Mappe di rischio sismico a scala nazionale con dati aggiornati sulla pericolosità sismica di base e locale

Le mappe di rischio sismico nazionale rappresentano un importante strumento per la sua mitigazione e possono essere utilizzate nella valutazione delle priorità di intervento per la messa in sicurezza degli edifici. La realizzazione di queste mappe è possibile valutando la pericolosità sismica, la vulnerabilità per le diverse classi di edifici presenti sul territorio italiano e l’esposizione. In questo articolo, oltre a presentare le nuove mappe di rischio sismico per l’Italia si vuole analizzare l’influenza del fattore di amplificazione litostratigrafica sui risultati ottenuti, mettendo a confronto le mappe di rischio che sono state sviluppate utilizzando sia i fattori di amplificazione litostratigrafica previsti dall’OPCM n°3274 che quelli previsti dalle NTC08. Inoltre, in modo innovativo rispetto agli studi condotti in Italia negli ultimi 10 anni, vengono considerate curve analitiche di vulnerabilità e valori di pericolosità sismica basati sugli spettri di accelerazione

Nonlinear dynamic analysis of masonry buildings and definition of seismic damage states

A large part of the building stock in seismic-prone areas worldwide are masonry structures that have been designed without seismic design considerations. Proper seismic assessment of such structures is quite a challenge, particularly so if their response well into the inelastic range, up to local or global failure, has to be predicted, as typically required in fragility analysis. A critical issue in this respect is the absence of rigid diaphragm action (due to the presence of relatively flexible floors), which renders particularly cumbersome the application of popular and convenient nonlinear analysis methods like the static pushover analysis. These issues are addressed in this paper that focusses on a masonry building representative of Southern European practice, which is analysed in both its pristine condition and after applying retrofitting schemes typical of those implemented in pre-earthquake strengthening programmes. Nonlinear behaviour is evaluated using dynamic response-history analysis, which is found to be more effective and even easier to apply in this type of building wherein critical modes are of a local nature, due to the absence of diaphragm action. Fragility curves are then derived for both the initial and the strengthened building, exploring alternative definitions of seismic damage states, including some proposals originating from recent international research programmes

Curvature-bias corrections using a pseudomass method

Momentum measurements for very high momentum charged particles, such as muons from electroweak vector boson decays, are particularly susceptible to charge-dependent curvature biases that arise from misalignments of tracking detectors. Low momentum charged particles used in alignment procedures have limited sensitivity to coherent displacements of such detectors, and therefore are unable to fully constrain these misalignments to the precision necessary for studies of electroweak physics. Additional approaches are therefore required to understand and correct for these effects. In this paper the curvature biases present at the LHCb detector are studied using the pseudomass method in proton-proton collision data recorded at centre of mass energy √(s)=13 TeV during 2016, 2017 and 2018. The biases are determined using Z→μ + μ - decays in intervals defined by the data-taking period, magnet polarity and muon direction. Correcting for these biases, which are typically at the 10-4 GeV-1 level, improves the Z→μ + μ - mass resolution by roughly 18% and eliminates several pathological trends in the kinematic-dependence of the mean dimuon invariant mass

Helium identification with LHCb

The identification of helium nuclei at LHCb is achieved using a method based on measurements of ionisation losses in the silicon sensors and timing measurements in the Outer Tracker drift tubes. The background from photon conversions is reduced using the RICH detectors and an isolation requirement. The method is developed using pp collision data at √(s) = 13 TeV recorded by the LHCb experiment in the years 2016 to 2018, corresponding to an integrated luminosity of 5.5 fb-1. A total of around 105 helium and antihelium candidates are identified with negligible background contamination. The helium identification efficiency is estimated to be approximately 50% with a corresponding background rejection rate of up to O(10^12). These results demonstrate the feasibility of a rich programme of measurements of QCD and astrophysics interest involving light nuclei

Momentum scale calibration of the LHCb spectrometer

For accurate determination of particle masses accurate knowledge of the momentum scale of the detectors is crucial. The procedure used to calibrate the momentum scale of the LHCb spectrometer is described and illustrated using the performance obtained with an integrated luminosity of 1.6 fb-1 collected during 2016 in pp running. The procedure uses large samples of J/ψ → μ + μ - and B+ → J/ψ K + decays and leads to a relative accuracy of 3 × 10-4 on the momentum scale

Seismic Behavior of R.C. Beam-Column Joints Designed for Gravity Only

The inherent seismic vulnerability of reinforced concrete beam-column connections designed for gravity load only is herein investigated. Experimental tests on six 2/3 scaled beam-column subassemblies, with structural deficiencies typical of Italian construction practice between the 50’s and 70’s, were performed under simulated seismic loads. Interior, exterior tee and knee joints, characterized by the use of smooth bars, inadequate detailing of the reinforcement (i.e. total lack of transverse reinforcement in the joint region), deficiencies in the anchorage (hook-ended bars) and the absence of any capacity design principles, were subjected to quasistatic cyclic loading at increasing levels of interstorey drift. The experimental results underlined the significant vulnerability of the joint panel zone region and the critical role of the slippage phenomena due to the use of smooth bars and of inadequate anchorage. A particular “concrete wedge” brittle failure mechanism, due to the interaction of shear cracking and stress concentration at the hook anchorage location, was observed in the exterior specimens. The inaccuracy of traditional shear degradation models for exterior joints in predicting similar damage mechanisms is discussed and possible modifications are suggested