Viscoelastic Model for the Rigid Body Vibrations of a Viaduct Depending on the Support Devices’ Rheological Model

Rezumat"/jats:title" "jats:p" Lucrarea abordează comportarea unui model de solid-rigid cu anumite simetrii structurale. Aceste simetrii permit simplificarea calculelor (ecuaţii de mişcare) şi, deci, a modelelor matematice. Dacă solidul rigid este conectat la structură prin patru legături elastice, modelul rămâne încă simplu şi uşor de rezolvat, vibraţiile putând fi decuplate în patru subsisteme de mişcare. "/jats:p" "jats:p"În final, se prezintă un studiu de caz pentru analiza modală a unui viaduct, modelat precum un corp solid-rigid, rezemat elastic, de pe autostrada Transilvania (km 29+602.75 m). Document type: Articl

Parametric correlations between experimental results and the base isolation, in situ, structural ones

The paper addresses the topic of the inconsistency between experimental, laboratory results for antiseismic devices and the dynamic stiffness, internal damping and dissipation parameters through additional devices. The necessary corrections of the stiffness and dissipation (damping) parameters will be presented when the antiseismic devices are equipped to satisfy the adequate functions in a complex structural system (buildings, viaducts, bridges) under the conditions of seismic motions characteristic to the Romanian territory. In this context, the kinematic excitation method, compared to the dynamic evaluation method of the vibration dissipation capacity, produced by a seismic shock is shown

Concepts and Models Regarding the Behavior of Antiseismic Devices for the Base Isolation System

The paper presents the main antiseismic devices, as component elements of the base isolation systems, in such a manner that the functional and constructive parameters are correlated with the inertial and stiffness characteristics of the dynamic isolated building. Also, each device will be characterized through a rheological model, which conditions the eigenvalues and eigenvectors spectrum, as well as the dynamic response to an exterior excitation of a seismic nature. In this context, antiseismic devices defined and characterized by the European Standard EN 15129 will be presented. Based on the requirements formulated in the norm, the devices can be identified and their laws of evolution established and checked as follows: antiseismic devices with permanent rigid connection; antiseismic devices with rigid connections with respect to the instantaneous displacement and antiseismic devices dependent on the velocity and on the velocity variation in time

Experimental Correlations with Calculus Parameters for a Dynamic System Equipped with Antiseismic Elastomeric Devices

The paper presents the result of experimental tests done at kinematic cycles with instantaneous harmonic displacements, for elastomeric elements with dynamic isolation role, in accordance with SR EN 1337-3 and SR EN 15129. The values of the internal damping determined on testing stands under the conditions specified in the reference documents, must be correlated with the values of the antiseismic elastomeric device system which equips a dynamic system subjected to exterior seismic actions

Dynamic Behavior of the Inertial Platform Related to the Research Facility Building Laser and Gamma at ELI-NP Bucharest

This paper aims to study the vibration of the large inertial platform from the Laser + Gamma building that is part of the ELI-NP project. In order to ensure a precisely positioned radiation beam, it is necessary that the shocks and vibrations coming from the external environment are damped or absorbed until they reach the work installations. This is ensured by the platform on which the devices are positioned, a platform that is supported on spring batteries and shock absorbers. A rigid body model is developed in this regard and a comparison with the finite element model of the concrete platform is conducted. It has been found that low vibration modes can be obtained with the help of the rigid model, which also has the advantage of simplicity and very little time is required to obtain results

Hysteretic Loops in Correlation with the Maximum Dissipated Energy, for Linear Dynamic Systems

This paper presents the outcomes of the theoretical and experimental research carried out on a real model at natural scale using Voigt–Kelvin linear viscoelastic type m, c, and k models excited by a harmonic force F(t) = F0 sinωt, where F0 is the amplitude of the harmonic force and ω is the excitation angular frequency. The linear viscous-elastic rheological system (m, c, k) is characterized by the fact that the c linear viscous damping—and, consequently, the fraction of the critical damping ζ—may be changed so that the dissipated energy can reach maximum W d max values. The optimization condition between the W d max maximum dissipated energy and the amortization ζ 0 = ± ( 1 − Ω 2 ) / 2 Ω modifies the structure of the relation F = F(x), which describes the elliptical hysteresis loop F–x in the sense that it has its large axis making an angle less than 90° with respect to the x-axis in Ω < 1 ante-resonance, and an angle greater than 90° in post-resonance for Ω > 1 . The elliptical Q–x hysteretic loops are tilted with their large axis only at angles below 90°. It can be noticed that the equality between the arias of the hysteretic loop, in the two representations systems Q–x and F–x, is verified, both being equal with the maximum dissipated energy W d max

Numerical Monitoring of the Dynamic Behavior in Frequency of the Parametric Systems in Forced Vibration Regime

The aim of the paper is to present a consistent monitoring method which can be used on construction sites for a rapid assessment of the work quality. The starting point is represented by the evolution processes with forced vibrations considering a system with one degree of freedom and the rheological model of Voigt-Kelvin whose elastic and viscous values can change during the technological process, in real time. Response functions are analyzed at the passing of the dynamic system from one state to another and the resulted families of curves are plotted

Viscoelastic Model for the Rigid Body Vibrations of a Viaduct Depending on the Support Devices’ Rheological Model

Lucrarea abordează comportarea unui model de solid-rigid cu anumite simetrii structurale. Aceste simetrii permit simplificarea calculelor (ecuaţii de mişcare) şi, deci, a modelelor matematice. Dacă solidul rigid este conectat la structură prin patru legături elastice, modelul rămâne încă simplu şi uşor de rezolvat, vibraţiile putând fi decuplate în patru subsisteme de mişcare

Dynamic Response of Zener-Modelled Linearly Viscoelastic Systems under Harmonic Excitation

A comprehensive investigation, including analytical modelling, numerical analysis and experimental tests, has been carried out on many linear viscoelastic systems and structures. This approach is the result of research conducted by two research institutes, ICECON and INCERC Bucharest, from Romania. Thus, analyses were performed on the dynamic behaviour of composite viscoelastic materials, anti-vibration viscoelastic systems made of discrete physical devices, road structures consisting of layers of natural soil with mineral aggregates and asphalt mixtures, and mixed mechanic insulation systems for industrial vibrations formed of elastic and viscous devices. The objectives pursued were as follows: (a) providing a mass dosage of the mixture of earth (clay, sand, mineral aggregates, water, and stabilizer) in five variants; (b) carrying out a test run with a Bomag vibratory roller with variable vibration parameters; (c) Experimental evaluation of the vibration parameters and the force transmitted to the ground, correlated with the determination of the compaction layer; (d) use of methods of analysis for physic-mechanical and geotechnical parameters; (e) rheological and numerical modeling based on Zener schematics, so the consistency and veracity of the experimental data with the numerical simulation can be determined. Finally, a study is presented for a test track, where experimental and correlated input and response data are determined to validate the rheological model with a high loading rate