Projektiranje zidanih stavb na ciljno potresno tveganje

Rihar, Jerica (avtor), Dolšek, Matjaž (mentor)

V magistrski nalogi je prikazan postopek projektiranja zidanih stavb na ciljno potresno tveganje. S predlaganim projektiranjem lahko upoštevamo vpliv potresnega tveganja objekta, česar v primeru projektiranja v skladu s standardom Evrokod 8 (SIST EN 1998, 2005) ni mogoče. V prvem delu naloge predstavimo izhodišča in osnovna določila projektiranja zidanih konstrukcij v skladu s standardoma Evrokod 6 (SIST EN 1996, 2006) in Evrokod 8 (SIST EN 1998, 2005). V nadaljevanju pojasnimo koncept ciljne zanesljivosti konstrukcij pri projektiranju in pomen ocene potresnega tveganja z vidika socialnih in ekonomskih posledic. V sklopu tretjega poglavja opišemo metode s katerimi lahko določimo potresno tveganje zidanih konstrukcij, kjer opazujemo verjetnost, da bodo prekoračena določena mejna stanja poškodovanosti. Tu podrobneje predstavimo tudi metode za analizo obnašanja konstrukcij s poudarkom na poenostavljeni nelinearni metodi na osnovi potisne analize. Matematično modeliranje obravnavanih zidanih konstrukcij izvedemo s poenostavljenimi nelinearnimi modeli pri čemer smo uporabili računalniška programa 3Muri in Tremuri. V nadaljevanju z inkrementalno dinamično analizo prikažemo odnos med intenziteto potresa in pomikom (IDA krivulje) na modelih z eno prostostno stopnjo. S statistično obdelavo intenzitet pospeškov iz IDA krivulj določimo mediano in disperzijo intenzitet potresov, ki povzročijo določena mejna stanja poškodovanosti. Nato narišemo krivulje ranljivosti, ki prikazujejo pogojno verjetnost prekoračitve posameznega mejnega stanja pri določeni intenziteti potresa. Na koncu izračunamo verjetnost porušitve objekta (prekoračitve mejnega stanja DS4) za obdobji enega in petdesetih let. Za izbrano zidano konstrukcijo, ki ima tri etaže in mansardo, je locirana v Ljubljani, ter projektirana glede na veljavne standarde, smo iterativno ponavljali opisan postopek izračuna potresnega tveganja in na ta način projektirali objekt. Pri tem smo za sprejemljivo verjetnost porušitve v petdesetih letih izbrali 1%, na osnovi katere ameriški predpis uvaja karte potresne nevarnosti, ki predstavljajo izhodišče za določitev projektne potresne sile. Največje sprejemljive verjetnosti prekoračitve mejnega stanja porušitve v 50 letih, ki jih predpisujejo drugi standardi, so za obravnavan primer bistveno prestroge, saj ne vključujejo upoštevanja potresnega vpliva. Izbrano zahtevano ciljno potresno tveganje dosežemo šele po peti iteraciji oziroma s peto varianto konstrukcije, kjer smo spreminjali debelino in izbrane mehanske lastnosti zidovja ter število etaž.

• Jezik: Slovenski jezik
• Ključne besede: potresno tveganje, potresna nevarnost, potresnoodporno projektiranje, zidane stavbe, nelinearna potisna (statična) analiza, inkrementalna dinamična analiza, krivulje ranljivosti, verjetnost porušitve, analiza negotovosti
• Vrsta gradiva: Magistrsko delo
• Tipologija: 2.09 - Magistrsko delo
• Organizacija: FGG - Fakulteta za gradbeništvo in geodezijo
• Založnik: [J. Riharl]
• Leto izida: 2016
• PID: 20.500.12556/RUL-85074
• UDK: 624.042.7 (043.3)
• COBISS.SI-ID: 7603553
• Datum objave v RUL: 28.05.2020

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Risk-targeted design of masonry buildings

Izvleček

In this master thesis we present the process of designing masonry buildings for target seismic risk. Using this approach we can explicitly consider the effect of seismic risk, which is not possible in case of designing of a building on the basis of Eurocode 8 (SIST EN 1998, 2005). First we present starting points and basic provisions of designing masonry buildings according to Eurocode 6 (SIST EN 1996, 2006) and Eurocode 8 (SIST EN 1998, 2005). Next we explain the concept of target reliability of constructions in design phase and the importance of seismic risk assessment from the point of view of social and economic consequences. In the third chapter we describe methods for seismic risk assessment of masonry buildings in terms of probability of exceedance of damage limit states. We also present in more detail the methods for seismic response analysis with an emphasis on the pushover-based method. The investigated masonry buildings were modeled by simplified nonlinear models by using software packages 3Muri and Tremuri. In the following we show relation between earthquake intensity and drift (IDA curves) on single degree freedom models (SDOF). With statistical analysis of intensity of the acceleration, which were obtained from IDA curves, we determine the median and dispersion of the earhquake intensities, which cause specific damage limit states. Then we draw fragility curves, which present conditional probability of exceedance of individual damage state at certain earthquake intensity. At the end we calculate the probability of collapse risk (exceedance of damage state DS4) for periods of one and fifty years. For the selected masonry building, which has three floors and a loft, is located in Ljubljana, and designed in accordance to Eurocode 8 (SIST EN 1998, 2005), we have iteratively repeated the above described calculation procedure of seismic risk and we designed the building in this maner. We have chosen 1% for the acceptable colapse probability in fifty years, based on which the USA regulation forms the maps of seismic hazard, which are the basis for determination of design seismic forces.The highest acceptable probabilities of exceeding of ultimate limit state in fifty years, that are regulated by other standards, are for the selected example too strict, since they are not accounted for the effects of earthqukes. We achieve the required target seismic risk after fifth iteration or with fifth building variant, where we were changing wall thickness, selected mechanical properties of masonry and number of storeys.

• Ključne besede: seismic risk, seismic hazard, design for earthquake safety, masonry buildings, nonlinear static pushover analysis, incremental dynamic analysis, fragility curves, probability of failure, uncertainty analysis