93 research outputs found

    On the Fresh/Hardened Properties of Cement Composites Incorporating Rubber Particles from Recycled Tires

    Get PDF
    This study investigates the ameliorative effects on some properties of cement-based materials which can be obtained by incorporating rubber particles as part of the fine aggregates. The aim is to find out optimal cement composite/mortar mixtures, containing recycled-tyre rubber particles, suitable for specific engineering applications. Different percentages of rubber particles, from 0% to 75%, were used and, for each percentage, the suitable amount of sand was investigated in order to achieve the best fresh/hardened performances. In particular the following characteristics were examined: density, compressive strength, modulus of elasticity, shrinkage, weight loss, flexural behaviour, thermal conductivity, rapid freezing and thawing durability, and chloride permeability. The experimental results were compared with the ones of cement composite specimens without rubber aggregates. Test results show that the proposed rubberized mortar mixes are particularly suitable for some industrial and architectural applications, such as under-rail bearings, road constructions, paving slabs, false facades, and stone backing

    Nonstationary First Threshold Crossing Reliability for Linear System Excited by Modulated Gaussian Process

    Get PDF
    A widely used approach for the first crossing reliability evaluation of structures subject to nonstationary Gaussian random input is represented by the direct extension to the nonstationary case of the solution based on the qualified envelope, originally proposed for stationary cases. The most convenient way to approach this evaluation relies on working in the time domain, where a common assumption used is to adopt the modulation of stationary envelope process instead of the envelope of modulated stationary one, by utilizing the so-called "preenvelope" process. The described assumption is demonstrated in this work, also showing that such assumption can induce some errors in the envelope mean crossing rate

    Evolutionary Modeling to Evaluate the Shear Behavior of Circular Reinforced Concrete Columns

    Get PDF
    Despite their frequent occurrence in practice, only limited studies on the shear behavior of reinforced concrete (RC) circular members are available in the literature. Such studies are based on poor assumptions about the physical model, often resulting in being too conservative, as well as technical codes that essentially propose empirical conversion rules. On this topic in this paper, an evolutionary approach named EPR is used to create a structured polynomial model for predicting the shear strength of circular sections. The adopted technique is an evolutionary data mining methodology that generates a transparent and structured representation of the behavior of a system directly from experimental data. In this study experimental data of 61 RC circular columns, as reported in the technical literature, are used to develop the EPR models. As final result, physically consistent shear strength models for circular columns are obtained, to be used in different design situations. The proposed formulations are compared with models available from building codes and literature expressions, showing that EPR technique is capable of capturing and predicting the shear behavior of RC circular elements with very high accuracy. A parametric study is also carried out to evaluate the physical consistency of the proposed models

    Dnevna slika migriranja kratkorepog raka, Maja crispata, Risso 1827 (Brachyura, Majidae)

    Get PDF
    Occurrence, distribution, and assemblage of crustaceans in the southern Adriatic Sea were determined from data collected during five seasonal (summer) trawl surveys carried out during 1996-2000. Trawls were conducted at a bathymetric range of 10-800 m, by the same vessel and same sampling gear in the framework of the E.U. Project, MEDITS. Fifty-two benthic-epibenthic, and nektonic species (three stomatopods, 49 decapods) were caught. Species density data (individuals per km2) were processed according to multivariate techniques to describe the composition and distribution of main pecies assemblages. The assemblages were consistent throughout the surveyed area with some differences between the western and eastern zones, mostly those found on shelf bottoms. The influence of oceanographic features, other than depth, is discussed.U sjevernom Jadranu su promatrana dnevna pomicanja populacije brahiurnog raka, Maja crispata. Odnos spolova, mužjaka prema ženkama, iznosio je 3:2. Mužjaci su imali maksimalnu dužinu oklopa 91 mm, a ženke 74 mm. Maja crispata češće se nalazila na šljunkovitom dnu nego na bilo kojem drugom habitatu. Sedmero promatranih primjeraka nije se pomicalo prema nekom određenom području, nego se zadržavalo većim dijelom na tvrdom supstratu, između 0,8 i 3,5 m dubine. Maksimalna udaljenost od početnog položaja postignuta je u 9 dana, a iznosila je 16 metara

    Optimal Design of Elastic Circular Plane Arches

    Get PDF
    Arches represent a structural system adopted in construction practice for thousand years, and they are still widely adopted if large spans have to be covered. The structural efficiency of arches principally depends on the minimization of the eccentricity of the pressure curve, which allow us to reduce their structural weight. Despite the millenarian use and a very abundant literature, there is still scope for design optimization of arches. This study is framed within this context and is focused on plane circular arches under uniformly distributed vertical load and self-weight. The arches are elastically clamped at both end sections. A semianalytical approach is developed to minimize the volume, with the aim of determining the fundamental mechanical parameters governing the optimal design. Finally, the results are charted to allow their use in a design process

    Classification-Based Screening of Parkinson’s Disease Patients through Graph and Handwriting Signals

    Get PDF
    Parkinson’s disease (PD) is one of the most common neurodegenerative diseases, affecting millions of people worldwide, especially among the elderly population. It has been demonstrated that handwriting impairment can be an important early marker for the detection of this disease. The aim of this study was to propose a simple and quick way to discriminate PD patients from controls through handwriting tasks using machine-learning techniques. We developed a telemonitoring system based on a user-friendly application for drawing tablets that enabled us to collect real-time information about position, pressure, and inclination of the digital pen during the experiment and, simultaneously, to supply visual feedback on the screen to the subject. We developed a protocol that includes drawing and writing tasks, including tasks in the Italian language, and we collected data from 22 healthy subjects and 9 PD patients. Using the collected signals and data from a preexisting database, we developed a machine-learning model to automatically discriminate PD patients from healthy control subjects with an accuracy of 77.5%
    • …