Human-induced vibrations of cross-laminated timber floors

This paper discusses vibration serviceability assessment of cross-laminated timber (CLT) floors induced by human activities, with special emphasis on vibrations induced by walking. In the first part current design criteria for vibration serviceability check of timber and CLT floors were analyzed in line with the more general vibration performance-based approach applicable to any floor structure regardless of the material used. The second part focuses on the ongoing research achievements in the design of vibration resistant CLT floors carried out at the Faculty of Civil Engineering, University of Belgrade. In addition, challenges for future research were formulated as well

Free vibration analysis of multiple cracked frames using dynamic stiffness method

Cracks are the most common type of structural damage in many engineering structures, introducing the local change in stiffness of structural elements and changing the dynamic properties of the structure. Therefore, it is of great importance to detect and locate the existing structural damage in its early phase to prevent crack propagation. In the paper, free vibration analysis of beams and frames with multiple cracks has been carried out. First, the dynamic stiffness matrix of beam element with multiple cracks based on Bernoulli-Euler theory has been derived. Using the developed model, extensive free vibration study of multiple-cracked frame structures has been conducted. Original Matlab code has been developed for the derivation of natural frequencies and plot of mode shapes. After the validation of the model against the existing data from the literature, several benchmark examples are provided. As expected, increasing size and number of cracks lead to decrease of natural frequencies due to the local stiffness degradation

Primena metode dinamičke krutosti u analizi slobodnih vibracija otvorenih kružnih cilindričnih ljuski

In this paper, the dynamic stiffness method has been applied in the free vibration analysis of open circular cylindrical shells having special boundary conditions. Dynamic stiffness matrix, based on the exact solutions of the free vibration problem according to the Flügge thin shell theory, is formulated and im-plemented in Matlab code to compute natural frequencies and mode shapes. The results of numerical examples for an open cylindrical shell with stepwise thickness variation, as well as for barrel roof, are pre-sented and compared to the results obtained by using the commercial finite element program Abaqus

Assessment of trafic-induced vibrations on humans and buildings according to BS and DIN standard

Traffic-induced vibrations has become great problem in the big cities. Although they can not cause damages of buildings they could have annoying effects on the citizens. In the goal of sustainable development of the cities, this phenomena has been experimentally and numerically investigated all around the world in the last years. The results are standards that defined threshold for building vibrations and some numerical and empirical models for prediction of vibrations. Such standard has not been adopted in Serbia, yet. In this work the assessment of traffic-induced vibrations for 24 buildings in Belgrade using BS and DIN standards were carried out and some conclusions are presented.Vibracije izazvane saobraćajem postaju sve veći problem u razvijenim gradovima. Iako ne mogu izazvati oštećenja zgrada te vibracije deluju veoma nepovoljno na ljude u njima. U cilju održivog razvoja gradova, veliki broj istraživanja u svetu bio je posvećen ispitivanju i numeričkom modeliranju tog fenomena poslednjih godina. Doneti su standardi koji definišu dozvoljeni nivo vibracija u zgradama i razvijeni su brojni numerički i empirijski modeli za predviđanje istih. U Srbiji ne postoje standardi za ocenu dejstva vibracija. U ovom radu je izvršena procena vibracija koje su izmerene na 24 objekta u Beogradu primenom BS i DIN standarda i izvedeni su određeni zaključci

Dynamic stiffness method in the vibration analysis of circular cylindrical shell

In this paper the dynamic stiffness method is used for free vibration analysis of a circular cylindrical shell. The dynamic stiffness matrix is formulated on the base of the exact solution for free vibration of a circular cylindrical shell according to the Flügge thin shell theory. The matrix is frequency dependent and, besides the stiffness, includes inertia and damping effects. The derived dynamic stiffness matrix is implemented in the code developed in a Matlab program for computing natural frequencies and mode shapes of a circular cylindrical shell. Several numerical examples are carried out. The obtained results are validated against the results obtained by using the commercial finite element program Abaqus as well as the available analytical solutions from the literature.U ovom radu korišćena je metoda dinamičke krutosti za analizu slobodnih vibracija kružne cilindrične ljuske. Dinamička matrica krutosti formulisana je na osnovu tačnog rešenja sistema diferencijalnih jednačina problema slobodnih vibracija po Flügge-ovoj teoriji ljuski. To je frekventno zavisna matrica koja u sebi, pored krutosti, sadrži uticaj inercije i prigušenja. Izvedena dinamička matica krutosti implementirana je u za tu svrhu napisani Matlab program za određivanje sopstvenih frekvencija i oblika oscilovanja kružne cilindrične ljuske. Urađen je niz primera. Rezultati dobijeni primenom dinamičke matrice krutosti upoređeni su s rezultatima dobijenim pomoću komercijalnog programa zasnovanog na metodi konačnih elemenata Abaqus, kao i sa dostupnim analitičkim rezultatima iz literature

Динамичка анализа система тло-конструкција применом спектралних елемената.

3D numerical model for dynamic response analysis of multi-storey frame structures including soil-structure interaction has been developed using the Spectral Element Method (SEM). The structure was modeled using the SEM, while the dynamic stiffness matrix of the soil – foundation interface was determined using the Integral Transform Method (ITM). The structure consists of one – dimensional elements: beams and columns, and two – dimensional elements: plates. The soil consists of horizontal layers over the bedrock or half space. The Projection method was used to develop the dynamic stiffness matrices for the transverse and in-plane vibration of plates with arbitrary boundary conditions. The method for coupling one-dimensional and twodimensional spectral elements was developed, as well as the coupling of the spectral elements with the soil spring – dashpot elements. Using the proposed numerical model 3D frame structures founded on soil of variable stiffness and subjected to ground vibrations induced by traffic were analyzed.У овом раду приказан је 3Д нумерички модел за динамичку анализу вишеспратних рамовских конструкција узимајући у обзир садејство између тла и конструкције. За моделирање конструкције коришћен je Метод спектралних елемената, док је динамичка матрица крутости тла одређена применом Методе интегралних трансформација. Конструкција се састоји од једнодимензионалних елемената: греда и стубова, и дводимензионалних елемената: плоча. Тло се састоји од хоризонталних слојева изнад круте базе или полупростора. Матрице крутости плоча напрегнутих на савијање и у својој равни одређене су применом Методе пројекције. Развијен је поступак спрезања једнодимензионалних и дводимензионалних спектралних елемената, као и спрезање тако формираног модела са тлом. Примена формираног 3Д модела приказана је на анализи 3Д рамовских конструкција фундираних на тлу различите крутости, изложених дејству вибрација изазваних саобраћајним оптерећењем

Vibracije usled saobraćaja - merenje, procena i predviđanje

Procedures for measurement, assessment and prediction of traffic induced vibrations in buildings, according to the existing British and German standards, are presented in this paper. Analysis of effects of traffic induced vibrations on buildings and building residents, as well as vibration prediction is carried out on 24 buildings in Boulevard of King Alexander in Belgrade. .U ovom radu dat je pregled postupaka za merenje, procenu i predviđanje vibracija izazvanih dejstvom saobraćaja, definisanih postojećim britanskim i nemačkim propisima. Procena i predviđanje dejstva vibracija od saobraćaja na objekte i ljude prikazan je na primeru vibracija od saobraćaja na 24 objekta u Bulevaru kralja Aleksandra u Beogradu.

Free vibration analysis of curved Bernoulli-Euler beam using isogeometric approach

Isogeometric analysis (IGA) is based on a concept that uses the same base functions for representing both the model geometry and the solution space. The most common base functions used in the IGA are NURBS (Non-Uniform Rational B-Splines) functions for their capability to analytically represent various geometries. In this paper, the IGA is applied in the free vibration analysis of rotation-free plane curved Bernoulli-Euler beam. The stiffness and mass matrices have been developed using basic concepts of continuum mechanics and the principle of virtual work. Geometry of the undeformed and deformed beam is defined using convective coordinates and cross section basis vectors. Results of the free vibration analysis for beam with arbitrary curvature are compared with the results obtained from the conventional finite element method (FEM) software. The significant advantages of the IGA approach over the FEM are shown and discussed