Showing papers on "Bending moment published in 1993"

Concise eurocode for the design of concrete buildings. based on bsi publication dd env 1992-1-1: 1992. eurocode 2: design of concrete structures. part 1: general rules and rules for buildings

Abstract: This document contains only that material from Eurocode 2 (EC2) necessary for the design of everyday reinforced and prestressed concrete structures. Other material not in EC2, including bending moment coefficients for beams and slabs and design charts are included in an appendix, so that designers have all the information they would expect to find in a British code. Recommendations are given for concrete cover and durability, and designs for the ultimate limit state in bending and axial load, shear resistance, and torsion is examined. The control of cracking and deflection is discussed. The guidance on prestressed concrete design is limited to structures in normal weight concrete where prestress is by fully bonded tendons. Advice is given on the required numbers of tendons, the prestressing force and the limit states. Anchorages and anchorage zones are considered.

Kinematic seismic response and bending of free-head piles in layered soil

Abstract: The paper studies the kinematic response of freehead piles. Such pile deformation has triggered structural damage in many strong earthquakes. In this Paper dimensionless parametric graphs for pile bending moments are presented which pertain to characteristic two-layer soil profiles. The results are derived by using an existing rigorous dynamic finite-element code, and by implementing a realistic beam-on-dynamic-Winkler-foundation formulation specifically developed for the kinematic response of piles in layered soil. The Winkler model is shown to reproduce quantitatively even detailed trends observed in the finite-element results; a simple analytical expression is thereby developed for estimating the Winkler stiffhess in terms of the local soil Young’s modulus and key dimensionless pile/ soil parameters. The study concludes that even relatively flexible piles may not exactly experience the wavy and abruptly changing ground deformation of the free field. The critical region of pile distress due to such kinematic loading is shown to he at or near the interface between alternating soft and stiff soil layers. The magnitude of the bending moment at such critical interface locations depends mainly on the stiffness contrast of the two layers through which the pile penetrates, the excitation frequency and the relative rigidity of the pile. A constraining cap may exert an important effect on such kinematic deformations.

Normal and shear stresses on a residual limb in a prosthetic socket during ambulation: comparison of finite element results with experimental measurements.

Abstract: Interface stresses on a below-knee amputee residual limb during the stance phase of gait calculated using an analytical finite element model were compared with experimental interface stress measurements. The model was quasi-static and linear. Qualitatively, shapes of analytical and experimental interface stress waveforms were similar in that they were double-peaked with some distinct features apparent. However, quantitatively analytical resultant shear stress magnitudes were less than experimental values at all transducer measurement sites. Analytical normal stresses were less than experimental values at postero-proximal, postero-distal, and anteromedial proximal sites, but were greater than experimental values at antero-lateral distal and antero-lateral proximal sites. Anterior resultant shear angles were directed more distally in the model than in clinical data, an expected result since there was no relief for the tibial crest in the model. Model sensitivity analyses to shank loads showed interface normal and resultant shear stresses were most sensitive to axial force, sagittal bending moment, or sagittal shear force. The finite element model presented in this paper is significant because it contributes toward development of an analytical modeling technique to predict interface stress distributions for proposed prosthetic designs, provides insight into physical explanations of features apparent in interface stress waveforms (thereby enhancing understanding of interface mechanics), and provides insight into nonlinear characteristics that need to be added to improve the model.

Structural modeling of composite beams with induced-strain actuators

Abstract: This paper presents an analytical-experimental investigation on structural modeling of coupled composite beams with distributed induced-strain actuators Analysis based on Vlasov theory is developed to include distributed piezoelectric actuators, either surface mounted or embedded Salient features of composite open-section beam analysis, like constrained warping and transverse shear deformation, were included Induced-strain actuation was introduced in the constitutive relations of plate segment of the open-section composite beams To evaluate the analytical predictions, several bending-torsion and extension-torsion coupled graphite-epoxy solid beams were fabricated using an autoclave molding technique These were surface mounted with piezoelectric actuators The actuators were excited to produce local bending moment and axial force on the beam, and the structural response was measured in terms of bending slope, induced twist, and surface strain Good correlation between analysis and experiment was achieved Because of the existence of a chordwise actuator moment, the induced twist of bending-torsi on coupled beams was significantly influenced by including the chordwise curvature of the plate segment of beam in the formulation For [45]i4 solid beams, the chordwise bending of the plate segment of beam was found to increase the tip twist by about

Part-circular surface cracks in round bars under tension, bending and twisting

Abstract: Circular-fronted cracks in round bars subject to tension, bending and twisting are considered. Numerical expressions are given allowing the calculation of stress intensity factors $K_I$, $K_{II}$, $K_{III}$ at every point on the crack front for a wide range of crack geometries. Comparisons are made with analytical, experimental and numerical results available in the literature. Crack shapes satisfying the iso-$K_I$ criterion are also determined, making it possible to investigate the problem of crack growth behaviour under tensile or bending fatigue loads.

Aircraft gas turbine engine thrust mount

Abstract: An engine mount assembly includes an axially pivotable engine support and a thrust mount with a three or four bar linkage which includes a thrust bar, as the first bar, pivotably joined to a forward axial position on the engine structure at the forward end of the first bar. The line of action of the thrust bar intersects the engine centerline at a forward vertical mount plane, which is generally perpendicular to the engine centerline and through which a forward pivotal support mount of the engine support acts to support the engine, substantially at the axial position where engine centerline and forward vertical support plane intersect. An alternate embodiment of the present invention provides a means to counter bending moments produced by aerodynamic forces acting on the nacelle of the engine particularly those referred to as lip loads. The line of action intersects the engine centerline a predetermined distance S aft of the forward vertical mount plane to induce a predetermined first bending moment due to thrust loads to counter a predetermined second bending moment due to aerodynamic loads acting on a nacelle of the engine such that the first and second bending moments act in opposite directions.

Water waves on flexible and porous breakwaters

Abstract: This is a theoretical study of the reflection and transmission of small‐amplitude waves by a flexible, porous, and thin beam‐like breakwater held fixed in the seabed. The fluid motion is idealized as a linearized, two‐dimensional potential flow and the breakwater is idealized as a one‐dimensional beam of uniform flexural rigidity and uniform mass per unit length. The velocity potentials of the wave motion are coupled with the equation of motion of the breakwater. Analytical solutions in closed forms are obtained for the reflected and transmitted velocity potentials together with the displacement of the breakwater. The free‐surface elevation, hydrodynamic force acting on the breakwater, and the overturning moment are determined. The dynamic response of the breakwater in terms of bending moment and shear force are also evaluated. It is found in general that hydrodynamic force increases as structural rigidity increases. The magnitude of the force is reduced dramatically for a stiffer porous breakwater. It is...

Response of the knee joint in lateral impact: effect of bending moment

Abstract: An experimental method for assessing the tolerance to bending moment in the lateral direction of the extended knee joint has been developed. The load response of the lower extremity was measured by means of force transducers. The bending moment transferred through the entire knee joint was calculated, and the motion of the specimen registered by high speed photography. The bending moment in the lateral direction at the first sign of damage of the entire extended knee joint was determined. Damages were assessed by both measuring the knee joint condition, and dissecting the knee region. Seventeen tests were carried out under dynamic conditions. The first and most common damage type to entire knee joint in this loading configuration was stretching and rupture or avulsion of the medial collateral ligament (MCL). These damages are generated by identical mechanisms, that is to say tensional forces acting on the medial knee structures. The mean peak moment correlated with this damage mechanism was 101 (about 21) Nm for an impact velocity of 16 km/h, and 123 (about 35) Nm for an impact velocity of 20 km/h. The mechanisms caused damage of the knee joint, when the lower extremity was bent approximately 10 degrees in the lateral direction at the knee joint. For the covering abstract of the conference see IRRD 860654.

Elastica of cantilevered beams with variable cross sections

Abstract: Numerical and experimental methods are developed for solving the elastica of cantilevered beams of variable cross sections subjected to combined loading. The beam model is based on Bernoulli-Euler beam theory. The Runge-Kutta and Regula — Falsi methods, respectively, are used to solve the governing differential equations and to compute the beam's horizontal deflection at the free end. Extensive numerical results, including deflected shapes and free-end rotations, are presented in non-dimensional form for elastic beams whose area moment of inertia (bending stiffness) varies linearly with beam length. In these studies, such beams are subjected to combinations of tip vertical loads, tip bending moments, and vertical distributed loads that vary linearly with beam length. Experimental studies are presented that complement the theoretical results.

Bending Stiffness In A Simulation Of Undersea Cable Deployment

Abstract: Bending stiffness is introduced in a three-dimensional model for submerged cable dynamics to eliminate singular behavior when cable tension becomes zero. The equations of motion are written in a local tangential-normal reference frame, and are simplified by neglecting the torsional rigidity of the cable. A centered-centered finite difference algorithm is used for the numerical simulation. The addition of bending stiffness eliminates the singularity for zero tension. However, because the bending stiffness is small, sharp gradients in the shear forces and bending moments occur at the boundaries. In this paper two sets of results are presented: configuration of an anchoring system during a steady tow, and the tension and geometry of a cable immediately following touchdown on the seafloor. The first result illustrates the discretization error caused by the sharp gradients in the curvatures and shear forces. The second result provides evidence that the bending stiffness does prevent singular behavior for negative or zero tension. It also illustrates that the contact of the cable with the seafloor only affects the cable geometry close to the seafloor.

The bending moment resistance of single-dowel corner joints in case construction

Abstract: This study was carried out to obtain background information concerning the bending moment resistance of single-pin dowel joints in particleboard and also to provide the background information needed to formulate expressions for predicting the bending moment resistance of single-dowel, L-type, corner joints in particleboard. Test results indicated that the bending moment resistance of the single-dowel corner joints increased significantly as dowel diameter increased from 1/4 to 3/8 inch and as the depth ofdowel embedment in the face member increased from 1 /4 to 5/8 inch. Changes in depth of embedment in the edge member from 3/4 to 1-1/2 inches, however, had no effect on bending moment resistance.

Bending and torsion models of beams with induced-strain actuators

Abstract: This paper develops one-dimensional pure bending, coupled bending and extension, and combined bending, extension and torsion models of isotropic beams with induced strain actuation. A finite thickness adhesive layer between the crystal and beam is included to incorporate shear lag effects. Experimental tests evaluate the accuracy and limitations of the models. The bending and coupled bending and extension models show acceptable correlation with static test results whereas the combined extension, bending, torsion model poorly predicts the system behavior and needs refinement.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Biaxial bending design of arbitrarily shaped reinforced concrete column

Abstract: The paper presents an iterative procedure to perform the exact design of arbitrarily shaped reinforced concrete members against a combination of axial force an biaxial bending moments. The suggested method is believed to be divergence-proof and is capable of handling sections with reinforcement layout so unsymmetrical that the origin of the Mx-My reference axes falls outside the iso-load contour corresponding to the applied axial load. The rate and reliability for convergence in this method make it suitable for use in practical design. Oddly shaped concrete sections commonly adopted in bridge abutments and core wall systems can be handled, and the minimum steel area required in resisting the design loadings is determined. This leads to a more economical and safer design for reinforced concrete structures.

On the strain energy release rate for a cracked plate subjected to out-of-plane bending moment

Abstract: For a through-the-thickness crack in an infinite plate subjected to out-of-plane uniform bending moment, the strain energy release rate is determined using the virtual crack extension and the variation of potential energy It is shown that the strain energy release rate for the Reissner's plate approaches the classical plate solution as the ratio of plate thickness to crack size becomes infinitesimally small By using this result, the limiting expression of the stress intensity factor can be explicitly obtained For general problems, the modified crack closure method is shown to be an efficient tool for evaluating the strain energy release rates from which the stress intensity factor can be calculated Both the classical plate element and the Mindlin plate element are investigated, and the applicability of the classical plate element is evaluated Because the stress-free conditions along the crack face lead to inter-penetration of the plate, a line contact model is assumed to investigate the closure effect using Reissner plate theory Closure at the compressive side is shown to reduce crack opening displacement and consequently the stress intensity factors When closure is considered, the strain energy rate based on the Reissner plate theory converges to the classical plate solution This is similar to the nonclosure case

Design considerations for adjustable-curvature, high-power, x-ray mirrors based on elastic bending

Abstract: The use of elastic bending to form the shapes of high-power x-ray mirrors for synchrotron radiation beamlines is considered. An approach in which the bending mechanism and the mirror are cut from the same monolithic block by electric-discharge-machining techniques is especially advocated. A discussion of the theory and practical design philosophies is given that includes circular and elliptical cylinder mirrors. The influence of gravity on the mirror shape is studied with emphasis on the optimum positions for the mirror supports that, for a uniform mirror, turn out to be at a spacing equal to the mirror length divided by root three.

Windscreen wiper blade with curved backing member

Abstract: A curved elongate backbone for a windscreen wiper has a loading profile that increases substantially from a central connector towards one or both ends of the backbone. The second differential of the bending moment also increases substantially from the connector towards the ends. The loading may increase right to the ends of the backbone or the backbone may have end portions with constant loading. In order to obtain the desired loading profile the width, thickness and free-form radius of curvature are suitably selected. In preferred embodiments, the backbone has a rectangular cross-sectional profile and the thickness and width decrease uniformly from the connector to the ends. However the thickness may also be constant for end portions.

Interactive buckling of thin-walled beam-columns with open and closed cross-sections

Abstract: The influence of interactive buckling on the postbuckling behaviour of thin-walled elastic beams with imperfections is studied. The investigation is concerned with thin-walled closed and open cross-section beam-columns under axial compression and a constant bending moment. The beams are assumed to be simply supported at the ends. The asymptotic expansion established by Byskov and Hutchinson is employed in the numerical calculations in the form of the transition matrix method. The paper's aim is to achieve the improved study of the equilibrium path in the postbuckling behaviour of imperfect structures with regard to the second-order approximation. The calculations are carried out for several types of beams.