1,354,571 research outputs found
Un dialogo tra Francesco Indovina e Laura Fregolent sull'analisi territoriale e sulla situazione presente dell'urbanistica e della città diffusa
No full textUn dialogo tra Francesco Indovina e Laura Fregolent sulle origini delle riflessioni sulla città diffusa, la scuola di analisi che anche intorno a questo tema si è sviluppata presso lo IUAV e sull'importanza delle analisi territoriali all'oggi
Introduzione. I perchè di un Atlante
No full textUna collaborazione tra Università IUAV di Venezia e Legambiente Veneto ha portato alla mappatura dei conflitti generati da trasformazioni territoriali presenti in Veneto, contenuti nell’Atlante del malessere territoriale consultabile on-line (http://mapserver.iuav.it/website/AtlanteMalessereTerritoriale/AtlanteMalessereTerritoriale.html).
Il libro è articolato in tre parti. Nella prima Laura Fregolent restituisce i risultati della ricerca condotta, i dati raccolti e la loro elaborazione. I 72 conflitti vengono descritti nelle loro caratteristiche principali, vengono raggruppati per tipologia al fine di dare un’interpretazione ad un fenomeno che ha assunto dimensioni così ampie. Le mappe a corredo del capitolo consentono di visualizzare in maniera chiara la dimensione e l’estensione delle proteste raccolte mettendo in evidenza proprio la numerosità delle conflittualità locali.
La seconda parte raccoglie alcuni saggi che si occupano in maniera puntuale di alcuni dei temi emersi ed individuati dall’analisi dei risultati dei dati contenuti nelle schede compilate dai diversi comitati coinvolti
Città informale VS città progettata #2 : intervista a Laura Fregolent
No full textChe cosa si intende per città informale e quali sono le relazioni con la pianificazione e i suoi strumenti, quali le azioni e le domande che pone al planne
Substructure decoupling without using rotational DoFs: fact or fiction?
No full textIn the framework of experimental dynamic substructuring, substructure decoupling consists in the identification of the dynamic behaviour of a structural subsystem, starting from the dynamic behaviour of both the assembled system and the residual subsystem (the known portion of the assembled system). On the contrary, substructure coupling identifies an assembled system starting from the component subsystems. The degrees of freedom (DoFs) of the assembled system can be partitioned into internal DoFs (not belonging to the couplings) and coupling DoFs. In substructure coupling, whenever coupling DoFs include rotational DoFs, the related rotational FRFs must be obtained experimentally. Does this requirement holds for substructure decoupling too, as it is commonly believed? Decoupling can be ideally accomplished by adding the negative of the residual subsystem to the assembled system (direct decoupling) and by enforcing compatibility and equilibrium at enough interface DoFs. Ideally, every DoF of the residual subsystem belongs to the interface between the assembled system and the residual subsystem. Hopefully, not all the coupling DoFs are necessary to enforce compatibility and equilibrium. This may allow us to skip coupling DoFs and specifically rotational DoFs. The goal of the paper is indeed to establish if rotational FRFs at coupling DoFs can be neglected in substructure decoupling. To this aim, after highlighting the possibility of avoiding the use of coupling DoFs from a theoretical standpoint, a test bed coupled through flexural and torsional DoFs is considered. Experimental results are presented and discussed
Inverse dynamic substructuring using the direct hybrid assembly in the frequency domain
No full textThe paper deals with the identification of the dynamic behaviour of a structural subsystem, starting from the known dynamic behaviour of both the coupled system and the remaining part of the structural system (residual subsystem). This topic is also known as decoupling problem, subsystem subtraction or inverse dynamic substructuring. Whenever it is necessary to combine numerical models (e.g. FEM) and test models (e.g. FRFs), one speaks of experimental dynamic substructuring. Substructure decoupling techniques can be classified as inverse coupling or direct decoupling techniques. In inverse coupling, the equations describing the coupling problem are rearranged to isolate the unknown substructure instead of the coupled structure. On the contrary, direct decoupling consists in adding to the coupled system a fictitious subsystem that is the negative of the residual subsystem. Starting from a reduced version of the 3-field formulation (dynamic equilibrium using FRFs, compatibility and equilibrium of interface forces), a direct hybrid assembly is developed by requiring that both compatibility and equilibrium conditions are satisfied exactly, either at coupling DoFs only, or at additional internal DoFs of the residual subsystem. Equilibrium and compatibility DoFs might not be the same: this generates the so-called non-collocated approach. The technique is applied using experimental data from an assembled system made by a plate and a rigid mass. (C) 2013 Elsevier Ltd. All rights reserved
Direct decoupling of substructures using primal and dual formulation
No full textThe paper considers the decoupling problem, i.e. the identification of the dynamic behaviour of a structural subsystem, starting from the known dynamic behaviour of the coupled system, and from information about the remaining part of the structural system (residual subsystem). Substructure decoupling techniques can be classified as inverse coupling techniques or direct decoupling techniques. In inverse coupling, the equations written for the coupling problem are rearranged to isolate (as unknown) one of the substructures instead of the coupled structure. Examples of inverse coupling are impedance and mobility approaches. Direct decoupling consists in adding to the coupled system a fictitious subsystem which is the negative of the residual subsystem. Starting from the 3-field formulation (dynamic balance, compatibility and equilibrium at the interface), the problem can be solved in a primal or in a dual manner. Compatibility and equilibrium can be required either at coupling DoFs only, or at additional internal DoFs of the residual subsystem. Furthermore DoFs used to enforce equilibrium might be not the same as DoFs used for compatibility: this generates the so called non collocated approach. In this paper, direct decoupling techniques are considered: primal and dual formulation are compared in combination with collocated and non collocated interface
Modal parameters evaluation of a structure when adding constraints
No full textIn the present paper the problem of determining the new modal parameters of a structure when subjected to additional constraints is considered. The aim is to avoid performing a new modal analysis when a structure is modified by adding constraints. The procedure, whose camputing efford is very low, is thouroughly explained for the determination of the new natural frequencies. The method can be applied to both numerically modelled structures and to data derived from experimental acquisition after the identification of the modal parameters is obtained
Decoupling of a substructure from modal data of the complete structure
No full textIn this paper the decoupling problem, i.e. the identification of the modal properties of a substructure that is part of a larger structure, is considered. The dynamic behaviour of the whole structure, in terms of modal properties, is assumed to be known, together with the physical (finite element) model of the second substructure. The decoupling procedure recalls the modal based structural modification procedure. Typically, the theoretical model of the known substructure has many more degrees of freedom than those experimentally measured on the whole structure. Therefore, an expansion of the experimental degrees of freedom is necessary to match theoretical and experimental data. The paper highlights the difficulties involved with the decoupling operation
OPERATIONAL MODAL ANALYSIS IN ABSENCE OF A RANDOM DISTRIBUTED LOAD
No full textIn this paper the performance of several modal parameter estimation techniques is compared by considering a simple mechanical structure as test bed. Specifically, among Input/Output (I/O) techniques, a frequency domain poly-reference method is considered. Among Operational Modal Analysis (OMA), Frequency Domain Decomposition and poly-reference least square complex frequency-domain techniques are used. I/O technique and OMA are performed using the measurements due to a random shaker excitation. In the first case the responses and the input force are used to calculate the FRFs. On the contrary, OMA is performed by using only the set of measured responses, by supposing unknown the input force. Note that the OMA hypothesis of a random distributed force is not observed. In order to characterise the performance of the examined methods, the results obtained by the OMA are compared to the result of the I/O technique
- …
