Showing papers on "Flexural rigidity published in 2008"
TL;DR: In this paper, the authors measured the mechanical properties of few-layer graphene and graphite flakes that are suspended over circular holes and predicted fundamental resonance frequencies of these nanodrums in the gigahertz range based on the measured bending rigidity and tension.
Abstract: We have measured the mechanical properties of few-layer graphene and graphite flakes that are suspended over circular holes. The spatial profile of the flake’s spring constant is measured with an atomic force microscope. The bending rigidity of and the tension in the membranes are extracted by fitting a continuum model to the data. For flakes down to eight graphene layers, both parameters show a strong thickness dependence. We predict fundamental resonance frequencies of these nanodrums in the gigahertz range based on the measured bending rigidity and tension.
355 citations
TL;DR: In this paper, the bending rigidity of and the tension in the membranes are extracted by fitting a continuum model to the data, and the fundamental resonance frequencies of these nanodrums in the GHz range are predicted.
Abstract: We have measured the mechanical properties of few-layer graphene and graphite flakes that are suspended over circular holes. The spatial profile of the flake's spring constant is measured with an atomic force microscope. The bending rigidity of and the tension in the membranes are extracted by fitting a continuum model to the data. For flakes down to eight graphene layers, both parameters show a strong thickness-dependence. We predict fundamental resonance frequencies of these nanodrums in the GHz range based on the measured bending rigidity and tension.
290 citations
TL;DR: In this article, the flexural behavior of an ultra-highperformance concrete (UHPC) was investigated through the testing and related analysis of a full-scale prestressed I-girder.
Abstract: The flexural behavior of an ultrahigh-performance concrete (UHPC) was investigated through the testing and related analysis of a full-scale prestressed I-girder. A 28 ksi (193 MPa) compressive strength steel fiber reinforced concrete was used to fabricate an 80 ft (24.4 m) long AASHTO Type II girder containing 26 prestressing strands and no mild steel reinforcement. Intermediate and final behaviors, including cracking, flexural stiffness, and moment capacity, were investigated. Test results are compared to predictions based on standard analytical procedures. A relationship between tensile strain and crack spacing is developed. The uniaxial stress-strain response of UHPC when subjected to flexural stresses in an I-girder is determined and is verified to be representative of both the stress and flexural stiffness behaviors of the girder. A flexural design philosophy for this type of girder is proposed.
186 citations
TL;DR: In this article, a micro-mechanics model for non-isotropic, open-celled foams is developed using an elongated tetrakaidecahedron (Kelvin model) as the repeating unit cell.
156 citations
TL;DR: In this paper, the effect of reinforcement corrosion on the behavior of concrete beams reinforced with plain round bars was investigated, and it was concluded that an enhancement of anchorage capacity was associated with reinforcement corrosion.
Abstract: This paper describes experimental work to investigate the effect of reinforcement corrosion on the behaviour of concrete beams reinforced with plain round bars. Particular attention is paid to the bond between reinforcement and concrete. Four groups of beam specimens were tested, each designed to investigate specific aspects of structural performance including stiffness and deflection under service loads, ultimate flexural and shear strengths and deformation capacity at failure. Beams were conditioned to induce loss of cross-sectional reinforcement of up to 10% owing to corrosion, equivalent to 0·3 mm corrosion penetration, and longitudinal crack widths of 1·0 mm. Flexural stiffness of specimens detailed for a flexural mode of failure was not impaired by corrosion. Strength of beams with corroded bars equalled or exceeded that of companion non-corroded specimens in all cases, despite loss of bar section. It is concluded that an enhancement of anchorage capacity, believed to be associated principally with ...
85 citations
TL;DR: In this paper, the effects of transverse shearing due to low shear modulus of microtubules are investigated using a Timoshenko-beam model, with detailed comparison between the Timoshenko beam model, classical isotropic Euler-Bernoulli beam model and a more accurate 2D orthotropic elastic shell model.
Abstract: Microtubules are characterized by extremely low shear modulus that is a few orders of magnitude lower than longitudinal modulus. In this paper, the effects of transverse shearing due to low shear modulus of microtubules are investigated using a Timoshenko-beam model, with detailed comparison between the Timoshenko-beam model, classical isotropic Euler–Bernoulli beam model and a more accurate 2D orthotropic elastic shell model. It is confirmed that transverse shearing is mainly responsible for the length-dependent flexural rigidity of an isolated microtubule reported in the literature, which cannot be explained by the widely used Euler–Bernoulli beam model. Indeed, the length-dependent flexural rigidity predicted by the Timoshenko-beam model is found to be in good quantitative agreement with known experimental data. In particular, the present Timoshenko-beam model predicts that, because of the length dependence of flexural rigidity, microtubules of different lengths could sustain almost equal maximum axial compressive force against column buckling, a conclusion that could have some interesting consequences to the mechanical behavior of cells. These results recommend that the Timoshenko-beam model offers a unified simple 1D model, which can capture the length dependence of flexural rigidity and be applied to various static and dynamic problems of microtubule mechanics.
73 citations
TL;DR: There are significant differences on the mechanical properties between urogynecology meshes under two types of mechanical tests.
Abstract: The aim of this study was the comparison of the stiffness of different meshes under two types of mechanical tests Five different mesh types were mechanically tested The methods used consisted on uniaxial tension test (tensile stiffness) and tape ring tests, experimental continuous compression of the mesh loops (flexural stiffness) The most significant difference of tensile stiffness behaviour appears between Aris™ and TVTO™ From the analysis of the experimental data, we divided the flexural stiffness, in two main groups The first group includes Auto Suture™ and Aris™ meshes The two meshes seem to have a similar flexural behaviour The second group includes TVTO™, Uretex™ and Avaulta™ The difference between these two groups is clearly evident comparing TVTO™ and Aris™ This study shows that there are significant differences on the mechanical properties between urogynecology meshes
70 citations
TL;DR: It was concluded that a three-dimensional elastic shell model of single-walled carbon nanotubes can be established with well-defined effective thickness.
Abstract: This paper proposes a two-dimensional elastic shell model to characterize the deformation of single-walled carbon nanotubes using the in-plane rigidity, Poisson ratio, bending rigidity and off-plane torsion rigidity as independent elastic constants. It was found that the off-plane torsion rigidity of a single-walled carbon nanotube is not zero due to the off-plane change in the π-orbital electron density on both sides of the nanotube. It was concluded that a three-dimensional elastic shell model of single-walled carbon nanotubes can be established with well-defined effective thickness.
64 citations
TL;DR: In this paper, the axial forces and the flexural stiffness of the end constraints of a tie-beams of arches and vaults were derived by one vibration frequency and three components of the corresponding mode shape.
60 citations
TL;DR: More rigorous analyses have been conducted in improving the classical capstan equation by including both the rod bending rigidity and a power-law friction (in place of the Amonton's law) into the formula as discussed by the authors.
55 citations
TL;DR: In this article, the optimal location and dimensions of longitudinal stiffeners in web plates under in-plane bending are investigated, and an equation for minimum required second moment of area of stiffeners is presented and compared to that recommended by AASHTO.
Abstract: Optimum location and dimensions of longitudinal stiffeners in web plates under in-plane bending are investigated. This parametric study is performed by numerical simulation utilizing finite element method. Several plates having various aspect ratios are analyzed and an equation for minimum required second moment of area of stiffeners is presented and compared to that recommended by AASHTO. Also, it is shown that the optimum location of stiffener mainly depends on its relative flexural rigidity.
TL;DR: In this paper, a homogenised model for the flexural stiffness is formulated employing Reddy and Bickford's quadratic shear in each layer, in contrast to the classical model of Oberst and Frankenfeld for thin beams, which does not take into account shear deformations.
TL;DR: A detailed, biophysical model is presented that accurately predicts the biophysical properties and behavior of microtubules directed by E-fields, which opens new avenues for the design of biomolecular nanotransport systems.
TL;DR: A theoretical model of the capstan problem including the extensibility and the Poisson's ratio of the rod is established in this paper, where several cases were examined to investigate the effects of important parameters on the tension transmission efficiency.
TL;DR: In this paper, a geometrically exact formulation of cables suffering axis stretching and flexural curvature is presented, which is based on nonlinearly viscoelastic constitutive laws for the tension and bending moment with the additional constitutive nonlinearity accounting for the no-compression condition.
Abstract: A geometrically exact formulation of cables suffering axis stretching and flexural curvature is presented. The dynamical formulation is based on nonlinearly viscoelastic constitutive laws for the tension and bending moment with the additional constitutive nonlinearity accounting for the no-compression condition. A continuation method, combined with a mixed finite-difference spatial discretization, is then employed to path-follow the static responses of cables subject to forces or support displacements. These computations, conducted in the quasistatic regime, are based on cables with linearly elastic material behaviors, whereas the nonlinearity is in the geometric stiffness terms and the no-compression behavior. The finite-difference results have been confirmed employing a weak formulation based on quadratic Lagrangian finite elements. The influence of the flexural stiffness on the nonlinear static responses is assessed comparing the results with those obtained for purely extensible cables. The properties of the frequencies of the linear normal modes of cables with flexural stiffness are also investigated and compared with those of purely extensible cables.
TL;DR: In this article, the problem of radiation (both heave and sway) of water waves by a submerged sphere in deep as well as in uniform finite depth water with an ice cover was formulated using the multipoles method, with the ice cover being modeled as an elastic plate of very small thickness.
Abstract: Using the multipoles method, we formulate the problems of radiation (both heave and sway) of water waves by a submerged sphere in deep as well as in uniform finite depth water with an ice-cover, with the ice-cover being modelled as an elastic plate of very small thickness. In each case this leads to an infinite system of linear equations which are solved numerically by standard techniques. The added-mass and damping coefficients for a heaving and swaying sphere are obtained and depicted graphically against the wave number for various values of the radius of the submerged sphere and flexural rigidity of the ice-cover to show the effect of the presence of ice-cover on these quantities. When the flexural rigidity is taken to be zero, the numerical results for the added-mass and damping coefficient for water with a free surface are recovered.
TL;DR: The relatively low flexural rigidity measured for barnacles suggests that a rigid punch approximation is not sufficient to account for the contributions to adhesion mechanics due to flexing of real barnacles during release.
Abstract: The mechanical properties of barnacle base plates were measured using a punch test apparatus, with the purpose of examining the effect that the base plate flexural rigidity may have on adhesion mechanics. Base plate compliance was measured for 43 Balanus amphitrite (=Amphibalanus amphitrite) barnacles. Compliance measurements were used to determine flexural rigidity (assuming a fixed-edge circular plate approximation) and composite modulus of the base plates. The barnacles were categorized by age and cement type (hard or gummy) for statistical analyses. Barnacles that were ‘hard’ (≥70% of the base plate thin, rigid cement) and ‘gummy’ (>30% of the base plate covered in compliant, tacky cement) showed statistically different composite moduli but did not show a difference in base plate flexural rigidity. The average flexural rigidity for all barnacles was 0.0020 Nm (SEM ± 0.0003). Flexural rigidity and composite modulus did not differ significantly between 3-month and 14-month-old barnacles. The relatively ...
TL;DR: The bending rigidity is negative and that on approach to the critical point it vanishes proportionally to the interfacial tension, both features are in agreement with Monte Carlo simulations.
Abstract: To describe the full spectrum of surface fluctuations of the interface between phase-separated colloid-polymer mixtures from low scattering vector q (classical capillary wave theory) to high q (bulklike fluctuations), one must take account of the interface's bending rigidity. We find that the bending rigidity is negative and that on approach to the critical point it vanishes proportionally to the interfacial tension. Both features are in agreement with Monte Carlo simulations.
TL;DR: In this paper, the bending rigidity of hexagonal prism β [111]-SiC nanowires was derived by considering a nanowire as a composite of a hypothetical bulk phase, a two-dimensional surface phase and a one-dimensional edge phase.
TL;DR: The buckling process based on the temperature dependence of the force-velocity relationship of kinesin motility is discussed and the flexural rigidity of a microtubule is measured.
TL;DR: In this paper, the post-buckling solutions of non-uniform linearly and non-linearly elastic rods are constructed via a higher-order perturbation approach.
TL;DR: Good agreement with available experimental data was obtained offering an atomic level explanation for stable bending of A-tract containing DNA molecules, and the DNA-bending persistence length estimated from the explicit solvent simulations is in good agreement with experiment.
Abstract: DNA-bending flexibility is central for its many biological functions. A new bending restraining method for use in molecular mechanics calculations and molecular dynamics simulations was developed. It is based on an average screw rotation axis definition for DNA segments and allows inducing continuous and smooth bending deformations of a DNA oligonucleotide. In addition to controlling the magnitude of induced bending it is also possible to control the bending direction so that the calculation of a complete (2-dimensional) directional DNA-bending map is now possible. The method was applied to several DNA oligonucleotides including A(adenine)-tract containing sequences known to form stable bent structures and to DNA containing mismatches or an abasic site. In case of G:A and C:C mismatches a greater variety of conformations bent in various directions compared to regular B-DNA was found. For comparison, a molecular dynamics implementation of the approach was also applied to calculate the free energy change associated with bending of A-tract containing DNA, including deformations significantly beyond the optimal curvature. Good agreement with available experimental data was obtained offering an atomic level explanation for stable bending of A-tract containing DNA molecules. The DNA-bending persistence length estimated from the explicit solvent simulations is also in good agreement with experiment whereas the adiabatic mapping calculations with a GB solvent model predict a bending rigidity roughly two times larger.
TL;DR: In this paper, an experimental investigation of the behavior of concrete-encased composite columns subjected to short-term axial load and biaxial bending is reported. But the main variables in the tests were considered as eccentricity of applied axial loads, concrete compressive strength, cross section, and slenderness effect.
Abstract: This paper reports an experimental investigation of the behaviour of concrete-encased composite columns subjected to short-term axial load and biaxial bending. In the study, six square and four L-shaped cross section of both short and slender composite column specimens were constructed and tested to examine the load-deflection behaviour and to obtain load carrying capacities. The main variables in the tests were considered as eccentricity of applied axial load, concrete compressive strength, cross section, and slenderness effect. A theoretical procedure considering the nonlinear behaviour of the materials is proposed for determination of the behaviour of eccentrically loaded short and slender composite columns. Two approaches are taken into account to describe the flexural rigidity (EI) used in the analysis of slender composite columns. Observed failure mode and experimental and theoretical load-deflection behaviour of the specimens are presented in the paper. The composite column specimens and also some composite columns available in the literature have been analysed and found to be in good agreement with the test results.
TL;DR: In this paper, the structural behavior of lapped connections over the internal supports in multi-span cold-formed steel Z purlin systems was investigated, and the moment resistance and effective flexural rigidity of two typical connection configurations, i.e., web bolts plus self-drilling screws at both flanges or at the top flange only, were considered.
Abstract: This paper reports an experimental investigation on the structural behavior of lapped connections over the internal supports in multi-span cold-formed steel Z purlin systems. The moment resistance and effective flexural rigidity of two typical connection configurations, i.e. web bolts plus self-drilling screws at both flanges or at the top flange only, are considered. In the moment resistance test, a total of 30 specimens with different connection configurations and connection lengths are tested, from which, after careful calibration, the assessment of moment resistance of such lapped connections as well as several useful design suggestions are proposed. In the effective flexural rigidity test, full-scale two-spanned purlins, with two external pin ends and one lapped connection over the internal support, are adopted. Lapped connections with different configurations and two practical connection lengths of 10% and 20% of span are concerned. Based on test results, the effective flexural rigidities of lapped connections studied in this paper are proposed, respectively, for the stress analysis and deflection analysis.
TL;DR: In this article, a closed form expression to determine the effective flexural modulus of a laminated composite beam is developed and applied to the bending, buckling and free vibration response of generally laminated composites with various boundary supports.
TL;DR: In this paper, a new tester which uses a cross-shaped specimen to measure fabric drape and stiffness is proposed, where the warp and the weft strips of the specimen are supported at the central part and bend under its...
Abstract: A new tester which uses a cross-shaped specimen to measure fabric drape and stiffness is proposed. The warp and the weft strips of the specimen are supported at the central part and bend under its ...
TL;DR: In this paper, the in-plane stiffness of carbon nanotubes is reported to be about 372-376J∕m2 and bending rigidity is found to be around 1.78eV.
Abstract: Molecular mechanics calculations for in-plane stiffness, shear modulus, and the bending rigidity of single-walled carbon nanotubes are reported in this work through the calculations of the strain energy for carbon nanotubes and graphite sheets subjected to various types of loading. Elastic rod and plate theories are employed to link the material properties of carbon nanotubes directly to the molecular mechanics calculations. The in-plane stiffness of carbon nanotubes is about 372–376J∕m2. The bending rigidity is found to be around 1.78eV for relatively large tubes and graphite sheets.
31 Mar 2008
TL;DR: A simplified mathematical model for free vibrations of nonuniform viscoelastic flexural beams is presented in this paper, where mass intensity, the material damping intensity and the flexural stiffness of the beam are assumed varying as power functions along the beam.
Abstract: A simplified mathematical model for free vibrations of nonuniform viscoelastic flexural beams is presented The mass intensity, the material damping intensity and the flexural stiffness of the beam are assumed varying as power functions along the beam An analytical solution for the fourth order differential equation of beam vibration under appropriate boundary conditions is obtained by factorization Mode shapes and damped natural frequencies of the beam are obtained for wide range of beam characteristics The model results agree with those found in literature for uniform beams
TL;DR: In this paper, the authors examined the flexural response of the vibration-damping type of laminated steel through the comparison of beam theory predictions with the experimental results for cantilever beam and three-point bending configurations.
Journal Article•
TL;DR: In this paper, the relationship between fabric stiffness and warp diameter, filling diameter, fabric modulus, and fabric density was analyzed, and the measured fabric stiffness values were compared with theoretical calculations that showed good agreement.
Abstract: Flexural rigidity of a fabric is among the important properties, especially for industrial applications of high performance fabrics. The relationships between various fabric properties and fabric stiffness were analyzed. Several monofilament fabrics were tested in the warp direction for this purpose. It was found that there were close relationships between fabric stiffness and warp diameter, filling diameter, fabric modulus and fabric density. As yarn diameters and fabric modulus increase, the stiffness of fabric also increases. It was evident that fabric design has also an effect on fabric stiffness for the tested fabrics. The measured fabric stiffness values were compared with theoretical calculations that showed good agreement