RINTC-E: Towards seismic risk assessment of existing residential reinforced concrete buildings in Italy

The RINTC research project (RINTC Workgroup, 2018), financed by the Italian Department of Civil Protection, is aimed at evaluating the seismic risk of buildings conforming to the Italian building code. Within the framework of this project, the attention has been recently focused on existing buildings, too. In this study, case-study structures, representative of the existing residential reinforced concrete (RC) building stock in Italy, are analyzed. These structures are three-storey buildings with compact rectangular plan, and they have been defined through a simulated design process, in order to represent two types of buildings, namely designed for gravity loads only during 1970s (gravity load designed, GLD) or for moderate seismic loads during 1990s (seismic load designed, SLD). GLD buildings are assumed to be located in three different sites, namely Milan, Naples and Catania, in increasing order of seismic hazard. SLD buildings are assumed to be located in L'Aquila. The assumed design typologies are consistent with the seismic classification of the sites at the assumed ages of construction. The presence of typical nonstructural masonry infill walls (uniformly distributed in plan as external enclosure walls) is taken into account, assuming three configurations along height, namely “bare” (without infills), uniformly infilled and “pilotis” (without infills at the bottom storey) buildings. Two (not code-based) Limit States are investigated, namely Usability-Preventing Damage, corresponding to an interruption of the building use, and Collapse. RC elements are modelled with a lumped plasticity approach, through an empirical-based macromodel. The possible occurrence of shear failures in columns is taken into account through a preliminary classification of the expected failure mode (flexure- or shear-controlled, in the latter case prior to or following flexural yielding) and, if needed, a modification of the backbone of the nonlinear moment-chord rotation response, through empirical models providing the expected deformation capacity at shear and axial failure, the latter meant as the (initiation of) loss of axial-load-carrying-capacity. The nonlinear response of beam-column joints is modelled, too, with a “scissors model” based on concentrated springs representing the nonlinear response of the joint panel, at the intersection of beams' and columns' centerlines, through a preliminary evaluation of the expected failure mode (i.e. prior to or following yielding of adjacent beam/column elements). Materials properties are provided by literature studies, consistent with the age of construction of the buildings. The in-plane response of infills is modelled, taking into account the presence of openings, too. Modeling should be considered as simplified and, from some points of view, still preliminary, since advances are foreseen within the project in order to capture further failure modes that can occur in structural and nonstructural elements of older, nonductile RC buildings. Nonlinear static analyses, allowing to identify the (top) displacement capacity at the investigated Limit States, are carried out. Multiple stripe nonlinear time history bi-directional analyses of the three-dimensional structural models are carried out in order to evaluate the demand, for ten stripes - each corresponding to a return period ranging from 10 to 105 years - and for twenty couples of records for each stripe. Records were selected, within the activities of the research project, based on a Probabilistic Seismic Hazard Analysis at the sites of interest for the selected return periods. Results are illustrated, highlighting the role of a - although obsolete - seismic design in the response of the buildings and in their capacity, more specifically in terms of displacement capacity at Collapse, but also in terms of demand estimated from multiple stripe analyses. Finally, demand-to-capacity ratios at the investigated Limit States are analyzed, which allow, within the scope of the project, the assessment of the seismic risk of the case study structures

The Sexual Long COVID (SLC): Erectile Dysfunction as a Biomarker of Systemic Complications for COVID-19 Long Haulers

Introduction: Long term complications of COVID-19, the disease caused by the SARS-CoV-2, involve many organ systems, dramatically worsening the quality of life, and finally contributing to impaired physical functioning. Despite the presence of well-identified pathogenetic mechanisms, the effect of "Long COVID" on sexual health has been only marginally addressed. Objectives: To provide coverage of the current literature on long COVID, its epidemiology, pathophysiology, and relevance for erectile function. Methods: Comprehensive review of literature pertaining to the epidemiology and pathophysiology of long COVID, and its relevance for erectile function. Results: Symptoms of long COVID are highly prevalent and involve almost all systems of the human body, with a plethora of clinical manifestations which range from minor nuisances to life-threatening conditions. "Brain fog" and fatigue are the most common complaints, although other neuropsychiatric complications, including sensory dysfunctions, anxiety, depression, and cerebrovascular events have also been reported. The respiratory and cardiovascular systems are also affected, with dyspnea, pulmonary fibrosis, endothelial dysfunction, and myocarditis occurring in some COVID long haulers. A subset of patients might develop endocrine manifestations, including onset of diabetes, thyroid dysfunction, and hypogonadism. Overall, long COVID features many complications which can impair erectile function by multiple pathogenetic mechanisms, and which could require tailored treatment: (i) careful investigation and management from the sexual medicine expert are therefore much needed, (ii) and future research on this topic is warranted. Conclusion: in COVID-19 long haulers, several complications can adversely affect erectile function which, upon future tailored studies, could be used as biomarker for the severity of the long COVID disease and for its follow-up. Sansone A, Mollaioli D, Limoncin E et al. The Sexual Long COVID (SLC): Erectile Dysfunction as a Biomarker of Systemic Complications for COVID-19 Long Haulers. Sex Med Rev 2021;XX:XXX-XXX

Recorded Motions of the Mw6.3 April 6, 2009 L’Aquila (Italy) Earthquake and Implications for Building Structural Damage: Overview.

The normal-faulting earthquake of 6 April 2009 in the Abruzzo Region of central Italy caused heavy losses of life and substantial damage to centuriesold buildings of significant cultural importance and to modern reinforcedconcrete- framed buildings with hollow masonry infill walls. Although structural deficiencies were significant and widespread, the study of the characteristics of strong motion data from the heavily affected area indicated that the short duration of strong shaking may have spared many more damaged buildings from collapsing. It is recognized that, with this caveat of shortduration shaking, the infill walls may have played a very important role in preventing further deterioration or collapse of many buildings. It is concluded that better new or retrofit construction practices that include reinforcedconcrete shear walls may prove helpful in reducing risks in such seismic areas of Italy, other Mediterranean countries, and even in United States, where there are large inventories of deficient structures.Published651-6844.1. Metodologie sismologiche per l'ingegneria sismicaJCR Journalreserve

Seismic assessment of a heavy-timber frame structure with ring-doweled moment-resisting connections

The performance of heavy-timber structures in earthquakes depends strongly on the inelastic behavior of the mechanical connections. Nevertheless, the nonlinear behavior of timber structures is only considered in the design phase indirectly through the use of an R-factor or a q-factor, which reduces the seismic elastic response spectrum. To improve the estimation of this, the seismic performance of a three-story building designed with ring-doweled moment resisting connections is analyzed here. Connections and members were designed to fulfill the seismic detailing requirements present in Eurocode 5 and Eurocode 8 for high ductility class structures. The performance of the structure is evaluated through a probabilistic approach, which accounts for uncertainties in mechanical properties of members and connections. Nonlinear static analyses and multi-record incremental dynamic analyses were performed to characterize the q-factor and develop fragility curves for different damage levels. The results indicate that the detailing requirements of Eurocode 5 and Eurocode 8 are sufficient to achieve the required performance, even though they also indicate that these requirements may be optimized to achieve more cost-effective connections and members. From the obtained fragility curves, it was verified that neglecting modeling uncertainties may lead to overestimation of the collapse capacity

Semi-empirical relationships to assess the seismic performance of slopes from an updated version of the Italian seismic database

Funder: Dipartimento della Protezione Civile, Presidenza del Consiglio dei Ministri; doi: http://dx.doi.org/10.13039/100012783; Grant(s): ReLUIS research project - Working Pachage 16: Geotechnical Engineering - Task Group 2: Slope stabilityAbstractSeismic performance of slopes can be assessed through displacement-based procedures where earthquake-induced displacements are usually computed following Newmark-type calculations. These can be adopted to perform a parametric integration of earthquake records to evaluate permanent displacements for different slope characteristics and seismic input properties. Several semi-empirical relationships can be obtained for different purposes: obtaining site-specific displacement hazard curves following a fully-probabilistic approach, to assess the seismic risk associated with the slope; providing semi-empirical models within a deterministic framework, where the seismic-induced permanent displacement is compared with threshold values related to different levels of seismic performance; calibrating the seismic coefficient to be used in pseudo-static calculations, where a safety factor against limit conditions is computed. In this paper, semi-empirical relationships are obtained as a result of a parametric integration of an updated version of the Italian strong-motion database, that, in turn, is described and compared to older versions of the database and to well-known ground motion prediction equations. Permanent displacement is expressed as a function of either ground motion parameters, for a given yield seismic coefficient of the slope, or of both ground motion parameters and the seismic coefficient. The first are meant to be used as a tool to develop site-specific displacement hazard curves, while the last can be used to evaluate earthquake-induced slope displacements, as well as to calibrate the seismic coefficient to be used in a pseudo-static analysis. Influence of the vertical component of seismic motion on these semi-empirical relationships is also assessed.</jats:p

Wavelet Analysis on Detecting Pulse-Like Earthquakes

A quantitative approach for identifying pulse-like ground motions is proposed herein. It is based on the use of the wavelet transform which has the peculiarity to detect sudden jumps in time histories by separating the contributions of different levels of frequency. Moreover, it has the advantage of low computational cost. Three different wavelet-based signal processing procedures are considered here in order to detect large pulses in near-fault ground motions. The first one is based on the direct decomposition of velocity time histories in frequency level and has been exploited elsewhere in the scientific literature. The other two are introduced here and take into account energy and power spectra. It is shown that wavelet analysis of the energy allows one to put in evidence even pulses that can be hardly recognized in the analysis of velocity time-histories. The proposed procedure permits also to distinguish the various energy contributions in different frequency ranges. By analyzing the wavelet coefficients, in fact, it is possible to verify if the mechanical energy release rate associated with a certain earthquake is due to a few severe events or to a series of 'small' events. It is also possible to evidence the frequency contents of a specific pulse (let say the one with highest amount of energy and corresponding power), isolating its analysis from the rest of the ground motion. © 2008 American Institute of Physics

Mitigation of seismic risk on high-rise buildings using rocking cores

Rocking systems consist of structures, or portions thereof, properly designed to oscillate at the base when subjected to ground motion excitations. The mitigation of the seismic risk is achieved by shifting the natural period of the fixed-base structure, which, in turns, provides a reduction of the seismic loads induced in the superstructure. This work investigates the performance of a multi-story steel frame with inner rocking braced core. This latter system includes viscous dampers, designed to provide effective dissipative behavior and mounted between the foundation and column bases. The benefits produced by the introduction of this novel protection system for withstanding severe ground motion excitations are discussed via numerical examples. The seismic performance of the integrated system with rocking core is compared with the mechanical behavior of a fixed-base building to evaluate its efficiency in alleviating severe damage. Response spectrum and time history analyses are performed. Long duration, standard and pulse-like records are considered to appreciate how different energy contents of the ground motion affect the seismic response of the building structure

An integrated topology optimization framework for three-dimensional domains using shell elements

In the last decades, topology optimization has been widely investigated as a preliminary design tool to minimize the use of material in a structure. Despite this, applications to realistic three-dimensional engineering problems are still limited. This study provides the instruments for the definition of a versatile and integrated framework in order to apply topology optimization to large-scale 3-D domains for the design of efficient and high-performing structures. The paper proposes a novel topology optimization strategy to identify the optimal layout of lateral resisting systems for tall buildings through the adoption of Mindlin–Reissner shell elements for the discretization of the continuum design domain. The framework is based on the practical interoperability between MATLAB, Ansys, and computer-aided design (CAD) environments to incorporate optimization routines in the conceptual design phase of structural systems. Finally, the paper examines a three-dimensional tall building case study in order to demonstrate the applicability of the proposed procedure to realistic Civil Engineering design problems and its robustness in finding optimal layouts free from mesh-dependency instabilities