Advances in structural robustness of reinforced concrete moment resisting frames

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Circuit modeling of a MEMS varactor including dielectric charging dynamics

Electrical models for MEMS varactors including the effect of dielectric charging dynamics are not available in commercial circuit simulators. In this paper a circuit model using lumped ideal elements available in the Cadence libraries and a basic Verilog-A model, has been implemented. The model has been used to simulate the dielectric charging in function of time and its effects over the MEMS capacitance value.Peer ReviewedPostprint (published version

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

Parametric and nonparametric two-sample tests for feature screening in class comparison: a simulation study

Background. The identification of a location-, scale- and shape-sensitive test to detect differentially expressed features between two comparison groups represents a key point in high dimensional studies. The most commonly used tests refer to differences in location, but general distributional discrepancies might be important to reveal differential biological processes.                                                         Methods. A simulation study was conducted to compare the performance of a set of two-sample tests, i.e. Student's t, Welch's t, Wilcoxon-Mann-Whitney, Podgor-Gastwirth PG2, Cucconi, Kolmogorov-Smirnov (KS), Cramer-von Mises (CvM), Anderson-Darling (AD) and Zhang tests (ZK, ZC and ZA) which were investigated under different distributional patterns. We applied the same tests to a real data example.                   Results. AD, CvM, ZA and ZC tests proved to be the most sensitive tests in mixture distribution patterns, while still maintaining a high power in normal distribution patterns. At best, the AD test showed a loss in power of ~ 2% in the comparison of two normal distributions, but a gain of ~ 32% with mixture distributions respect to the parametric tests. Accordingly, the AD test detected the greatest number of differentially expressed features in the real data application.   Conclusion. The tests for the general two-sample problem introduce a more general concept of 'differential expression', thus overcoming the limitations of the other tests restricted to specific moments of the feature distributions. In particular, the AD test should be considered as a powerful alternative to the parametric tests for feature screening in order to keep as many discriminative features as possible for the class prediction analysis

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

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

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 RELIABILITY OF BRIDGES EQUIPPED WITH FPS

The present analysis deals with the seismic reliability of isolated multi-span continuous deck bridges considering as the main aleatory uncertainties relevant to the problem the sliding friction coefficient of the friction pendulum (FP) isolators together with the seismic records characteristics. A six-degree-of-freedom model is defined to simulate the elastic response of the reinforced concrete pier, the infinitely rigid response of the deck supported by the seismic devices and the non-linear velocity-dependent behavior of the FPS bearings. The reinforced concrete abutment is modelled as a rigid support above which a FPS device is located. A set of natural records with different charac-teristics is properly selected and scaled to increasing intensity levels. The randomness on the fric-tion coefficient is described by an appropriate probability density function to sample. For different system and isolator properties, fragility curves of both the reinforced concrete pier and FP devices supporting the deck are estimated. In accordance with the hazard curve of the design site, the seis-mic reliability curves are derived by means of the convolution integral

Influence of Masonry Infills on Seismic Performance of an Existing RC Building Retrofitted by Means of FPS Devices

The safety assessment of existing structures in areas with a relevant seismic hazard is one of the major topics for engineers since many existing reinforced concrete structures have been realized disregarding seismic design with minimal details with respect to present practice. In this context, seismic assessment is a primary issue in order to identify the best retrofitting solution with the aim of enhancing the efficiency of existing buildings. In recent years, with the aim to enhance the seismic behavior of reinforced concrete (RC) structures (with particular care to existing ones), the system of seismic isolation adopting friction pendulum (FPS) devices proved to be among the most diffuse and effective solutions. The purpose of this paper is to explore the effectiveness of the refurbishment using FPS with single concavity devices on the performance of one irregular existing RC building placed in a highly seismic area of central Italy. First, the geometric and material characteristics of the building have been determined within the approach based on the "knowledge levels". Second, a suitable numerical model based on a fiber-modeling approach has been established using SAP2000, including relevant mechanical non-linearities. Then, a set of 21 natural seismic inputs, inclusive of 3 accelerations over vertical and horizontal directions, was adopted with the aim of performing non-linear (NL) dynamic simulations. The NL dynamic simulations have been performed considering the structural system, both inclusive and not inclusive of the FPS isolator devices. The influence of the actual distribution of infill masonry panels on the overall behavior of the structure has also been evaluated in both of the cases mentioned above. Finally, the outcomes deriving from the NL dynamic simulations were helpful in assessing the advantages of the intervention of retrofitting to improve the seismic performance of the building, highlighting the influence of masonry infills

Sex-specific differences in left ventricular mass and myocardial energetic efficiency in non-diabetic, pre-diabetic and newly diagnosed type 2 diabetic subjects

Background: Women with type 2 diabetes (T2DM) have a higher excess risk for cardiovascular disease (CVD) than their male counterparts. However, whether the risk for CVD is higher in prediabetic women than men is still debated. We aimed to determine whether sex-related differences exist in left ventricular mass index (LVMI), and myocardial mechano-energetic efficiency (MEEi) in with normal glucose tolerant (NGT), pre-diabetic and newly diagnosed type 2 diabetic subjects. Methods: Sex-related differences in LVMI and myocardial MEEi, assessed by validated echocardiography-derived measures, were examined among 1562 adults with NGT, prediabetes, and newly diagnosed T2DM, defined according to fasting glucose, 2-h post-load glucose, or HbA1c. Results: Worsening of glucose tolerance in both men and women was associated with an increase in age-adjusted LVMI and myocardial MEEi. Women with newly diagnosed T2DM exhibited greater relative differences in LVMI and myocardial MEEi than diabetic men when compared with their NGT counterparts. Prediabetic women exhibited greater relative differences in myocardial MEEi, but not in LVMI, than prediabetic men when compared with their NGT counterparts. The statistical test for interaction between sex and glucose tolerance on both LVMI (P < 0.0001), and myocardial MEEi (P < 0.0001) was significant suggesting a sex-specific association. Conclusions: Left ventricle is subject to maladaptive changes with worsening of glucose tolerance, especially in women with newly diagnosed T2DM. The sex-specific increase in LVM and decrease in MEEi, both being predictors of CVD, may have a role in explaining the stronger impact of T2DM on the excess risk of CVD in women than in men