A new boundary element formulation for wave load analysis

A new boundary element (BEM) formulation is proposed for wave load analysis of submerged or floating bodies. The presented formulation, through establishing an impedance relation, permits the evaluation of the hydrodynamic coefficients (added mass and damping coefficients) and the coefficients of wave exciting forces systematically in terms of system matrices of BEM without solving any special problem, such as, unit velocity or unit excitation problem. It also eliminates the need for scattering analysis in the evaluation of wave exciting forces. The imaginary and real parts of impedance matrix give, respectively, added mass and damping matrices whose elements describe the fluid resistance against the motion of the body. The formulation is explained through the use of a simple fluid-solid system under wave excitations, which involves a uniform fluid layer containing a solid cylindrical body. In the formulation, the solid body is taken first as deformable, then, it is specialized when it is rigid. The validity of the proposed method is verified by comparing its result with those available in literature for rigid submerged or floating bodies

Analysis of fiber-reinforced elastomeric isolators under pure "warping"

As a relatively new type of multi-layered rubber-based seismic isolators, fiber-reinforced elastomeric isolators (FREIs) are composed of several thin rubber layers reinforced with flexible fiber sheets. Limited analytical studies in literature have pointed out that "warping" (distortion) of reinforcing sheets has significant influence on buckling behavior of FREIs. However, none of these studies, to the best knowledge of authors, has investigated their warping behavior, thoroughly. This study aims to investigate, in detail, the warping behavior of strip-shaped FREIs by deriving advanced analytical solutions without utilizing the commonly used "pressure", incompressibility, inextensibility and the "linear axial displacement variation through the thickness" assumptions. Studies show that the warping behavior of FREIs mainly depends on the (0 aspect ratio (shape factor) of the interior elastomer layers, (ii) Poisson's ratio of the elastomer and (iii) extensibility of the fiber sheets. The basic assumptions of the "pressure" method as well as the commonly used incompressibility assumption are valid only for isolators with relatively large shape factors, strictly incompressible elastomeric material and nearly inextensible fiber reinforcement

Elastic layers bonded to flexible reinforcements

Elastic layers bonded to reinforcing sheets are widely used in many engineering applications. While in most of the earlier applications, these layers are reinforced using steel plates, recent studies propose to replace "rigid" steel reinforcement with "flexible" fiber reinforcement to reduce both the cost and weight of the units/systems. In this study, a new formulation is presented for the analysis of elastic layers bonded to flexible reinforcements under (i) uniform compression, (ii) pure bending and (iii) pure warping. This new formulation has some distinct advantages over the others in literature. Since the displacement boundary conditions are included in the formulation, there is no need to start the formulation with some assumptions (other than those imposed by the order of the theory) on stress and/or displacement distributions in the layer or with some limitations on geometrical and material properties. Thus, the solutions derived from this formulation are valid not only for "thin" layers of strictly or nearly incompressible materials but also for "thick" layers and/or compressible materials. After presenting the formulation in its most general form, with regard to the order of the theory and shape of the layer, its applications are demonstrated by solving the governing equations for bonded layers of infinite-strip shape using zeroth and/or first order theory. For each deformation mode, closed-form expressions are obtained for displacement/stress distributions and effective layer modulus. The effects of three key parameters: (i) shape factor of the layer, (ii) Poisson's ratio of the layer material and (iii) extensibility of the reinforcing sheets, on the layer behavior are also studied