excitations is presented in this paper. This solution shows that input mobilities of finite ribbed plates are bounded by the input mobilities of the uncoupled plate and beam that form the ribbed plate. It is found that point force input mobilities of a finite ribbed plate are controlled by the plate bending stiffness when the excitation force is more than a quarter wavelength away from the beam. The input mobilities are mainly dominated by the beam flexural stiffness when the force acts on or very close to the beam, and when the beam flexural stiffness is far greater than the plate bending stiffness. Similar result is found in the moment excitation case when the moment axis is perpendicular to the beam neutral axis (bending moment excitation). In contrast, the input mobilities of the ribbed plate do not vary much from that of the corresponding uncoupled plate when the moment axis parallels to the beam’s neutral axis (torsional moment excitation) where the input mobilities are mainly dominated by the plate bending stiffness. The reductions in plate kinetic energy due to beam insertions are discussed.

Journal ArticleDOI
TL;DR: In this paper, the tensile modulus of yarn and yarn geometry and structural parameters was analyzed and it was shown that yarn bending rigidity decreases as the ratio of tensile to shear modulus increases.
Abstract: The bending behavior of yarn is affected by mechanical properties, arrangement and interaction between its constituent fibers and yarn geometry. In this study the yarn bending rigidity was obtained from the tensile modulus of its constituent fibers and yarn geometry and structural parameters and it was shown that the dimensionless yarn bending rigidity decreased as the ratio of tensile modulus to the shear modulus of the constituent fibers increased. Furthermore, the yarn bending rigidity decreased as the surface helix angle of the yarn increased. When compared with previous research, there was good agreement between the findings of Owen, Zurek, and Platt’s and the results of this study.

Journal ArticleDOI
TL;DR: These effects of friction and wire properties on canine movement (tipping and rotational angles) are combined by using a single parameter, EI/P, where EI is the flexural rigidity of the archwire, and P is the net force acting on the canine.

Journal ArticleDOI
TL;DR: In this paper, a cost-effective shear-strengthening technique for timber stringers that is environmentally friendly and leads to a durable structure was developed, where two strengthening schemes were investigated; incorporating vertical and diagonal glass fiber-reinforced polymer (GFRP) sheets applied to both shear spans.
Abstract: The objective of this study was to develop a cost-effective shear-strengthening technique for timber stringers that is environmentally friendly and leads to a durable structure. Testing was performed on creosote-treated Douglas fir beams, with dimensions of 100×400×3,650 mm , removed from a 40 year old bridge. Two strengthening schemes were investigated; incorporating vertical and diagonal glass fiber-reinforced polymer (GFRP) sheets applied to both shear spans. The diagonal scheme proved effective in increasing the average ultimate load, flexural stiffness, and deformability of the beams. Performance of the members reinforced using the vertical scheme, however, was poor compared to diagonally reinforced beams. The contribution of the diagonal sheets to the shear capacity of the stringers was around 12% at service loads and 40% at ultimate load. In conclusion, this study has shown that diagonal GFRP sheets are more effective than vertical sheets in shear-strengthening timber stringers with horizontal spli...

Journal ArticleDOI
TL;DR: The first quantitative evidence of a very significant material anisotropy in sickle hemoglobin fibers is presented, as might arise from the difference between axial and lateral contacts within the fiber.

Journal ArticleDOI
TL;DR: In this article, a simple mathematical model is proposed for assessing periods of vibration and mode shapes of common cantilever bents used in concrete structures, such as shear walls, coupled walls, rigid frames and wall-frame assemblies.
Abstract: A simple mathematical model is proposed for assessing periods of vibration and mode shapes of common cantilever bents used in concrete structures, such as shear walls, coupled walls, rigid frames and wall-frame assemblies. The bent is treated as a continuum and the proposed model is based on the technique of decomposing a cantilever bent into two complementary subsystems (a flexural and a wall-frame bent) and on the finding that the use of Dunkerley's formula for calculating natural frequencies yields reasonable results for the first three modes of vibration. The objective in proposing this model is to consider the effect of column axial shortenings in the analysis of structural bents. With this model any cantilever bent may be approximated by a simple incompressible shear–flexure system of equal flexural rigidity, but of equivalent modal shear rigidity. This approach has the advantage that the response of different structural bents may be combined in buildings composed of these bents in any arrangement. All bents are approximated by equivalent shear–flexure models and therefore the complete structure may be analysed by a simple methodology, which has been extensively used in the past. Particularly in symmetrical buildings, frequencies may be determined by a simple formula and modal response quantities by available design charts. A quick estimate of these quantities is of particular importance at the early stages of structural design, prior to a full dynamic analysis. In order to illustrate the application of the proposed model a symmetrical building of varying height, composed of different structural bents, is analysed and comparisons are made with more accurate results obtained by 3D computer dynamic analyses. Copyright © 2006 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this article, the influence of a full range of variables on effective flexural stiffness (EI) used for the design of slender, tied, composite columns in which steel shapes are encased in concrete, and also examined the existing ACI EI equations.
Abstract: The ACI standard 318-02 permits the use of a moment magnifier approach for the design of slender composite steel-concrete columns. This approach is strongly influenced by the effective flexural stiffness (EI) , which varies due to the nonlinearity of the concrete stress-strain curve and the cracking along the column length among other factors. The EI equations given in the ACI code are approximate when compared to the EI values computed from the axial load-bending moment-curvature relationships. This study was undertaken to determine the influence of a full range of variables on EI used for the design of slender, tied, composite columns in which steel shapes are encased in concrete, and also to examine the existing ACI EI equations. Approximately 12,000 isolated square composite columns, each with a different combination of specified properties of variables, were simulated and used to generate the stiffness data. The columns studied were subjected to short-term ultimate loads and equal and opposite end mo...

Patent
10 Jul 2006
TL;DR: In this article, a double feed sensing device was proposed for detecting double feed of paper sent out for the first time, which includes a thickness sensing unit for sensing thickness of cut paper conveyed, a rigidity sensing unit to measure bending rigidity of the conveyed paper, and a double-feed determining unit for comparing a value of the thickness of the paper sensed by the thickness unit and a value that measured by the rigidity unit with threshold values of thickness and rigidity.
Abstract: The invention provides a double feed sensing device capable of sensing double feed of paper sent out for the first time. The double feed sensing device includes a thickness sensing unit for sensing thickness of cut paper conveyed, a rigidity sensing unit for sensing bending rigidity of the conveyed paper, and a double feed determining unit for comparing a value of the thickness of the paper sensed by the thickness sensing unit and a value of the bending rigidity of the paper sensed by the rigidity sensing unit with threshold values of thickness and rigidity of the paper set based on values of thickness and bending rigidity of one sheet of the paper and values of thickness and bending rigidity of stacked sheets of the paper, so as to determine whether the paper is double-fed or not.

Journal ArticleDOI
D. Pasini1
TL;DR: Pasini et al. as mentioned in this paper derived the flexural stiffness domains for optimizing the vibration frequency of a multilayered microresonator, and showed that for a given eigenvalue, flexural properties of a two-materials system, including all possible symmetric and asymmetric multiple-layers arrangements, fall into a domain limited by two curves.
Abstract: Flexural stiffness domains have been determined for optimizing the vibration frequency of a multilayered microresonator. It is demonstrated in an efficiency map that, for a given eigenvalue, the flexural properties of a two-materials system, including all possible symmetric and asymmetric multiple-layers arrangements, fall into a domain limited by two curves. These low and upper boundaries describe symmetric three-layers systems consisting of two dissimilar materials. The flexural response model adopted in this paper is based on the Euler-Bernoulli theory, and the results are obtained by extending a scheme for modeling efficiency of monolithic structures (see D. Pasini, "Shape transformers for material and shape selection of lightweight beams", J. Mater. Design, 2006). Shape parameters are introduced to explore the impact on the resonator vibrations of the cross-section shape, the arrangement, symmetry and number of layers, as well as the materials properties and their volume fraction. The application of the maps to a case study shows that the method can assist to exploit geometry and material potential of microstructures, especially at the concept stage of design