1,721,111 research outputs found
THE DISSIPATIVE COLUMN AS A NEW STEEL DAMPER
No full textA new replaceable hysteretic damper to better control seismic building damage, consisting of two adjacent steel vertical elements connected to each other with continuous mild/low strength steel shear links, is proposed and investigated in this study. New Dampers, called Dissipative Columns (DC), continuously linked with X-shaped steel plates, provide additional stiffness and damping to a lateral system by using a basic and minimally invasive construction element: the column. Work-ing in a way similar to coupled shear walls, the proposed element behavior is theoretically ana-lyzed at linear and non-linear ranges. The Dissipative Column has been conceived or as a device installed within a frame either external damper to provide macro-dissipation. In fact, considering different configurations, a parametric analysis is developed in order both to evaluate the effect of the main geometrical and structural parameters and provide the design capacity curves of this new damper. In particular, non-linear pushover and cyclic analyses have been carried out in ABAQUS in order to characterize the local and global behavior of the device. The DC can be considered a new damping device, easy to install in new as well as existing buildings in order to protect them from seismic damage
FEM SIMULATIONS OF A NEW HYSTERETIC DAMPER: THE DISSIPATIVE COLUMN
No full textA new replaceable hysteretic damper to better control seismic building damage,
consisting of two adjacent steel vertical elements connected to each other with continuous Xshaped
mild/low strength steel shear links, is investigated in this study. New Dampers, called
Dissipative Columns (DC), provide additional stiffness and damping to a lateral system by
using a basic and minimally invasive construction element: the column. The Dissipative
Column has been conceived or as a device installed within a frame either external damper to
provide macro-dissipation. In fact, considering different configurations, a parametric analysis,
based on FEM simulations, is developed in order to evaluate the effect of the main geometrical
and structural parameters as well as provide the design capacity curves of this new damper.
In particular, non-linear pushover and cyclic analyses have been carried out in ABAQUS in
order to characterize the local and global behaviour of the device also considering different
steel grades
Experimental tests on the cyclic response of common steelwork hysteretic devices
No full textThis paper investigates the performance of two conventional steelwork elements which can be employed as dissipative devices in Y-shaped eccentric braces (EB). After the description of such devices, the key results obtained in recent tests carried out at the Laboratory Materials testing and Structures (LMS) of the University of Salerno is reported. Particularly, the results of cyclic tests carried out according to two different experimental protocols are considered to determine the low-cycle fatigue curve, which fully describes their performance under cyclic actions and can be properly employed in seismic design of steel bracings equipped with such devices. Finally, the proposed experimental results will be utilised in the future steps of this research to formulate sound design criteria, duly taking into account the actual cyclic nature of the expected seismic actions. This will be the basis for a wide application of these cost-competitive solutions for realising hysteretic steel devices to be properly adopted in seismic retrofitting of ordinary existing structures
Cost-competitive hysteretic devices for seismic energy dissipation in steel bracings: experimental tests and low-cycle fatigue characterisation
No full textThis paper presents the results of experimental tests intended at investigating the behaviour of two costcompetitive solutions for realising dissipative devices to be adopted as link elements in Y-shaped eccentric braces (EB), widely employed both for seismic protection of newly designed structures and retrofitting of existing ones. These structural components, generally referred to as Steel Slit Shape (SSS) and Short Link (SL) devices, were realised through standard welding and cutting procedures generally employed in steel workshops. Experimental tests with both constant and variable displacement amplitude protocols were carried out for observing the mechanical performance for these devices under cyclic actions. Since a fast degradation in shear strength was generally observed for all the tested specimens, a low-cycle fatigue was identified: it resulted that the same curve can be employed describing the number of cycles leading to low-fatigue failure for a given amplitude of the imposed cyclic displacement history.
This curve is an essential tool for describing the behaviour of this devices that, although characterised by poorer mechanical performance under cyclic actions, have the potential to be utilised as dissipative components, for instance in Y-shaped steel bracings adopted for retrofitting reinforced concrete structures in medium-to-low seismic intensity area
On the cyclic response of two common steelwork members conceived as hysteretic devices for steel bracings
No full textSeveral technical solutions have been developed and are currently available on the market to realise dissipative
devices to be employed in steel bracing systems. They are characterised by different geometrical materials, configurations and energy dissipation mechanisms, based on yielding under either shear, bending or torsion actions.
This paper investigates the performance of two cost-competitive devices obtained through conventional steelwork procedures, which can be employed as link elements on Y-shaped eccentric braces (EB), widely adopted especially for seismic retrofitting of existing structures. After a description of such devices, the key results obtained in recent tests carried out at the Laboratory Material testing and Structures of the University of Salerno is reported. Particularly, the results of cyclic tests carried out according to two different experimental protocols are considered
to determine the low-cycle fatigue curve which fully describes their performance under cyclic actions and can be properly employed in seismic design of steel bracings equipped with such devices
Confronto del'accuratezza diagnostica tra urea breath test e test fecale in pazienti con infezione da Helicobacter pylori dopo trattamento eradicante
No full textThe diagnostic accuracy of the UBT and the stool test for H. pylori (HpSA) has been investigated in 350 infected patients after eradicating treatment. In 43 (12.3%) patients, discordant or indeterminate results on UBT or HpSA were obtained. Thirty-three out of 43 patients underwent upper g.i. endoscopy with gastric biopsies for histological, immunohistochemical and coltural analysis for H. pylori. In 32 of 33 patients, the UTB, but not the HpSA, correctly determined the H. pylori status while in one case the UBT was indetemninate (with a negative HpSA test). These findings show that the HpSA test has a lower diagnostic accuracy than the UBT in the post-treatment setting. No coccoid forms of H. pylori were observed in patients with a positive HpSA and a negative UBT
Composite materials for masonry structures: the adhesion issue
No full textMasonry is often a non-engineered material used for building constructions during the past decades; those kind of structures have been rarely designed against horizontal actions induced by earthquakes and usually have been simply realized according to rules of common practice. Consequently, they are often in need for strengthening in order to fit the safety standards assumed by the modern codes.
Strengthening interventions on ordinary structures can be particularly addressed to improve in-plane shear strength of masonry walls that are, on the contrary, rather fit to sustain axial loads. Ferrocement-based techniques have been often utilized though resulting in non-negligible increase of structural masses and quite irreversible intervention. More reversible and less invasive interventions can be carried out by using fiber-based materials such as Fiber Reinforced Plastics (FRP) or Fiber Reinforced Cement Matrices (FRCM) even made of carbon or glass fibers.
Adhesion between the strengthening materials and masonry often controls the effectiveness of the intervention as a whole, resulting in an upper limit for shear strength enhancement of masonry walls.
On the bases of a wide collection of experimental results, the present paper is devoted to calibrate a general relation for determining the key mechanical properties characterizing the interface behaviour between the composite strengthening and the masonry support. The behaviour of both polymer- and cement-based matrix composites will be examined. Such parameters (namely the value of fracture energy or other relevant measures of the adhesion strength) can be suitably utilized for evaluating shear strength of masonry walls strengthened through composite materials
Cyclic shear-compression tests on masonry walls strengthened with alternative configurations of CFRP strips
No full textThis work reports the results of an experimental programme aimed at investigating the in-plane behaviour of clay-brick masonry walls externally strengthened by carbon fiber reinforced polymer (CFRP) strips. Particularly, four different geometrical layouts were considered for the CFRP strips, though keeping unchanged the quantity of composites employed in each wall. Firstly, a preliminary experimental work was carried out on samples of the constitutive materials for quantifying their key mechanical properties and evaluating the bond behaviour of FRP strips on the masonry substrates. Then, eleven cyclic shear-compression tests were performed to observe the response of strengthened
walls and the influence of the strengthening layouts under investigation. The proposed experimental report is intended as a contribution to the current state of knowledge about the behaviour of FRP-strengthened masonry walls: it is available to assess the accuracy and
possibly improve the predictive capacity of design-oriented capacity models. Finally, the comparison of the reported experimental results with the predictions obtained by applying the analytical relationships proposed by a recently issued guideline for FRP strengthening of masonry structures is proposed
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
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