Journal of Engineering Mechanics

A static and a quasi‐static cyclic bending of a cantilever cable is considered in order to investigate the friction losses in cables. It is assumed that slippage due to twisting of wires is a source of internal friction. Slippage takes place within finite segments along the wire. It starts near the clamp and then propagates along the cable with the increase in load. The load‐deflection characteristic becomes essentially nonlinear after the load exceeds some critical magnitude below which there is no slippage. Two types of hysteretic loops are investigated: (1) Local, characterizing losses in a wire cross section; and (2) global, associated with the point of load application. It is shown that the local loop is symmetrical and closed and that a unique correspondence exists between a load versus twisting characteristic of a wire in a simple bending and friction losses in this cross section in a cyclic bending. Similar correspondence between global characteristics of a cable is introduced. Numerical results for a one lay cable are given.

Tsunami hazard is investigated using the indirect approach with simple seismological and hydrodynamic models. It is assumed that earthquakes of random magnitude may originate anywhere with equal likelihood from a single straight fault when the site is located on the perpendicular plane bisecting the fault. The ground displacement is instantaneous and consists of a block uplift type of movement, which may be circular or elongated in plan view. The hydrodynamic model is based on linear long‐wave theory, wherein the ocean is infinite in the horizontal extent, the earth is flat, and water is of constant depth. Tsunami hazard is computed for various values of the parameters and a sensitivity study is carried out to examine the effect of certain parameters on hazard.

The well‐known formulation of the optimal design of plastic frames presupposes that all the relevant data are known deterministically. It is realistic to recognize that more usually this information is known only imprecisely. In the paper it is shown how imprecision regarding the stipulations may be encoded in a fuzzy programming format and how this class of problems can be transformed to a standard linear programming form. Two methods are outlined. In the first the objectives are restated as fuzzy goals and incorporated in the constraint set. The optimal solution is that solution which maximizes the grade of membership within the constraints. This maximal grade of membership can be considered to be a measure of the degree of acceptability of the design in the face of the imprecision of the data. The second method retains the original objective function and adds an additional constraint which sets a lower limit on the degree of acceptability. Both methods involve only a slight increase in computational effort when compared with the corresponding deterministic formulation. Some numerical illustrations are presented.

A solution for a thin elastic cylindrical lining embedded in an infinite, cylindrically orthotropic medium and subjected to a uniaxial stress field has been obtained. The solution, by separation of variables, is found by utilizing Lekhnitskii's stress function whereas the lining is analyzed using thin shell theory. Equilibrium and continuity are completely satisfied along the interface between the shell and the orthotropic medium. It is shown how the general solution provides insight into maximum stress and deformations that characterize cylindrical linings in an orthotropic medium where cylindrically orthotropic constants were transformed from orthotropic medium data. Since an orthotropic medium is more representative of a large class of glass‐fiber reinforced plastics, the results differ considerably with the picture obtained from calculations for an isotropic medium. The lining and the orthotropic medium are shown to greatly affect tangential stress distribution. These results represent only a concise example; any situation of interest can be computed since the general solutions are given.

Analytic solutions are presented for the interaction of a thick‐walled circular cylindrical structure (tunnel) buried deeply underground. The medium is assumed to be homogeneous, isotropic, and linearly elastic so that Michell's formulation of the Airy stress function can be applied. The general expressions for the stresses and displacements in the cylindrically orthotropic structure are formulated using both the elasticity and shell‐theory approaches. Solutions are then obtained by considering the boundary conditions at the structure inner surface and at the tunnel‐medium interface. The shell theory employed is an improved shear‐deformable version of the well‐accepted Sanders shell theory. A technique is also developed to predict the transverse stresses in the structure. The results show a close agreement with those obtained by the theory of elasticity for a shell with an outer radius‐to‐thickness ratio of 5.

A simplified approach for the nonassociative behavior of granular (geological) materials is proposed. The basic concept is that the plastic potential can be obtained by controlling or correcting the yield function used for associative plasticity. This is achieved by correcting the hardening, evolution or growth function, which involves only one additional parameter above those for the associative model. Determination of constants and verification with respect to two granular soils tested under a variety of multiaxial stress paths are presented. It is shown that incorporation of the nonassociative behavior through the correction of the growth function yields remarkably satisfactory predictions for volumetric and stress‐strain responses of the material response.

All floating structures are subject to wave disturbances which vary in severity with the wind. It therefore seems natural to consider the possibility of active control of the motion of such structures to improve their dynamic behavior and hence their reliability. The feasibility of the active control of floating structures supported by open‐bottom chambers is presented. In order to accomplish the control the pressure of the air trapped beneath the chambers is adjusted. For ease of analysis and experiment, sea waves are assumed to be known and sinusoidal. Furthermore, only the heave motion is considered and the wave‐structure interaction is neglected in the analysis. Controls that completely eliminate the heave motion for a rigid platform are dealt with analytically and experimentally. The experiment performed indicated that the active control of structures significantly improved the response behavior.

The mathematical foundation of the general bounding surface constitutive formulation in plasticity is presented. Along these lines the concept of hypoplasticity is formally introduced, and it is shown that a particular class of hypoplastic formulations arises naturally from certain bounding surface models, with the distinguishing feature being the dependence of the elastoplastic moduli and/or the plastic strain rate direction on the stress rate direction. The general analytical perspective allows the better understanding and improvement of existing bounding surface plasticity and hypoplasticity models, which are briefly discussed, and suggests the proper way to construct new ones for future applications.