Application of modal flexibility-based deflections for damage diagnosis of a steel frame structure

Abstract In this paper a modal flexibility-based approach for damage diagnosis is presented and discussed. Modal flexibility matrices of structural systems can be derived from vibration tests and changes in these matrices can be associated to structural damage. One of the main challenges is to apply modal flexibility-based methods on real-life civil structures, to detect damage on structures using ambient vibration data. A recent method has been formulated for damage detection, localization, and quantification of building structures; it is based on the modal flexibility-based deflections of such structures under uniform loads. The method was originally formulated for frame buildings that can be modeled as plane shear-type structures. The objective of the paper is to test this methodology on generic buildings that, in principle, cannot be easily modeled as plane shear-type structures. The method was applied to the ambient vibration data of a steel frame structure that has a monitoring system with acceleration sensors. Various damage configurations were induced to the structure by removing diagonal braces on the external surface of the frame. The results showed that the method is able to identify the stories and the directions of the frame that have been affected by the damage

No evidence of association between prothrombotic gene polymorphisms and the development of acute myocardial infarction at a young age

Background : we investigated the association between 9 polymorphisms of genes encoding hemostasis factors and myocardial infarction in a large sample of young patients chosen because they have less coronary atherosclerosis than older patients, and thus their disease is more likely to be related to a genetic predisposition to a prothrombotic state Methods and Results : this nationwide case-control study involved 1210 patients who had survived a first myocardial infarction at an age of 45 years who underwent coronary arteriography in 125 coronary care units and 1210 healthy subjects matched for age, sex, and geographical origin. None of the 9 polymorphisms of genes encoding proteins involved in coagulation (G-455A -fibrinogen: OR, 1.0; CI, 0.8 to 1.2; G1691A factor V: OR, 1.1; CI, 0.6 to 2.1; G20210A factor II: OR, 1.0; CI, 0.5 to 1.9; and G10976A factor VII: OR, 1.0; CI, 0.8 to 1.3), platelet function (C807T glycoprotein Ia: OR, 1.1; CI, 0.9 to 1.3; and C1565T glycoprotein IIIa: OR, 0.9; CI, 0.8 to 1.2), fibrinolysis (G185T factor XIII: OR, 1.2; CI, 0.9 to 1.6; and 4G/5G plasminogen activator inhibitor type 1: OR, 0.9; CI, 0.7 to 1.2), or homocysteine metabolism (C677T methylenetetrahydrofolate reductase: OR, 0.9; CI, 0.8 to 1.1) were associated with an increased or decreased risk of myocardial infarction Conclusions : this study provides no evidence supporting an association between 9 polymorphisms of genes encoding proteins involved in hemostasis and the occurrence of premature myocardial infarction or protection against it

Cap. Luoghi di lavoro, Le attrezzature di lavoro ed i dispositivi di protezione individuale

La necessit\ue0 di verificare il funzionamento ed i relativi requisiti di sicurezza di macchine ed attrezzature di lavoro (art. 70) \ue8 sempre stata strettamente collegata, in tutta la normativa vigente dagli anni \u201950 in poi, alla necessit\ue0 di assicurare la sicurezza e la salute dei lavoratori. I requisiti di sicurezza devono essere verificati per le diverse condizioni di impiego delle attrezzature e per le varie attivit\ue0 lavorative. Gi\ue0 prima dell\u2019entrata in vigore del D.Lgs. 81/08 per le attrezzature di lavoro ed in particolare per quelle il cui malfunzionamento poteva mettere in pericolo l\u2019incolumit\ue0 dei lavoratori e/o l\u2019integrit\ue0 dell\u2019ambiente circostante, vigeva un sistema che prescriveva una serie di verifiche obbligatorie a scadenza prestabilit\ue0 ed effettuate da organismi pubblici. Con l\u2019entrata in vigore delle Direttive europee di prodotto e dei relativi decreti di recepimento (DPR N. 459 del 24/07/1996 \u201cRegolamento per l'attuazione delle direttive 89/392/CEE, 91/368, 93/44 e 93/68 concernenti il riavvicinamento delle legislazioni degli Stati membri relative alle macchine\u201d e Decreto Legislativo 25 febbraio 2000, n. 93 "Attuazione della direttiva 97/23/CE in materia di attrezzature a pressione") alcune attivit\ue0 di omologazione statale venivano soppresse e sostituite dalle attivit\ue0 di certificazione della conformit\ue0 affidate ad Organismi notificati o, in alcuni casi, agli stessi fabbricanti. In questo modo si veniva in qualche modo a recuperare l\u2019impostazione data sin dagli inizi degli anni \u201950 dal DPR 547/55. Anch\u2019esso infatti concentrava la propria attenzione sul fabbricante che doveva assicurare che l\u2019attrezzatura o l\u2019impianto fosse il pi\uf9 possibile sicuro, sul datore di lavoro che doveva controllare l\u2019integrit\ue0 nel tempo delle attrezzature o degli impianti ed infine sul lavoratore che aveva l\u2019obbligo di utilizzare le macchine in modo conforme al manuale d\u2019uso. In estrema sintesi tutte le attrezzature di lavoro devono: - essere conformi alle disposizioni legislative e regolamentari di recepimento delle direttive comunitarie di settore; - nel caso non fossero ancora state emesse specifiche disposizioni o per fabbricazioni avvenute prima del recepimento, essere conformi ai requisiti di sicurezza descritti all\u2019All. V (Requisiti di sicurezza delle attrezzature di lavoro costruite in assenza di disposizioni legislative e regolamentari di recepimento delle Direttive comunitarie di prodotto, o messe a disposizione dei lavoratori antecedentemente alla data della loro emanazione)

Cap. Segnaletica di salute e sicurezza sul lavoro

Alcuni obblighi sull\u2019utilizzo della segnaletica al fine di integrare le informazioni sulle misure di sicurezza erano gi\ue0 presenti sin dagli anni \u201950 nel DPR n.547/1955 (Art. 13 Vie e uscite di emergenza e Art. 14 Porte e portoni e tabella A ad esso allegata), nel DPR n.303/1956 e nel DPR n.164/1956. La prima normativa che affrontava in modo sistematico l\u2019argomento della segnaletica di sicurezza sul posto di lavoro \ue8 il DPR 8 giugno 1982, n. 524 che recepiva una Direttiva comunitaria sull\u2019argomento oggi abrogata. Il D.Lgs 493 del 14 agosto 1996 \u201cAttuazione della Direttiva 92/58/CEE concernente le prescrizioni minime per la segnaletica di sicurezza e/o di salute sul luogo di lavoro\u201d che ha appunto recepito la direttiva 92/58/CEE, nona direttiva particolare della direttiva 89/391/CEE, ha quindi abrogato il DPR degli anni \u201980. Il D.Lgs 493/96 \ue8 stato ripreso in toto dal Titolo V del D.Lgs. 81/2008 s.m. e i. ed oggi regolamenta ogni forma di trasmissione di informazioni sulla sicurezza mediante segnaletica negli ambienti di lavoro. Il titolo si compone di due capi di cui il primo tratta le disposizioni generali ed \ue8 formato da quattro articoli (dal 161 al 164); il secondo consta di due articoli (165 e 166) di cui l\u2019art. 166 \ue8 stato abrogato dall\u2019art.92 del D.Lgs. 106/2009. Molto opportunamente e riproponendo la stessa struttura del D.Lgs 493/96 le specifiche relative alle diverse tipologie di segnaletica sono raccolte separatamente in una serie di allegati di cui risulta rapida la consultazione e la valutazione delle prescrizioni di specifico interesse. Accanto alle prescrizioni di legge riportate nel Titolo V e negli Allegati del TUS \ue8 importante segnalare la serie di norme UNI sull\u2019argomento, che pur non essendo cogenti, sono da considerarsi norme di buona tecnica riconosciute e quindi forniscono un valido supporto al lavoro di tecnici, progettisti, dirigenti e datori di lavoro. La loro applicazione risulta opportuna ogniqualvolta risulti possibile

A direct method for the design of viscous dampers to be inserted in existing buildings

A direct procedure to determine the supplemental damping ratio required for the retrofit of existing buildings with viscous dampers is proposed here. The method has been developed following both analytical and graphical formulations. The graphical formulation is based on the construction of constant design acceleration or constant design displacement curves. These curves allow to estimate the required effective damping as a function of the effective period, associated to the secant stiffness at maximum displacement. Combining these curves with constant ductility curves, which provide a correlation between the effective damping and the supplemental damping for given available ductility and damper typology, it is possible to obtain the required supplemental damping and to design the damping system. The effectiveness of the proposed method has then been evaluated through the comparison with nonlinear dynamic analyses of selected RC frames and the application to real case studies. In these applications, nonlinear viscous dampers have been considered for the retrofit

On the seismic analysis of structures with friction pendulum isolators subjected to horizontal and vertical ground motions

This research focuses on the different modeling approaches for the simulation of the seismic response of structures with friction pendulum isolation systems. The behavior of such systems is strongly affected by several parameters, as for example the friction coefficient and the axial load. The latter has a particular importance in presence of seismic actions characterized by the simultaneous presence of high horizontal and vertical accelerations. To study these aspects several nonlinear dynamic analyses have been performed considering a two degree of freedom model isolated at the base and subjected to recorded horizontal and vertical ground motions. The response of the isolation systems have been studied through different models, starting by the more simple ones based on constant friction coefficient to the more complex ones based on a friction coefficient varying as a function of sliding velocity and axial force. The records have been also applied considering increasing values of intensity, in order to determine the collapse acceleration. The results have allowed to compare the different models and to study the effect of the vertical seismic component on the response of the isolators

Extension of displacement-based assessment to infilled RC frames

The purpose of this research was to assess the seismic response of RC infilled frames. In order to evaluate the behaviour of these structures, it was fundamental to define an appropriate analytical model. Several models were proposed in literature for the masonry infills. In this study the equivalent strut model for monotonic loading proposed by Al-Chaar was considered. This model was extended to the case of cyclic loading by calibrating the degradation of strength and stiffness and the residual strength with available experimental results. The model was then applied for investigating the seismic response of infilled RC frames: pushover and nonlinear dynamic analyses were carried out for obtaining the response in terms of base shear-top displacement and for estimating the configuration of collapse. On the basis of the results of these analyses, a displacement-based method for the assessment of infilled frames was proposed. The effectiveness of this method was verified through comparison between the displacement demand estimated with the proposed procedure and that obtained from nonlinear dynamic analyses

Time-history analysis of unreinforced masonry walls in out-of-plane bending: Influence of diaphragm flexibility

The purpose of this paper is to study the dynamic out-of-plane response of the external walls of unreinforced masonry buildings with flexible diaphragms. In particular, the influence of diaphragms flexibility on the displacement capacity and demand of walls has been investigated. A two-degree-of-freedom model (2DOF) has been developed to perform the dynamic analyses. The wall has been modelled as an assemblage of two rigid bodies connected by an intermediate hinge and restrained at the top by a spring: the damping has been modelled through the introduction of the coefficient of restitution. The equations of motion of the 2DOF system have been derived and integrated in the time domain. Time-history analyses of a set of walls with Gaussian impulses and recorded ground motions have been performed in order to compare the response of the simply supported wall with that of the wall with an elastic spring at the top