Vpliv požara v načrtovanem jeklenem prizidku na nosilnost obstoječega armiranobetonskega objekta

V magistrski nalogi je predstavljena napredna požarna analiza konstrukcije v primeru, ko pride do izbruha požara v jeklenem prizidku, ki je bil naknadno postavljen k obstoječi armiranobetonski proizvodni hali. Nosilna konstrukcija prizidka je pri tem sidrana neposredno v konstrukcijo obstoječega dela. Prizidek pri tem predstavlja ločen požarni sektor. Zaradi raztezanja jekla pri visokih temperaturah med požarom lahko pride do znatnega povečanja sil na stiku obeh delov objekta. V nalogi predpostavljamo, da lahko te pomembno vplivajo tudi na stabilnost obstoječega AB dela hale, čeprav ostaja ta na hladni strani požara, na kar projektanti v vsakdanji inženirski praksi pogosto pozabljajo. Ker teh sil ne moremo določiti s poenostavljenimi računskimi postopki, ki so na voljo v Evrokodu, izbrano konstrukcijo preverimo z napredno požarno analizo. Jekleni del konstrukcije, ki je požaru izpostavljen neposredno, pri tem obravnavamo z geometrijsko in materialno nelinearno analizo po metodi končnih elementov, pri čemer uporabimo volumske končne elemente. Ker so takšne analize pogosto numerično zahtevne, se naloga sočasno ukvarja tudi z možnimi poenostavitvami modela. Zaključki pokažejo, da je povečanje sil na stiku starega in novega dela objekta med požarom res izrazito. Pri tem se lahko osno-upogibna obremenitev znatno poveča, tudi v sicer hladnem AB delu konstrukcije, in sicer do nivoja, ki je primerljiv s tisto, ki odgovarja stalnim oziroma potresnim projektnim stanjem. Dodatno zaključki pokažejo, da bi bila za analizo poleg zelo natančnega naprednega modela mogoča uporaba tudi precej poenostavljene različice modela, ki bi bila na varni strani. Žal bi ta pomenila kar 30 % višje upogibne obremenitve obstoječega AB dela objekta, kar bi lahko vodilo do cenovno manj ugodnih projektantskih rešitev. The master’s thesis presents advanced fire analysis of the construction in a case of a fire outbreak in a steel extension that was later built next to the existing production hall made of reinforced concrete. Load bearing structure of the extension is directly anchored into the construction of the existing part of the hall. The extension represents a separate fire sector. Due to the expansion of steel in case of high temperatures during a fire, a significant increase of forces on a contact of both parts of the building can occur. In the thesis, we assume that these forces can have a significant impact on the stability of the existing part of the hall made of reinforced concrete, although it is situated on the cool side of the fire. Engineers often forget about this in every day engineering practice. As these forces cannot be defined by simplified calculation procedures available in Eurocode, we verify the chosen structure by an advanced fire analysis. A steel part of the construction that is directly exposed to the fire is dealt with using a geometrical and material non-linear finite element analysis using solid finite elements. Such analyses are often numerically demanding, thus at the same time the thesis deals with the possible simplifications of a model. Conclusions reveal that there is really a distinct increase of forces on the contact of a new and old part of the building during a fire. Therefore the axial-bending load can be significantly increased also in otherwise cold part of the construction made of the reinforced concrete, namely to the level that is comparable with the one corresponding to persistent and seismic design state. Furthermore, conclusions reveal that in addition to the very precise construction model, a much simplified version of the model would be possible which would be on the safe side. Unfortunately, this would mean as much as 30 % higher bending loads of the existing part of the building made of a reinforced concrete, which could lead to less favourably solutions in terms of costs.