Search results for " frames"
showing 10 items of 175 documents
Sul controllo del meccanismo di collasso di controventi eccentrici
2007
The effectiveness of different non-linear static procedures, for the detection of the collapse mechanism of eccentric braced frames, is investigated. EBFs introduced into truss frame structures are considered. For such a typology of structures, plastic deformations are concen-trated in a single resistant element at each floor, greatly increasing the risk of the formation of soft storey mechanisms, even if the structure is designed according to the capacity design. The results of different non-linear static procedures are compared to those obtained by incremental dynamic non-linear analysis, considering a meaningful set of artificially generated stationary accelerograms, compatible with a ta…
Localization of the spectra of dual frames multipliers
2022
This paper concerns dual frames multipliers, i.e. operators in Hilbert spaces consisting of analysis, multiplication and synthesis processes, where the analysis and the synthesis are made by two dual frames, respectively. The goal of the paper is to give some results about the localization of the spectra of dual frames multipliers, i.e. to individuate regions of the complex plane containing the spectra using some information about the frames and the symbols.
Analysis of infilled frames using A coupled finite element and boundary element solution scheme
1988
The behaviour of infilled frames subjected to horizontal loads is analysed by an iterative numerical procedure. The stiffness of the structural system is determined with variations in geometrical and mechanical characteristics. The analysis is carried out utilizing the boundary element method (BEM) for the infill and opportunely dividing the frame into finite elements, so as to transform the mutual interactions of the two subsystems into stresses distributed along the boundary for the infill and into nodal actions for the frame. This makes it possible to take into account the separation arising between the two substructures when mutual tensile stresses are involved. At first, infills withou…
Numerical modelling of out-of-plane response of infilled frames: State of the art and future challenges for the equivalent strut macromodels
2017
Abstract Infill-frame interaction constitutes a still open question both in research and in practicing engineering. Computational models used to predict this interaction are, in most cases, addressing the estimation of the response of the infilled frames when subjected to actions parallel to their plane. However, the observation of the post-earthquake damage has demonstrated that infills, weakened by the in-plane actions, may fail out-of-plane increasing the risks associated to the earthquake scenarios. In spite of this, different studies have shown that infills, if properly designed and supported by the frame, exhibit a significant strength and displacement capacity when called to resist t…
Molecular Characterization of the Leucine Plasmid from Buchnera aphidicola , Primary Endosymbiont of the Aphid Acyrthosiphon pisum
2000
The complete sequence of the leucine plasmid of Buchnera aphidicola from the aphid Acyrthosiphon pisum (pLeu-BAp) is reported. Its gene organization was concordant with those of other leucine plasmids of Buchnera from aphids of the Aphidini and Macrosiphini tribes. Three inverted repeats are present in pLeu-BAp. Two of them are also present in pLeu from the family Aphididae: (i) SIR1, located downstream the leucine operon, resembles a rho-independent terminator of transcription, and (ii) LIR1, located upstream of the leucine operon, is suggested to be involved in transcription termination or messenger stability. The third, located near the putative ATGC repeats involved in the origin of rep…
Iterative Optimal Design of Special Moment Resisting Devices for Steel Frames
2021
Abstract The present paper proposes an iterative procedure devoted to reaching the optimal design of an innovative, recently proposed, moment resisting device. This special device, called Limited Resistance Plastic Device (LRPD), can be utilized, as an example, to equip a steel frame when it is required that the frame must be designed to substitute a masonry panel, i.e., it must be characterized by a structural behaviour as close as possible to the one of the replaced masonry wall. This purpose can be reached by designing the relevant frame imposing appropriate constraints on the elastic stiffness and on the limit resistance. The result can be obtained just by ensuring that the elastic stif…
Optimal design of elastic plastic frames accounting for seismic protection devices
2013
The optimal design of elastic perfectly plastic steel frames with or without suitable protection devices and subjected to static as well as seismic loadings is studied. Two minimum volume problem formulations are proposed, on the grounds of the so-called statical approach, accounting for three different resistance limits: the purely elastic limit, the (elastic) shakedown limit and the instantaneous collapse limit. The adopted load combinations are characterized by the presence of fixed loads, of quasi-static perfect cyclic loads and dynamic (seismic) loads. The linear elastic effects of the dynamic actions are studied by utilizing a modal technique. The proposed treatment is referred to the…
Optimal design of steel frames accounting for buckling
2013
A formulation of a special design problem devoted to elastic perfectly plastic steel frame structures subjected to different combinations of static and dynamic loads is presented. In particular, a minimum volume design problem formulation is presented and the structure is designed to be able to elastically behave for the assigned fixed loads, to elastically shakedown in presence of serviceability load conditions and to prevent the instantaneous collapse for suitably chosen combinations of fixed and ultimate seismic loadings as well as of fixed and wind actions. The actions that the structure must suffer are evaluated by making reference to the actual Italian seismic code. The dynamic respon…
Traditional vs. sliding-joint masonry infilled frames: Seismic reliability and EAL
2020
Abstract In reinforced concrete (RC) multi-storey buildings, the important role of the seismic interaction of structural frames with masonry infills has been revealed by several earthquakes and investigated by many authors. Recently, several innovative infill solutions have been proposed to mitigate such interaction, which could result in widespread damage in both the masonry and the RC structure and sometimes jeopardize the building stability and the occupants’ safety. One solution consists in the partitioning of the masonry infill into several sub-panels, relatively sliding along specific joints. This paper investigates the seismic assessment of this technological solution in the framewor…
Casimir-Polder interaction between an accelerated two-level system and an infinite plate
2007
We investigate the Casimir-Polder interaction energy between a uniformly accelerated two-level system and an infinite plate with Dirichlet boundary conditions. Our model is a two-level atom interacting with a massless scalar field, with a uniform acceleration in a direction parallel to the plate. We consider the contributions of vacuum fluctuations and of the radiation reaction field to the atom-wall Casimir-Polder interaction, and we discuss their dependence on the acceleration of the atom. We show that, as a consequence of the noninertial motion of the two-level atom, a thermal term is present in the vacuum fluctuation contribution to the Casimir-Polder interaction. Finally we discuss the…