Dynamic Modification and Damage Propagation of a Two-Storey Full-Scale Masonry Building

The progressive change of modal characteristics due to accumulated damage on an unreinforced masonry (URM) building is investigated. The stone URM building, submitted to five consecutive shakings, has been experimentally studied on the shaking table of EUCENTRE laboratory (Pavia, Italy). The dynamic characteristics of the test specimen are analytically estimated using frequency and state-space modal identification from ambient vibration stationary tests carried out before the strong motion transient tests at various levels of damage. A singular value (SV) decomposition of the cross-correlation matrix of the acceleration response in the frequency domain is applied to determine the modal characteristics. In the time domain, the subspace state-space system identification is performed. Modal characteristics evolve from the initial linear state up to the ultimate collapse state in correlation with accumulated damage. Modal frequencies shorten with increasing intensity, whereas modal damping ratios are enhanced. Modal shapes also change with increasing level of accumulated damage. Comparing the evolution of modal characteristics, it is concluded that modal damping ratio shift can be better correlated with the system's actual performance giving a better representation of damage than that of natural frequency shift ratio or the modes difference

Simplified methodologies for assessing the out-of-plane two-way bending seismic response of unreinforced brick masonry walls: lessons from recent experimental studies

This paper describes a simplified methodology for the assessment of unreinforced masonry (URM) walls under out-of-plane two-way bending seismic action. The methodology involves a force-based check derived from the principle of virtual work. This check is proposed based on experimental observations of significant cracking resistance associated with two-way spanning URM walls, indicating methodologies considering such walls to be pre-cracked or to be non-laterally supported as overly conservative. The methodology incorporates several findings and developments from recent experimental campaigns: ranging from novel characterization tests on masonry couplets to incremental dynamic tests on full-scale buildings. Such incorporations include new formulation to calculate the torsional shear strength of a bed joint and accounting for possible changes in the boundary conditions of an OOP wall during dynamic loading. Testing standards as well as recommendations in several international guidelines for masonry structures addressing the input properties required to implement the proposed methodology are enlisted and reviewed. The methodology requires the definition of the period of vibration of the assessed URM walls, to calculate which plate theory based formulation is provided. Open research questions and potential avenues for further development of the methodology are ultimately highlighted

Effects of vertical ground motions on the dynamic response of URM structures: Comparative shake-table tests

This paper discusses the results of an experimental study aimed at evaluating the influence of the vertical ground motion component on the seismic performance of unreinforced brick-masonry buildings. The research was motivated by post-earthquake observations of significant structural damage in the vicinity of the fault, where horizontal and vertical ground motions are often strong and synchronized. Vertical accelerations can fluctuate gravity loads, which control the in-plane lateral load capacity of masonry piers and affect the out-of-plane overturning stability of thin walls. Such phenomena seem not to be sufficiently explained in existing literature, while experimental evidence is undoubtedly missing. Here, the damage potential of vertical accelerations was investigated through a series of multidirectional shake-table tests on full-scale structures under simulated near-source ground motions of increasing intensity. The experiments comprised three nominally identical building specimens subjected to the principal horizontal component alone, the horizontal component combined with the vertical one, and the full three-component ground motion. The buildings included structural/nonstructural elements (e.g., gables, chimneys, and parapets) sensitive to gravity load variations due to their low axial loads. Two different sets of three-component earthquake records were employed to assess the effects of both tectonic and induced seismicity scenarios. Overall, the vertical earthquake motion did not cause appreciable differences in the behavior of the buildings. Any influence on the strength and peak response of structural/nonstructural walls was marginal and non-systematic. Data and observations from these experiments add substantially to our understanding of the vertical acceleration effects on masonry structures

In-plane shear behaviour of stone masonry piers: A numerical study

Post-earthquake investigations have shown that if out-of-plane mechanisms are prevented, the seismic performance of a masonry building depends mainly on the in- plane capacity of spandrels beams and especially piers. For this reason, several investigations were done in the past to characterize the in-plane behaviour of masonry walls. A large majority of these studies consist of experimental programmes, testing the lateral response of piers. Nevertheless, very few studies focused on carrying out numerical studies and their potential was disregarded. A numerical investigation to study the in-plane behaviour of masonry piers was carried out, based on an experimental campaign performed on stone masonry piers. The experimental programme included masonry piers with two slenderness ratios subjected to two distinct levels of axial compression. Finite element models were built on the advanced software, DIANA, and according to the experimental setup test of each wall, with the aim of simulating the experimental tests. Afterwards, the non-linear numerical simulations were compared against the in-plane cyclic test results. The calibration and validation of the numerical models according to the experimental results was conducted. The results of the non-linear analyses carried out on the validated models are presented and discussed. Good agreement between experimental and numerical results was achieved both considering the force- displacement behaviour and failure mechanisms. The numerical strategy can be seen as a complementary way to study masonry piers, particularly useful for further parametrical studies.The first author acknowledges the financial support from the Portuguese Science Foundation (Fundação de Ciência e Tecnologia, FCT) through grant SFRH/BD/71599/2010

Modelling of the in-plane behaviour of stone masonry panels

Stone masonrywalls are the most relevant structural element in the seismic response of a masonry building. Once the out-of-plane mechanism are adequately prevented, the seismic response of a building depends on the in-plane strength capacity of its walls. This paper presents a discussion on the in-plane behaviour of masonry panels with different slenderness ratios and distinct levels of compression load, subjected to shear loading, using advanced numerical simulations. The numerical study is based on an experimental campaign performed at the University of Pavia on stone masonry piers. The calibrated models were also used to carry out parametric analysis varying the geometric wall configuration and the pre-compression level. Distinct walls subjected to different stress levelswere assessed and the influence of these parameters on the in-plane behaviour is discussed.The second author would like to express her gratitude to the National Foundation for Science and Technology (FCT) for the PhD grant SFRH/BD/71599/2010. This work was supported by FCT, within ISISE, project UID/ECI/04029/2013

Natural stone masonry characterization for the shaking-table test of a scaled building specimen

This paper discusses the material characterization tests on stone masonry specimens, and the in-plane cyclic shear-compression tests on four half-scale unreinforced stone masonry piers, which complement a shaking-table test on a half-scale building aggregate prototype. Material characterization tests allowed defining a mortar composition suitable for satisfying the similitude relationships associated with the half-scale tests. Vertical and diagonal compression tests provided a complete description of the mechanical properties of masonry assemblies, while in-plane cyclic shear-compression tests allow determining the hysteretic behavior of masonry piers with different aspect ratios and axial compression levels. Strength and displacement capacities corresponding to the observed damage mechanisms and failure modes were also identified and associated with the specimens geometric and loading conditions. These activities are part of an experimental and numerical research project jointly carried by the University of Pavia, Italy, and the École Polytechnique Fédérale de Lausanne, Switzerland, which aims at assessing the seismic vulnerability of natural stone masonry building aggregates of the historical center of Basel, Switzerland

A Machine Learning Approach to Monitor the Emergence of Late Intrauterine Growth Restriction

Late intrauterine growth restriction (IUGR) is a fetal pathological condition characterized by chronic hypoxia secondary to placental insufficiency, resulting in an abnormal rate of fetal growth. This pathology has been associated with increased fetal and neonatal morbidity and mortality. In standard clinical practice, late IUGR diagnosis can only be suspected in the third trimester and ultimately confirmed at birth. This study presents a radial basis function support vector machine (RBF-SVM) classification based on quantitative features extracted from fetal heart rate (FHR) signals acquired using routine cardiotocography (CTG) in a population of 160 healthy and 102 late IUGR fetuses. First, the individual performance of each time, frequency, and nonlinear feature was tested. To improve the unsatisfactory results of univariate analysis we firstly adopted a Recursive Feature Elimination approach to select the best subset of FHR-based parameters contributing to the discrimination of healthy vs. late IUGR fetuses. A fine tuning of the RBF-SVM model parameters resulted in a satisfactory classification performance in the training set (accuracy 0.93, sensitivity 0.93, specificity 0.84). Comparable results were obtained when applying the model on a totally independent testing set. This investigation supports the use of a multivariate approach for the in utero identification of late IUGR condition based on quantitative FHR features encompassing different domains. The proposed model allows describing the relationships among features beyond the traditional linear approaches, thus improving the classification performance. This framework has the potential to be proposed as a screening tool for the identification of late IUGR fetuses

AUTOCOUNTER, an ImageJ JavaScript to analyze LC3B-GFP expression dynamics in autophagy-induced astrocytoma cells

An ImageJ JavaScript, AUTOCOUNTER, was specifically developed to monitor and measure LC3B-GFP expression in living human astrocytoma cells, namely T98G and U373-MG. Discrete intracellular GFP fluorescent spots derived from transduction of a Baculovirus replication-defective vector (BacMam LC3B-GFP), followed by microscope examinations at different times. After viral transgene expression, autophagy was induced by Rapamycin administration and assayed in ph-p70S6K/p70S6K and LC3B immunoblotting expression as well as by electron microscopy examinations. A mutated transgene, defective in LC3B lipidation, was employed as a negative control to further exclude fluorescent dots derived from protein intracellular aggregation. The ImageJ JavaScript was then employed to evaluate and score the dynamics changes of the number and area of LC3B-GFP puncta per cell in time course assays and in complex microscope examinations. In conclusion, AUTOCOUNTER enabled to quantify LC3B-GFP expression and to monitor dynamics changes in number and shapes of autophagosomal-like vesicles: it might therefore represent a suitable algorithmic tool for in vitro autophagy modulation studies

Seismic performance of historical buildings based on discrete element method: an adobe church

This article presents the main concepts and the application of the discrete element method (DEM) for evaluating the seismic performance of historical buildings. Furthermore, the out-of-plane behavior of an adobe church with thick walls, in which the morphology of the cross-section can have an influence on the response, was evaluated by the DEM. The performance of rigid and deformable blocks models was compared, and the sensitivity of the numerical model to the variation of critical parameters was investigated. The results allowed the identification of the most vulnerable elements and a proposal of recommendations for reducing the seismic vulnerability

Predictive ability of the estimate of fat mass to detect early-onset metabolic syndrome in prepubertal children with obesity

Body mass index (BMI), usually used as a body fatness marker, does not accurately dis-criminate between amounts of lean and fat mass, crucial factors in determining metabolic syndrome (MS) risk. We assessed the predictive ability of the estimate of FM (eFM) calculated using the following formula: FM = weight − exp(0.3073 × height2 −10.0155×d-growth-standards/standards/body-mass-index-for-age-bmi-for-age weight−1 +0.004571×weight− 0.9180×ln(age) + 0.6488×age0.5 + 0.04723×male + 2.8055) (exp = exponential function, score 1 if child was of black (BA), south Asian (SA), other Asian (AO), or other (other) ethnic origin and score 0 if not, ln = natural logarithmic transformation, male = 1, female = 0), to detect MS in 185 prepubertal obese children compared to other adiposity parameters. The eFM, BMI, waist circumference (WC), body shape index (ABSI), tri-ponderal mass index, and conicity index (C-Index) were calculated. Patients were classified as hav-ing MS if they met ≥ 3/5 of the following criteria: WC ≥ 95th percentile; triglycerides ≥ 95th percen-tile; HDL-cholesterol ≤ 5th percentile; blood pressure ≥ 95th percentile; fasting blood glucose ≥ 100 mg/dL; and/or HOMA-IR ≥ 97.5th percentile. MS occurred in 18.9% of obese subjects (p < 0.001), with a higher prevalence in females vs. males (p = 0.005). The eFM was correlated with BMI, WC, ABSI, and Con-I (p < 0.001). Higher eFM values were present in the MS vs. non-MS group (p < 0.001); the eFM was higher in patients with hypertension and insulin resistance (p <0.01). The eFM shows a good predictive ability for MS. Additional to BMI, the identification of new parameters determi-nable with simple anthropometric measures and with a good ability for the early detection of MS, such as the eFM, may be useful in clinical practice, particularly when instrumentation to estimate the body composition is not available