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Showing papers on "Deflection (engineering) published in 2008"


Journal ArticleDOI
TL;DR: In this paper, a microstructure-dependent Timoshenko beam model is developed using a variational formulation, which is based on a modified couple stress theory and Hamilton's principle.
Abstract: A microstructure-dependent Timoshenko beam model is developed using a variational formulation. It is based on a modified couple stress theory and Hamilton's principle. The new model contains a material length scale parameter and can capture the size effect, unlike the classical Timoshenko beam theory. Moreover, both bending and axial deformations are considered, and the Poisson effect is incorporated in the current model, which differ from existing Timoshenko beam models. The newly developed non-classical beam model recovers the classical Timoshenko beam model when the material length scale parameter and Poisson's ratio are both set to be zero. In addition, the current Timoshenko beam model reduces to a microstructure-dependent Bernoulli–Euler beam model when the normality assumption is reinstated, which also incorporates the Poisson effect and can be further reduced to the classical Bernoulli–Euler beam model. To illustrate the new Timoshenko beam model, the static bending and free vibration problems of a simply supported beam are solved by directly applying the formulas derived. The numerical results for the static bending problem reveal that both the deflection and rotation of the simply supported beam predicted by the new model are smaller than those predicted by the classical Timoshenko beam model. Also, the differences in both the deflection and rotation predicted by the two models are very large when the beam thickness is small, but they are diminishing with the increase of the beam thickness. Similar trends are observed for the free vibration problem, where it is shown that the natural frequency predicted by the new model is higher than that by the classical model, with the difference between them being significantly large only for very thin beams. These predicted trends of the size effect in beam bending at the micron scale agree with those observed experimentally. Finally, the Poisson effect on the beam deflection, rotation and natural frequency is found to be significant, which is especially true when the classical Timoshenko beam model is used. This indicates that the assumption of Poisson's effect being negligible, which is commonly used in existing beam theories, is inadequate and should be individually verified or simply abandoned in order to obtain more accurate and reliable results.

995 citations


Journal ArticleDOI
TL;DR: In this article, a unified approach for analyzing the static and dynamic behaviors of functionally graded beams (FGB) with the rotary inertia and shear deformation included is presented, where all material properties are arbitrary functions along the beam thickness.

450 citations


Journal ArticleDOI
TL;DR: In this article, a third order zigzag theory based model for layered functionally graded beams in conjunction with the modified rule of mixtures (MROM) for effective modulus of elasticity is validated through experiments for static and free vibration response.

277 citations


Journal ArticleDOI
TL;DR: In this paper, a theoretical analysis to the FGM (functionally graded materials) thin plates based on the physical neutral surface is presented, which has more merits in the engineering application, because it is easier and simpler than classical laminated plate theory based on geometric middle surface.

272 citations


Journal ArticleDOI
TL;DR: In this article, an experimental and analytical investigation of hollow and concrete filled steel square hollow (SHS) section beams subjected to low velocity, large mass transverse impacts at the beam mid-span was conducted.

167 citations


Journal ArticleDOI
TL;DR: In this paper, a modified energy-balance model coupled with the law of conservation of momentum is proposed to extend the validity of elastic impact models beyond the elastic regime, and three parameters were derived from the static load-deformation response: the elastic stiffness, the critical load at the onset of damage, and the damaged stiffness.

159 citations


Journal ArticleDOI
TL;DR: In this paper, the authors employed the commercial finite element analysis package ANSYS to model the thermal and structural behavior of isolated CFT columns in fire, including the influence of an air gap and slip at the steel/concrete interface on column temperatures and structural behaviour, the sensitivity of CFT fire resistance to concrete tensile behaviour and CFT column initial imperfections.

139 citations


Journal ArticleDOI
TL;DR: In this article, the authors proposed a solution of the problem of buckling and deflection of a circular porous plate with simply supported edge under radial uniform compression and uniformly distributed load (pressure).
Abstract: The main goal of this paper is a solution of the problem of buckling and deflection. A circular porous plate with simply supported edge under radial uniform compression and uniformly distributed load (pressure) is considered. Mechanical properties of the isotropic porous material vary across the thickness of the plate. Middle plane of the plate is its symmetry plane. A field of displacements (geometric model of nonlinear hypothesis) is described. The principle of stationarity of the total potential energy allowed to get a system of differential equations that govern the plate stability. A critical load and a deflection are determined. The results obtained for porous plates are compared to homogeneous circular plates.

131 citations


Journal ArticleDOI
TL;DR: In this paper, a test series consisting of carbon FRP (CFRP) and steel bars reinforced concrete beams are reported, and the results indicated that the behaviour of CFRP and steel reinforced beams was similar in many aspects.

108 citations


Journal ArticleDOI
TL;DR: In this paper, the deformation of a cantilever beam under point load at the free tip is investigated by an analytic method, namely the homotopy analysis method (HAM).

101 citations


Journal ArticleDOI
TL;DR: The authors theoretically demonstrate a plasmonic beam deflector based on the particular properties of surface Plasmon polaritons in metallic nanoslits, showing good agreement with theoretical analysis.
Abstract: The authors theoretically demonstrate a plamonic beam deflector based on the particular properties of surface plasmon polaritons in metallic nanoslits. Beam deflection ranging from 0° to 90° can be achieved by designing the deflector with appropriate structural parameters. Numerical illustrations of deflectors for variant deflection angles are presented through finite-difference time-domain simulation, showing good agreement with theoretical analysis. The efficiency and some factors influencing the deflection behavior are also discussed.

Journal ArticleDOI
TL;DR: In this article, the authors developed efficient strategies for controlling the force-induced surface dimensional errors in peripheral milling of thin-walled structures, where the focus was on how to select the feed per tooth and depth of cut simultaneously for tolerance specification and maximization of the feed each tooth simultaneously.
Abstract: This paper aims at developing efficient strategies for controlling the force-induced surface dimensional errors in peripheral milling of thin-walled structures. Emphasis is put on how to select the feed per tooth and depth of cut simultaneously for tolerance specification and maximization of the feed per tooth simultaneously. Three methods are presented. The first one proceeds by optimally selecting the maximum feed per tooth without tolerance violation. The second one is to find the appropriate cutting parameters by solving a linear programming problem. To show the efficiency of the first two methods, the third one, i.e. the so-called mirror error compensation method taken from references, is also addressed for comparison. Mechanistic model for cutting force estimation, cantilever beam model for cutter deflection estimation and finite element method for workpiece deflection estimation are used in all three methods. Besides, improvements on the calculation scheme of the surface dimensional error have been made and both numerical and experimental results are adopted for verification.

Journal ArticleDOI
TL;DR: In this paper, the performance of restrained steel beams in fire experiments that were completed recently in the Fire Laboratory of Tongji University has been described, and it is shown that restrained steel beam have better fire-resistant capability than isolated steel beams.

Journal ArticleDOI
TL;DR: In this article, the results of testing two simply and three continuously supported concrete beams reinforced with glass fiber-reinforced polymer (GFRP) bars are presented, and the amount of GFRP reinforcement was the main parameter investigated.
Abstract: The results of testing two simply and three continuously supported concrete beams reinforced with glass fiber-reinforced polymer (GFRP) bars are presented. The amount of GFRP reinforcement was the main parameter investigated. Over and under GFRP reinforcements were applied for the simply supported concrete beams. Three different GFRP reinforcement combinations of over and under reinforcement ratios were used for the top and bottom layers of the continuous concrete beams tested. A concrete continuous beam reinforced with steel bars was also tested for comparison purposes. The experimental results revealed that over-reinforcing the bottom layer of either the simply or continuously supported GFRP beams is a key factor in controlling the width and propagation of cracks, enhancing the load capacity, and reducing the deflection of such beams. Comparisons between experimental results and those obtained from simplified methods proposed by the ACI 440 Committee show that ACI 440.1R-06 equations can reasonably pred...

Journal ArticleDOI
TL;DR: In this article, the authors used finite element code (ADINA) to analyze numerical tunnel model of 9 segment rings and the analysis results indicate attitude deflection of shield machine causes biggish dislocation between segments, and the most affected and weakest part in same ring which causes irregular displacement and dislocation in whole tunnel structure.

Journal ArticleDOI
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 ...

Journal ArticleDOI
TL;DR: In this article, a rotating beam finite element in which the interpolating shape functions are obtained by satisfying the governing static homogenous differential equation of Euler-Bernoulli rotating beams is developed.

Journal ArticleDOI
TL;DR: 3D simulation system is presented which is employed in order to predict cutting forces and tool deflection during end-milling operation and results indicate that the simulation is capable of predicting thecutting forces and tools deflection.

Journal ArticleDOI
TL;DR: The aim of this study was to evaluate the effect of tools and probes on deflection angle and irrigation flow volume in the latest generation of flexible renoscopes.
Abstract: Introduction: Flexible renoscopes offer access to almost all points within the collecting system. For stone workup, excellent visualization is mandatory. Therefore, irrigation flow is of critical importance. The aim of this study was to evaluate the effect of tools and probes on deflection angle and irrigation flow volume in the latest generation of flexible renoscopes. Methods: Five flexible renoscopes [Wolf (Viper), Storz (FlexX2), ACMI (DUR-8 Elite, DUR-D), Olympus (URF-P5)] were tested. Deflection angle, lowest diameter of the bent tip, and flow rates were measured. Recorded parameters were deflection angle and flow rate of the empty and loaded scopes. A laser probe (273 μm), biopsy forceps (2.4–3.0 French), and tipless nitinol baskets (1.5–2.4 French) were tested. Results: Deflection has no influence on flow rate. The size of the basket has no influence on the maximum angle of deflection. Introducing the laser fiber or the biopsy forceps leads to relevant loss of deflection (laser fiber: 4.44%–10.21%...

Journal ArticleDOI
TL;DR: In this article, the effects of shrinkage restraint cracking and loading history on deflection of reinforced concrete flexural members are examined and the authors make recommendations for changes to ACI 318.
Abstract: This paper examines the effects of shrinkage restraint cracking and loading history on deflection of reinforced concrete flexural members. Findings show that deflections of lightly reinforced members are highly sensitive to both shrinkage restraint cracking and loading history, while deflections of more heavily reinforced members are insensitive to these effects at full service load. Results of a deflection example are presented along with recommendations for changes to ACI 318. One recommended change is the adoption of a lower cracking moment than the one currently specified in the code to account for shrinkage restraint stresses. It is also recommended that the code evaluate deflection using an effective moment of inertia based on the full dead plus live service load to account for preloading from construction loads prior to installation of nonstructural elements. An evaluation of these changes show that the recommendations will have a significant influence on deflection of lightly reinforced concrete members.

Patent
16 Sep 2008
TL;DR: In this paper, a catheter that provides bi-directional steering and allows for deflection sensitivity adjustment is presented, where a rotatable pulley arm and two pulleys are used to adjust a maximum degree of deflection of the tip section.
Abstract: A catheter that provides bi-directional steering and allows for deflection sensitivity adjustment includes a catheter body, a deflectable tip section and a control handle, wherein the control handle has a deflection member adapted for user manipulation, a deflection assembly responsive to the deflection member to draw on a tensile puller member for deflecting the tip section, and an adjustment mechanism adapted to adjust sensitivity of the deflection member. The adjustment mechanism also correspondingly adjusts a maximum degree of deflection of the tip section. The deflection assembly includes a rotatable pulley arm and two pulleys, and a deflection sensitivity adjustment mechanism with a cam device that varies a separation distance between the pulleys. The cam device is internally located in the pulley arm and is rotatable via deflection sensitivity knob by the user to increase the separation distance for greater deflection sensitivity in a deflection member user interface, or to decrease the separation distance for greater maximum degree of tip deflection.

Journal ArticleDOI
TL;DR: In this paper, the authors measured the dynamic response of end-clamped monolithic beams and sandwich beams by loading the beams at mid-span using metal foam projectiles and found that the performance of the sandwich beams with a transverse core orientation is very similar to that of the monolithic beam.

Journal Article
TL;DR: A semi-mechanistic, semi-empirical analysis technique has been developed in South Africa in terms of which deflection bowl parameters, measured with the FWD, are used in a relative benchmarking methodology in conjunction with standardised visual survey methodology to give guidance on individual layer strengths and pinpoint rehabilitation needs.
Abstract: The falling weight deflectometer (FWD) is used worldwide as an established, valuable, nondestructive road testing device for pavement structural analyses. The FWD is used mostly for rehabilitation project level design investigations and for pavement management system (PMS) monitoring on a network basis. In project level investigations, design charts based on both empirical relations and mechanistic or theoretically based approaches are often used to provide structural evaluations and rehabilitation options. The full mechanistic approach normally uses multi-layer linear elastic theory and back-calculation procedures that have come under scrutiny owing to the inaccuracy of results. A semi-mechanistic, semi-empirical analysis technique has been developed in South Africa in terms of which deflection bowl parameters, measured with the FWD, are used in a relative benchmarking methodology in conjunction with standardised visual survey methodology to give guidance on individual layer strengths and pinpoint rehabilitation needs. This benchmark methodology enables the determination of the relative structural condition of the pavement over length and in depth without the requirement for detailed as-built data. A further correlation study with calculated surface moduli and deflection bowl parameters is presented here for granular base pavements, which can enhance benchmarking methodology.

Journal ArticleDOI
TL;DR: In this article, the authors derived analytical solutions for simply supported beam-column elements with bi-symmetric I sections under combined bending and axial forces, and validated the proposed solutions by recourse to non-linear FEM software where shell elements are used in mesh process.
Abstract: Based on a non-linear stability model, analytical solutions are derived for simply supported beam-column elements with bi-symmetric I sections under combined bending and axial forces. An unique compact closed-form is used for some representative load cases needed in design. It includes first-order bending distribution, load height level, pre-buckling deflection effects and presence of axial loads. The proposed solutions are validated by recourse to non-linear FEM software where shell elements are used in mesh process. The agreement of the proposed solutions with bifurcations observed on non-linear equilibrium paths is good. It is proved that classical linear stability solutions underestimate the real resistance of such element in lateral buckling stability especially for I section with large flanges. Numerical study of incidence of axial forces on lateral buckling resistance of redundant beams is carried out. When axial displacements of a beam are prevented important tension axial forces are generated in the beam. This results in important reduction of displacements and for some sections, the beam behaviour becomes non-linear without any bifurcation.

Journal ArticleDOI
TL;DR: In this article, the authors compared three widely used pull-in theoretical models (i.e., one-dimensional lumped model, linear supposition model and planar model) by considering both cantilever and fixed-fixed type mi cro and nano-switches.
Abstract: The existing three widely used pull-in theoretical models (i.e., one-dimensional lumped model, linear supposition model and planar model) are compared with the nonlinear beam mode in this paper by considering both cantilever and fixed-fixed type mi cro and nano-switches. It is found that the error o f the pull-in parameters between one-dimensional lumped model and the nonlinear beam model is large because the denominator of the electrostatic force is minim al when the electrostatic force is computed at the maximum deflection along the beam. Since both the linear superposition model and the slender planar model consider the variation of electrostatic force with the beam’s deflection, these two models not o nly are of the same type but also own little error of the pull-in parameters with the nonlinear beam model, the error brought by these two models attributes to tha t the boundary conditions are not completely satisf ied when computing the numerical integration of the def lection.

Journal ArticleDOI
TL;DR: In this paper, the authors presented a pilot application of Brillouin optical time domain reflectometry to measure strain profiles along the steel girders of a continuous slab-on-girder bridge subjected to diagnostic load testing.
Abstract: Fiber optic sensing technologies are emerging as valid alternatives for the health monitoring of civil structures. Distributed sensors based on Brillouin scattering add the unique capability of measuring strain and temperature profiles along optical fibers. Measurement is performed by establishing the correlation between fiber strain and temperature, and the frequency shift of the Brillouin backscattered light induced by a monochromatic light pulse. The technology holds potential for use on large structures and integrated transportation infrastructure. Its effectiveness has been assessed through scaled laboratory experiments, whereas field validation is limited to very few demonstration projects conducted to date. This paper presents a pilot application of Brillouin optical time domain reflectometry to measure strain profiles along the steel girders of a continuous slab-on-girder bridge subjected to diagnostic load testing. One of the exterior continuous girders required heat-straightening after falling during construction due to wind. The significance of applying a distributed measurement technique lies in the potential to assess the global girder response, which would be impractical and uneconomical using discrete measurement techniques. A 1.16 km long sensing circuit was installed onto the web of four girders. The circuit comprises bare optical fiber sensors, and a novel adhesively bonded fiberglass tape with embedded sensing fibers for strain measurement and thermal compensation. The strain profiles were first converted into deflection profiles and validated against discrete deflection measurements performed with a high-precision total station system. Structural assessment based on comparison of the strain profiles with the results of three-dimensional finite-element analysis of the bridge superstructure, and with specification mandated criteria, indicated that the response of the girder under investigation was within the design limits, and did not pose serviceability concerns. Factors that may affect measurement accuracy are finally discussed on the basis of the experimental and numerical results.

Journal ArticleDOI
TL;DR: In this paper, both the angle of attack and the deflection are modeled as a sinusoidal wave and the outputs (the deflection and the transition point position) are well controlled and the results are very good.
Abstract: steps for the deflection but adds a sinusoidal component for the angle of attack; this simulation is closer to the cruise flight regime. During the third simulation, both the angle of attack and the deflection are modeled as a sinusoidal wave. The outputs (the deflection and the transition point position) are well controlled and the results are very good. Hence, it is concluded that this original method of control is suitable for the control of the transition point position from the laminar to turbulent region on a morphing wing airfoil.

Journal ArticleDOI
TL;DR: In this article, a C 0 nonlinear finite element formulation of the random nonlinear problem based on higher order shear deformation theory in the von Karman sense is presented.

Journal ArticleDOI
TL;DR: In this paper, a verified strict model for smart composite plate deflection, which embedded with the SMA wires, using response surface method (RSM), was developed to estimate deflection ratio as a mathematical function of the main process planning parameters.
Abstract: Optimization of the volume fraction, the orientation and the through thickness location of the shape memory alloy (SMA) wires was used in order to minimize the maximum transverse deflection of the hybrid composite plate during the low-velocity impact phenomena. The prediction of optimal conditions of good geometrical properties of SMA wires in smart hybrid composites plays an important role in process planning. The present work deals with the study and development of a verified strict model for smart composite plate deflection, which embedded with the SMA wires, using response surface method (RSM). This method helped us to estimate deflection ratio as a mathematical function of the main process planning parameters. The experimentation was carried out with the first-order shear deformation theory, the Fourier series method and solving analytically the system of governing differential equations of the plate. The interaction between the impactor and the plate also modeled with a system having two-degrees-of-freedom, consisting of springs-masses. A nonlinear mathematical model, in terms of the volume fraction and layer sequence (the orientation and the through thickness location) of the SMA wires was delivered. The results indicated that the volume fraction is a more important factor affecting the optimization and the design process of the structures.

Journal ArticleDOI
TL;DR: In this paper, a 25m long and 1.8m deep bulb-tee prestressed concrete girder was compositely fabricated with a 2m wide and 22 cm thick reinforced concrete deck.