Projektiranje armiranobetonskega mostu za vpliv potresne obtežbe in ocena potresnega tveganja

Possnig, Luka (author), Isaković, Tatjana (mentor), Dolšek, Matjaž (comentor)

Premostitvene konstrukcije nam omogočajo premoščanje naravnih in umetnih ovir ter so ključnega pomena za povezovanje in združevanje ljudi. Zaradi njihove pomembnosti je te konstrukcije potrebno projektirati in zgraditi tako, da tudi v primeru ekstremnih naravnih vplivov (npr. močan potres) ohranijo svoj namen in tako še vedno omogočajo komunikacijo s prizadetimi območji. Ker so močni potresi razmeroma redek dogodek, konstrukcijam zaradi neekonomičnosti v postopku projektiranja ne zagotovimo elastičnega odziva. Konstrukciji običajno zagotovimo nekoliko manjšo nosilnost in s tem dovolimo, da se v konstrukciji v določenih izbranih delih pojavijo poškodbe, ki jih lahko po močnem potresu popravimo. Sposobnost konstrukcije, da prenese poškodbe (plastične deformacije) imenujemo duktilnost konstrukcije. Plastične deformacije pri premostitvenih konstrukcijah običajno dopuščamo le v stebrih, in sicer na mestu stika s temeljem in/ali na mestu stika s prekladno konstrukcijo. V magistrski nalogi je prikazan postopek projektiranja tipičnega krajšega armiranobetonskega mostu v skladu s standardom Evrokod 8/2, ki vsebuje takšen pristop k projektiranju konstrukcij. Kljub temu, da je odziv mostov pri močnih potresih izrazito nelinearen, postopki projektiranja v splošnem še vedno temeljijo na rezultatih linearno-elastične analize. Potresni odziv konstrukcije smo s tem razlogom ocenili tudi s pomočjo poenostavljene nelinearne analize, ki temelji na potisni analizi, ki je bila določena z metodo N2. Metoda vsebuje nelinearno statično analizo modela konstrukcije z več prostostnimi stopnjami (MDOF sistem) in nelinearno dinamično analizo ekvivalentnega modela konstrukcije z eno prostostno stopnjo (SDOF sistem). Ker standard ne predvideva eksplicitne kontrole potresnega tveganja, varnost konstrukcije preverjamo s primerjavo vnaprej določenega ciljnega potresnega tveganja z izračunanim potresnim tveganjem. V sklopu magistrske naloge smo varnost konstrukcije preverili s pomočjo zahtevnejše inkrementalne dinamične analize IDA in nedavno predlagane metode 3R, ki nam pove ali je ciljno tveganje porušitve konstrukcije preseženo.

• Language: Slovenian
• Keywords: premostitvena konstrukcija, projektiranje, armiran beton, nelinearna statična in dinamična analiza, potisna analiza, potresno tveganje, potresna nevarnost, metoda 3R, inkrementalna dinamična analiza
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FGG - Faculty of Civil and Geodetic Engineering
• Year: 2016
• PID: 20.500.12556/RUL-82790
• COBISS.SI-ID: 7472993
• Publication date in RUL: 25.05.2016

Secondary language

• Language: English
• Title: Seismic design of reinforced concrete bridge and estimation of the seismic risk

Abstract

Bridge structures enable us to span natural and artificial barriers and are the key meaning for connecting and the agglomeration of people. Because of their importance it is necessary to design and build them in a way that they even in a case of extreme natural events (e.g. a strong earthquake) keep their purpose and allow communication with affected areas. Because strong earthquakes are a comperatively rare event, we do not assure structures within the process of designing to have an elastic response, because of the uneconomical aspect. Usually we assure structures a bit smaller load capacity and with that we allow damage within chosen elements of the structure that can be renovated after a strong earthquake. Ability of the structure to withstand damage (plastic deformation) is called structure ductility. When designing bridge structures we usually allow plastic deformation in columns at the connection with the foundation and/or at the connection with the slab. In this master's thesis we show a procedure of designing a typical short reinforced concrete bridge in accordance with the standard Eurocode 8/2 that contains such approach for designing structures. Even though that bridge response in case of strong earthquakes is explicitly nonlinear, design procedures generally still base on results of a linear-elastic analysis. Because of this, we also evaluated the seismic response of the structure with help of the simplified nonlinear analysis, which is based on a pushover analysis that was proposed with the N2 method. This method contains the nonlinear static analysis of the structure model with multiple degrees of freedom (MDOF system) and the nonlinear dynamic analysis of the equivalent structure model with a single degree of freedom (SDOF system). Because the standard does not foresee the explicit control of the seizmic risk, we have to evaluate the safety of the structure with comparison of in advance chosen target collapse risk with the calculated collapse risk. In this master's thesis the safety of the structure was evaluated with a more demanding incremental dynamic analysis IDA and recently proposed 3R method, that tells us if the structure target collapse risk is exceeded.

• Keywords: bridge structure, design, reinforced concrete, nonlinear static and dynamic analysis, pushover analysis, seismic risk, seismic hazard, 3R method, incremental dynamic analysis