SEISMIC PERFORMANCE OF BRIDGES ISOLATED WITH DCFP DEVICES

The paper analyzes the influence of double concave friction pendulum (DCFP) isolator properties on the seismic performance of isolated bridges. The behavior of these systems is analyzed by employing an eight-degree-of-freedom model accounting for the first five vibra-tional modes of the pier and the presence of a rigid abutment, whereas the DCFP isolator behaviour is described combining two single FPSs in series. The uncertainty in the seismic input is taken into account by considering a set of natural records with different character-istics. The variation of the statistics of the response parameters relevant to the seismic per-formance is investigated through an extensive parametric study carried out for different sys-tem properties

MODEL UNCERTAINTIES IN NLFEAS OF RC SYSTEMS UNDER CYCLIC LOADS

This work is focused on the resistance model uncertainties in non-linear finite element anal-yses (NLFEAs) for reinforced concrete structures under cyclic loading conditions. In detail, different walls experimentally tested are numerically reproduced by means of appropriate plane stress finite elements (FE) structural models within different assumptions and numeri-cal codes. After that, the values of the global resistances computed through numerical simu-lations are compared to the experimental outcomes to evaluate the influence of the different assumptions on the mechanical behaviour of reinforced concrete members subjected to cy-clic loads

SEISMIC PERFORMANCE OF BRIDGES EQUIPPED WITH FPS

The scope of the present study is focused on the evaluation of the seismic response of bridges iso-lated by single concave sliding pendulum isolators (FPS) for the different structural properties when the presence of the rigid abutment is considered or neglected (i.e., isolated viaducts). In this way, they have been defined two specific multi-degree-of-freedom (mdof) models to simulate the elastic behavior of the reinforced concrete pier in combination to the infinitely rigid presence of the deck and to the presence of the rigid abutment if considered. Both the numerical models also account for the non-linear velocity-dependent behavior of the FPS bearings. Considering the alea-tory uncertainty in the seismic input by means of several natural records with different character-istics, a parametric analysis is developed for several structural properties. The relevant results ex-pressed as the statistics in non-dimensional form with respect to the seismic intensity have permit-ted to study the differences between the two numerical models in relation to the effectiveness of the seismic isolation

SEISMIC PERFORMANCE OF BRIDGES ISOLATED BY DCFP DEVICES: A PARAMETRIC ANALYSIS

The present investigation examines how the properties of the double concave friction pendulum (DCFP) devices influence the seismic performance of isolated multi-span continuous deck bridges. The numerical simulations are carried out using an eight-degree-of-freedom model to reproduce the elastic behavior of the pier, associated to the assumption of both rigid abutment and rigid deck, and the non-linear velocity-dependent behavior of the two surfaces of the double concave friction pen-dulum isolators under a set of natural records with different characteristics. The results in terms of the statistics related to the relevant response parameters are computed in non-dimensional form with respect to the seismic intensity considering different properties of both DCFP isolators and bridge

Epidemiology and Microbiology of Skin and Soft Tissue Infections: Preliminary Results of a National Registry

Skin and soft tissue infections (SSTIs) represent a wide range of clinical conditions characterized by a considerable variety of clinical presentations and severity. Their aetiology can also vary, with numerous possible causative pathogens. While other authors previously published analyses on several types of SSTI and on restricted types of patients, we conducted a large nationwide surveillance programme on behalf of the Italian Society of Infectious and Tropical Diseases to assess the clinical and microbiological characteristics of the whole SSTI spectrum, from mild to severe life-threatening infections, in both inpatients and outpatients. Twenty-five Infectious Diseases (ID) Centres throughout Italy collected prospectively data concerning both the clinical and microbiological diagnosis of patients affected by SSTIs via an electronic case report form. All the cases included in our database, independently from their severity, have been managed by ID specialists joining the study while SSTIs from other wards/clinics have been excluded from this analysis. Here, we report the preliminary results of our study, referring to a 12-month period (October 2016–September 2017). During this period, the study population included 254 adult patients and a total of 291 SSTI diagnoses were posed, with 36 patients presenting more than one SSTIs. The type of infection diagnosed, the aetiological micro-organisms involved and some notes on their antimicrobial susceptibilities were collected and are reported herein. The enrichment of our registry is ongoing, but these preliminary results suggest that further analysis could soon provide useful information to better understand the national epidemiologic data and the current clinical management of SSTIs in Italy

Optimal response of isolated bridges subjected to near fault seismic inputs

This work deals with the evaluation of the seismic performance of multi-span continuous deck bridges isolated with single concave friction pendulum bearings. A sixdegree- of-freedom system is modelled to represent the seismic behaviour of the bridge, while the friction pendulum device is modelled by including the non-linear dependency of the friction coefficient from the sliding velocity. The isolator is considered on top of the abutment and of the pier. Different bridge models are obtained by changing different properties (i.e., deck and pier masses and fundamental periods) within a parametric study. Then, for each of the bridge models, a non dimensional analysis is performed to normalize the equations of motion with respect to the ratio between the peak ground acceleration and the peak ground velocity and those equations are solved for a set of 40 near fault seismic inputs. The final goal is to elaborate an optimal value of the friction coefficient in order to reduce the seismic response of the pier

SEISMIC RELIABILITY OF STEEL STRUCTURAL SYSTEMS ISOLATED BY FPS

The paper deals with the seismic reliability of steel structural systems equipped with friction pen-dulum isolators (FPS). The behavior of these systems is analysed by employing a two-degree-of-freedom model accounting for the superstructure flexibility, whereas the FPS device behaviour is described by adopting a widespread model which considers the variation of the friction coefficient with the velocity. The uncertainty in the seismic inputs is taken into account by considering a set of artificial records, obtained through the power spectral density method as well as the friction coefficient at large velocity is considered as random variable modelled through a uniform prob-ability density function. Incremental dynamic analysis are developed in order to evaluate the fra-gility curves related to both superstructure and isolation level for different structural system prop-erties. Finally, considering the seismic hazard curve related to a site near L’Aquila (Italy), the seismic reliability of the overall system is evaluated providing reliability-based abacuses useful to design the radius in plan of the friction pendulum devices

EFFETCS OF CLASS B SITE ON THE SEISMIC RELIABILITY OF BASE-ISOLATED STEEL SYSTEMS

Seismic reliability of steel structures isolated using the frictional pendulum system bearings and subjected to artificial earthquake ground motions is studied herein. The superstructure is idealised as a linear shear-type flexible building as well as the FPS devices are described by adopting a widespread model which considers the variation of the friction coefficient with the velocity. The uncertainty affecting both the seismic inputs, modelled as non stationary random processes within the power spectral density method, and the friction coefficient at large velocity is considered through appropriate probability density functions. Incremental dynamic analyses are developed in order to evaluate the fragility curves related to both superstructure and isolation level. Finally, considering the seismic hazard curve related to a site near Sant’Angelo dei Lombardi (Italy), the seismic reliability of the overall steel system is evaluated

SEISMIC RELIABILITY-BASED DESIGN OF STRUCTURES ISOLATED BY FPS

The paper deals with the seismic reliability of base-isolated structural systems equipped with friction pendulum isolators (FPS) in order to provide useful design recommendations. A two-degree-of-freedom model is adopted by accounting for the superstructure flexibility, whereas the FPS isolator behaviour is described by adopting a widespread model which considers the variation of the friction coefficient with the velocity. The spectral displacement corresponding to the isolated period has been chosen as intensity measure (IM). The uncertainty in the seismic inputs as well as the friction coefficient at large velocity are considered as random variables modeled through appropriate probability density functions. Monte Carlo simulations are developed in order to evaluate the probabilities exceeding different limit states related to both superstructure and isolation level defining the seismic fragility curves. Finally, considering the seismic hazard curve related to an Italian site, closedform expressions are derived with the aim to design the radius in plan of the friction pendulum isolators in function of the expected reliability level