Projektiranje armiranobetonskih stavb na potresno obtežbo po kriteriju sil z upoštevanjem ciljne zanesljivosti : doktorska disertacija

Žižmond, Jure (author), Dolšek, Matjaž (mentor)

V doktorski disertaciji smo predlagali iterativni postopek in zaključen izraz za izračun projektnega pospeška tal na osnovi ciljne zanesljivosti. Ta način omogoča vpogled v odnos med ciljno zanesljivostjo, povratno dobo projektnega potresa, nosilnostjo in deformacijsko kapaciteto objekta. Projektni pospešek tal na osnovi ciljne zanesljivosti smo uporabili kot osnovo za izpeljavo faktorja obnašanja. Z novo definicijo faktorja obnašanja smo razložili t.i. »empirično komponento« faktorja obnašanja, saj smo na osnovi ciljne zanesljivosti pojasnili, da mora biti faktor obnašanja za običajne objekte precej manjši od produkta redukcijskega faktorja dodatne nosilnosti in duktilnosti. Nova definicija faktorja obnašanja zato omogoča bolj racionalno odločitev glede prave vrednosti faktorja obnašanja in izračun faktorja obnašanja za poljubno izbrano potresno tveganje, kar smo demonstrirali na primeru večetažne armiranobetonske okvirne stavbe s privzeto srednjo stopnjo duktilnosti. Za obravnavan primer smo pokazali, da faktor obnašanja, ki ga predpisuje Evrokod 8, približno ustreza ciljni verjetnosti porušitve 5∙10-5. V drugem delu disertacije smo preučevali vpliv projektnih dejavnikov po standardu Evrokod 8 na potresne parametre konstrukcije. Za obravnavane konstrukcije se je izkazalo, da imajo projektni dejavniki, ki navadno zahtevajo precej dela projektanta, relativno majhen vpliv na potresne parametre konstrukcij. Po drugi strani pa imajo projektni dejavniki, ki zahtevajo relativno malo dela (npr. upoštevanje projektnih vrednosti materialnih karakteristik), razmeroma velik vpliv na potresne parametre konstrukcij, kar bi lahko bil eden izmed vzrokov za modernizacijo postopkov potresnoodpornega projektiranja stavb. V disertaciji smo preučevali tudi možne pristope za izračun projektnih prečnih sil na osnovi ciljne zanesljivosti in nelinearne dinamične analize. Ugotovili smo, da moramo strižno porušitev praktično preprečiti, če želimo, da morebitne strižne porušitve stebrov nimajo vpliva na verjetnost porušitve. Na ta način smo potrdili načelo metode načrtovanja nosilnosti, čeprav se je izkazalo, da je projektna prečna sila, ki je določena v skladu s standardom Evrokod 8, včasih podcenjena. Strižna porušitev je bila tudi v teh primerih preprečena, vendar le zaradi upoštevanja kriterija o minimalnem deležu armiranja. Zato smo predlagali alternativni postopek za določitev projektnih prečnih sil na osnovi inkrementne dinamične analize, ki se izvede za skrbno izbrane akcelerograme.

• Language: Slovenian
• Keywords: grajeno okolje, gradbeništvo, disertacije, potresnoodporno projektiranje, projektni pospešek tal, potresno tveganje, potresna nevarnost, Evrokod 8, potisna analiza, nelinearna dinamična analiza, verjetnostna analiza potresnih zahtev, faktor obnašanja q, metoda načrtovanja nosilnosti, projektna prečna sila
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FGG - Faculty of Civil and Geodetic Engineering
• Place of publishing: Ljubljana
• Publisher: [J. Žižmond]
• Year: 2016
• Number of pages: XXVIII, 144 str., [18] str. pril.
• PID: 20.500.12556/RUL-86792
• UDC: 624.042.7(043)
• COBISS.SI-ID: 7724385
• Publication date in RUL: 07.11.2016

ŽIŽMOND, Jure, 2016, Projektiranje armiranobetonskih stavb na potresno obtežbo po kriteriju sil z upoštevanjem ciljne zanesljivosti : doktorska disertacija [online]. Doctoral dissertation. Ljubljana : J. Žižmond. [Accessed 4 April 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=86792

Secondary language

• Language: English
• Title: Force-based seismic design of reinforced concrete buildings for target reliability : doctoral thesis

Abstract

A new methodology for the calculation of the risk-targeted design peak ground acceleration has been proposed. The closed-form solution of this methodology provides a useful insight into the relationships between seismic risk, the return period of the design earthquake, the strength and deformation capacity of the building. It can thus provide a basis for the derivation of risk-targeted behaviour factor, which can be used to explain the so-called empirical component of the conventional behaviour factor. The first part of the dissertation clearly shows that, in order to achieve adequate collapse safety of new buildings, the value of the behaviour factor should be much smaller than the product of overstrength and ductility reduction factor. This new definition of the behaviour factor thus allows for more rational decisions about what the adequate values of the behaviour factor are, and better estimations of the behaviour factor for a selected collapse risk. This was demonstrated for the case of a reinforced concrete frame building with prescribed ductility class medium. It is demonstrated for the building in question that the behaviour factor pursuant to Eurocode 8 nearly corresponds to a target collapse risk of 5∙10-5. The second part of dissertation explores the impact of design factors on the seismic response of structures. It was shown for the analysed structures that those design factors, which are usually derived upon extensive consideration by the designer, often only have a small impact on the seismic performance of a structure. On the other hand, the application of simple design factors (e.g. design values of the material characteristics) can significantly improve the calculated seismic response of a structure, even though some designers are not even aware of these design factors. This suggests that standards dealing with earthquake-resistant design of buildings could perhaps be modernized. In the last part of the dissertation, some possible approaches to the calculation of design shear forces were examined based on target reliability and nonlinear dynamic analysis. It was found that the shear failure of columns has to be prevented in order to ensure that the impact of this type of failure is neglectable in the context of collapse risk. This confirms the adequacy of the capacity design approach. However, it is discussed that shear failure of columns designed in line with Eurocode 8 is sometimes prevented due to minimum requirements for shear reinforcement and not due to the design shear force, which is estimated on the basis of the capacity design approach. Hence, a methodology was proposed for the estimation of design shear forces based on incremental dynamic analysis. It was shown that merely a few carefully selected ground motions can suffice to estimate the maximum shear forces in columns.

• Keywords: building environment, civil engineering, thesis, seismic resistant design, design peak ground acceleration, seismic risk, seismic hazard, Eurocode 8, pushover analysis, nonlinear dynamic analysis, seismic demand hazard analysis, behavior factor q, capacity design, design shear force