Projektiranje armiranobetonskih okvirnih stavb na osnovi potresnega tveganja in poenostavljenih nelinearnih modelov : doktorska disertacija

Lazar Sinković, Nuša (author), Dolšek, Matjaž (mentor)

Projektiranje stavb po veljavnih standardih ne omogoča jasnih informacij o varnosti pred porušitvijo, saj vrednotenje verjetnosti porušitve v standardu ni predvideno. V doktorski disertaciji zato predlagamo nov postopek projektiranja, ki temelji na ciljnem potresnem tveganju. Takšno projektiranje je iterativno in zahteva uporabo nelinearne metode analize. Izhodišče je začetna konstrukcija, ki jo postopno prilagajamo dokler ocenjeno potresno tveganje ni manjše od ciljnega tveganja. Predlagan postopek projektiranja pa lahko postane nepraktičen, če je število iteracij veliko. Zato smo predlagali enostavne smernice za prilagajanje armiranobetonskih okvirnih stavb na osnovi rezultatov potisne analize trenutne konstrukcije. Z njihovo uporabo se s primernim večanjem prečnih prerezov elementov in vzdolžne armature stebrov izboljšuje deformacijska kapaciteta in nosilnost stavbe. Poleg smernic za prilagajanje konstrukcije smo vpeljali tudi stopnjevanje zanesljivosti projektiranja, pri čemer se računsko manj zahtevne metode analize uporabijo v začetnih iteracijah, bolj zahtevne, ki so običajno tudi bolj natančne, pa za kontrolo rezultatov projektiranja na osnovi poenostavljenih metod. Del raziskav je bil usmerjen tudi v izboljšanje natančnosti ocene potresnega tveganja. Razvili smo nove enačbe za oceno potresnega tveganja, kjer upoštevamo fizikalno opredeljeni mejni vrednosti intenzitete potresa. Ugotovili smo namreč, da neupoštevanje spodnje in zgornje meje intenzitete potresa v nekaterih primerih povzroči precenjeno vrednost potresnega tveganja. Predlagan postopek projektiranja smo z upoštevanjem novih enačb za oceno potresnega tveganja uporabili na dveh primerih armiranobetonskih okvirnih stavb. Kljub grobi določitvi začetne konstrukcije smo ciljno potresno tveganje dosegli zgolj s štirimi oz. tremi iteracijami. Upoštevanje zgornje meje intenzitete potresa lahko znatno zmanjša ocenjeno verjetnost porušitve, kar posledično vpliva na izbrano konstrukcijo.

• Language: Slovenian
• Keywords: grajeno okolje, gradbeništvo, disertacije, projektiranje, potresno tveganje, potresna nevarnost, intenziteta potresa, spodnja meja intenzitete potresa, zgornja meja intenzitete potresa, okvirna AB stavba, potisna analiza, dinamična analiza
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FGG - Faculty of Civil and Geodetic Engineering
• Place of publishing: Ljubljana
• Publisher: [N. Lazar Sinković]
• Year: 2015
• Number of pages: XXX,142 str.
• PID: 20.500.12556/RUL-73149
• COBISS.SI-ID: 7245409
• Publication date in RUL: 24.10.2015

Secondary language

• Language: English
• Title: Risk-based seismic design of reinforced concrete frame buildings using simplified nonlinear models : doctoral thesis

Abstract

Most current standards that are concerned with the seismic design of buildings do not provide sufficiently clear information about safety against collapse. For this reason a new procedure for the risk-based seismic design of buildings is proposed, which is iterative and based on the use of nonlinear methods of analysis. The proposed design procedure starts by the selection of an initial structure, which is gradually adjusted by means of iterations until the estimated seismic risk is lower than the target risk. Since the number of such iterations may become excessive, simple guidelines have been developed for the structural adjustment of reinforced concrete frame buildings, which can be used to improve the building's strength and deformation capacity by appropriately adjusting the structural elements selected on the basis of the results of pushover analysis from the current iteration. The concept of differentiation in the reliability of design is also implemented, so that less demanding analytical methods are used in the initial iterations, whereas more demanding, and usually more accurate methods are used to verify the design results obtained by using simplified methods. Part of the research was aimed at the improvement of the accuracy of seismic risk estimation, which is an important component of the proposed design procedure. New equations for seismic risk assessment, which take into account the physically defined limits of ground-motion intensity, have been derived. It was found that sometimes, if the lower and upper limits of the ground-motion intensity are insufficiently taken into account, overestimated values of the seismic risk may be obtained. The suitability of the proposed design procedure, which takes into account the newly developed equations for seismic risk assessment, was demonstrated on two examples of reinforced concrete frame buildings, one having 8 storeys and the other 15 storeys. The target risk was achieved after only four and three iterations, respectively, even though their corresponding initial structures had been only roughly defined. Taking into account the upper bound of the seismic intensity can result in a reduction in the estimated probability of collapse, which can in turn have a significant effect on the final design of the structure.

• Keywords: building environment, civil engineering, thesis, design, seismic risk, seismic hazard, ground-motion intensity, lower bound of ground-motion intensity, upper bound of ground-motion intensity, RC frame building, pushover analysis, dynamic analysis