Graphical dynamic trends for earthquake incidence response of plan-asymmetric systems

A Graphical Dynamic model is derived to describe the directional earthquake response of two-ways plan-asymmetric systems, which retains the insightful educational evidence of traditional graphical static methods and the accuracy of computational methods of analysis. The dynamic directional response is expressed in terms of modal rotational kinematics about modal centers of rotation, referred to as modal torsional pivots. Seismic forces and response decomposition are handled through geometric modal torsional trends and the earthquake incidence response envelopes are described through directional modal participation radii and graphic spectrum-based "8-shaped" directional influence circles. The graphic approach provides good predictions of the maximum response and of the critical angle computed through CQC3 and other directional analysis methods

Seismic retrofit of an existing RC building with isolation devices applied at base

Nowadays, seismic retrofit through isolation strategy represents a consolidated technique of protection against design earthquakes. This technique is also applied on existing structures extensively, due to the fact that it usually does not require any interruption of the building use and occupants evacuation. If applicable, it rapidly allows the seismically retrofitting of a building installed with seismic devices with low horizontal stiffness between the structure and the foundation decoupling, in fact, this allows the motion of the superstructure from the ground one. In this paper an application on an existing RC building of the seismic isolation is presented. The chosen building was built in the ‘90s only for vertical loads and realized without any detailing rule for structural ductility. The seismic retrofitting requirement stems from the fact that only recently, after the National seismic hazard maps update in 2003, the considered area has been upgraded to a medium-low seismic intensity zone, while at construction time no seismic classification was in existence by law. The case study peculiarity is that the seismic retrofitting has required an addition to seismic devices at the base, with related interventions such as the application of a bracing system consisting of two elastic steel frames. This intervention is required for stiffening the superstructure and, therefore, minimizing the higher vibration modes effects. The paper presents the main results obtained with a FEM model, implemented for simulating the initial and the design state when the interventions are considered. Finally, some results of non-linear dynamic time-history analyses are illustrated and commented for verifying superstructure elements and seismic devices

Numerical analysis on a reversible connection for steel modular buildings

Modular buildings are a new type of structural system composed by prefabricated modular units and assembled on site through inter-modular connections. These structures can form complete building blocks with suspended ceilings and installations, including electrical and water systems. These modular solutions can be adapted to any use like hospitals, housing schools, etc. This work focuses on the analysis of structural behavior on a reversible steel connection modelling with finite element approach. To this scope, in the paper an ideal case study is considered, characterized by steel elements. The modules are assembled by inter-module connections that allow for rapid assembly onsite, without any need of skilled workmanship reducing the welding and the use of bolts. Therefore, Midas Fea NX is used to define the contact between steel elements in detail

INFLUENCE OF BOND-SLIP ON NUMERICAL FRAGILITY CURVES AND STRUCTURAL RELIABILITY OF RC STRUCTURAL INTERNAL BEAM-COLUMN SUB-ASSEMBLY

In this paper results obtained from monotonic nonlinear static analyses performed on Re-inforced Concrete (RC) internal beam-column sub-assembly are shown. Bond-slip phenome-non between steel longitudinal bars and surrounding concrete is also taken into account in order to predict the numerical response under lateral actions of the RC internal beam-column sub-assembly investigated. The study is addressed, through parametric models and Monte Carlo simulations, to pro-pose preliminary fragility curves for different damage states of the RC internal beam-column sub-assembly, including materials inherent uncertainties

Ketogenic diet-induced weight loss is associated with an increase in vitamin d levels in obese adults

Vitamin D is an important micronutrient involved in several processes. Evidence has shown a strong association between hypovitaminosis D and cardio-metabolic diseases, including obesity. A ketogenic diet has proven to be very effective for weight loss, especially in reducing fat mass while preserving fat-free mass. The aim of this study was to investigate the effect of a ketogenic diet-induced weight loss on vitamin D status in a population of obese adults. We enrolled 56 obese outpatients, prescribed with either traditional standard hypocaloric Mediterranean diet (SHMD) or very low-calorie ketogenic diet (VLCKD). Serum 25(OH)D concentrations were measured by chemiluminescence. The mean value of serum 25-hydroxyvitamin D (25(OH)D) concentrations in the whole population at baseline was 17.8 +/- 5.6 ng/mL, without differences between groups. After 12 months of dietetic treatment, in VLCKD patients serum 25(OH)D concentrations increased from 18.4 +/- 5.9 to 29.3 +/- 6.8 ng/mL (p < 0.0001), vs 17.5 +/- 6.1 to 21.3 +/- 7.6 ng/mL (p = 0.067) in the SHMD group (for each kilogram of weight loss, 25(OH)D concentration increased 0.39 and 0.13 ng/mL in the VLCKD and in the SHMD groups, respectively). In the VLCKD group, the increase in serum 25(OH)D concentrations was strongly associated with body mass index, waist circumference, and fatty mass variation. In a multiple regression analysis, fatty mass was the strongest independent predictor of serum 25(OH)D concentration, explaining 15.6%, 3.3%, and 9.4% of its variation in the whole population, in SHMD, and VLCKD groups, respectively. We also observed a greater reduction of inflammation (evaluated by high-sensitivity C reactive protein (hsCRP) values) and a greater improvement in glucose homeostasis, confirmed by a reduction of HOMA values, in the VLCKD versus the SHMD group. Taken together, all these data suggest that a dietetic regimen, which implies a great reduction of fat mass, can improve vitamin D status in the obese

Evaluation of an advanced directionally solidified gamma/gamma'-alpha Mo eutectic alloy

An attempt was made to improve on the properties of the candidate jet engine turbine blade material AG-60, a gamma/gamma prime-alpha Mo eutectic composite. Alloy 38 (AG-170) was evaluated in the greatest detail. This alloy, Ni-5.88 A1-29.74 Mo-1.65 V-1.2C Re (weight percent), represents an improvement beyond AG-60, based on mechanical testing of the transverse and/or longitudinal orientations over a range of temperatures in tension, shear, rupture, and rupture after thermal exposure. It is likely that other alloys in the study represent a similar improvement

A non-linear static approach for the prediction of earthquake-induced deformation of geotechnical systems

This paper illustrates an original and simple method to predict earthquake-induced deformations of geotechnical systems. The method is an extension of static non-linear analysis, and is conceived to predict the behaviour of geotechnical systems, like supported and unsupported excavations, that during the seismic motion accumulate displacements in a single direction. The seismic capacity of the system is described by its capacity curve, obtained either from a numerical push-over analysis or through a simplified procedure. The corresponding seismic demand is described by a combination of the elastic response spectrum, including basic information on the maximum amplitudes of the seismic motion, and a cyclic demand spectrum, that provides additional information about the equivalent number of cycles that contribute to the accumulation of displacements. In the paper, the method is described in detail and is validated through different procedures, namely: comparisons with experimental results obtained in the geotechnical centrifuge; comparison with results of advanced numerical analyses; extensive comparison, using a large database of seismic records, with the results of non-linear time-domain analyses. In its final part, the paper provides guidance for the practical use of the method for design

Editorial: Recent Advances in Seismic Risk Assessment and Its Applications

This special issue discusses recent advances in seismic risk assessment with particular attention to the development and validation of new procedures that are capable of assessing failure modes and the fragility curves of existing buildings. The studies presented have also a probabilistic background, and show the importance of typological characteristics in the seismic response of a building. Furthermore, non-linear numerical analyses have confirmed the importance of implementing specific models in order to design appropriate interventions aimed at reducing the seismic risk of a specific construction

Typological seismic losses assessment by damaged masonry buildings after L’Aquila 2009 and Emilia 2012 earthquakes

In this paper a seismic risk analysis of masonry buildings based on damage data from the 2009 L'Aquila and 2012 Emilia earthquakes. The seismic vulnerability is described by fragility curves from which economic loss curves are derived for each representative typological class of masonry buildings. The information on the buildings was collected by the Italian Civil Protection Department with the AeDES form and available in the Observed Damage Database (D.a.D.O.). The reliability of the database considered, however, was improved by carrying out a process of estimating undamaged buildings from data from the 15th ISTAT census. Finally, for each damage level, according to EMS-98 scale, a procedure to derive the Expected Annual Loss is presented, so as to express its percentage contribution in the seismic risk assessment

Seismic risk analysis on masonry buildings damaged by L’Aquila 2009 and Emilia 2012 earthquakes

Earthquakes in the recent past continue to provide more and more information on the seismic behavior of existing buildings and on the related economic losses. For the reason it is interesting to compare the damage of buildings stocks archived after earthquakes survey activities. In this paper a study of the damage occurred on masonry buildings after L’Aquila 2009 and Emilia 2012 earthquakes is carried out, by considering the data available in the web-gis Da.D.O platform. Firstly, fragility curves are illustrated and compared by considering the vulnerability classes of Da.D.O. (Class A, Class B and Class C1). Then, an approach is proposed in order to evaluate the total Expected Annual Loss (EALtot) and its contributions due to the several damage level (D1, …, D5). The preliminary obtained results show that, with reference to the two masonry buildings stocks considered, the higher contribution to the (EALtot) is given by the damage level D3, that may be considered as the life safety limit state. In the case analyzed, the corresponding EALD3 results almost equal to 1/3 of EALtot