1,721,319 research outputs found
Problemi di stabilità del Palazzo della Loggia di Brescia
No full textDottorato in Progetto e conservazione delle strutture, XIII° ciclo. Università degli Studi di Trieste, Università degli Studi di Brescia, Università degli Studi di Padova, Università degli Studi di Trento, Istituto Universitario di Architettura di Venezia (IUAV)
Numerical study on the seismic response of a post-WWII reinforced concrete building strengthened with concentric bracings
No full textIl lavoro presenta un progetto di rinforzo anti-sismico di un edificio esistente in calcestruzzo armato, progettato e realizzato negli anni 70’ nell’Italia settentrionale per resistere ai soli carichi verticali. L’edificio, rappresentativo di una tipologia molto diffusa nel Secondo Dopoguerra, è stato rinforzato con controventi concentrici X realizzati con piatti e posti all’interno del telaio perimetrale in CA. Analisi numeriche statiche e dinamiche non lineari agli elementi finti hanno permesso di valutare le prestazioni dell’edificio rinforzato, mostrando l’efficacia del sistema proposto nel soddisfare le richieste di spostamento di accelerogrammi naturali opportunamente scalati per il sito di riferimento posto in una zona di moderata intensità sismica.The paper presents the seismic-retrofit of a reference existing reinforced concrete building (RC) designed for gravity loads only and built in Northern Italy after World War II. Concentric Xbracings realized with steel plates are placed within the thickness of the external exiting RC frame to enhance the lateral strength and resistance of the building. The numerical results of non-linear push over and dynamic numerical analysis show the capability of the proposed solution to withstand the displacement demand of scaled natural accelerograms of a moderate seismic zone, with a lateral drift lower than 0.5% uniformly distributed over the building height
Coperture scatolari antisismiche
No full textA wooden roof strengthening technique aimed at transforming the roof pitches into anti-seismic shear resisting diaphragms is presented in this paper. Shear diaphragms gather and transfer the seismic loads to the shear resisting walls. The roof box structure forms a sort of “cover” of the masonry building, which avoids the overturning of the walls undergoing out-of-plane loads, and which allows triggering a global box structure behavior. Plywood diaphragms are built on top of the existing structures without significantly modifying the roof overall layout. The proposed strengthening technique is lightweight, mainly reversible, minimally impairing of the building integrity, and can be easily applied for the construction of anti-seismic wooden roofs in new buildings. A simplified design approach, which allows identifying the static role of each structural element, is presented in this paper. The approach can be adopted to validate the results obtained by means of advanced analytical methods, such as the finite element method. An analytical method for the estimate of the box structure displacements, as well as a short digression on the displacement control requirements are also illustrated. The diaphragm technique was recently applied for the anti-seismic retrofit of some monumental buildings in Italy. A case study, as well as the basic design criteria for applying this technique are presented in this paper
Analysis of reinforced concrete elements including shear effects
No full textThis paper deals with the analysis of reinforced concrete (RC) plane frames under monotonic and cyclic loading, including axial, bending, and shear effects. A force-based two-dimensional (2D) element based on the Timoshenko beam theory is introduced. The element formulation is general and yields the exact solution within the Timoshenko beam theory. A simple, nonlinear shear force-shear deformation law is used at the section level, together with a classical fiber section for the axial and bending effects. Shear deformations are thus uncoupled from axial and bending effects in the section stiffness, but shear and bending forces become coupled at the element level because equilibrium is enforced along the beam element. The element is validated through comparisons with experimental data on the shear performance of bridge columns. The seismic analysis of a viaduct that collapsed during the 1995 Kobe earthquake is presented
Wooden roof box structure for the anti-seismic strengthening of historic buildings
No full textA wooden roof strengthening technique aimed at transforming the roof pitches into anti-seismic shear-resisting diaphragms is presented in this article. Shear diaphragms gather and transfer the seismic loads to the shear-resisting walls. Diaphragms are built on top of the existing structures without significantly modifying the roof overall layout. The proposed strengthening technique is mainly reversible, minimally impairing the building integrity, and can be easily applied for the construction of anti-seismic wooden roofs in new buildings. A simplified design approach is presented, which allows identification of the static role of each element. An analytical method for the estimate of the box structure displacements, as well as a short digression on the displacement control requirements is also illustrated. The diaphragm technique was recently applied for the anti-seismic retrofit of some monumental buildings in Italy. A few case studies, as well as the basic design criteria for applying this technique are presented in this article
Problems of roofing of Early Minoan Tholos Tombs: the case of Kamilari A tholos tomb in the western Mesara plain
Full text linkThe Minoan tholos tomb (known also as the Mesara-type tomb) is a stone-built circular structure, widespread in the Mesara plain during the Early Minoan period, with some re-use during the Middle Minoan and Late Minoan periods. These circular structures, not covered by soil and therefore visible above ground, usually had a small entrance on the east side; annex rooms were at some point added mostly on the east side, together with other structures, such as rectangular funerary buildings, peribolos-walls, paved area, altars and platforms. Archaeological excavations have shown that Minoan tholos tombs have been found isolated or clustered in groups. They have been used over several centuries, for multiple burials, with primary and secondary burial practices attested within the main chambers and the external rooms.
Although a number of these circular buildings show traces of a corbelled roof, the argument of a stone vault has been discussed by various scholars in the past years often with open or not unanimous conclusions . Aside from the scholars who deny the existence of any vault, those who have argued for a vaulted roof have suggested several solutions (stones or lighter and perishable materials, such as mud bricks or wood), each of them supported by defined arguments, but each interpretation has always avoided the discussion of a possible true vault, since its first appearance must be placed in the Mycenaean period.
The present article will try to explore once again the question of the vaulted roof by examining the case of Kamilari A Minoan tholos tomb. Thanks to the good state of conservation of the walls, preserved at a significant height in some parts, the following analysis will try to verify whether the tholos tomb had a vaulted roof or not, and to argue about possible reasons for its collapse. The following analysis does not aim to extend the hypothesis of roof profiles to all Minoan tholos tombs, especially if one bears in mind the peculiar state of preservation of Kamilari tholos A as well as the fact that it was one of the latest buildings of this type to be constructed at the beginning of II millennium BC
Thin-folded shell for the renewal of existing wooden roofs
Full text linkIn this article, a technique for the renewal of historic building wooden roofs is presented. The solution can be used for the strengthening of existing wooden roofs against excessive lateral thrusts on the peripheral wall or for the recovery of the attics, as it allows removing the existing structural elements, such as possible wooden truss-works of no artistic value. With minor adaptations, the solution can be addressed to enhance the building seismic performance. The technique is minimally impairing on existing buildings and can be applied also in new constructions. The technique is based on the construction of a thin folded shell, overlaying the existing pitches. Emphasis is given to lightweight folded shells, obtained by overlaying thin plywood panels on the existing roof rafters and planks, without modifying the overall architectural layout. The technique conceptual design is discussed and a simplified analytical method is proposed, which allows for the clarification of the role of each structural component and can be adopted for the folded shell proportioning and design. The analytical results are validated against numerical results obtained with reference to some case studies. Ultimately, emphasis is given to the detailing, whose correct execution is mandatory for the success of the proposed structural intervention
Strengthening of shear wall with high performance RC jacket
No full textA new technique for the strengthening of existing R/C shear walls based on the application of thin high performance jackets is presented in this paper. The strengthening jacket is made of high performance concrete, having a compression resistance higher than 150 MPa, and reinforced by means of an high strength steel mesh. The experimental study is carried out on a 1:3 scale R/C wall, proportioned to resist the vertical loads only, and reinforced by means of a 15 mm thick high performance jacket. Cyclic loads of increasing magnitude are applied to the experimental shear wall up to collapse. The experimental results show the efficiency of the proposed strengthening solution. The strengthening jacked allow doubling the structure resistance, and the structure ductility is increased up to nine times the ductility of the unreinforced structure. The remarkable increase in the structure ductility is the result of the large deformability of the jacket and the absence of strain localization. © 2009 Taylor & Francis Group
Il crollo, la ricostruzione ed il raddrizzamento del muro di cinta del castello di Lonato
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