1,720,964 research outputs found
EXPERIMENTAL AND NUMERICAL SEISMIC RESPONSE OF MULTI-STOREY POST-TENSIONED TIMBER FRAMED BUILDINGS WITH SUPPLEMENTAL DAMPING SYSTEMS
Full text linkThis doctoral project aims to contribute to advancement of the research in the field of innovative and resilient timber buildings with high seismic performance and minimum environmental impact in a green and sustainable way.
Recent seismic events have raised questions about the adequacy of the current seismic design in code provisions. In modern seismic codes, the performance objectives are expressed in terms of life safety of the occupants and according to capacity design rules a certain damage level of structures is accepted under strong earthquakes. The resultant seismic damages are often difficult and financially prohibitive to repair. In order to significantly reduce structural and non-structural damage and avoid high economic loss, in the last decades research studies focused on the development of low damage design and technologies.
In this thesis, seismic design and performance of multi-storey post-tensioned timber framed buildings with different dissipative systems have been investigated in order to develop new low-damage construction systems for high seismic areas. An extensive experimental campaign was performed at the structural laboratory of the University of Basilicata (Italy), in collaboration with the University of Canterbury (New Zealand), considering a three-dimensional, two-third scale, three-storey, post-tensioned glulam timber frame building. Different testing configurations were considered: i) the bare timber frame with post-tensioning only at the beam-column connections (free rocking); ii) the post-tensioned timber frame with dissipative devices at the beam-column and column-foundation connections (dissipative rocking); and iii) the post-tensioned timber frame with dissipative bracing systems at all storey (dissipative bracing). The seismic response of test specimen was investigated through unidirectional shaking table tests under consecutive ground motions at increasing PGA intensities, while the cyclic behaviour of hysteretic dampers was characterized by means of quasi-static tests.
In particular, the testing configuration with dissipative bracing, which had not been previously implemented in post-tensioned glulam timber structures, has been deeply investigated in this research. The estimation of equivalent viscous damping has been proposed in order to optimize the displacement-based design procedure for sizing the hysteretic dissipative devices of the bracing systems. The experimental seismic response of the braced model is evaluated in terms of global and local behaviour and nonlinear numerical analysis have been carried out within two different FEM software (Sap 2000 and OpenSees). The comparison of the results obtained from all configurations demonstrated that the dissipative bracing system improved the seismic performance of post-tensioned timber buildings reducing inter-storey drift with full re-centring capability. During all seismic tests no damages were observed to structural elements, only localized breakage of external replaceable devices occurred during the test with strongest earthquake. More than one hundred inelastic cycles were experimentally recorded from dynamic tests before the failure of devices.
The reliability of quasi-static testing procedures proposed by current seismic and guidelines codes for type tests and factory production control tests was also investigated. The number of cycles estimated from shaking table tests and non-linear dynamic analyses shows a decreasing trend with the increase of ductility demand in line with American standards testing requirements
Experimental estimation of energy dissipated by multistorey post-tensioned timber framed buildings with anti-seismic dissipative devices
No full textThe need to satisfy high seismic performance of structures and to
comply with the latest worldwide policies of environmental sustainability is leading engineers and researchers to higher interest in timber buildings. A posttensioned timber frame specimen was tested at the structural laboratory of the University of Basilicata in Italy, in three different configurations: i) without dissipation (post-tensioning only-F configuration); ii) with dissipative angles (DFdissipative rocking configuration) and iii) with dissipative bracing systems (BF - braced frame configuration). The shaking table tests were performed considering a set of spectra-compatible seismic inputs at different seismic intensities. This paper describes the experimental estimation of energy dissipated by multistorey
post-tensioned timber prototype frame with different anti-seismic hysteretic dissipative devices used in the DF and BF testing configurations. The main experimental seismic key parameters have also been investigated in all testing configurations
MODELLING OF POST-TENSIONED TIMBER-FRAMED BUILDINGS WITH SEISMIC ROCKING MECHANISM AT THE COLUMN-FOUNDATION CONNECTIONS
No full textThe need to mitigate damage of buildings even after strong earthquakes has led to the development of high-performance seismic resisting systems. Extensive studies have been made in the last decade on the development and use of jointed ductile connections and on the effects of rocking vibration systems in reducing seismic damage of buildings. A recently developed technology for construction of multi-storey timber buildings called Pres-Lam system uses long lengths of prefabricated laminated timber and binds them together using pre-stressing steel tendons. When appropriately combining unbounded post-tensioned tendons, or rocking columns with additional sources of energy dissipation devices, a hybrid system is obtained, with self-centering and dissipative properties, leading to a characteristic flag-shape hysteresis behaviour.
A three-dimensional, three-storey, two-third scaled, post-tensioned timber frame model was tested at the structural laboratory of the University of Basilicata. During shaking table tests, two different configurations of the test model have been studied considering column-table connections with and without the activation of dissipative steel angles. This paper focuses on different numerical modelling of the rocking mechanisms at the column-foundation connections. Two different modelling have been considered for two different test configurations by means of a pinned base or an appropriate combination of nonlinear rotational springs, for free rocking and a suitable combination of gap elements and linear springs or rotational springs, for dissipative rocking. The numerical outcomes of nonlinear dynamic analysis are compared with experimental test results providing an adequate representation of the seismic respons
Interventions for out-of-plane failure mechanisms prevention of existing masonry buildings
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EXPERIMENTAL SEISMIC POST-TENSIONING PERFORMANCE AND LONG-TERM EFFECTS OF A POST-TENSIONED TIMBER FRAMED MODEL WITH DISSIPATIVE SYSTEMS
No full textIn recent years, post-tensioned timber framed buildings, recognized as one of the most effective sustainable and anti-seismic solutions, are developing throughout the world. Posttensioning (PT) loss in timber framed buildings with post-tensioned beam to column joints is a crucial aspect which governs the moment capacity of the connection and the global seismic performance of the frame. This paper investigates on the variations of the post-tensioning force of a 2/3 scaled, threestorey, post-tensioned timber frame experimental model investigated in three different configurations:
bare frame; with dissipative rocking mechanism; with dissipative bracing system. The variation of post-tensioning during shaking table testing a set of seven spectracompatible earthquakes at increasing PGA levels has been evaluated and the long-term losses over about four years have been investigated
Nonlinear analysis of base isolated buildings with curved surface sliders including over-stroke displacements
Full text linkeismic isolation represents one of the most suitable strategies for mitigating the seismic risk of structures and infrastructures. Acceptable probabilities of collapse for seis-mically isolated buildings could be achieved by an appropriate isolator displacement capacity. This paper investigates the effects of the over-stroke capacity of double concave curved sur-face sliding isolators, in addition to the nominal displacement capacity, on the seismic response of base isolated structures. The case study building is a reinforced concrete frame structure designed for high hazard seismic site. The level of performance of global collapse prevention has been investigated considering the earthquake intensity levels at the Collapse Limit State (with a return period of 1000 years). The results of the nonlinear static and dynamic analysis highlights that the seismic isolation without the over-stroke capability show a limited margin against collapse for seismic intensities beyond the design limit state lev
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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