INFLUENCE OF EARTHQUAKE RECORDS PROPERTIES ON NONLINEAR STRUCTURAL RESPONSE

Potresno djelovanje predstavlja iznenadno oslobađanje energije koje rezultira potresanjem tla. Gibanja tla bilježe se raznim uređajima te se stvaraju vrlo komplicirani nizovi podataka koji se opisuju velikim brojem karakteristika s ciljem povezivanja s oštetljivosti konstrukcija. Kako su s brojnim klimatskim promjenama potresi postali sve učestaliji tako je i povećan broj potresnih analiza zbog želje za smanjenjem njegovih posljedica. U analizi diplomskog rada istražio se utjecaj deset izdvojenih karakteristika potresnih zapisa na nelinearni odziv konstrukcije te su definirane karakteristike s najvećim utjecajem na oštetljivost konstrukcije. Analiza je obavljena na numeričkom nelinearnom modelu koji je prethodno kalibriran jer se temelji na eksperimentalnom modelu ICONS koji je primjer “postojećih zgrada”, zgrada koje su projektirane bez primjene potresnih propisa prije 40-ak godina i koje prevladavaju u promatranim gradovima, Zagrebu i Dubrovniku, koji su seizmički najosjetljivija područja Hrvatske. Analiza je zahtjevala proces odabira 60 potresnih zapisa na temelju vršnog ubrzanja tla (PGA), magnitude (M) i udaljenosti od epicentra (R) koji su rezultati disagregacije i uniformnog hazard spektra te su u konačnici dinamičkom analizom zapisa potresa u vremenu dobijeni pomaci katova iz kojih su proračunate krivulje usporedbe pojedinih karakteristika i maksimalnih međukatnih pomaka kao mjere oštetljivosti konstrukcije (IDR). Analiza je pokazala kako postoji značajna podudarnost između krivulja promatranih karakteristika potresa i oštetljivosti konstrukcije, te da vršna brzina tla (PGV), specifična gustoća energije (SED) i Housnerov intenzitet (HI) imaju najveći utjecaj na oštetljivost konstrukcija i stoga su navedene karakteristike najpouzdanije za procjenu konstrukcijske oštetljivosti te bi se ubuduće trebale uzimati u obzir pri odabiru potresnih zapisa pri analizama konstrukcijskih oštetljivosti.Seismic activity is a sudden release of energy which is expressed thru ground motions. Ground motions can be recorded by various devices and thus create very complicated series of data that are described by number of characteristics in order to achieve relation with the structure vulnerability. An earthquakes have become more frequent with many climate changes, accordingly the number of seismic analysis is increased with desire of reducing earthquake consequences. The analysis of these master thesis investigated the influence of ten selected seismic record characteristics on nonlinear structure response with result of defined characteristics with greatest influence on structural vulnerability. The analysis was performed on the numerical nonlinear model that was previously calibrated on the ICONS experimental model. This model is an example of “existing buildings”, that were designed without the use of seismic regulations before 40 years ago. This type of buildings prevail in the observed cities of Zagreb and Dubrovnik, which are seismically the most vulnerable parts of Croatia. The analysis required the selection process of 60 seismic records based on peak ground acceleration (PGA), magnitude (M) and distance from the epicenter (R), which are results of the disaggregation and uniform hazard spectrum. Performed dynamic time history analysis of the seismic records resulted in the storeys displacements from which calculated comparison curves of certain characteristics and maximum interstorey drift ratios (IDR) as a structural damage measure) were defined. The analysis showed significant correlation between record properties and damage curves, and accordingly peak ground velocity (PGV), specific energy density (SED) and Housner intensity (HI) have the greatest influence on structural vulnerability and therefore these characteristics are most reliable for structural vulnerability assessments and they should be considered at the selections of seismic records in structural damage analyses