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The three-dimensional stress concentration factor (SCF) at the edge of elliptical and circular holes in infinite plates under remote tension has been extensively investigated considering the variations of plate thickness, hole dimensions and material properties, such as the Poisson’s coefficient. This study employs three dimensional finite element modeling to numerically investigate the effect of plate width on the behavior of the SCF across the thickness of linear elastic isotropic plates with a through-the-thickness circular hole under remote tension. The problem is governed by two geometric non-dimensional parameters, i.e., the plate half-width to hole radius (W/r) and the plate thickness to hole radius (B/r) ratios. It is shown that for thin plates the value of the SCF is nearly constant throughout the thickness for any plate width. As the plate thickness increases, the point of maximum SCF shifts from the plate middle plane and approaches the free surface. When the ratio of plate half-width to hole radius (W/r) is greater than four, the maximum SCF was observed to approximate the theoretical value determined for infinite plates. When the plate width is reduced, the maximum SCF values significantly increase. A polynomial curve fitting was employed on the numerical results to generate empirical formulas for the maximum and surface SCFs as a function of W/r and B/r. These equations can be applied, with reasonable accuracy, to practical problems of structural strength and fatigue, for instance.

Great attention has been given, in the scientific literature, to the effect of initial imperfections on the structural behavior of experimental samples under compression loads. Geometrical reconstruction of the as-built surface is therefore required to allow accurate numerical modeling. High-precision systems for inverse engineering are expensive, and most of the times geometrical imperfections are rather complex to be described without high computational efforts. In this paper, an imagebased approach to model the surface of imperfect structures using open-source software and a common digital camera is presented. The proposed approach aims to generate high-quality surfaces from real imperfect structures, by employing the surface-from-motion and multi-view stereo techniques. A controlled frame capture is introduced to decrease both the computational effort and number of repeated correspondences. The surface fit is then computed by meshing the dense cloud of points and adjusting several surface regions describing the samples' profiles. The procedure is illustrated by using two damaged tubular member samples reconstructed by the proposed approach. Then, resulted geometries are verified by comparing measures from a three-dimensional high-precision laser scanner and a common mechanical procedure. Finally, a comparison of three-dimensional mappings of a ship panel with proposed approach and commercial photogrammetry software is performed. Verification results refer to the possibility of prototyping geometry surfaces from real imperfect samples by using inexpensive hardware and public domain software tools with acceptable level of accuracy.

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In offshore oil &gas production there is a large concentration of platforms in a limited area of the sea, with the consequent increase of vessel traffic in the region. Platform supply vessels (PSVs), shuttle tankers and maintenance and safety units operate very close to these production platforms, creating a propitious scenario for collisions. Thus, the risk of collision between vessels and platforms has significantly increased, causing concern from the point of view of life loss, material damage and marine environment degradation. It is important to adequately design the structures and to predict the effects of accidents on the involved vessels. In the structural analysis of collision, geometric and material nonlinearities must be considered, as well as the striking ship velocity, the vessels draft difference, among other variables. In this work, the collision of a platform supply vessel with a single-hull Floating Production Storage and Offloading (FPSO) platform is studied through numerical simulation using the ANSYS LS-DYNA computational system. Damage is locally characterized by the collision force on the FPSO hull and the depth of penetration (displacement). In addition, it is also shown the energy absorption capacity of each type of structural element for the collision scenarios studied and a criterion is proposed to determine which structural element group should receive more attention in the design phase in order to reduce the effects of a collision. Both the longitudinal strengths of the intact FPSO as well as the remainder after collision are evaluated by assessing the bending moment versus curvature curves. It is observed that a single-hull FPSO platform with the thicknesses of the structural elements maintained unchanged in the conversion of the original oil tanker (VLCC) shows a significant ultimate longitudinal strength even after collision of a larger support vessel at higher velocity than recommended by the IACS rule.