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Optimum design of elastic moduli for the multiple load problems PDF Print E-mail
T. Lewiński, Optimum design of elastic moduli for the multiple load problems,  Archives of Mechanics vol. 73 (1), pp 27-66, 2021,
 DOI: 10.24423/aom.3607
https://am.ippt.pan.pl/am/article/view/3607

Abstract
The paper deals with minimization of the weighted average of compliances of structures, made of an elastic material of spatially varying elasticity moduli, subjected to n load variants acting non-simultaneously. The trace of the Hooke tensor is assumed as the unit cost of the design. Three versions of the free material design are discussed: designing the moduli of arbitrary anisotropy (AMD), designing the moduli of an isotropic material (IMD), designing of Young’s modulus for a fixed Poisson ratio (YMD). The problem is in all cases reduced to the Linear Constrained Problem (LCP) of Bouchitté and Fragalà consisting of two mutually dual problems: stress based and strain based, the former one being characterized by the integrand of linear growth depending on the trial statically admissible stresses. The paper shows equivalence of the stress fields solving the (LCP) problem and those appearing in the optimal body subjected to subsequent load cases.

 
On incorporating warping effects due to transverse shear and torsion into the theories of straight elastic bars PDF Print E-mail
T. Lewiński, S.Czarnecki, On incorporating warping effects due to transverse shear and torsion into the theories of straight elastic bars, Acta Mech (2020).

https://doi.org/10.1007/s00707-020-02849-7

Abstract
By endowing El Fatmi’s theories of bars with first-order warping functions due to torsion and shear, a family of theories of bars, of various applicability ranges, is effectively constructed. The theories thus formed concern bars of arbitrary cross-sections; they are reformulations of the mentioned theories by El Fatmi and theories by Kim and Kim, Librescu and Song, Vlasov and Timoshenko. The Vlasov-like theory thus developed is capable of describing the torsional buckling and lateral buckling phenomena of bars of both solid and thin-walled cross-sections, which reflects the non-trivial correspondence, noted by Wagner and Gruttmann, between the torsional St.Venant’s warping function and the contour-wise defined warping functions proposed by Vlasov. Moreover, the present paper delivers an explicit construction of the constitutive equations of Timoshenko’s theory; the equations linking transverse forces with the measures of transverse shear turn out to be coupled for all bars of asymmetric cross-sections. The modeling is hierarchical: the warping functions are numerically constructed by solving the three underlying 2D scalar elliptic problems, providing the effective characteristics for the 1D models of bars. The 2D and 1D problems are indissolubly bonded, thus forming a unified scientific tool, deeply rooted in the hitherto existing knowledge on elasticity of elastic straight bars.
 
Projektowanie w procesie BIM PDF Print E-mail
Zbigniew Kacprzyk, Projektowanie w procesie BIM, Oficyna Wydawnicza Politechniki Warszawskiej, Warszawa 2020, ISBN 978-83-8156-117-4.

Projektowanie w procesie BIMCelem monografii jest przybliżenie zagadnień BIM szczególnie na etapie przygotowania projektu. Podstawy teoretyczne pozwolą na lepsze zrozumienie systemów CAD wykorzystywanych w procesie BIM. W przypadku wykorzystania systemów obliczeniowych (CAE) brak podstaw teoretycznych jest po prostu niebezpieczny dla konstruktora.
Model cyfrowy obiektu zawiera model geometryczny, informacje fizyczne o materiałach, informacje techniczne (aprobaty, cykle przeglądów itp.), harmonogramy, wyceny robót budowlanych, organizację placu budowy, harmonogramy dostaw materiałów, zarządzanie całym cyklem życia obiektu i wiele innych informacji wytwarzanych w czasie realizacji przedsięwzięcia.

BIM jako koncepcja wciąż się rozwija, definicje, które można napotkać w dostępnej literaturze różnią się. Różnią się też podejścia do BIM-u w różnych krajach.

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Optimal archgrids spanning rectangular domains PDF Print E-mail
Grzegorz Dzierżanowski, Radosław Czubacki, Optimal archgrids spanning rectangular domains, Computers and Structures, volume 242 (1 January 2021), article 106371
https://doi.org/10.1016/j.compstruc.2020.106371

Abstract
The theory of archgrids of minimal weight has been formulated in the late 1970s and recently reconsidered by means of duality theory in the calculus of variations. In the current study, we follow this approach by putting forward an efficient computational scheme. Trial functions for both primal and dual problems are decomposed in two function bases: trigonometric (Fourier) and polynomial (Legendre). Our focus is on structures composed of arches forming a rectangular grid, i.e. running in two mutually perpendicular directions and spanning a given rectangular domain. In the course of discussion, we show that the numerical algorithm is quickly convergent, CPU time efficient, and robust. In particular, it provides clear-cut solutions in which optimal parts of a structure are sharply distinguished from the non-optimal, hence redundant, ones.
 
Applications of Michell’s Theory in Design of High-Rise Buildings, Large-Scale Roofs and Long-Span Bridges PDF Print E-mail
C. Graczykowski, T. Lewiński, Applications of Michell’s Theory in Design of High-Rise Buildings, Large-Scale Roofs and Long-Span Bridges, Computer Assisted Methods in Engineering and Science (CAMES) 27(2-3) 2020
https://cames.ippt.pan.pl/index.php/cames/article/view/288.
DOI: https://doi.org/10.24423/cames.288.

Abstract
This paper analyzes the relations between the theory of Michell structures, which is one of the most important theories in structural optimization, and some remarkable engineering structures, including selected high-rise buildings, large-scale roof coverings and long-span bridges. The first part of this study briefly presents the development of Michell’s theory, its basic concepts, assumptions, and examples and fundamental features of Michell structures. Then, several untypical engineering structures that make use of said concepts are presented, including skyscrapers proposed by the Polish structural designer W. Zalewski and the international architectural office of Skidmore, Owings and Merill (SOM). Next, large-scale roof coverings of “Spodek” arena in Poland as well as selected bridges are thoroughly analyzed in the context of similarity to Michell structures. The conducted
study reveals that considered structural forms of the analyzed structures follow some of the concepts known from Michell’s theory and thus possess many features of the optimal structural designs.
 
Optimal Form-Finding of Cable Systems PDF Print E-mail
Dzierżanowski Grzegorz, Wójcik-Grząba Izabela, Optimal Form-Finding of Cable Systems, Archives of Civil Engineering, vol. 66, nr 3, 2020, ss. 305-321
DOI:10.24425/ace.2020.134399

online>>

Abstract
Tensile structures in general, achieve their load-carrying capability only after the process of initial form-finding. From the mechanical point of view, this process can be considered as a problem in statics. As cable systems are close siblings of trusses (cables, however, can carry tensile forces only), in our study we refer to equilibrium equation similar to those known from the theory of the latter. In particular, the paper regards designing pre-tensioned cable systems, with a goal to make them kinematically stable and such that the weight of so designed system is lowest possible. Unlike in typical topology optimization problems, our goal is not to optimize the structural layout against a particular applied load. However, our method uses much the same pattern. First, we formulate the variational problem of form-finding and next we describe the corresponding iterative numerical procedure for determining the optimum location of nodes of the cable system mesh. We base our study on the concept of force density which is a ratio of an axial force in cable segment to its length.
 
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