Showing papers on "Deflection (engineering) published in 1970"

Reinforced Concrete response to simulated earthquakes

Abstract: A series of reinforced concrete specimens has been subjected to static tests as well as periodic and simulated earthquake motions to develop realistic analytical models for the earthquake response of the elements and materials involved. During some of the dynamic tests the specimen responded with a displacement of the order of six times the initial yield deflection. The stiffness and energy absorbing capacity of the specimens changed considerably and, at times, very rapidly during the dynamic tests. A realistic conceptual model for predicting the dynamic response of a reinforced concrete member should be based on a static force-displacement relationship which reflects the changes in stiffness for loading and unloading as a function of the previous loading history. The dynamic response calculated on the basis of the proposed force-displacement relationship resulted in satisfactory agreement with the measured response. With the hysteresis loops defined by the proposed force-displacement relationship, it was not necessary to invoke additional sources of energy absorption for a satisfactory prediction of the dynamic response.

Deflection of an optical guided wave by a surface acoustic wave

Abstract: The experimental demonstration of deflection of an optical film‐guided wave by a surface acoustic wave is reported. When Bragg conditions are satisfied, 0.18 W acoustic power gives rise to 66% deflection efficiency as measured by the depletion of the incident optical guided wave.

Stress and Deflection in the Lithosphere near Lake Kariba—I

Abstract: Summary Calculations of incremental stress and deflection in the crust have been made as part of a study of load-induced seismic activity at Lake Kariba. A general method is described for computing any desired stress components anywhere in an elastic half-space near a load of any shape on its surface. The program also computes the elastic depression and the gravitational energy converted to stored elastic strain energy. The static incremental stress and depression in the lithosphere near Lake Kariba are discussed with the aid of vertical sections and maps. The maximum shear stress under the deepest part of the lake rises to 2.12 bars, and the downward normal stress to 6.68 bars. The maximum depression in the Sanyati Basin is 23.5 cm. Computed depression differences along the Makuti-Kariba road are shown to be in excellent agreement with results of repeated precise levelling. The deflection is therefore mainly elastic and Young's modulus is near 0.85 megabars for the lithosphere in the area. Some evidence is available which suggests vertical movements of blocks on fault planes, no doubt associated with the earthquakes. Extended relevelling should give results of great scientific and engineering value. Stress differences produced by the lake in the upper mantle are too small to produce flow there, so that inelastic depression of the crust toward isostatic compensation of the load is not to be expected.

Lateral Load Tests on Piles-Arkansas River Project

Abstract: FIELD LATERAL LOAD TESTS WERE MADE ON A VARIETY OF PILES DRIVEN WITH DIFFERENT HAMMERS TO DEVELOP CRITERIA FOR THE DESIGN AND CONSTRUCTION OF PILE FOUNDATIONS IN SAND FOR LOCKS AND DAMS OF THE LOWER ARKANSAS RIVER. THE INVESTIGATION INCLUDED DETERMINATION OF THE EFFECTS OF PILE BATTER, REPETITIVE LOAD, JETTING AND PREJETTING, AND DENSIFICATION OF THE FOUNDATION SOILS ON THE FLEXURAL AND LATERAL LOAD-DEFORMATION BEHAVIOR OF INDIVIDUAL PILES. THE PILE TESTS SHOWED THAT: (1) TRIANGULAR DISTRIBUTION OF MODULUS OF HORIZONTAL SUBGRADE REACTION NH WITH RESPECT TO DEPTH IS A GOOD APPROXIMATION; (2) COEFFICIENT NH IS DEPENDENT ON THE PILE DEFLECTION; (3) REPETITIVE LOADING INCREASES TOTAL DEFLECTION AT A GIVEN LOAD LEVEL BY ABOUT 100%; (4) FOR A GIVEN LATERAL LOAD, FULLY JETTED PILES DEFLECT 20% TO 50% MORE THAN UNJETTED PILES; (5) DENSIFICATION OF THE FOUNDATION SANDS INCREASES NH VALUE BY ABOUT 100%; AND (6) THE LATERAL LOAD CAPACITY OF A PILE IS ESSENTIALLY INDEPENDENT OF THE HAMMER USED TO DRIVE THE PILE. /ASCE/

Axisymmetric Behavior of an Elastic Spherical Shell Compressed Between Rigid Plates

Abstract: Abstract : The paper presents an analysis of stresses and deflections produced in a thin, complete spherical shell when it is compressed between two parallel rigid plates. The analysis accounts for finite deflections and rotations, but assumes that the material remains linearly elastic throughout the deformation. It is also assumed that the region of the shell which is in contact with the plate remains flat. The deformation state at which the contact region buckles is given. (Author)

Optimization of structural design

Abstract: Typical problems of optimal structural design are discussed to indicate mathematical techniques used in this field. An introductory example (Section 2) concerns the design of a beam for prescribed maximal deflection and shows how suitable discretization may lead to a problem of nonlinear programming, in this case, convex programming. The problem of optimal layout of a truss (Section 3) is discussed at some length. A new method of establishing optimality criteria (Section 4) is illustrated by the optimal design of a statically indeterminate beam of segmentwise constant or continuously varying cross section for given deflection under a single concentrated load. Other applications of this method (Section 5) are briefly discussed, and a simple example of multipurpose design (Section 6) concludes the paper.

SYNOPTIC: Finite Deflection Discrete Element Analysis of Sandwich Plates and Cylindrical Shells with Laminated Faces

Abstract: A discrete element analysis capability for predicting the geometrically nonlinear behavior of sandwich plate and cylindrical shell structures with unbalanced laminated faces is reported. The geometric admissibility conditions of the principle of minimum total potential energy are conveniently satisfied by employing bicubic Hermite interpolation polynomials to approximate the displacement behavior. Specialization for the finite deflection analysis of thin anisotropic and transversely heterogeneous plate and cylindrical shell systems is achieved by simply considering one face of the sandwich. Numerical solutions are obtained by direct minimization of the total potential energy using a scaled conjugate gradient algorithm. Several problems are solved which illustrate the potential of the method for predicting the finite deflection and elastic postbuckling behavior of sandwich and thin laminated structures.

Inclusion of shear deflection in the stiffness matrix for a beam element

Abstract: Shear-deflection terms arise naturally in a finite beam element in bending if the stiffness matrix is obtained on the basis of stress assumption, rather than the more usual displacement assumption.If the displacement assumption is used, an erroneous addition of the shear-deflection terms to the bending terms can be made if an apparently straightforward approach is utilized.

Theoretical Analysis of Suspension Roofs

Abstract: The finite deflection theory analysis of a spatial system of nets on the basis of nonlinear theory and a more accurate representation of the material's stress-strain relationship is presented. The structures considered comprise cables and truss members which are assumed incapable of resisting bending. The theory is valid regardless of the magnitude of the displacements as long as the stresses are within the elastic limits. An actual stress-strain curve is used for members stressed beyond the proportional limit. A derivation is given for the tangent stiffnes matrix of a space structure at a state of deformation. The joint equations of equilibrium are transformed into linear equations at any intermediate state of deformation, and a solution tangent to the load-deflection curve is obtained. The displacements are determined by means of an iterative technique. The analysis is given for three problems: (1) Cable; (2) prestressd suspension roof; and (3) truss stressed beyond the proportional limit.

The Effect of Shear Flexibility and Rotatory Inertia on the Natural Frequencies of Uniform Beams

Abstract: An energy approach has been used to obtain approximations to the natural frequencies of uniform beams when the effects of shear flexibility and rotatory inertia are included. The characteristic functions of simple beams are used to describe the bending deflection and the necessity for an assumed shear deflection shape has been eliminated by the use of simple relationships which exist between the effects of shear flexibility and rotatory inertia. A comparison of the approximate frequencies with the exact frequencies shows good agreement even at the higher frequencies. The method has been applied to hinged-hinged, fixed-free, free-free, fixed-fixed, fixed-hinged and free-hinged beams.

Device for correcting the deflection of a large wide endless belt

Abstract: An endless belt is trained over at least a pair of rollers, including at least one driven roller, and one of the other rollers is mounted for swinging about a pivot axis perpendicular to its axis of rotation. A pair of belt deflection detecting rollers are rotatably mounted adjacent respective opposite side edges of the belt and are spaced apart a distance slightly greater than the width of the belt so as normally to be out of engagement with the adjacent belt side edge. The detecting rollers are operatably connected to the mounting means for the swingable roller and are operable, responsive to rotation of the detecting roller by engagement with a belt side edge as a result of belt deflection, to swing the swingable roller about the pivot axis thereof in a direction to correct belt deflection.

Safety bumper for driverless vehicle

Abstract: A DRIVERLESS SELF-PROPELLED INDUSTRIAL VEHICLE IS PROVIDED WITH A DEFLECTABLE SAFETY BUMPER AND A VEHICLE STOPPING CONTROL WHICH INCLUDES A PHOTOELECTRIC SCANNER ON THE VEHICLE AND A REFLECTOR ON THE BUMPER TO SENSE DEFLECTION THEREOF AND AUTOMATICALLY STOP THE VEHICLE WHEN THE BUMPER ENCOUNTERS AN OBSTRUCTION.

Non-tensioned steel in prestressed concrete beams

Abstract: A STUDY OF THE EFFECTS OF NON-TENSIONED STEEL ON THE BEHAVIOR OF PRESTRESSED CONCRETE BEAMS IS PRESENTED. EFFECTS ON CAMBER, LOSS OF PRESTRESS FORCE, CRACKING, AND DEFLECTIONS ARE INCLUDED. ANALYTICAL RESULTS ARE COMPARED WITH THE OBSERVED BEHAVIOR OF TWELVE, SIMPLY SUPPORTED, PRESTRESSED CONCRETE BEAMS, TEN OF WHICH CONTAINED NON-TENSIONED STEEL. /PCIJ/

A conforming triangular finite element plate bending solution

Abstract: A conforming plate bending solution using simple polynomial deflection functions of third-degree inside each triangular element is presented In order to avoid normal slope discontinuities along the sides of the elements, the plate displacement parameters are subjected to ‘slope continuity conditions’ acting as constraints to the minimum potential energy problem This is then solved by the classical method of Lagrange introducing multipliers as new auxiliary variables If a special variational formulation of the problem is used, it can be shown that the Lagrangean multipliers are generalized stress parameters The suggested solution is therefore basically a ‘mixed’ solution, the unknown variables of the problem being both displacement and stress parameters Several numerical results are presented

Theoretical elastic deflections of a thick horizontal circular mirror on a ring support.

Abstract: This paper shows how exact, closed-form expressions can be determined for the deflections under its own weight of a thick, horizontally oriented, circular mirror on a ring support. A theory developed by Reissner for thick plates that includes shear deformations is used, and the results are reduced to those of classical plate theory. An optimum support radius is obtained, for which the center deflection is equal to the deflection of the outer edge. For mirrors having thickness-to-diameter ratios greater than approximately one-tenth, shearing deformations can contribute significantly to the total deflection and hence should not be neglected.

Model Study of Laterally Loaded Piles

Abstract: Tests on scaled models of the locks and dams used in the Arkansas River Navigation Project were performed to develop design criteria for pile foundations in sand. The relationships between the lateral load-deformation behavior of isolated single piles and groups of piles scaled after the prototype foundations were determined. The flexural behavior of the piles was also investigated. The subgrade modulus applicable to piles in sand was shown to increase linearly with respect to depth. Cyclic loading caused the magnitude of deflection for a given load level to double, approximately. Hrennikoff's method of analyzing groups of piles was experimentally verified after the effects of pile group behavior and variation of subgrade modulus with respect to depth were accounted for. Deflection of a pile group for a given load increased as the pile spacing decreased below approximately eight pile widths, indicating a reduced subgrade modulus. A relationship was determined between pile spacing and the magnitude of reduction in the subgrade modulus.

Cross-mixing baffle

Abstract: A cross-mixing device which is arranged in the flow stream of electrostatic developing material for mixing the material as it flows therethrough. The device is formed with a plurality of deflection elements which effect small incremental movements of some of the material from some zones of the flow stream transversely to other zones thereof utilizing gravitational forces exclusively.

Flexible Plate Finite Element on Elastic Foundation

Abstract: A step-by-step linear incremental procedure for large deflection analyses of plates on elastic foundations using finite elements is presented. The incremental stiffness matrices for a conforming rectangular plate finite element, which are appropriate for large deflection analysis, are formulated and presented explicitly. Evaluative analyses are made by using the incremental stiffness formulations and piecewise incremental procedures. Examples include uniformly loaded rectangular plates with different length-to-width ratios, various boundary conditions and foundation moduli. Comparisons are made in those cases where the alternative analytic solutions are available. Good agreements are found.

Controlled deflection roll with controlled temperature

Abstract: A controlled deflection roll having a stationary shaft supported at its ends, a roll shell rotatably positioned on the shaft and fluid support means between the shaft and shell transmitting the force of a load on the shell to the shaft, the fluid support means having a lubricating fluid in engagement with the inner surface of the shell, and a heat exchanger supported on the shaft circulating the lubricating fluid and controlling its temperature to control the temperature of the shell with a heat exchange fluid pumped from outside the roll shell to the heat exchanger.

Thermal stability of bimetallic shallow spherical shells

Abstract: The paper considers the thermal stability of a simply supported bimetallic shallow spherical shell. Only rotationally symmetric modes of deflection are considered. It is found that the minimum initial height of the shell for which buckling is possible is strongly dependent upon the material properties of the shell. It is conjectured that if the edges of the shell are clamped, no buckling is possible.

Sensor for determining band saw blade deflection

Abstract: Blade deflection sensor comprises a deflectable cantilevered arm of a rigid member, mechanically coupled to a band saw blade and adapted to bear against the base-emitter junction of a piezotransistor mounted on the rigid member in response to a deflection of the blade.

Central deflection of a transversely struck beam

Abstract: Experimental investigations were performed in order to verify the maximum impact force and the time function of the central deflection which were derived by a simplified theory. This theory is only applicable in the short time interval after contact when the stresses in the vicinity of the contact point are only a function of the interaction between the colliding bodies. It will be assumed that the reflected elastic waves have no influence on these stresses. The maximum impact force can be expected to occur in this time interval.

Deflection And Tearing Of Clamped Stiffened Circular Plates Subjected To Uniform Impulsive Blast Loads

Abstract: The large deformation of structural components such as beams, plates and shells subjected to blast loads can be predicted with favourable correlation with experimental data. This work deals with the more complex situation of combining these structural components. Experiments using a 100mm diameter circular plate stiffened with a single beam of width 8mm clamped across the diameter of the plate is presented. Beams of thickness 3,4,5 and 6mm were used. Results show that an optimum beam-thickness/plate-thickness combination is required.

Bi-directional television scan system

Abstract: A television scansion system generates symmetrical triangular waveform horizontal deflection signals and linear ramp stairstep vertical deflection signals. The raster produced by these deflection signals is characterized as bi-directional horizontal scanning with vertical steps at alternate ends of the scans.