Vibration analysis of pedestrian bridge over the river Drava in Osijek

Viseći most može svladati velike raspone uz minimalan utrošak materijala i pogodni su za estetsko oblikovanje. Kolnička konstrukcija obješena je preko vješaljki na glavnu nosivu užad, koja je razapeta između pilona usidrenih na krajevima mosta. Ukrućena je zateznim kabelima radi smanjenja deformacija i sprječavanja vibracija. Ujedno i simbol grada, Pješački most vrlo je važan za stanovnike grada i okolice, stoga je načinjen numerički model na temelju dostupne dokumentacije u svrhu ocjenjivanja njegovog ponašanja. Promatrane su dominantne frekvencije i periodi. Vibracije su važne jer ih korisnici najviše osjete prilikom uporabe mosta. Ukoliko vibracije stvaraju pretjeranu nelagodu i strah kod korisnika, te ih to sprječava u prelaženju, most ne ispunjava svoju funkciju i GSU je prekoračeno. Područje frekvencija oko 2 Hz je najnepogodnije jer se vlastita frekvencija mosta i pješaka nalaze u tom području. Problem se rješava dodatnim ukrućenjem mosta, povećanjem prigušenja mosta i postavljanjem prigušivača vibracija. Numerički model napravljen je u programskom paketu SAP2000. Nakon analize rezultati su se usporedili s rezultatima prethodnog istraživanja iz 2006. i 2019. godine, te na kraju u obzir su uzete pukotine u betonu prema američkim i europskim normama. Konstrukcija je izvan zone opasnih frekvencija.The suspension bridge can handle large spans with minimal material consumption and is suitable for aesthetic design. The pavement structure is hung over hangers on the main supporting ropes, which is crucified between the pylons anchored at the ends of the bridge. It is stiffened with tension cables to reduce deformation and prevent vibration. At the same time a symbol of the city, the Pedestrian Bridge is very important for the inhabitants of the city and its surroundings, so a numerical model was made based on the available documentation for the purpose of assessing its behaviour. Dominant vibrations and periods were observed. Vibrations are important because users feel them most when using a bridge. If the vibrations create excessive discomfort and fear in the user, and this prevents them from crossing, the bridge does not fulfil its function and the GSU is exceeded. The frequency range around 2 Hz is the most inconvenient because the natural frequency of the bridge and pedestrians are located in that area. The problem is solved by additional stiffening of the bridge, increasing the damping of the bridge and installing vibration dampers. The numerical model was made in the SAP2000 software package. After the analysis, the results were compared with the results of the previous research from 2006 and 2019, and finally the cracks in the concrete were taken into account according to American and European standards. The construction is outside the dangerous frequency zone