Showing papers on "Bending moment published in 1979"

Stress and temperature in the bending lithosphere as constrained by experimental rock mechanics

Abstract: Summary. Previous attempts to deduce the stress distribution in the bending lithosphere near a consuming plate margin have relied on the observed bathymetry and an assumed constitutive relation for lithospheric behaviour, eg. perfectly elastic, viscous/perfectly plastic, or elastic perfectly plastic. From the point of view of rock mechanics, each of these approximations fails to describe one or more of several basic phenomena, including brittle failure of rock, temperature dependence of elasticity, and temperature and/or strain rate dependence of ductile behaviour. In order to formulate a more realistic constitutive relation, a limiting yield strength curve, which is primarily a function of temperature, is constructed from data from brittle failure and ductile flow experiments. The moments which can be supported by plates with this constitutive behaviour are compared to the moments calculated from bathymetric profiles. The comparison indicates that moments required by the bathymetric data are consistent with moments supported by plates with experimentally determined constitutive laws as extrapolated to geo- logically reasonable temperatures and strain rates. The stresses developed in such models are required to reach values greater than 100 MPat in the depth range 25-45 km. Geotherms necessary for strength curves consistent with moments calculated from the bathymetric data match those derived from heat flow data for the Aleutian, Bonin, Mariana and Tonga trenches. Of the trenches studied, only the geotherm inferred from the Kuril trench data is significantly different, perhaps implying that the Kuril plate is weaker than the others. The strength curves show that as a first approximation it is better to assume that bending moment is independent of curvature of the plate than to assume that bending moment and curvature are linearly related.

The Fibre Composite Helicopter Blade: Part I: Stiffness Properties: Part II: Prospects for Aeroelastic Tailoring

Abstract: In Part 1 expressions are derived for the coupled torsional, extensional and flexural stiffnesses of a fibre composite tube, such as a helicopter blade, which is subjected to torsion, longitudinal tension, chordwise and flapping bending moments and shear. The theory is an extension of Batho-Bredt engineering analysis and is valid for a cylindrical tube of arbitrary cross-section with an arbitrary circumferential distribution of fibre composite plies. Particular attention is paid to the coupling effects in which an asymmetric fibre lay-up results in a twisting of the tube under bending and/or tension. Consideration is also given to the influence on the stiffness characteristics of an initial twist in the tube. In Part 2 the analysis of Part 1 is developed numerically for tubes representative of GFRP blades. Static and dynamic aspects are considered which pave the way for aeroelastic tailoring studies of such blades.

Behavior and Design of Long-Span Metal Culverts

Abstract: The interaction between flexible metal culverts and the surrounding backfill is examined by means of finite element analyses that simulate the placement of backfilling and subsequent application of live loads. Although metal culverts are flexible in bending, they are stiff in ring compression, and the ring compression forces are therefore greater than those corresponding to the weight of backfill above the structure. The bending moments in metal culverts are dependent on the relative flexibility of the culvert and the backfill, which can be expressed in terms of a dimensionless flexibility number. Comparisons between finite element results and field measurements show the suitability of the method as a basis for design. A simplified rational design procedure is described that considers both bending and ring compression. /Author/

Transverse shear effect in a circumferentially cracked cylindrical shell

Abstract: The objectives of the paper are to solve the problem of a circumferentially-cracked cylindrical shell by taking into account the effect of transverse shear, and to obtain the stress intensity factors for the bending moment as well as the membrane force as the external load. The formulation of the problem is given for a specially orthotropic material within the framework of a linearized shallow shell theory. The particular theory used permits the consideration of all five boundary conditions as to moment and stress resultants on the crack surface. The effect of Poisson's ratio on the stress intensity factors and the nature of the out-of-plane displacement along the edges of the crack, i.e., bulging, are also studied.

Analysis of through cracks in cylindrical shells by the quarterpoint elements

Abstract: Axial and circumferential through cracks in cylindrical shells are analyzed using the quarter-point thick shell elements. These elements were shown to account for transverse shear deformations which alleviate several difficulties encountered in the use of classical thin shell theory when applied in the neighborhood of crack tip discontinuity. Both extensional and bending stress intensity factors for pressure and bending moment cases are given. The principle stress distribution around the crack tip for selected configurations of circumferentially and axially cracked cylinders are also given and the direction of crack propagation is discussed.

Wave induced bending moments in ships--a quadratic theory

Abstract: The paper presents a theory for the prediction of the nonlinear vertical response of surface ships in irregular stationary waves. Special treatment is given to the separate predictions of wave-induced hogging and sagging bending moments in ships sailing in moderate head seas. The theory is based on a perturbation procedure in which the linear terms are identical to those of the classical linear strip theories. Order from NSFI as No. 18494.

Constant moment weigh scale with floating flexure beam

Abstract: A weigh scale apparatus in which forces caused by the applied load are transformed into moments of opposite sense and applied to opposite ends of a substantially rigid beam. Deflection of the beam is measured by centrally disposed strain gage resistors to produce an electrical signal quantity proportional to the applied load. The conversion of applied load to moments of opposite sense is accomplished by a pair of spaced parallel pivot members which are suspended by straps between the load receiving pan and the base such that the pivots tend to rotate in opposite directions. The beam is mechanically connected between the pivots such that it is subjected to the bending moment over substantially its entire length. A split scale device is provided by a composite pan, one portion of which is connected to the pivots directly and another portion of which is connected to the pivots through long lever arms to provide moment multiplication. A vibrator device for dithering the pivots is provided. .Iadd.

Response using the Rayleigh-Ritz method

Abstract: As an example of the extension of the Rayleigh-Ritz method to response calculations, analysis is outlined for a damped rectangular plate. For harmonic excitation amplitudes of displacement and bending moment are compared with values from a modal solution from the plate equation. In general, the Rayleigh-Ritz method predicts displacements of acceptable accuracy, but for a given number of terms accuracy is less for response calculations than for the determination of comparable eigenvalues. Bending moments may converge slowly to the true values, as the number of terms in the assumed series is increased.

Bending properties of wire‐reinforced bone cement for applications in spinal fixation

Abstract: PMMA beam specimens were tested in four-point bending to determine if the bending strength of acrylic bone cement, as used in posterior spinal fusion, could be improved by metal-wire reinforcement. The result showed that the load-carrying capacities of 1- and 0.5-mm diam stainless-steel-wire-reinforced PMMA specimens in bending were significantly higher than similar unreinforced normal PMMA samples. On an average, steel reinforcement comprising approximately 1% of the cross-sectional area of the PMMA specimens caused a 15% increase in bending strength. Even after the cement fractured, the reinforcing wires still sustained an appreciable amount of bending moment, thus preventing catastrophic failure of cement alone.

Ultra light weight golf club shaft

Abstract: An ultra light weight golf club shaft tapered in a step pattern having a reinforced wall at the region where maximum bending moment occurs during play.

Front fork construction for motorcycle

Abstract: A front wheel suspension assembly for a motorcycle includes parallel telescoping forks of the hydraulic shock absorber type which straddle the wheel and which are inclined in a forward direction. The bending moment imposed on the telescoping parts by this inclination is partly or fully opposed by a counter bending moment imposed by one or more springs positioned rearward of a vertical plane containing the wheel axis and below a bottom bridge joining the front fork tubes. The purpose is to reduce the frictional resistance between telescoping forks in their axial sliding motion. The springs apply the compensating bending moment between the telescoping parts.

On the Motions of a Floating Structure which Consists of Two or Three Blocks with Rigid or Pin Joints

Abstract: Motions of a floating structure which consists of two or three blocks with rigid or pin joints are investigated experimentally and theoretically. Barge and semi-submergible type are adopted as floating structures. The motions in head waves represent heave, pitch, relative angles between blocks, and the internal shearing force and bending moment at the joint part. The strip method is used for the numerical calculations. From the experiments, the following deductions may be drawn: 1) The rigid joint gives smaller amplitudes of the heave and pitch motions than the pin joint does, on the contrary the amplitudes of the shear force and bending moment get smaller in the pen joint than in the rigid joint. 2) The semi-submergible type obtains smaller amplitudes of the shear force and bending moment than the barge type does, while the amplitudes of heave, pitch and relative angle depend on the length of the incident waves and are the functions of the type of a model, that is to say, in the case of lambda/L sub o less than 2.0 the semi-submergible model gets smaller amplitudes than the barge model and in the case of lambda/L sub o 2.0 the barge model obtains smaller amplitudes than the semi-sub does. 3) With regard to the relative angle, the three blocks model gets larger amplitude than the two blocks model does. The comparison of the experimental results with calculated results indicates that the strip method is successful for barge models, even for the three blocks model with the pin joints, however, it shows also that one has to take into account of the effect of the viscous damping of the sectional heave mode, if the corresponding wave making damping is very small and the expected frequency range contains the wave free frequency.

Nonlinear Behaviour of Unsymmetric, Angle-Ply, Rectangular Plates under in-Plane Edge Shear:

Abstract: A nonlinear analysis of unsymmetric, angle-ply, rectangular plates under uniform in-plane edge shear is presented. The solution is based on the von Karman-type large-deflection equations, with the force function and the transverse deflection expressed as double series in terms of appropriate beam functions. The prescribed boundary conditions, including those for the vanishing of normal bending moment at the edges of simply supported plates, are satisfied. Numerical results for the buckling loads and for the post-buckling deflections, membrane forces and bending moments are presented for plates composed of high-modulus, fibre-reinforced epoxy composites.

Simplified Design of Wood Structures

Abstract: Preface to the Sixth Edition. Preface to the First Edition. Introduction. 1. Structural Uses of Wood. 1.1 Sources of Wood. 1.2 Tree Growth. 1.3 Density of Wood. 1.4 Defects in Lumber. 1.5 Seasoning of Wood. 1.6 Nominal and Dressed Sizes. 1.7 Use Classification of Structural Lumber. 1.8 Grading of Structural Lumber. 1.9 Fabricated Wood Products. 2. Design Issues and Methods. 2.1 Design Goals. 2.2 Methods of Investigation and Design. 2.3 Choice of Design Method. 3. Structural Investigation. 3.1 General Concerns. 3.2 Forces and Loads. 3.3 Direct Stress. 3.4 Kinds of Stress. 3.5 Deformation. 3.6 Elastic Response and Limit. 3.7 Inelastic Behavior and Ultimate Strength. 3.8 Modulus of Elasticity. 3.9 Permissible Values for Design. 4. Design Data and Criteria. 4.1 General Concerns. 4.2 Reference Design Values for Allowable Stress Design (ASD). 4.3 Adjustment of Design Values. 4.3 Modification for Loading with Relation to Grain Direction. 4.4 Design Controls for LRFD. 5. Beam Functions. 5.1 General Considerations. 5.2 Moments. 5.3 Beams Loads and Reaction Forces. 5.4 Beam Shear. 5.5 Bending Moment. 5.6 Tabulated Values for Beam Behavior. 5.7 Multiple Span Beams. 6. Behavior of Beams. 6.1 Shear in Beams. 6.2 Bending in Beams. 6.3 Deflection. 6.4 Bearing. 6.5 Buckling of Beams. 6.6 Unsymmetrical Bending. 6.7 Behavior Considerations for LRFD. 7. Design of Beams. 7.1 Design Procedure. 7.2 Beam Design Examples. 7.3 Joists and Rafters. 7.4 Alternative Spanning Elements. 8. Wood Decks. 8.1 Board Decks. 8.2 Plank Decks. 8.3 Wood Fiber Decks. 8.4 Plywood Decks. 8.5 Spanning Capability of Decks. 9. Wood Columns. 9.1 Slenderness Ratio for Columns. 9.2 Compression Capacity of Simple Solid Columns. 9.3 Column Load Capacity, LRFD. 9.4 Round Columns. 9.5 Stud Wall Construction. 9.6 Spaced Columns. 9.7 Built-up Columns. 9.8 Columns with Bending. 10. Connections for Wood Structures. 10.1 Bolted Joints. 10.2 Nailed Joints. 10.3 Screws. 10.4 Mechanically-Driven Fasteners. 10.5 Shear Developers. 10.6 Split-Ring Connectors. 10.7 Formed Steel Framing Elements. 10.8 Concrete and Masonry Anchors. 10.9 Plywood Gussets. 11. Trusses. 11.1 General Considerations. 11.2 Types of Trusses. 11.3 Bracing for Trusses. 11.4 Loads on Trusses. 11.5 Investigation for Internal Forces in Planar Trusses. 11.6 Design Forces for Truss Members. 11.7 Combined Actions in Truss Members. 11.8 Truss Members and Joints. 11.9 Timber Trusses. 11.10 Manufactured Trusses. 12. Miscellaneous Wood Products and Elements. 12.1 Engineered Wood Products. 12.2 Glued Laminated Structural Members. 12.3 Structural Composite Lumber. 12.4 Wood Structural Panels. 12.5 Plywood. 12.6 Prefabricated Wood I-Joists. 12.7 Built-Up Panel and Lumber Beams. 12.8 Flitched Beams. 12.9 Pole Structures. 13. Wood Structures for Lateral Bracing. 13.1 Application of Wind and Earthquake Effects. 13.2 Horizontal Diaphragms. 13.3 Vertical Diaphragms (Shear Walls). 13.4 Investigation and Design of Wood-Framed Shear Walls. 13.5 Trussed Bracing for Wood Frames. 13.6 Special Lateral Bracing. 14. General Considerations for Building Structures. 14.1 Choice of Building Construction. 14.2 Structural Design Standards. 14.3 Loads for Structural Design. 14.4 Dead Loads. 14.5 Building Code Requirements. 14.6 Live Loads. 14.7 Lateral Loads (Wind and Earthquake). 14.8 Load Combinations and Factors. 14.9 Determination of Design Loads. 14.10 Structural Planning. 14.11 Building System Integration. 14.12 Economics. 15. Building Design Examples. 15.1 Building One: Single Story Light Wood Frame. 15.2 Building Two: Multistory Light Wood Frame. 15.3 Building Three: Masonry and Timber Structure. 15.4 Building Four: Steel and Wood Structure. Appendix A: Properties of Sections. Appendix B: Study Aids. Appendix C: Answers to Problems. Glossary. References. Index.

Prediction of still-water bending moments in containerships

Abstract: Design criteria for longitudinal members of container ships are discussed. It is common practice to assume certain loading cases chosen somewhat artificially. In practice, a broad spectrum of loading cases occurs due to the random nature of container number, weight and arrangement. Theoretically, the stowage could be based on the criterion of minimum bending moments, with some trim and stability requirements treated as constraints. In practice, however, containers have to be sorted within the ship according to ports of origin and destination to facilitate the loading-unloading operations.

Multicyclic Controllable Twist Rotor Data Analysis

Abstract: Rsults provide functional relationship between rotor performance, blade vibratory loads and dual control settings and indicate that multicyclic control produced significant reductions in blade flatwise bending moments and blade root actuator control loads. Higher harmonic terms of servo flap deflection were found to be most pronounced in flatwise bending moment, transmission vertical vibration and pitch link vibratory load equations. The existing test hardware represents a satisfactory configuration for demonstrating MCTR technology and defining a data base for additional wind tunnel testing.

Propeller blade pressure distribution due to loading and thickness effects

Abstract: : A theoretical approach is developed and a computational procedure adaptable to a high speed digital computer is established for the evaluation of the blade pressure distribution of a marine propeller due to thickness and loading effects The dual role of the blade thickness is considered The contribution of the nonplanar thickness to the propeller loading and pressure distribution and the effect of the flow distortion thickness are studied by means of the thin body approximation The surface integral equation which relates the unknown loading to the known velocity distribution on the blades is solved by the mode approach in conjunction with the lift operator technique The analysis treats both design and off-design conditions in steady-state and unsteady flows, and the proper chordwise modes are selected for each condition The numerical solution yields the blade loading and resulting hydrodynamic forces and moments and blade bending moments, and, in addition, the blade pressure distributions on each blade face due to both loading and thickness effects, thus providing information necessary for the prediction of cavitation inception Calculations have been performed for a set of three 3-bladed propellers of different EAR operating in a screen-generated wake, for comparison with experimental data

The loading behaviour of initially bent large scale laboratory piles in sand

Abstract: Field measurements indicate that piles are sometimes bent during driving. This paper reports on the results of an experimental study, at laboratory scale, of the behaviour of bent single piles when subjected to vertical loads. Varying degrees of bend were adopted for both friction and end bearing piles. The test piles, which were embedded in a cohesionless soil, were instrumented to measure the distributions of axial load, bending moment, and transverse shear along the pile shaft.The behaviour of bent piles was found to be far more complex than that of straight piles. For both the friction and end bearing piles, the response of the piles was governed by the degree of bend and the magnitudes of the moments and shears were significant at all levels of the applied load. An important feature in the pile response was the large residual moments and shears locked in the pile on unloading. The implications of the observed pile behaviour in relation to practice are discussed. A review of the reported cases of pile...

Retainining Wall Performance during Backfilling

Abstract: Field data relating to the structural failure of a long reinforced concrete cantilever retaining wall are presented The results of a survey of the defected form of the wall are included Analyses of the wall are carried out using classical earth pressure theories with geotechnical data Using the measured soil parameters, the predicted bending moment at the base of the wall stem was found to be less that 5% of the actual bending moment realized This discrepancy is due to the effects of lateral earth pressures induced by compaction A simple method of analysis is proposed to take into account the effects of compaction Reanalysis of the wall using this method and the measured soil parameters gives a bending moment that is in very close agreement with actual bending moment developed

Crash test dummy lower leg instrumentation for axial force and bending moment.

Abstract: Instrumented anthropomorphic dummy surrogates of humans have been used in automobile occupant crash protection research and development programs for many years. Lower leg instrumentation provides the safety engineer with a valuable tool for gaining otherwise unavailable insights into occupant restraint system performance. Instrumentation described in this paper constitutes an advancement of the state of the art of dummy test technology. A more comprehensive study of crash victim leg loadings is possible with only the traditional femur (upper leg) axial force transducer. Each lower leg has five electrical resistance strain gage circuits to monitor orthogonal bending moments and axial force. Stress analysis and Wheatstone bridge theories are combined in the paper to define strain gage locations and predict transducer sensitivities. Transducer fabrication and calibration precedures are also discussed. Language: en