Residual Strength of Tubular Columns With Localized Thickness Loss

This paper provides a comprehensive finite element analysis to investigate the ultimate capacity of corroded members under concentric axial loads. The paper investigates previous experimental work on stocky and slender tubular columns with simulated patch corrosion and provides a numerical model that can estimate the columns capacities. Further, a parametric study is performed to investigate the effect of geometric parameters such as location, height, and width of corrosion patch on the ultimate capacity of corroded columns. Finally, the paper presents a comparison between laboratory tests to the formulae of superseded standards and numerical analysis using nonlinear finite element methods. The numerical model proposed in this paper show good agreement with the results from the experimental work.

On the role of localizations in buckling of axially compressed cylinders

The collapse of axially compressed cylinders by buckling instability is a classic problem in engineering mechanics. We revisit the problem by considering fully localized post-buckling states in the form of one or multiple dimples. Using nonlinear finite-element methods and numerical continuation algorithms, we trace the evolution of odd and even dimples into one axially localized ring of circumferentially periodic diamond-shaped waves. The growth of the post-buckling pattern with varying compression is driven by homoclinic snaking with even- and odd-dimple solutions intertwined. When the axially localized ring of diamond-shaped buckles destabilizes, additional circumferential snaking sequences ensue that lead to the Yoshimura buckling pattern. The unstable single-dimple state is a mountain-pass point in the energy landscape and therefore forms the smallest energy barrier between the pre-buckling and post-buckling regimes. The small energy barrier associated with the mountain-pass point means that the compressed, pre-buckled cylinder is exceedingly sensitive to perturbations once the mountain-pass point exists. We parameterize the compressive onset of the single-dimple mountain-pass point with a single non-dimensional parameter, and compare the lower-bound buckling load suggested by this parameter with over 100 experimental data points from the literature. Good correlation suggests that the derived knockdown factor provides a less conservative design load than NASA's SP-8007 guideline.

Influence of sizes of abutments and fixation screws on dental implant system: a non-linear finite element analysis

The purpose of this study is to discuss the influence of sizes of abutments and fixation screws on immediately loaded dental implants in mandibular bones using nonlinear finite element methods. Abutments with three unilateral wall thicknesses and fixation screws with three diameters are analyzed to compare the stresses and deformations under a vertical or oblique force of 130 N. The nonlinearity due to friction contacts between the fixation screw, the abutment, the implant, and the bone is taken into account. The results showed that improper sizes of abutments and fixation screws would increase the stress and deformation of the dental implant system. If possible, the diameter of fixation screw should not be smaller than Φ1.0 mm, the diameter between Φ1.0 mm and Φ1.2 mm is acceptable. The fixation screw diameter preferably exceeds Φ1.4 mm. The unilateral wall thickness >0.5 mm is optimal selection for abutments.

Icebreaker Grillage Structural Interaction and the Characteristic Stiffness Curve

The structural components of a typical icebreaker hull grillage section consist of hull plating, main frames, web frames and stringers. The grillage section is the main structure resisting local ice loads during icebreaking and maneuvering operations. As such, the structural integrity of the icebreaker is largely dependent on the design strength of the grillage sections along the length of the vessel. The latest release of the IACS Unified Requirements for Polar Ships specifically pertains to structural design of these local grillage sections. Within the IACS Unified Requirements, prescriptive formulas are used to define the hull plating and main frame strength requirements as a function of stiffening direction, longitudinal/vertical location and operational requirements. The stringer and web frame stability requirements however, are limited to meeting empirical criteria. Limited examples of stringer and web frame prescriptive design strength formulations are available in the literature. These formulations may lead to an overly conservative stringer or web frame section design due to the challenge of representing the grillage section structural component interaction. To properly understand the structural interaction of icebreaker grillage section components, LR has used nonlinear finite element methods to compute the characteristic stiffness curve well into plasticity. The characteristic stiffness curve is considered representative of the effective structural interaction of the section components and has been found to relate directly to the section design methodology (elastic or plastic). This paper presents the development of these stiffness curves; the relationship between stiffness curve characteristics and design methodology; and how stiffness curves may be used for structural design and verification.

Buckling of Thin-Walled Cylindrical Shells of Desulphurizing Tower under Wind Loading

On the project background of the large-scale thin-walled cylindrical shells of a practical desulphurizing absorption tower, the investigations are conducted into the buckling mode and buckling capacity of the large-scale thin-walled cylindrical shells under wind loading by nonlinear finite element methods. In the buckling path, it firstly presents the buckling mode similar to that of the stocky cylinder under uniform external radial compression. In the post-buckling stage, the snap-through takes place, the buckling mode turns to being similar to the axial compressive buckling mode of the medium-height cylinder that horizontal buckles occur in the upper half of the front area. The buckling capacity of the cylindrical shells of desulphurizing tower is some more than the linear elastic buckling pressure of the cylinder under uniform radial pressure.

Study on Punching Resistance of Slab-Column Nodes Strengthened with CFRP Sheets by Nonlinear Finite Element Methods

During punching shear failure process, the stress states near slab-column node are complex and nonlinear characters of reinforced concrete make the problems more complicated. In this paper, by considering nonlinear characters of reinforced concrete, punching carrying capacities of slab-column nodes are to analyze by using nonlinear finite element methods, and then the reasonable reinforcement schemes at slab-column nodes have been determined. The slab-column nodes are strengthened by using CFRP sheets. Compare punching bearing capacities of nodes in reinforcement structure with that in unreinforcement structure, the results show that this strengthened method can effectively improve punching resistance bearing capacities of slab-column nodes.

Study of Rheological Effects on the Stress and Deformation of the Sand-Gravel-Fill Dam

This paper analyses and selects the rheological mechanism and rheological analysis of the sand-gravel-fill dam, and combines with concrete-face sand-gravel-fill dam engineering practice, using three-dimensional nonlinear finite element methods to analyze the rheological effects on stress and deformation of the dam, using two calculation program of considering sand-gravel rheological effects or not. Then analyze and compare the results of the two calculation program, and systematically summarize the rheological effects on stress and deformation of the dam.