Showing papers on "Bending moment published in 1990"

Ink-jet recording device

Abstract: PURPOSE: To make a beam member displaced by thermal energy of an exothermic body without allowing said body to make contact with recording liquid by providing the exothermic body to the beam member separately from the recording liquid, and by making the beam member bend by thermal energy of the exothermic body. CONSTITUTION: A cantilever deforms suddenly from its stationary state to a state of displacement in the direction marked with an arrow by bending moment produced by expansion that is brought about by supplying of electricity to a heater 7 of a cantilever-supporting member 10. The movement of the cantilever at this time make ink inside an ink chamber 8 be ejected in the form of ink drops 12 through nozzles of a nozzle plate 11, and recording is made therewith on recording paper. In the above-mentioned process, bending by effect of thermal stress is utilized by heating (by giving thermal shock) only the surface of the cantilever that is made in a single-layer structure. It is necessary to provide the device with better radiation characteristics for improvement of recording frequency. Therefore, it is desirable to arranged the heater 7 in a liquid chamber containing insulating cooling liquid that is provided separately from the liquid chamber 8, or to make the heater 7 to be air-cooled with a fan or the like. In the case where the structure is such that the beam is supported at the opposite ends, the two heaters 7 are arranged on the supporting members on the opposite ends. COPYRIGHT: (C)1992,JPO&Japio

Case studies of the bending vibration and whirling motion of drill collars

Abstract: This paper describes two principal sources of bottomhole-assembly (BHA) bending vibration: drill-collar whirling and linear coupling between weight-on-bit (WOB) fluctuations and bending vibration of an initially curved BHA. It also evaluates the consequences of bending vibration in terms of drill-collar wear and connection fatigue. Equations are given for forward and backward whirl rate and for tangential velocity at the borehole wall. Downhole measurements of bending moment are used to detect and to identify bending-vibration events, and data taken with a downhole vibration-measurement system are sued to illustrate cases of linearly coupled bending vibration, forward and backward whirl, and bit bounce.

Prestressed composite girders under positive moment

Abstract: According to the 1986 U.S. Federal Highway Administration statistics, there are 575,607 bridges on the highway systems. About half of these bridges are structurally deficient and/or functionally obsolete. To strengthen the structurally deficient bridges without replacing the girders, external prestressing techniques can be used. In this paper, the behavior of prestressed, composite steel-concrete beams under positive bending moment is examined, and the benefits of different types of prestressing are compared. Three specimens were tested to study various aspects of prestressed composite girders, including tendon type and profile. Two methods of analysis are discussed, i.e., the transformed area method and the strain compatibility method. The test results show that prestressing a composite girder increases the range of elastic behavior, reduces deflections, increases ultimate strength, and adds to the redundancy by providing multiple stress paths. Based on the experimental results, a comparison was made between three tendon types and profiles. It was concluded that strands are more effective than bars for the tendon type, and a straight tendon profile is more effective than a draped profile with regard to stiffness.

Vehicle Model for Highway Bridge Impact

Abstract: This paper suggests a simple vehicle model that may be used to estimate impact in highway bridges. In this model each axle load consists of a constant load together with a sinusoidally varying dynamic component with a frequency equal to the natural frequency of the bridge. For maximum impact the dynamic load components must be in phase with respect to time. Maximum bending moments in a simple girder are determined by the span, the static axle loads, the relative magnitude of the dynamic load component, and a bridge factor defined as the number of dynamic load maxima applied by an axle during its passage over the bridge. It is shown that for many bridges, the first natural frequency is simply related to the span and that the bridge factor is about 6. Impact values are predicted for a range of spans with a dynamic load component equal to 10% of the static load. A companion paper uses field studies to review this percentage.

Deformation-based model for reinforced sand

Abstract: A closed‐form solution for determining the development of tension in soil reinforcements is incorporated in a rigid‐plastic soil model. The model accounts for the plastic work to deform the soil and the elastic work to deform the reinforcements in tension and bending. The model is used to evaluate experimental results obtained in large‐scale direct‐shear tests. The results show that the mobilization of tension in the reinforcements is a function of the reinforcement properties and the deformation characteristics of the reinforced soil. The reinforcement properties affect the width of the shear zone and the increase in the strength of the reinforced soil is not linearly proportional to the reinforcement concentration. The contribution of reinforcement tensile stresses to the increased strength of the reinforced soil is as much as one order of magnitude greater than the bending stresses. Thus, the use of limit equilibrium methods for analysis of reinforced structures, ignoring the bending moment contributio...

Vehicle model for highway bridge impact

Abstract: This paper suggests a simple vehicle model that may be used to estimate impact in highway bridges. In this model each axle load consists of a constant load together with a sinusoidally varying dynamic component with a frequency equal to the natural frequency of the bridge. For maximum impact the dynamic load components must be in phase with respect to time. Maximum bending moments in a simple girder are determined by the span, the static axle loads, the relative magnitude of the dynamic load component, and a bridge factor defined as the number of dynamic load maxima applied by an axle during its passage over the bridge. It is shown that for many bridges, the first natural frequency is simply related to the span and that the bridge factor is about 6. Impact values are predicted for a range of spans with a dynamic load component equal to 10% of the static load. A companion paper uses field studies to review this percentage.

Behaviour of flexible piles under inclined loads

Abstract: The lateral soil pressures, bending moments, pile displacements at ground surface, and bearing capacity of instrumented vertical single flexible model piles in homogeneous loose sand and soft clay ...

Stabilization of beams by pointwise feedback control

Abstract: A flexible structure consisting of serially connected Euler–Bernoulli beams with co-located sensors and actuators is considered. Controls are point forces and point bending moments applied at the nodes. It is known that uniform exponential stability can be achieved with linear velocity feedback. A sensitivity analysis of the system’s spectrum with respect to feedback coefficients is set up. It is also proved that in a particular case exponential decay rate can be obtained from the spectrum of the system.

Design of stud-shear reinforcement for slabs.

Abstract: Extensive tests presented earlier have establidhed the effectiveness of stud-shear reinforcement in increasing the punching-shear strength and ductility of slab-column connections transfering axial force V and bending moment M. The shear reinforcement is composed of vertical rods mechanically anchored at their top and bottom ends. This paper presents rules to design and detail stud-shear reinforcement in accordance with the 1989 ACI Building Code (ACI 318-89). Three numerical examples illustrate the design of shear studs and their distribution in slabs in the vicinity of interior, edge, and corner columns transferring V and M. Because of effective anchorage, design rules that reduce the amount of shear reinforcement are suggested and applied. Rules for the design according to the Canadian standard CAN3-A23.3-M84 are also given.

Plastic deformation of higly doped Silicon

Abstract: Heavily boron doped membranes are shown to be under tensile intrinsic stress with a negative intrinsic bending moment. However, the use of an oxide etc

Arch shape optimization using force approximation methods

Abstract: The objective of this paper is to provide a method of optimizing areas of the members as well as the shape of both two-hinged and fixed arches. The design process includes satisfaction of combined stress constraints under the assumption that the arch ribs can be approximated by a finite number of straight members. In order to reduce the number of detailed finite element analyses, the Force Approximization Method is used. A finite element analysis of the initial structure is performed and the gradients of the member end forces (axial, bending moment) are calculated with respect to the areas and nodal coordinates. The gradients are used to form an approximate structural analysis based on first order Taylor series expansions of the member end forces. Using move limits, a numerical optimizer minimizes the volume of the arch with information from the approximate structural analysis. Numerical examples are presented to demonstrate the efficiency and reliablity of the proposed method for shape optimization. It is shown that the number of finite element analysis is minimal and the procedure provides a highly efficient method of arch shape optimization.

Effect of heavy weather maneuvering on the wave-induced vertical bending moments in ship structures

Abstract: Statistical data are collected to quantify the probability of occurrence of voluntary course changes in heavy weather and their dependence on significant wave height and ship heading Decision rules are established about when and how to change course, based on an analysis of operational data and interviews with experienced shipmasters A Monte Carlo simulation is performed to determine how an omnidirectional distribution of initial headings is changed by voluntary course changes for different significant wave heights Finally, the effect of the nonuniform distribution of headings on the mean wave-induced vertical bending moment is calculated It is shown that although heavy weather maneuvering eases ship motions, it can increase the wave-induced bending moments and thus increase the probability of structural failure

Free Bending of Spiral Strands

Abstract: For a given axial mean load, the response of a helical strand to an applied bending moment is considered. For the critical case near the terminations, the theoretical stiffness formulations describing the slippage between the layers in the strand have been derived in an analytical form, which is then used as an input to the differential equation describing the behavior of individual wires. The final results cast some light on an interesting phenomenon observed in previously reported bending fatigue experiments, where the first wire to fail was invariably the one that entered the socket on the bending neutral axis rather than (as might be expected) the wires in the extreme‐fiber position. The theoretical results are of obvious value as an input to the interwire fretting fatigue analysis of strands. In particular, the paper should prove useful for the proper design and interpretation of the very expensive fatigue tests on large‐diameter strands.

An experimental investigation of ship hull ultimate strength

Abstract: This paper summarises results of an experimental investigation to determine the ultimate strength of ship hull girders. The 2-year experimental investigation was conducted at the University of California experimental facility. In the first phase a stiffened steel hull model of approximate dimensions 42 ft x 8 ft x 30 inches was tested. The model represented the middle section of a 75,600 dwt tanker and was subjected to a sagging moment in order to examine the failure behaviour of the deck under compression. The second model (phase 2) was designed to reflect several possible modes of failure of an open deck ship. It was tested with loads simulating a hogging bending moment along with lateral pressure on the bottom. A comparison between simple theoretical analyses and the experimental results for the two models are presented. Approximate methods for including the effects of residual stresses and initial distortions on the moment capacity of the models are also discussed. A number of possible reasons for the discrepancy between theoretical and experimental results are investigated in detail. Recommendations are also made for further research.

Two‐Dimensional Contact Pressure Distribution of a Radial Tire

Abstract: Two‐dimensional contact pressure distribution of a radial tire, statically compressed to a flat roadway, is analyzed using a rectangular contact patch. The tire structure is modeled by a spring‐bedded ring belt comprised of a laminated‐biased composite strip. The belt is supported by radial springs simulating the sidewall. The spring constant Kr was well defined previously by one of the authors. Deformation of the rectangular flat belt is obtained theoretically. The belt is subjected to inflation pressure, reaction forces transmitted from the spring bed of the tread rubber, and shearing force and bending moment along the belt boundaries brought from side‐wall springs and the detached part of the ring belt. In‐plane membrane forces, which are not uniform in the contact area, due to the friction forces acting between the tread surface and the roadway are also applied. The resulting contact pressure distributions in the circumferential direction are shown to be convex along the shoulder, but concave...

Model-based Control for Three-Roll Bending Process of Channel Bar

Abstract: A three-roll bending process with an automatic control system for producing a bar with a U-shaped cross section is studied. The relationship between the bending moment and the curvature of the workpiece is calculated by an elementary method. The calculated relationship is used to build up a process model combining the geometry of the three-roll bending process. This process model is applied to a real time control system for the process. Experiments are performed with the aid of a control system for obtaining products with a constant curvature as well as with continuously varying curvature. The desired curvatures are obtained with good accuracy.

Stabilization of Euler-Bernoulli beam by nonlinear boundary feedback

Abstract: We study the damping of transversal vibrations of a system of non-homogeneous connected Euler-Bernoulli beams. Controls are forces or torques applied at one end of the system. These controls are assumed to be nonlinear functions of the observed velocities of deflection. We show that the problem is well-posed and that asymptotic stability is achieved when the nonlinear feedback is monotone dissipative. No assumption involving monotonicity in the bending moment or linear mass distributions is necessary.

Comparison of measurements and calculations of wave induced vertical bending moments in ship models

Abstract: Wave-induced bending moments are calculated using a linear theory of ship motions and are compared with measurements on ship models. While the results show the generally good engineering accuracy of the linear theory, they indicate that its extent depends upon the block coefficient of the model and on model heading and speed. Measurements on similar ships at different laboratories compare differently with the calculations, and calculations with different computer codes yield dissimilar results when applied to the same ship. The conclusion is that the level of accuracy to be expected from the calculations cannot be better than the uncertainties involved in the calculations or measurements.

Analysis Procedure for Ribbed and Grid Plate Systems Used for Bridge Decks

Abstract: A methodology to develop analytically the deflection function characterizing the behavior of bridge decks in which the concrete slab rests on top of a network of steel beams is presented. The systems analyzed are categorized as ribbed plate systems, where the beams are parallel to the longitudinal span of the decking, and grid plate systems, where the slab is supported on a beam grid system. The plate systems are analyzed using an energy-based approach, where polynominal functions are used to model deflections and moments in the slab. In the analysis only plates that are simply supported on two edges and that are subjected to particular types of uniformly distributed and concentrated load patterns are considered. Sufficient cases are analyzed, and prediction equations for maximum bending moments and deflections of the slab are developed using regression analysis procedure.

Consistency aspects of out‐of‐plane bending, torsion and shear in a quadratic curved beam element

Abstract: Curved beams in civil engineering applications call for out-of- plane bending and torsion under the action of out-of-plane transverse shear loads. The design of a quadratic displacement type curved beam element capable of representing shear deformation as in the Timoshenko beam theory will call for special attention to be-paid to the manner in which the shear strain is to be represented. Field-inconsistent representations of the out- of- plane transverse shear strain will result in a loss Gf efficiency and introduce spuriou oscillations in the bending moment, torsional moment and shear force. The optimal field-consistent assumed strain interpolation for the shear is derived here and it is demonstrated that it has very high accuracy and is free from spurious force and moment oscillations.

Apparatus for clamping a test sample without any bending moment

Abstract: Test samples, especially samples made of ceramic materials, are tested under tension and/or compression loads while simultaneously avoiding the application of a bending moment to the test sample. For this purpose, each end of the test sample is held by a holding element having spherical outer surfaces received in spherical segment recesses of clamping jaws. Each test sample end is held by its holding element in a form-locking force-transmitting manner without a direct contact between the clamping jaws and the test sample. The application of bending moments to the test sample is avoided because the cooperating spherical surfaces permit an adjustment of the testing sample into a vertical position without any canting of the test sample.

Load-transfer problems for transversely isotropic elastic media

Abstract: This paper presents a unified solution procedure to analyze the load transfer from a partially embedded long (finite) cylindrical elastic bar into a transversely isotropic elastic half‐space. The bar may be subjected to a torque, an axial force, a horizontal force, or a bending moment at the top end. The solution approach is different from that proposed by Muki and Sternberg (1970). It is based on the interaction between a one‐dimensional elastic bar and a three‐dimensional elastic half‐space with a cylindrical cavity. The displacement compatibility is achieved along the contact surface between the bar and the half‐space. A variational technique coupled with a boundary integral equation scheme based on a set of exact Green's functions is used in the analysis. The boundary conditions at the top end of the bar are incorporated into the variational formulation through a set of Lagrange multipliers. Selected numerical results are presented for elastic bars embedded in some representative transversely isotropi...

Asymptotic behavior of solutions to plate equations with nonlinear dissipation occurring through shear forces and bending moments

Abstract: We consider the question of strong stability of solutions to plate equations with nonlinear dissipation in the boundary conditions. Two cases are discussed: (1) dissipation occurring through the nonlinear forces applied on the boundary and (2) dissipation acting through the nonlinear moments. Asymptotic stability results are presented for both cases. In the first case the results are established under the natural geometric conditions imposed on the domain, while in the second case certain restrictions on the curvature on the active portion of the boundary are required.

Limit‐States Design of Prestressed Concrete Pipe. II: Procedure

Abstract: A rational method for the design of prestressed concrete cylinder pipe subjected to the combined effects of external load and internal pressure is presented. This method is based on certain limit‐states criteria on serviceability, elastic limits, and strengths of the constituent materials. The design criteria and the rationale for their selection is presented in the first paper of this series. In this paper, the procedures developed for the computation of the combined loads corresponding to each design limit state are presented. The procedures include the computation of moment capacities for the thrusts resulting from prestressing and combined loads, including internal pressure, external load, and pipe and fluid weights, and a simplified method to account for moment redistribution from the invert and the crown of the pipe to the springline as the core and the coating undergo strain softening and cracking.