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In this paper, the effect of the FE discretization density on the results of both convex and nonconvex‐nonsmooth frictional contact and adhesive contact interface problems is investigated. The tool for this study is a variational formulation leading to an iterative method for the numerical solution of the arising nonconvex‐nonsmooth optimization problems. Various cases of monotone and nonmonotone interface laws are considered and interesting results are obtained.

The purpose of this paper is to investigate the influence of the resolution with which interfaces of fractal geometry are represented, on the contact area and consequently on the contact interfacial stresses. The study is based on a numerical approach. The paper focuses on the differences between the cases of elastic and inelastic materials having as primary parameter the resolution of the interface.

A multi‐resolution parametric analysis is performed for fractal interfaces dividing a plane structure into two parts. On these interfaces, unilateral contact conditions are assumed to hold. The computer‐generated surfaces adopted here are self‐affine curves, characterized by a precise value of the resolution δ of the fractal set. Different contact simulations are studied by applying a horizontal displacement s on the upper part of the structure. For every value of s, a solution is taken in terms of normal forces and displacements at the interface. The procedure is repeated for different values of the resolution δ. At each scale, a classical Euclidean problem is solved by using finite element models. In the limit of the finest resolution, fractal behaviour is achieved.

The paper leads to a number of interesting conclusions. In the case of linear elastic analysis, the contact area and, consequently, the contact interfacial stresses depend strongly on the resolution of the fractal interface. Contrary, in the case of inelastic analysis, this dependence is verified only for the lower resolution values. As the resolution becomes higher, the contact area tends to become independent from the resolution.

The originality of the paper lies on the results and the corresponding conclusions obtained for the case of inelastic material behaviour, while the results for the case of elastic analysis verify the findings of other researchers.

In order to determine the ductility features of steel structures, several approaches have been introduced in the bibliography. In this paper a certain method is proposed which considers the actual form of the moment‐rotation curve, including the possible softening branches. Moreover, stability phenomena are also taken into account as they significantly influence the overall response of the structure. For the effective application of the considered method, a solution algorithm was developed, mainly based on the nonconvex optimization theory. The numerical applications that follow demonstrate the applicability of the adopted approach.

The purpose of this paper is to provide the research and practising engineers with insight on the benefits of using low‐yield point steel with respect to ordinary steel as a construction material for shear wall panels. The paper seeks to focus on the behaviour of such panels when installed in new or existing structures in order to improve their seismic performance.

Finite element models are applied in order to approximate the structural response of low‐yield steel panels, used for seismic applications. Owing to the specific characteristics of the problem at hand, geometric and material nonlinearities have to be accurately considered. For comparison reasons, low‐yield point steel and ordinary steel are considered as construction materials for the aforementioned panels. The paper examines both the case of “pure shear” steel panel and also the more realistic case that the panel is encased in the surrounding frame.

The paper reaches a number of interesting conclusions. The beneficial behaviour of low‐yield steel panels with respect to ordinary steel panels is verified. Comments are made distinguishing the differences in the behaviour of panels surrounded by strong elements (“encased” panels) compared with that of panels submitted to pure shear. Finally, the improved seismic behaviour of existing structures retrofitted by shear wall panels is verified.

The paper exhibits numerically the advantages of low‐yield point steel with respect to ordinary steel as a construction material for panels and, second, contributes to the comprehension of the realistic panel behaviour of encased panels. More specifically, the paper focuses on the differences in the behaviour of encased steel panels with respect to the “pure shear” steel panels.

In this paper, the influence of fractal interface geometry to the evolution of the friction mechanism is studied. The paper is based on fractal approaches for the modeling of the multiscale self‐affine topography of these interfaces. More specifically, these approaches are based on scale‐independent parameters such as the fractal dimension. Here, friction between rough surfaces is assumed to be the result of the gradual plastification of the fractal interface asperities. In order to study the resulting highly nonlinear problem a variational formulation is used in order to describe contact between the interfaces. The numerical method used here leads to the successive solution of quadratic optimization problems. Finally, structures with different fractal interfaces are analyzed in order to obtain results for the relation between the fractal dimension and the overall response of the structures.

The design of compliant towers in deep waters is greatly affected by their dynamic response to wave loads as well as by the geometrical and material nonlinearities that appear. In general, a nonlinear time history dynamic analysis is the most appropriate one to be applied to capture the exact response of the structure under wave loading. However, this type of analysis is complex and time-consuming. This paper aims to develop a simplified methodology, which can adequately approximate the maximum response yielded by a dynamic analysis by means of a static analysis.

Various types of time history dynamic analysis are first applied on a detailed structural model, ranging from linear to fully nonlinear, that are used as reference solutions. In the sequel, a simplified analysis model is formulated, capable of reproducing the response of the entire structure with significantly reduced computational cost. In the next stage, this model is used to obtain the linear and nonlinear response spectra of the structure. Finally, these spectra are used to formulate a simplified design approach, based on equivalent static loads.

This simplified design approach produces good results in cases that the response is mainly governed by the first eigenmode, which is the case when compliant towers are considered.

The present paper borrows ideas from the area of earthquake engineering, where simplified methodologies can be used for the design of a certain class of structures. However, the development of a simplified methodology for the approximation of the dynamic behavior of offshore structures under wave loading is a much more complex problem, which, to the authors’ knowledge, has not been addressed till now.

The purpose of this paper is to illustrate the many aspects of Poincare recurrence time theorem for an archetype of a complex system, the logistic map.

At the beginning of the twentieth century, Poincare's recurrence theorem had revolutionized modern mechanics and statistical physics. However, this theorem did not attract considerable attention, at least from a numerical and computational point of view. In a series of relatively recent papers, Balakrishnan, Nicolis and Nicolis have addressed the recurrence time problem in a firm basis, introducing notation, theory, and numerical studies. Motivated by this call, the paper proposes to illustrate the many aspects of Poincare recurrence time theorem for an archetype of a complex system, the logistic map. The authors propose here in different tests and computations, each one illuminating the many aspects of the problem of recurrence. The paper ends up with a short discussion and conclusions.

In this paper, the authors obtain new results on computations, each one illuminating the many aspects of the problem of recurrence. One striking aspect of this detailed work, is that when the sizes of the cells in the phase space became considerable, then the recurrence times assume ordinary values.

The paper extends previous results on chaotic maps to the logistic map, enhancing comprehension, making possible connections with number theory, combinatorics and cryptography.

Given a time‐series, what is the best partitioning of the state space in order to obtain reasonable values for the block entropies? The purpose of this paper is to provide a simple answer (an algorithm), although approximative, in connection with symbolic dynamics and statistical properties of 1‐d maps on the interval.

The logistic map is examined as an archetype of a Complex System with different behaviors, namely: periodicity, order‐to‐chaos period‐doubling transition, weak chaos, parametric intermittent chaos, developed chaos and fully developed chaos. For the logistic map the generating partition is known, and allows comparison with other prescriptions in the literature. The partitioning of the phase space with the easy generated bipartition induced by the mean value of a curve in the plane, gives results in good agreement (roughly up to a 20 per cent difference) with the results of the generating partition, if the trajectory of the system is in parametric intermittent chaos and in developed chaos (DC). In the case of fully developed chaos (FDC), the agreement is perfect.

The authors confirm that a statistical partitioning is almost equivalent with the exact partitioning for the logistic map.

The paper updates previous results and proposes a better understanding on the partitioning for symbolic dynamics.

The primary purpose of this paper is the development of a fire–structure interface (FSI) model, which is referred in this study as a simplified “dual-layer” model. It is oriented for design purposes, in the cases where fire-compartments exceed the “regular” dimensions, as they are defined by the guidelines of the codes (EN 1991-1-2).

The model can be used at the post-processing stage of computational fluid dynamics (CFD) analysis and it is based on the gas-temperature field (spatial and temporal) of the fire-compartment. To use the “dual-layer” model, first the gas-temperature (discrete) function along the height of the fire-compartment, at discrete plan–view points should be determined through the output of the CFD analysis. The model “compresses” the point data to (spatial) virtual zones, which are divided into two layers (with respect to the height of the fire-compartment) of uniform temperature: the upper (hot) layer and the lower (cold) layer.

The model calculates the temporal evolution of the gas-temperature in the fire compartment in every virtual zone which is divided in two layers (hot and cold layer).

The main advantage of this methodology is that actually only three different variables (height of interface upper-layer temperature and lower-layer temperature) are exported during the post-processing stage of the CFD analysis, for every virtual zone. Next, the gas-temperature can be used for the determination of the temperature profile of structural members using simple models that are proposed in EN 1993-1-2.

The purpose of this paper is to present a vision for the future development of Kybernetes under a new editorship.

The new Editors are introduced, the strengths and history of the journal reviewed, and plans for its future development described.

The future of Kybernetes will build on its long and distinguished heritage, noting especially the strengths of interdisplinarity, internationality, and strong links with major cybernetic societies across the world. While maintaining these strengths, the new Editors will seek to develop further the conversations between diverse fields contributing to the journal and to bring a new emphasis to the interdisciplinary study of information, to studies of the social implications of cybernetics and related fields, and to profiles of thinkers in cybernetics, systems and management science.

This is only the second time that there has been a change of editor in the more than 40 years that Kybernetes has been published. The journal (and the whole field of cybernetics and systems) owes the past editors a great debt of thanks for their outstanding work, but the time has come for change. This paper starts to identify new directions under the new Editors.