Požarna analiza delno razslojenih ukrivljenih armiranobetonskih linijskih konstrukcij : doktorska disertacija

Ružić, Dušan (author), Planinc, Igor (mentor), Hozjan, Tomaž (comentor)

V disertaciji je predstavljen nov delno povezan numerični model za nelinearno analizo homogenih in delno razslojenih ukrivljenih armiranobetonskih linijskih konstrukcij v pogojih požara. Zaradi zahtevnosti je model razdeljen v dve fazi. V prvi fazi določimo časovno in krajevno razporeditev temperatur zmesi plinov v požarnem prostoru s pomočjo CFD modelov oziroma požarnih krivulj (samo temperature). S temi rezultati v drugi fazi predstavljenega numeričnega modela določimo razporeditev temperatur, pornih tlakov, koncentracij vode in zmesi suhega zraka in vodne pare, deformacij in napetosti v homogenih in delno razslojenih ukrivljenih armiranobetonskih linijskih konstrukcijah. Ena izmed novosti predstavljenega modela predstavlja druga faza, kjer toplotno-vlažnostni in mehanski del požarne analize obravnavamo delno povezano. Povezavo med analizama upoštevamo s spremenjeno geometrijo konstrukcije, ki je posledica eksplozijskega luščenja betona. Drugo novost predstavljenega numeričnega modela predstavlja mehanski del modela. Tu je predstavljena nova družina deformacijskih končnih elementov za nelinearno analizo homogenih in delno razslojenih ukrivljenih armiranobetonskih linijskih konstrukcij v pogojih požara in pri sobni temperaturi. Končni elementi so zasnovani na geometrijsko točnem Reissnerjevem modelu ukrivljenega ravninskega nosilca in temperaturno odvisnih nelinearnih materialnih modelih betona in armature ter stika med slojema. Dodatno so v tem delu modela z adicijskim razcepom upoštevane tudi temperaturne deformacije betona in armature, viskozno lezenje armature in lezenje betona pri povišanih temperaturah in prehodne deformacije betona. Vplivi oviranih deformacij konstrukcije, na primer zaradi zemljine v predorih, so v predstavljenem modelu upoštevani z diskretnimi nelinearnimi vzmetmi. Z numeričnimi analizami smo ugotovili, da je predstavljeni numerični model zelo natančen in zato primeren za oceno požarne varnosti homogenih in delno razslojenih ukrivljenih armiranobetonskih linijskih konstrukcij, tudi predorov; z detajlnimi parametričnimi študijami pa, da spremenjena geometrija konstrukcije zaradi odluščenega betona odločilno vpliva na njeno požarno varnost in da togost stika med slojema vpliva na razporeditev notranjih sil v ukrivljenih linijskih konstrukcijah v pogojih požara.

• Language: Slovenian
• Keywords: grajeno okolje, gradbeništvo, disertacije, ukrivljen armiranobetonski kompozitni nosilec, požar v predoru, FDS, povezan prenos vlage in temperature po betonu, kritični čas konstrukcije, eksplozijsko luščenje betona
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FGG - Faculty of Civil and Geodetic Engineering
• Place of publishing: Ljubljana
• Publisher: [D. Ružić]
• Year: 2015
• Number of pages: XVIII, 92 str.
• PID: 20.500.12556/RUL-32771
• UDC: 519.6:614.841.45:624.014(043.3)
• COBISS.SI-ID: 7028833
• Publication date in RUL: 10.07.2015

RUŽIĆ, Dušan, 2015, Požarna analiza delno razslojenih ukrivljenih armiranobetonskih linijskih konstrukcij : doktorska disertacija [online]. Doctoral dissertation. Ljubljana : D. Ružić. [Accessed 11 April 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=32771

Secondary language

• Language: English
• Title: Fire analysis of partially delaminated curved reinforced concrete beam structures : doctoral thesis

Abstract

In the dissertation a new partly coupled numerical model for non linear analysis of homogeneous and partly delaminated curved RC structures exposed to mechanical and temperature load is introduced. Due to its complexity the model is divided into two phases. In the first phase the time and spatial distribution of temperatures in fire compartment is defined by temperature-time fire curves and FDS models. Obtained temperatures from the first phase and mechanical load are used as input parameters in the second phase of the presented model, where the distribution of temperatures, pore pressures, gaseous mixture of dry air and water vapour and stress-strain state are calculated. One of the novelties of the introduced model is the second phase, where chemical-hygro-thermal part and mechanical part of the fire analysis are partly coupled. The connection between the parts is considered with the changed geometry of structure due to concrete spalling. The second novelty of the introduced model is the mechanical part of the fire analysis, where a new group of strain based finite elements for non linear analysis of homogeneous and partly delaminated curved RC structures during fire has been developed. Finite elements are based on kinematically exact planar beam theory of Reissner, non linear material models for concrete and steel at elevated temperatures and costitutive laws for contact surface between beam layers. With the principle of additivity of strain increments temperature strains of concrete and steel, viscous strains of steel, transient strains and creep strains at elevated temperatures for concrete are considered. The restraining effect of soil on tunnel structure is employed with discrete non linear springs. Detailed numerical analyses have revealed, that the introduced model has good efficiency and accuracy and it si perfectly suitable for fire analysis of all kinds of homogeneous and partly delaminated curved RC structures, even tunnels. The parametric studies have showed that the changed geometry of structure due to concrete spalling significantly affects the time and the form of failure of tunnels during fire and that the contact stiffness between the beam layers strongly influences the distribution of internal forces in curved RC structures during fire.

• Keywords: building environment, civil engineering, thesis, curved RC composite beam, tunnel fire, FDS, heat and mass transfer in concrete, critical time, concrete spalling