Dynamic Response of a Single-storey Model With Suspended Mass Subject to Seismic Base Excitation

Ovaj završni rad bavi se problemom dinamičkog odgovora jednokatnog okvirnog modela na potresnu pobudu podloge, s time da je na model okvira ovješena masa kao pasivni prigušivač. Cilj istraživanja je ispitati učinkovitost ovješene mase na smanjivanje oscilacija jednokatnog okvira. Na početku je izvedena jednadžba kretanja jednokatnog okvirnog modela s masom koncentriranom na vrhu uslijed dinamičke pobude podloge, a zatim jednadžba kretanja istog okvira na koji je užetom ovješena masa. Odabrane su karakteristike ovješene mase (masa i duljina užeta) te je eksperimentalno ispitan dinamički odgovor okvirnog modela uslijed nekoliko izabranih dinamičkih pobuda. Svi eksperimenti su provedeni na okvirnom modelu, bez i s ovješenom masom, pričvršćenom za potresnu platformu koja simulira harmonijsku funkciju pomaka podloge i odabrane potresne zapise iz povijesti. Ponašanje je praćeno optičkim mjernim sustavom. Usporedbom eksperimentalno dobivenih dinamičkih odgovora okvira bez i s ovješenom masom uočeno je da odabrana ovješena masa najčešće doprinosi smanjenju oscilacija. Kako se pokazalo da pri nekim pobudama ovješena masa može imati negativan efekt, preporuča se precizno odrediti njene parameter i dodati prigušivač.This undergraduate thesis deals with the problem of dynamic response of a single-storey frame model to a seismic base excitation, provided that there is a mass suspended on the frame model as a passive damper. The aim of the research is to examine the effectiveness of suspended mass on reducing the oscillations of a single-storey frame. At the beginning of the thesis, equation of motion for a single-storey frame model with mass concentrated at the top, due to dynamic excitation of the base, is derived. Same procedure is repeated for the frame model with suspended mass. The characteristics of the suspended mass (mass and length of the rope) are chosen and experiments of the frame model due to several selected dynamic simulations are carried out. All the experiments are conducted for a frame model, without and with the suspended mass, attached to a seismic platform that simulates the harmonic function of the base displacement and selected historical seismic records. The dynamic response is monitored using an optical measuring system. Based on the comparison between experimentally obtained dynamic response of the frames without and with added suspended mass, it is noticed that the suspended mass is usually beneficial for reducing the oscillations. However, the negative effect of the suspended mass is observed in case of some excitation functions, so it is advised to precisely determine its characteristics, as well as add a damping element