Structural Assessment and Upgrading for an Old Building Belonging to an Historical Multi-Sports Center in Naples

A significant number of non-ductile existing reinforced concrete frame buildings, built in different seismic regions around the world but without adequate seismic detailing requirements, suffered damages, or collapse after past earthquakes. In fact, these reinforced concrete frame buildings are much more susceptible to high level of damage or to collapse than modern code-conforming frames. A crucial issue in the community of the earthquake engineering is the assessment and the upgrading of these non-ductile reinforced concrete structures. In particular, a careful assessment of the existing buildings is very important in order to understand the failure mechanisms that govern the achievement of predefined limit states or the collapse of the structures. Only after an in depth seismic assessment, the best upgrading/retrofit strategy can be designed and applied to the structure. In some cases, the historical value of these buildings makes the assessment procedure and the upgrading design more complicated due to the constraints related to the limited possibility of interventions. In this work, a building belonging to an old multi-sports center, is used as case study. The complex orbits around the soccer stadium called Collana and located in Naples. This soccer stadium was initially built in the late '20s and then it was completely rebuilt in the post-war period and used as a sports center for different sporting activities. Currently, the complex includes a soccer field, an athletic track, three indoor gyms, three tennis fields, a medical center sports, and the indoor pool building investigated herein. The analysis of seismic vulnerability implemented for the case study building shows an unsafe condition under both vertical and seismic loads. The building upgrading is provided choosing the best strategy among different options in order to achieve a certain predefined threshold of the seismic safety for the building. Definitively, the paper presents a real upgrading design case study for a building belonging to an historical complex. Assessment and upgrading are shown based both on linear and dynamic non-linear analyses procedures. Finally, the effectiveness of the structural interventions of upgrading is measured coherently with the new Italian guidelines for seismic risk classification of constructions

PERFORMANCE BASED ASSESSMENT AND RETROFIT FOR EXISTING RC STRUCTURES

The scope of this thesis is to propose a journey through probabilistic performance based assessment and retrofit design based on nonlinear dynamic analysis tools. The thesis aims to address the performance-based assessment paradigm by developing seismic fragilities and earthquake loss estimation. The “Performance-based earthquake engineering” (PBEE) for design, assessment and retrofit of building structures seeks to enhance seismic risk decision-making through assessment and design methods that have a strong scientific basis and support the stakeholders in making informed decisions. The PBEE is based on a consistent probabilistic methodological framework in which the various sources of uncertainty in seismic performance assessment of structures can be represented. The methodology can be used directly for performance assessment, or can be implemented for establishing efficient performance criteria for performance-based design. In particular, the PBEE aims to maximize the utility for a building by minimizing the expected total cost due to seismic risk, including the costs of construction and the incurred losses due to future earthquakes. The PBEE advocates substituting the traditional single-tier design against collapse and its prescriptive rules, with a transparent multi-tier seismic design, meeting more than one discrete “performance objective” by satisfying the corresponding “performance level” (referred to as the “limit state” in the European code) expressed in terms of the physical condition of the building as a consequence of an earthquake whose intensity would be exceeded by a mean annual rate quantified as the “seismic hazard level”. In other words, PBEE distinguishes itself from the prescriptive requirements of the traditional building codes by envisioning explicit verification of satisfying various performance objectives. Last but not least, the PBEE is fundamental to seismic assessment of existing buildings, seen as an indispensable step in the seismic retrofit design process. The principal elements of the PBEE procedure can be summarized as description, definition, and quantification of earthquake intensity measures, engineering demand parameters, damage measures, and decision variables. The process encompasses the following steps: (1) calculation of ground motion hazard by representing the uncertainty in ground motion with a probabilistic model for a parameter (or vector of parameters) related to ground motion and known as the intensity measure (IM); (2) estimation of the uncertainty in structural response expressed as a group of engineering demand parameters EDP (e.g., force and deformation-related engineering parameters) conditioned on each IM level; (3) estimation of the uncertainty in damage measure DM (i.e., physical states of damage, that describes the condition of the structure and its components) conditioned on the EDP and IM; (4) estimation of the uncertainty in the decision variable DV expressing the decision-related consequences (e.g., financial losses, fatalities, business interruption, etc.) given DM, EDP and IM. One interesting and useful characteristic of the PBEE procedure is that any of the above-mentioned intermediate steps can be collapsed. For example, the damage measure DM can be conditioned directly on intensity measure IM by collapsing the intermediate step related to the engineering demand parameter EDP. It is important to note that the performance levels should ideally be described in terms of the decision variable(s) DV. However, many modern codes and guidelines express the various discrete performance levels in terms of the incurred damage (i.e., DM). An important focus in this thesis is dedicated to the estimation of the conditional probability of exceeding a damage measure DM expressed as the critical demand to capacity ratio throughout the structure and a given ground motion time-history and relating it directly to IM (by collapsing the intermediate EDP step). The conditional probability of exceeding a given level of DM given IM can be expressed as the structural fragility for a given performance level. In fact, the assessment of analytic structural fragility for existing buildings is one of the fundamental steps in the modern performance-based engineering. In general, methods for assessing the structural fragility for a given performance level or limit state range from the simplest methods based on the response of an equivalent single-degree-of-freedom (SDOF) model to complex nonlinear dynamic analysis procedures performed for a structural model subjected to a set of ground-motion records. In the past fifteen years, many research efforts have been dedicated to an in-depth study of the implementation, the nuances and the potential complications of non-linear dynamic analysis procedures. These efforts have led to different methodologies such as Incremental Dynamic Analysis (IDA), Multiple-Stripe Analysis (MSA) with conditional mean spectrum, and Cloud Analysis. This work focuses on the non-linear dynamic analysis procedure known as the Cloud Analysis. This analysis is based on fitting a linear regression model in the logarithmic scale to the pairs of structural response parameter (e.g., maximum inter-story drift) and IM (e.g., first-mode spectral acceleration) for a suite of as-recorded ground motions. This method is well-known both for the simplicity of its underlying formulation and for the relatively small number of structural analyses required. However, the Cloud Analysis is also notorious for being based on a few simplifying assumptions (fixed standard error of regression, mean response varying linearly as a function of IM in the logarithmic scale, and structural response given IM being modeled as a Lognormal distribution), and for being sensitive to the selected suite of records. A functional variation to the original Cloud Analysis is presented in order to take into account the cases leading to structural collapse. Moreover, to reduce record-selection-dependence of the results, a Bayesian version of the Cloud Analysis considering the “collapse-cases” is presented in which the uncertainty in the structural fragility model parameters is considered. This leads to a Robust Fragility estimate and a desired confidence interval defined around it. The entire method is based on the adoption of a normalized demand to capacity ratio as the damage measure/decision performance variable. Herein, as said, a normalized demand to capacity ratio coined as “critical demand to capacity ratio” and denoted as DCR, takes the structure closest to the onset of a prescribed limit state LS, is adopted. The adoption of DCRLS as performance variable is also central to a new nonlinear dynamic analysis procedure referred to as “Cloud to IDA” that exploits the Cloud Analysis to perform IDA in a more efficient manner. Evaluation of structural behaviour under seismic actions for an existing building encompasses the consideration of numerous sources of uncertainty associated with the seismic action and the structural modelling. In the past decades, significant research efforts have been carried out and substantial progress has been made towards the consideration of various sources of uncertainty into structural performance assessment and design frameworks. Several alternative methods have been proposed that combine reliability methods such as the first order second moment (FOSM and MVFOSM) methods, response surface methods, simulation-based methods (e.g., Monte Carlo, Latin Hypercube Sampling) with non-linear dynamic procedures such as IDA based on recorded ground motions in order to take into account sources of uncertainties other than record-to-records variability. This thesis aims to quantify the impact of structural modeling uncertainties on the seismic performance assessment for an existing case-study building. Herein, the proposed version of the Cloud Analysis, considering the collapse cases, is implemented to consider the record-to-record variability, the structural modeling uncertainties and also the uncertainties in the parameters of the adopted fragility model, through a Bayesian procedure. The presented procedure can lead to reliable results with a considerably lower computational effort in comparison to the methods available in literature. Finally, the PBEE methodology is implemented for the case-study building in order to choose the most appropriate seismic retrofit design that maximizes the utility (by minimizing the expected costs) and satisfies the safety-checking for three different performance levels. To this end, the non-ductile older RC frame of the case-study is retrofit designed based on different strategies aimed to improve the seismic performance of the frame. The case-study moment resisting frame is modeled using structural elements with fiber sections in order to take into account the flexural-axial interactions. Furthermore, the flexural-axial-shear interactions and the fixed end rotations due to bar slip in the columns are considered by adding zero-length springs to column ends. The performance-based safety-checking procedure is based on the Demand and Capacity Factored Design (DCFD) format. Amongst the viable retrofit designs that satisfy the risk-related safety-checking DCFD criteria, the one that corresponds to the minimum expected loss over the life cycle of the building is identified

Empirical fragility assessment using conditional GMPE-based ground shaking fields: application to damage data for 2016 Amatrice Earthquake

AbstractRecent earthquakes have exposed the vulnerability of existing buildings; this is demonstrated by damage incurred after moderate-to-high magnitude earthquakes. This stresses the need to exploit available data from different sources to develop reliable seismic risk components. As far as it regards empirical fragility assessment, accurate estimation of ground-shaking at the location of buildings of interest is as crucial as the accurate evaluation of observed damage for these buildings. This implies that explicit consideration of the uncertainties in the prediction of ground shaking leads to more robust empirical fragility curves. In such context, the simulation-based methods can be employed to provide fragility estimates that integrate over the space of plausible ground-shaking fields. These ground-shaking fields are generated according to the joint probability distribution of ground-shaking at the location of the buildings of interest considering the spatial correlation structure in the ground motion prediction residuals and updated based on the registered ground shaking data and observed damage. As an alternative to the embedded coefficients in the ground motion prediction equations accounting for subsoil categories, stratigraphic coefficients can be applied directly to the ground motion fields at the engineering bedrock level. Empirical fragility curves obtained using the observed damage in the aftermath of Amatrice Earthquake for residential masonry buildings show that explicit consideration of the uncertainty in the prediction of ground-shaking significantly affects the results

Seismic and Fire Assessment and Upgrading Process for Historical Buildings: The Case Study of Palazzo Colonna in Caggiano

The assessment and retrofit of existing masonry structures with historical and cultural value in highly seismic zones are challenging issues in earthquake engineering. In fact, the historic and recent earthquakes have shown the problem of the seismic vulnerability of existing masonry constructions. A historical masonry palace located in Caggiano (Salerno, Italy) is used herein as a case study, showing the vulnerability assessment and the seismic upgrading process. The case study building has a masonry structural type at the first two floors while there is a third floor realized in reinforced concrete and a fourth floor realized with a wood structure. The building was characterized by a remarkable seismic vulnerability and needed seismic upgrading operations. After the vulnerability assessment process, some design suggestions are proposed for the seismic upgrading of the building. The structure before and after the upgrading operations has been checked through nonlinear static and dynamic analyses. Then, coherently with the "Sismabonus" approach, the attribution of the seismic risk class, performed through numerical analyses, is founded on two parameters, namely, the expected annual mean losses (PAM), related to economic factors, and the Life Safety Index (IS-V), related to the structure seismic safety. Finally, the overcoming of the different classes of risk is shown and compared with the amount of the retrofit operations, their costs, and the impact on the existing space. Moreover, fire assessment has been investigated. In fact, in many cases, the buildings such as the case study structure are intended for public activities such as museums, so specific fire requirements, like fire resistance, are necessary. This topic became relevant especially if the structure is equipped with particular structural retrofit interventions which can be altered and modified in case of a fire. The paper presents the results of advanced thermomechanical analyses on the historical masonry palace under investigation. Since the case study building has a masonry structural type at the first two floors while there is a third floor realized in reinforced concrete, the fire analyses were conducted on the third and fourth floors, which may be more vulnerable to fire

Lower Bounds to Quality Factor of Small Radiators through Quasistatic Scattering Modes

The problem of finding the optimal current distribution supported by a small radiator yielding the minimum quality ($Q$) factor is a fundamental problem in electromagnetism. $Q$ factor bounds constrain the maximum operational bandwidth of devices including antennas, metamaterials, and open optical resonators. In this manuscript, a representation of the optimal current distribution in terms of quasistatic scattering modes is introduced. Quasi-electrostatic and quasi-magnetostatic modes describe the resonances of small plasmonic and high-permittivity particles, respectively. The introduced representation leads to analytical and closed form expressions of the electric and magnetic polarizability tensors of arbitrarily shaped objects, whose eigenvalues are known to be linked to the minimum $Q$. Hence, the minimum $Q$ and the corresponding optimal current are determined from the sole knowledge of the eigenvalues and the dipole moments associated with the quasistatic modes. It is found that, when the radiator exhibits two orthogonal reflection symmetries, its minimum $Q$ factor can be simply obtained from the $Q$ factors of its quasistatic modes, through a parallel formula. When an electric type radiator supports a spatially uniform quasistatic resonance mode, or when a magnetic type resonator supports a mode of curl type, then these modes are guaranteed to have the minimum $Q$ factor

Early cardiac abnormalities and increased C-reactive protein levels in a cohort of children with sleep disordered breathing

This study aims to evaluate left ventricular (LV) structure and function and inflammation in a paediatric population with sleep disordered breathing (SDB) and in control subjects. Forty-nine children with SDB and 21 healthy, age-matched subjects were enrolled. The diagnosis of obstructive sleep apnoea syndrome (OSAS) was confirmed by the laboratory polysomnography, showing an obstructive apnoea/hypopnoea index of more than one per hour, according to the criteria of the American Academy of Sleep Medicine and modified for paediatric population. Fasting blood samples for the biochemical evaluation (including high-sensitivity C-reactive protein (hsCRP) were drawn in the morning, after the polysomnographic examination in all patients with SDB and in the control group. All children underwent a two-dimensional colour Doppler cardiac examination with LV mass assessment and systolic and diastolic function evaluation. Higher hsCRP levels were observed in subjects with OSAS than in children with primary snoring and in controls (0.8 +/- 0.7 vs 0.3 +/- 0.1 ng/dl, p = 0.001, and 0.4 +/- 0.2 ng/dl, p = 0.01, respectively). The LV diastolic dysfunction was significantly more frequent in patients with severe OSAS and higher hsCRP levels than in control group. This study shows that OSAS in children is associated with higher LV mass, early LV diastolic dysfunction and a pro-inflammatory state (high CRP levels). These findings might help to explain the higher incidence of cardiovascular morbidity in patients with OSAS

E2 regulates epigenetic signature on neuroglobin enhancer-promoter in neuronal cells

Estrogens are neuroprotective factors in several neurological diseases. Neuroglobin (NGB) is one of the estrogen target genes involved in neuroprotection, but little is known about its transcriptional regulation. Estrogen genomic pathway in gene expression regulation is mediated by estrogen receptors (ERα and ERβ) that bind to specific regulatory genomic regions. We focused our attention on 17β-estradiol (E2)-induced NGB expression in human differentiated neuronal cell lines (SK-N-BE and NT-2). Previously, using bioinformatics analysis we identified a putative enhancer in the first intron of NGB locus. Therefore, we observed that E2 increased the enrichment of the H3K4me3 epigenetic marks at the promoter and of the H3K4me1 and H3K27Ac at the intron enhancer. In these NGB regulatory regions, we found estrogen receptor alpha (ERα) binding suggesting that ERα may mediate chromatin remodeling to induce NGB expression upon E2 treatment. Altogether our data show that NGB expression is regulated by ERα binding on genomic regulatory regions supporting hormone therapy applications for the neuroprotection against neurodegenerative diseases

A Novel Functional Domain of Tab2 Involved in the Interaction with Estrogen Receptor Alpha in Breast Cancer Cells

Tab2, originally described as a component of the inflammatory pathway, has been implicated in phenomena of gene de-repression in several contexts, due to its ability to interact with the NCoR corepressor. Tab2 interacts also with steroid receptors and dismisses NCoR from antagonist-bound Estrogen and Androgen Receptors on gene regulatory regions, thus modifying their transcriptional activity and leading to pharmacological resistance in breast and prostate cancer cells. We demonstrated previously that either Tab2 knock-down, or a peptide mimicking the Estrogen Receptor alpha domain interacting with Tab2, restore the antiproliferative response to Tamoxifen in Tamoxifen-resistant breast cancer cells. In this work, we map the domain of Tab2 responsible of Estrogen Receptor alpha interaction. First, using both co-immunoprecipitation and pull-down with recombinant proteins, we found that the central part of Tab2 is primarily responsible for this interaction, and that this region also interacts with Androgen Receptor. Then, we narrowed down the essential interaction region by means of competition assays using recombinant protein pull-down. The interaction motif was finally identified as a small region adjacent to, but not overlapping, the Tab2 MEKK1 phosphorylation sites. A synthetic peptide mimicking this motif efficiently displaced Tab2 from interacting with recombinant Estrogen Receptor alpha in vitro, prompting us to test its efficacy using derivatives of the MCF7 breast carcinoma cell lines that are spontaneously resistant to Tamoxifen. Indeed, we observed that this mimic peptide, made cell-permeable by addition of the TAT minimal carrier domain, reduced the growth of Tamoxifen-resistant MCF7 cells in the presence of Tamoxifen. These data indicate a novel functional domain of the Tab2 protein with potential application in drug design