Abstract
New modern bridges and older structures exposed to accelerated deterioration need permanent condition monitoring. The major tools used in bridge condition evaluation are based on the results of the experimental modal analysis of bridge structures. This paper focuses on the methodology of Forced Vibration Tests performed by means of mechanical exciters. A comprehensive testing system called MANABRIS, developed at Wroclaw University of Technology, is presented. The system is equipped with a rotational eccentric mass exciter and dedicated software for programming and controlling the tests and for acquiring and processing measurement data. The results of a Forced Vibration Test carried out on a typical railway bridge are compared with the results of a conventional modal test of the structure excited by trains. The precision of the considered testing techniques is evaluated and the range of their effective application is proposed. Santrauka Naujų šiuolaikinių tiltų ir senesnių konstrukcijų, kurias veikia greitesnio nusidėvėjimo procesai, būklę reikia nuolat stebėti. Pagrindinės priemonės, taikomos tilto būklei vertinti, pagrįstos tilto konstrukcijų eksperimentinės modalinės analizės rezultatais. Šiame straipsnyje pagrindinis dėmesys skiriamas priverstinės vibracijos testams (angl. Forced Vibration Tests), atliktiems naudojant mechaninio žadinimo generatorius. Pristatoma išsami bandymo sistema, pavadinta MANABRIS, kuri buvo sukurta Vroclavo technologijos universitete. Sistemoje yra sukamasis ekscentriškas masės sužadintuvas ir programinė įranga, skirta testams programuoti ir kontroliuoti, norint gauti ir apdoroti matavimų duomenis. Priverstinės vibracijos testo (angl. Forced Vibration Test), atlikto su įprastu geležinkelio tiltu, rezultatai lyginami su tradicinio modalinio testo rezultatais, gautais konstrukcijas veikiant traukiniais. Vertinamas testo tikslumas ir siūlomi jo efektyvaus pritaikymo būdai.
Highlights
The transport network of each developed country belongs to the busiest and most heavily exploited systems
− Excitation with exciters can be repeated at the same parameters many times, whereby a large structure can be tested using a small set of sensors
− In comparison with wind excitation, the use of an exciter is more independent of the weather and the strength of the wind
Summary
The transport network of each developed country belongs to the busiest and most heavily exploited systems. Bień et al 2006; Ewins 2000; Skoczyński et al 2006, 2009; Zwolski 2007) Through such an experimental modal analysis one can determine the natural vibration frequencies, the corresponding mode shapes and the damping characteristics of bridges. The exciter was tested in a laboratory in order to determine its parameters (the range of excitation frequency, the excitation force amplitude vs frequency, the stability of the excitation force and frequency, etc.) and in field tests of over 10 bridge structures (Zwolski 2007) On this basis, software and hardware tools for dynamic bridge testing by means of mechanical exciters were developed and improved. The tuned harmonic signal is used in sweep tests where the excitation frequency is continuously changed in a single test
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