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V magistrskem delu obravnavamo potresno odpornost prizidka Inštituta za informacijske znanosti v Mariboru v skladu s standardom Evrokod 8. V prvem delu smo se osredotočili na linearno statično potresno analizo objekta. Želeli smo določiti najbolj optimalen način modeliranja v programu ETABS, ki bi nam pri najkrajšem času modeliranja in izračuna podal sprejemljivo točne rezultate. S tem namenom smo izdelali 15 modelov. Modele smo ločili na inženirsko uporabne ter generične modele, ki zaradi nepravilnosti v praksi niso uporabni, vendar pripomorejo k razumevanju vrednotenja napačnega modeliranja konstrukcije. Rezultati dokazujejo, da se geometrijo modelov do neke mere izplača poenostaviti. V praksi so uporabni tako ploskovni, linijski ali kombinirani modeli. Za kateri model se bomo odločili pa je odvisno predvsem od zasnove konstrukcije in vrste potresne analize. Uporaba togih odsekov za povezovanje vertikalnih elementov z gredami ter povezovanje linijskih in ploskovnih elementov je pomembna za pravilno modeliranje togosti konstrukcije. Ročni vnos mase konstrukcije v masna središča na nivojih etaž zahteva nekoliko več časa za modeliranje, vendar se s tem pospeši sama analiza in omeji prostostne stopnje na trikratnik števila etaž. Glede na primerjavo rezultatov analize modela z ročnim in avtomatskim deljenjem, smo prišli do zaključka, da ročno deljenje ni smotrno, saj zahteva veliko časa, rezultati pa niso bistveno bolj točni. Določili smo tudi optimalno velikost končnih elementov, ki znaša 0,5/0,5 m. V drugem delu magistrske naloge smo na obravnavanem objektu predstavili poenostavljeno nelinearno analizo – N2 metodo. Gre za kombinacijo nelinearne statčine analize modela konstrukcije z več prostostnimi stopnjami (MDOF sistem) in nelinearno spektralno analizo ekvivalentnega modela konstrukcije z eno prostostno stopnjo (SDOF sistem). V modelu za nelinearno potisno analizo smo upoštevali bilinearen odnos med momentom in rotacijo na robovih linijskih elementov. Na osnovi rezultatov potisne analize smo določiti kapaciteto pomika za tri mejna stanja na nivoju konstrukcije, ki jih navaja Evrokod: mejno sanje omejitve poškodb (DL), mejno stanje pomembnih poškodb (SD) in mejno stanje blizu porušitve (NC). V našem primeru bi objekt dosegel mejno stanje blizu porušitve pri pospešku 0,53 g za modalno oziroma 0,67 g za enakomerno porazdelitev sil. Evrokod 8-1 eksplicitno ne podaja mejnega pospeška pri katerem bi bila konstrukcija še sprejemljiva. Smatra se, da je objekt ustrezen, če je projektiran skladno s standardom. Za bolj utemeljeno oceno obnašanja bi morali izhajati iz sprejemljive verjetnosti prekoračitve mejnih stanj, kar presega okvire magistrske naloge. This master thesis deals with the seismic performance assessment of building of Institute of Information science in Maribor. The analyses are performed in compliance with Eurocode 8. First part of the thesis focuses on linear elastic seismic analysis of building with an objective to achieve optimal modeling of the building by using ETABS. Fifteen different models, which were split into two groups, were developed. First group contains models that are accurate and can be used to solve real problems, while the second group contains generic models that are mostly used to enhance our understanding of calculation errors that can be introduced with incorrect models. Results show us that in some cases models can be simplified. Shell, frame and combined models are useful in practical situations. For specific situation we should choose the type of model based on structure type and type of seismic analysis. The use of stiff elements for connection of vertical elements with beams and connection of frame and area elements is important for correct modeling of construction stiffness. Data about mass was also manually entered into the center of mass on storey level. Such an approach is slightly more time consuming, but significantly simplify the analysis and its results. However, it was also found that manual meshing of shell elements is too time consuming and don't have large impact on analysis results. At the end optimal size of finite elements was determined to 0,5/0,5 meters. The second part of the thesis presents simplified non-linear analysis N2 method, which was applied to the investigated building. The N2 method is combination of nonlinear static (pushover) analysis of entire building in combination of inelastic spectra based on an equivalent model with single degree of freedom (SDOF system). In model for non-linear pushover analysis, bilinear relationship between moment and rotation was taken into account at the edges of frame element. On basis of results, given by pushover analysis, limit-state displacements were determined for three states proposed by Eurocode standard: damage limitation state (DL), significant damage state (SD) and near collapse state (NC). The peak ground acceleration causing collapse was estimated to 0,53 g and 0,67g in the case of modal distribution of forces and uniform distribution of forces, respectively. It is assumed that the seismic performance of the building is acceptable since it is designed according to Eurocode 8-1. For more informed decision-making the estimated limit-state peak ground acceelerations should be compared to those values based on tolerable risk, which is beyond objectives of this thesis. |
