Search results for " Isolation"
showing 10 items of 374 documents
On the optimal design of base isolation devices
2013
The paper deals with the optimal design of a base isolation system for a given structure subjected to seismic loads. In particular, an appropriate minimum displacement seismic protection device optimal design formulation is proposed for an assigned elastic perfectly plastic steel frame constrained to behave in conditions of elastic shakedown. The chosen base isolation device is constituted by elastomeric isolators. Suitable combinations of fixed and seismic loads are considered. According to the unrestricted shakedown theory, the seismic input is given as any load history appertaining to a suitably defined seismic load admissibility domain. The relevant dynamic structural response is obtain…
Hybrid Passive Control Strategies for Reducing the Displacements at the Base of Seismic Isolated Structures
2019
In this paper, the use of hybrid passive control strategies to mitigate the seismic response of a base-isolated structure is examined. The control performance of three different types of devices used for reducing base displacements of isolated buildings is investigated. Specifically, the Tuned Mass Damper (TMD), the New Tuned Mass Damper (New TMD) and the Tuned Liquid Column Damper (TLCD), each one associated to a Base Isolated structure (BI), have been considered. The seismic induced vibration control of base-isolated structures equipped with the TMD, New TMD or the TLCD is examined and compared with that of the base-isolated system without devices, using real recorded seismic signals as e…
Assessment of the tuned mass damper inerter for seismic response control of base‐isolated structures
2020
In this paper, the hybrid control of structures subjected to seismic excitation by means of tuned mass damper inerter (TMDI) and base-isolation subsystems is studied with the aim of improving the dynamic performance of base-isolated structures by reducing the displacement demand of the isolation subsystem. The seismic performance of TMDI hybrid controlled structures is investigated in a comparative study, considering simple isolated systems and systems equipped with other absorber devices such as the tuned mass damper (TMD) and the tuned liquid column damper (TLCD). The TMDI has been optimized by performing a simplified approach based on minimizing the base-isolation subsystem displacement …
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…
Optimization of structures with unrestricted dynamic shakedown constraints
2015
The unrestricted dynamic shakedown theory is here utilized with the aim to formulate different optimal design problems for structures mainly subjected to seismic loads. In particular, reference is made to plane frame structures constituted by elastic perfectly plastic material subjected to load combinations characterized by the presence of simultaneous fixed and seismic actions. The design problems, formulated on the ground of a statical approach, are devoted to structures with and without seismic protection devices, with special emphasis to seismic isolators. For the proposed design problem formulations different constraints are utilized; actually, for structures without protection devices…
Smart structures through nontraditional design of Tuned Mass Damper Inerter for higher control of base isolated systems
2020
Abstract This paper introduces a smart structure design through the definition of an innovative passive control strategy, referred to as New Tuned Mass Damper Inerter (New TMDI), coupled with a base isolation system (BI), to control displacements in base isolated structures under seismic excitations. The herein proposed New TMDI comprises a recently developed nontraditional Tuned Mass Damper (known as New TMD), in which a secondary mass system is connected to the base plate of the BI system by a spring and to the ground by a dashpot, and of an inerter device placed in parallel with the damper. An optimization procedure which minimizes the base displacement variance of the BI system, conside…
Low-pressure pyrolysis of tBu2SO: synthesis and IR spectroscopic detection of HSOH.
2005
Sulfenic acid (HSOH, 1) has been synthesized in the gas-phase by low-pressure high-temperature (1150 degrees C) pyrolysis of di-tert-butyl sulfoxide (tBu(2)SO, 2) and characterized by means of matrix isolation and gas-phase IR spectroscopy. High-level coupled-cluster (CC) calculations (CCSD(T)/cc-pVTZ and CCSD(T)/cc-pVQZ) support the first identification of the gas-phase IR spectrum of 1 and enable its spectral characterization. Five of the six vibrational fundamentals of matrix-isolated 1 have been assigned, and its rotational-resolved gas-phase IR spectrum provides additional information on the O-H and S-H stretching fundamentals. Investigations of the pyrolysis reaction by mass spectrome…
H2O2 resistant mesoangioblast clone isolation with a distinct survival advantage in vitro and in vivo
2017
The release of molecules from damaged tissues stimulates both resident and circulating stem cells to initiate a tissue repair programme. 1 However, during transplantation procedures the therapeutic efficacy of stem cells is compromised by reduced homing capability towards the target site.2,3 Furthermore, cell survival is very low and many studies focused on improving cell viability upon implantation. In this study, we performed in vitrosevere oxidative stress to select some more resistant mouse mesoangioblasts, vessel-associated progenitor stem cells endowed with the ability of multipotent mesoderm differentiation. We found that the selected subpopulation retains selfrenewal and myogenic di…
1993
Biology tells us about the processes and mechanisms which are able to explain effectively the changes occurring in organisms and species. Palaeontology, with the temporal dimension at its disposal, adds to this data which are indispensable for our understanding of speciation and of the patterns and rhythms of evolutionary change. Only through this we are able to observe the historical development of the evolution, of the living world as it took place through geological time. Based on data obtained from other branches of the earth sciences, palaeontology is able to evaluate the external constraints which frequently act at random on the living organism and which control the formation of new s…
1993
The history of life may be compared to a huge cable enclosing as many strands as there are fossil and present species. The biosphere, with its 2 million species, would then correspond to a transverse section through this cable.