Showing papers on "Deflection (engineering) published in 1985"

On the impact of initially stressed composite laminates

Abstract: The impact response behavior of initially stressed composite laminates is investigated using the finite element method. An experimentally established contact law is incorporated into the finite element program. The Newmark time integration algorithm is used for solving the time dependent equations of the plate and the impactor. Numerical results, including the contact force history, deflection, and strain in the plate, are presented. Effects of impact velocity, initial stress, and the mass and size of the impactor are discussed.

Fatigue crack deflection and fracture surface contact: Micromechanical models

Abstract: The variation of cyclic crack propagation rates, under thecombined influence of crack kinking (deflection) and fracture surface contact (closure), is estimated from simple linear elastic analyses of tilted cracks. The predictions of the models are consistent with the experimental results of linear and kinked crack advance in high strength aluminum alloys testedin vacuo. Examples of crack deflection in various engineering alloy systems and some generalizations ofaverage deflection parameters based on microstructural and mechanical factors are discussed. The individual contributions to overall growth rates from deflection and closure processes are evaluated for different mechanical and metallurgical conditions. The significance, implications, and limitations of the models are outlined.

Counterintuitive Behavior in a Problem of Elastic-Plastic Beam Dynamics

Abstract: In a particular example of short pulse loading on a pin-ended beam, the permanent deflection is predicted by a numerical solution to be in the direction opposite that of the load. Analysis of a Shanley-type model shows that this surprising behavior may occur as a consequence of plastic irreversibility combined with geometric nonlinearity, when the peak deflection produced by the pulse lies in a certain range of small magnitudes. Results from a number of well-known structural dynamics codes are shown. These exhibit a wide spread in the predicted final deflections, indicating strong sensitivities of both physical and computational nature.

Illi-pave-based response algorithms for design of conventional flexible pavements

Abstract: In a mechanistic design procedure a structural model is used to predict pavement responses (stresses, strains, displacements). The ILLI-PAVE structural model considers nonlinear, stress-dependent resilient modulus material models and failure criteria for granular materials and fine-grained soils. The computational techniques of the ILLI-PAVE computer program are too costly, complex, and cumbersome to be used for routine design. To incorporate ILLI-PAVE structural model concepts into a mechanistic design concept, simplified analysis algorithms that reliably predict ILLI-PAVE response solutions for typical flexible pavements are needed. ILLI-PAVE-based design algorithms for conventional flexible pavements asphalt concrete (AC) surface plus granular base and subbase are presented for AC radial strain, surface deflection, subgrade deviator stress, subgrade deviator stress ratio, subgrade vertical strain, and subgrade deflection. Pertinent design algorithm inputs are AC thickness, AC modulus, granular layer thickness, and subgrade resilient modulus (E sub Ri). Additional algorithms relating AC radial strain and subgrade deviator stress ratio and surface deflection are also presented. The algorithms are sufficiently accurate for inclusion in mechanistic design procedures.

Auto accessory floor mat

Abstract: An accessory floor mat designed to overlie and protect a portion of the original carpeted floor of an automobile is preformed into a tray-like configuration which also conforms to the contours of the floor portion. The mat snugly fits into the carpeted floor well on a side of the vehicle and thereby resists mat sliding. The stiffness of the mat is such that it maintains its original position in the vehicle under foot exerted lateral forces and also retains its shape while being removed for cleaning. Mat stiffness is defined in terms of forced-to-bend values at specified deflection angles in both a machine direction and a cross direction, as measured in accordance with ASTM D747 on a Tinius Olsen stiffness tester.

Racking Deformations in Wood Shear Walls

Abstract: The theory presented in this paper predicts racking deformations in wood‐stud shear walls. The energy method employed defines the wall performance in terms of the lateral nonlinear load‐slip behavior of the nails which fasten the sheathing to the frame. Using power curves to define the nail loadslip relationship, the theory predicts that wall deformation due to nail slip will also be defined by a power curve. The theory also includes linear deformation due to shear distortion of the sheathing material, and provides accurate estimation of wall performance up to moderate load levels. The method presented should be of interest to engineers who design light frame structures, to researchers, and to those who are concerned with building codes.

Static and Dynamic Formulation of a Symmetrically Laminated Beam Finite Element for a Microcomputer

Abstract: A formulation, an efficient solution procedure, a microcomputer program, and a graphics routine for an anisotropic symmetrically laminated beam finite element in cluding the effect of shear deformation is introduced. The emphasis of the formulation and solution procedure is for simplicity, efficiency, and easy implementation on microcomputers. The element possesses six d.o.f.'s at each of the two nodes: trans verse deflection and slope due to bending and shear, respectively, and a twisting angle and its derivative with respect to the beam axis. The formulation, solution procedure, and the program have been evaluated by performing a systematic choice of examples; whenever possible, the present solutions are compared with alternative existing solu tions.

Shock absorbing assembly for an athletic shoe

Abstract: A shock absorbing assembly for an athletic shoe having a resilient metal plate in the form of a beam which is supported at its end portions by a pair of laterally spaced relatively non-compressible supports. Included between the spaced supports is an open area to permit downward deflection of the metal plate between the supports caused by the weight of a person wearing the shoe whereby the application of downward pressure on the heel portion by a person wearing the shoe downwardly deflects the resilient plate and cradles the heel of said person.

Prestressed Loss and Deflection of Precast Concrete Members

Abstract: rviceability, particularly deflection, is today becoming a more important criterion than in the past due to the utilization of modern design procedures and the use of high strength materials which result in slender members more susceptible to large deflections. This is especially true in prestressed concrete applications, particularly when members are allowed to develop cracks under service loads. Cracking could cause a sizable drop in member stiffness and increased deflections. It is difficult to calculate member deflections with a high degree of accuracy even in a controlled testing laboratory. This is due to the random variations of some of the contributory factors such as the concrete modulus of elasticity, creep, and shrinkage. In field conditions not only are the variations greater, but in addition the number of variables increase. Examples are the uncertainties about levels and duration of loading and seasonal weather variations_ Calculated deflection should therefore be viewed as an "estimate." Acceptable deflection analysis should not be highly complicated mathematically, which would give a false impression of exactness, nor should it be oversimplified, which would compound the probable errors resulting from uncertainties in material properties and loading variations. In this paper a simplified approach to computing instantaneous and long-term deflections is proposed. The approach rationally accounts for all the important parameters, yet it involves certain ap-

Static and Fatigue Tests on Partially Prestressed Beams

Abstract: The fatigue behavior of 12 different sets of partially prestressed concrete beams was experimentally investigated. All beams were rectangular, 9×4.5 in. (229×114mm) in cross section, simply supported on a 9 ft (2.74 m) span and loaded in 4 point bending. Each set consisted of 2 identical specimens designed with the same input parameters. One control beam was tested under static load up to ultimate. The second beam was tested in cyclic fatigue at a constant load range varying between 40% and 60% of the ultimate load capacity of the static specimen. The main input variables were the partial prestressing ratio PPR and the reinforcing index ω¯. Four different levels of PPR and three different levels of ω¯ covering both fully prestressed and fully reinforced were explored. Typical results and observed trends are described. Throughout the tests, measurements of strains in the reinforcement, deflections, crack widths, curvatures and their variation under static and cyclic fatigue loading were systematically reco...

Model for Beam-Mode Buckling of Buried Pipelines

Abstract: An attempt at modeling the so-called “beam mode buckling” exhibited under compression in pipelines is presented. The line is modeled as a long heavy beam on a contacting surface. The reacting surface is modeled first as an elastic and subsequently as a rigid foundation, with the additional constraint that it only reacts to compressive loads. The problem is assumed to possess a localized imperfection. Under compressive axial load, a section of the beam lifts off the foundation. The problem is studied through a large deflection extensional beam nonlinear formulation. The large deflection response of the beam is found to exhibit a limit load which is shown to be imperfection sensitive. A parametric study of the problem as well as a number of examples with actual pipeline parameters are presented.

Dynamics of Falling Weight Deflectometer

Abstract: An elastodynamic analysis of pavement response to Falling Weight Deflectometer blows is presented. The analysis is based on a Fourier synthesis of a solution for periodic loading of elastic or viscoelastic horizontally layered strata. The method is applied to selected flexible AASHO test sections for which high quality experimental data are available in the literature. The results show that inertial effects are important in the prediction of the pavement response. Conventional static analyses yield significantly different results and, therefore, yield erroneous (unconservative) predictions of pavement moduli back‐calculated from deflection data. Elastodynamic analyses, based on fundamental material parameters (Young's modulus, mass density) appear to provide a useful vehicle for correlating pavement response between different loading modes (impulse, vibratory, etc.). Since resonance is a less important factor in the displacement response characteristics of pavements subjected to transient loading, deflect...

Strength of Biaxially Loaded SRC Columns

Abstract: The paper presents the results of an experimental study on the elasto-plastic behavior of 'Steel reinforced concrete (SRC)' columns subjected to biaxially eccentric compression load. The specimen has a 160 multiplied by 160 mm square section containing a rolled H-section, H-100 multiplied by 100 multiplied by 6 multiplied by 8, encased in concrete. Effects of eccentricity, angle between load point and major axis, and slenderness ratio on the load-deflection behavior and the maximum load carrying capacity are investigated. It is observed in the results of test and analysis that a sharp peak appears on the load-deflection curve of a short column because of a concrete crush, while P DELTA effect is more pronounced in a long column and a gradual unloading takes place. In some cases, the deflection corresponding to the strong axis bending stops increasing in the large deflection range, and the column behaves as if it is subjected to the uniaxial bending.

Measurement of apparent young's modulus in the bending of cantilever beam by heterodyne holographic interferometry

Abstract: Detection of micromechanical phenomena in material requires a sufficiently high-accuracy measurement This paper shows the possibility of applying heterodyne holographic interferometry to such experimental verification The effects of the ratios of thickness to grain size on the apparent Young's modulus are evaluated based on the deflection patterns of the cantilever beam The characteristic length l of couple-stress theory is calculated by applying the analytical results of Koiter to our experimental results This value is about one fifth of the grain size

Sheet-bending press incorporating a device for continuous monitoring of the bending angle

Abstract: A press has an upper table carrying a punch and a lower table bearing a tool-carrier. A jack for compensating the deflection inherent in the bending process is fitted in the lower table. The bending device enables the bending angle obtained in the workpiece to be monitored continuously. The bending device includes a series of paired measuring rods, circular in section and longitudinally machined to provide a flat surface for the lower surface of the workpiece to rest on, associated with devices for measuring the rotational angle of the measuring rods, and a control device connected to the rotational angle measuring device, to a device for controlling the jacks that actuate the punch and to the actuating device of the jack for compensating the deflection. A very accurate and constant bending angle is obtained throughout the length of the workpiece. The bending process is automatic and continuous once the operator has fed in the required bending angle.

Creep in chipboard: Part 5: An improved model for prediction of creep deflection

Abstract: On propose un modele a 5 parametres pour la prevision a long terme de la deflexion par fluage de panneaux de particules, particulierement aux faibles niveaux de contraintes