Special issue on multiscale computations for solids and fluids Adnan Ibrahimbegovic
Abstract; Full Text (897K) .	pages 1-4.	DOI: 10.12989/csm.2020.9.1.001

Abstract
This special issue contains selected papers first presented in a short format at the 4th International Conference ECCOMAS MSF 2019 – Multiscale Computations for Solids and Fluids, organized in Bosnian capital Sarajevo, September 18-20, 2019.

Key Words
multiscale computations; solid mechanics; fluid mechanics

Address
Adnan Ibrahimbegovic: Universite de Technologie Compiegne – Sorbonne Universities, Laboratoire Roberval de Mecanique,
Centre de Recherche Royallieu, Compiegne, France; Institut Universitaire de France (IUF); Academy of Sciences and Arts BiH

Finite volumes vs finite elements. There is a choice Ismet DemirdZic
Abstract; Full Text (2664K) .	pages 5-28.	DOI: 10.12989/csm.2020.9.1.005

Abstract
Despite a widely-held belief that the finite element method is the method for the solution of solid mechanics problems, which has for 30 years dissuaded solid mechanics scientists from paying any attention to the finite volume method, it is argued that finite volume methods can be a viable alternative. It is shown that it is simple to understand and implement, strongly conservative, memory efficient, and directly applicable to nonlinear problems. A number of examples are presented and, when available, comparison with finite element methods is made, showing that finite volume methods can be not only equal to, but outperform finite element methods for many applications.

Key Words
solid mechanics; finite volume method; finite element method; fluid-solid interaction

Address
Ismet Demirdzic: Department of Mechanical Engineering, University of Sarajevo, Sarajevo, 71000, Bosnia and Herzegovina

Buckling analysis of complex structures with refined model built of frame and shell finite elements Emina Hajdo, Adnan Ibrahimbegovic and Samir Dolarevic
Abstract; Full Text (1944K) .	pages 29-46.	DOI: 10.12989/csm.2020.9.1.029

Abstract
In this paper we deal with stability problems of any complex structure that can be modeled by beam and shell finite elements. We use for illustration the steel plate girders, which are used in bridge construction, and in industrial halls or building construction. Long spans, slender cross sections exposed to heavy loads, are all critical design points engineers must take into account. Knowing the critical load that will cause lateral torsional buckling of the girder, or load that can lead to web buckling, as an important scenario to consider in a design process. Many of such problem, including lateral torsional buckling with influence of lateral supports and their spacing on critical load can be solved by the proposed method. An illustrative study of web buckling also includes effects of position and spacing of transverse and longitudinal web stiffeners, where stiffeners can be modelled optionally using shell or frame elements.

Key Words
stability; steel plate girder; web buckling; lateral torsional buckling; critical load; shell model

Address
Emina Hajdo, Samir Dolarevic: Faculty of Civil Engineering, University of Sarajevo, Sarajevo, Bosnia and Herzegovina
Adnan Ibrahimbegovic: Laboratoire Roberval, Universite de Technologie de Compiegne / Sorbonne Universites, France

Instability phenomena and their control in statics and dynamics: Application to deep and shallow truss and frame structures Rosa Adela Mejia-Nava, Adnan Ibrahimbegovic and Rogelio Lozano-Leal
Abstract; Full Text (1872K) .	pages 47-62.	DOI: 10.12989/csm.2020.9.1.047

Abstract
In this paper we study the control for nonlinear geometric instability problem of a deep or a shallow truss or yet a frame structure. All the structural models are built with geometrically exact truss and beam finite elements. The proposed models can successfully handle large overall motion under static or dynamic conservative load. The control strategy considers adding a damping from either friction device or viscous damper. This kind of control belong to well-known concept of passivity. Different examples are presented in order to illustrate the proposed theoretical developments.

Key Words
instability; control; viscous damping; friction damping

Address
Rosa Adela Mejia-Nava, Adnan Ibrahimbegovic: Universite de Technologie Compiegne, Laboratoire Roberval of Mechanics, France
Rogelio Lozano-Leal: Universite de Technologie Compiegne, Heudiasyc UMR CNRS 7253, France

Towards isotropic transport with co-meshes Christina Paulin, Eric Heulhard de Montigny and Antoine Llor
Abstract; Full Text (2687K) .	pages 63-75.	DOI: 10.12989/csm.2020.9.1.063

Abstract
Transport is the central ingredient of all numerical schemes for hyperbolic partial differential equations and in particular for hydrodynamics. Transport has thus been extensively studied in many of its features and for numerous specific applications. In more than one dimension, it is most commonly plagued by a major artifact: mesh imprinting. Though mesh imprinting is generally inevitable, its anisotropy can be modulated and is thus amenable to significant reduction. In the present work we introduce a new definition of stencils by taking into account second nearest neighbors (across cell corners) and call the resulting strategy \"co-mesh approach\". The modified equation is used to study numerical dissipation and tune enlarged stencils in order to minimize transport anisotropy.

Key Words
transport; numerical diffusion; isotropy; mesh imprinting; modified equation

Address
Christina Paulin, Eric Heulhard de Montigny and Antoine Llor: CEA, DAM, DIF, F-91297 Arpajon, France

Non-stationary mixed problem of elasticity for a semi-strip Viktor Reut, Natalya Vaysfeld and Zinaida Zhuravlova
Abstract; Full Text (982K) .	pages 77-89.	DOI: 10.12989/csm.2020.9.1.077

Abstract
This study is dedicated to the dynamic elasticity problem for a semi-strip. The semi-strip is loaded by the dynamic load at the center of its short edge. The conditions of fixing are given on the lateral sides of the semistrip. The initial problem is reduced to one-dimensional problem with the help of Laplace\'s and Fourier\'s integral transforms. The one-dimensional boundary problem is formulated as the vector boundary problem in the transform\'s domain. Its solution is constructed as the superposition of the general solution for the homogeneous vector equation and the partial solution for the inhomogeneous vector equation. The matrix differential calculation is used for the deriving of the general solution. The partial solution is constructed with the help of Green\'s matrix-function, which is searched as the bilinear expansion. The case of steady-state oscillations is considered. The problem is reduced to the solving of the singular integral equation. The orthogonalization method is applied for the calculations. The stress state of the semi-strip is investigated for the different values of the frequency.

Key Words
semi-strip; dynamic problem; steady-state oscillation; singular integral equation; Green matrix-function

Address
Viktor Reut, Natalya Vaysfeld and Zinaida Zhuravlova: Faculty of Mathematics, Physics and Informational Technologies, Odessa I.I. Mechnikov National University,
Dvoryanska Str., 2, Odessa, Ukraine