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STATIC AND DYNAMIC ANALYSIS OF HIGH-RISE BUILDINGS
Get PDFThis thesis is focused on the structural behaviour of high-rise buildings subjected to transversal loads expressed in terms of shears and torsional moments. As horizontal reinforcement, the resistant skeleton of the construction can be composed by different vertical bracings, such as shear walls, braced frames and thin-walled open section profiles, having constant or variable geometrical properties along the height. In this way, most of the traditional structural schemes can be modelled, from moment resisting frames up to outrigger and tubular systems. In particular, an entire chapter is addressed to the case of thin-walled open section shear walls which are defined by a coupled flexural-torsional behaviour, as described by Vlasov's theory of the sectorial areas. From the analytical point of view, the three-dimensional formulation proposed by Al. Carpinteri and An. Carpinteri (1985) is considered and extended in order to perform dynamic analyses and encompass innovative structural solutions which can twist and taper from the bottom to the top of the building. Such approach is based on the hypothesis of in-plane infinitely rigid floors which assure the connection between the vertical bracings and, consequently, reduce the number of degrees of freedom being only three for each level. By means of it, relevant design information such as the floor displacements, the external load distribution between the structural components, the internal actions, the free vibrations as well as the mode shapes can be quickly obtained. The clearness and the conciseness of the matrix formulation allow to devise a simple computer program which, starting from basic information as the building geometry, the number and type of vertical stiffening, the material properties and the intensity of the external forces, provides essential results for preliminary design
Conceptual Design of Tall and Unconventionally Shaped Structures: A Handy Analytical Method
No full textNowadays high-rise buildings are a worldwide architectural phenomenon. In the last decades, next to economics, municipal regulations and politics, aesthetics has got a leading role in planning and design of these structures, giving rise to bizarre shapes, from diagrid systems to twisted, tapered and tilted ones. In their structural design, the choice of an appropriate model able to thoroughly identify the key parameters governing the response of the structure as well as the force flow acting within the stiffening members is all along a crucial factor. In this paper a threedimensional formulation is proposed to evaluate the lateral load distribution of external actions in tall buildings, in which the geometry of the stiffeners can vary along the height. This method takes into account any combination of bracings, including elements with open thin-walled cross-section, which are analysed in the framework of Timoshenko-Vlasov's theory of sectorial areas. In order to evaluate the effectiveness and the suppleness of the formulation, comparisons with other approaches derived from the literature and numerical examples regarding new architectural trends are carried out
Structural analysis of high-rise buildings under horizontal loads: A study on the Intesa Sanpaolo Tower in Turin
No full textIn the last decades, the expansion of high-rise buildings has reached even those countries in which the past architectural conceptions and the municipal regulations have hampered their construction. Suffice it to say that in Turin (Italy), in the last few years, two tall buildings have been designed, both with an height comparable to the Mole Antonelliana, which has so far been the major landmark building of the city. The design of these structures is very complex. Indeed, from the structural viewpoint, the horizontal actions caused by wind and earthquakes represent a key issue for the designers. Therefore, the choice of an appropriate model able to thoroughly identify the foremost parameters governing the response of the structure is all along crucial. For this purpose, in this paper the three-dimensional formulation of Carpinteri et al. (2010) [32], which evaluates the displacements and the lateral load distribution of external actions in tall buildings having any combination of bracings, is reviewed. The present work evaluates the effectiveness of the method by means of a numerical example regarding the 39-storey (166 m) Intesa Sanpaolo Tower, designed by Renzo Piano. The results are compared, in terms of displacements and rotations, with those shown in the final project of the building. Finally curves concerning the main internal actions of a single bracing are presente
FORMULAZIONE ANALITICA PER LA PROGETTAZIONE DEI CONTROVENTI VERTICALI IN EDIFICI DI GRANDE ALTEZZA
No full textThe structural design of high-rise buildings is a complex procedure whose development is mainly defined by some leading factors, such as the outstanding height and the groundbreaking shapes. From a scientific point of view, these issues need advanced methods of analysis. Analytical formulations, based on some simplifying hypotheses, allow to model the resistant skeleton of the building with a quick procedure and to determine the best solution for the specific load case. Starting from conditions of equilibrium and congruence, an analytical formulation for the analysis of high-rise buildings subjected to horizontal actions is proposed. The method takes into consideration the most common solutions employed to stiffen horizontally a building, such as shear walls, frames and braced frames. A faster data preparation as well as a more transparent method of analysis, but also the capabilities to identify the distribution of the external forces within the stiffeners as well as the trend of the main stresses in each bracing represent the benefit provided by the formulation. Furthermore, for the case of thin-walled open section shear walls, the bimoment action is clearly derived. In order to highlight the effectiveness of the proposed method, an example regarding tall buildings is carried ou
L'effetto della deformazione di ingobbamento sul comportamento strutturale di edifici irrigiditi da mensole a sezione sottile aperta
No full textLa teoria di Vlasov riguarda l’analisi di travi a sezione sottile aperta sottoposte ad
azione torsionale. In questo caso, infatti, la sezione tende a ruotare attorno al centro di torsione e
subisce contemporaneamente una deformazione fuori dal piano che la contiene. Tale deformazione,
nota in letteratura con il nome di ingobbamento, determina uno stato tensionale diretto nella
direzione dell’asse della trave. Questo contributo tensionale, da un lato, favorisce l’incremento
della rigidezza torsionale della sezione, dall’altro può comportare una riduzione della capacità
portante della trave stessa. Il seguente lavoro si concentra sulla valutazione della deformazione di
ingobbamento per travi a sezione sottile aperta. In prima analisi si è verificato sperimentalmente il
comportamento descritto dalla teoria di Vlasov. Per questo motivo è stato realizzato un modello
sperimentale di trave a sezione sottile aperta, incastrata ad un’estremità secondo lo schema di una
mensola orizzontale. Analisi specifiche sono state svolte in laboratorio con l’ausilio di un
dispositivo ottico. In questo modo è stato possibile cogliere la componente di deformazione
relativa alla distorsione fuori dal piano della sezione. Infine, i dati ottenuti sperimentalmente ed il
confronto con un modello ad elementi finiti (FEM) hanno permesso di validare un programma di
calcolo, ideato per la valutazione del comportamento strutturale di edifici di notevole altezza
irrigiditi da mensole a sezione sottile aperta. Il codice di calcolo che implementa la formulazione
di Vlasov fa altresì riferimento alla formulazione matriciale proposta da Carpinteri per la
distribuzione delle azioni fra diversi elementi strutturali ed alle ipotesi indicate da Capurso per
l’analisi di mensole di controventamento sottoposte ad azioni trasversali concentrate. Al fine di
valutare l’efficacia del programma proposto, viene svolto un esempio di calcolo in cui vengono
messe in evidenza le capacità del metodo di fornire informazioni difficilmente ricavabili da un
programma ad elementi finiti. In particolare, per le pareti di controventamento aventi sezione
sottile aperta, il programma è in grado di individuare la sollecitazione di bimomento, che è causa
dell’ingobbamento di questo tipo di sezioni
Lateral load effects on tall shear wall structures of different height
Get PDFA three-dimensional formulation is proposed to analyze the lateral loading distribution of external actions in high-rise buildings. The method is extended to encompass any combination of bracings, including bracings with open thin-walled cross-sections, which are analyzed in the framework of Timoshenko-Vlasov's theory of sectorial areas. More in detail, the proposed unified approach is a tool for the preliminary stages of structural design. It considers infinitely rigid floors in their own planes, and allows to better understand stress and strain distributions in the different bearing elements if compared to a finite element analysis. Numerical examples, describing the structural response of tall buildings characterized by bracings with different cross-section and height, show the effectiveness and flexibility of the proposed method. The accuracy of the results is investigated by a comparison with finite element solutions, in which the bracings are modelled as three-dimensional structures by means of shell elements
The effect of the warping deformation on the structural behaviour of thin-walled open section shear walls
No full textThin-walled open section beams are carefully analysed by Vlasov's theory of the sectorial areas. It allows to take into account their peculiar warping deformation which appears in presence of torsional actions. This behaviour determines a further stress state along the axis of the element which is rarely considered in structural analyses. The aim of the present paper is the evaluation of the warping deformation of thin-walled open section beams subjected to torsion. Firstly, the analytical theory proposed by Vlasov is verified through an experimental test on a steel specimen defined by a U profile. Specific analyses are performed with the aim of a sophisticated optical device in order to assess the transverse distortion of the section. Then, the results obtained experimentally and confirmed by a Finite Element (FE) program permit to validate a computer program based on the analytical theory and devised to study the structural behaviour of high-rise buildings stiffened by thin-walled open section shear walls. In order to evaluate the effectiveness of the program, an example which highlights the benefits provided by the present method compared to FE program is carried out
Experimental Evaluation of the Warping Deformation in Thin-Walled Open Section Profiles
No full textThe analysis of thin-walled open section beams can be performed by means of Vlasov's theory of the sectorial areas. It is well-known that this type of profiles, when subjected to torsional actions, are characterised by the warping deformation and, consequently, by a further stress state whose intensity is comparable with that produced by mere flexural deformations. In the literature many papers are focused on the structural behaviour of these elements, but, to the Author's best knowledge, none proposed an experimental technique to evaluate first-hand this particular behaviour. In order to verify the classical theory of the sectorial areas, in the present paper an experiment regarding a thin-walled open section profile subjected to flexural and torsional loads is performed. With the help of a specific optical device, suitable for precision measurements, the warping displacements of a U-shaped section are easily acquired. These are compared to those derived, first, from an analytical formulation, originally devised to deal with vertical thin-walled bracings belonging to the structural core of a tall building, and, secondly, from a FE program, in which the steel profile is modelled by means of thin-shell elements. The numerical comparison confirms the reliability of the analytical formulation
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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