20.500.12556/RUL-177319 Naknadno prednapeti prostorski betonski nosilec pri požarni obtežbi Post-tensioned spatial concrete beam exposed to fire V doktorski disertaciji je predstavljen nov numerični model za analizo naknadno prednapetih betonskih nosilcev z ukrivljenimi kabli pri delovanju sočasne mehanske in požarne obtežbe. Model temelji na treh zaporednih in matematično ločenih korakih: (i) analizi razvoja požara v neposredni okolici konstrukcije, (ii) toplotno-vlažnostni analizi in (iii) mehanski analizi, v kateri so armiranobetonski nosilec in prednapeti kabli obravnavani kot ločene komponente, kar omogoča podrobno spremljanje njihovega mehanskega odziva in morebitne porušitve. Glavni prispevek disertacije je v formulaciji in implementaciji novega modela linijskega nosilca, ki je v primerjavi z 2D- ali 3D-končnimi elementi, pogosto uporabljenimi v literaturi, bistveno bolj računsko učinkovit in obenem ohranja visoko natančnost rezultatov. Pri formulaciji končnega elementa so kot interpolirane neznanke uporabljene izključno deformacijske spremenljivke, kar preprečuje numerično blokiranje, značilno za alternativne pristope, ki temeljijo na interpolaciji pomikov. Na osnovi predpostavke o majhnih pomikih in zasukih so ravnotežne enačbe nosilca linearizirane, medtem ko je soodvisnost med napetostmi in deformacijami opisana s poljubnimi nelinearnimi funkcijami. Tak pristop omogoča tako implicitno kot eksplicitno upoštevanje prehodnih in lezenjskih deformacij materiala. Opisane značilnosti skupaj omogočajo učinkovito analizo večjih konstrukcijskih sistemov, in ne le posameznih elementov. Validacija z eksperimentalnimi raziskavami potrjuje natančnost in numerično stabilnost modela, njegova nizka računska zahtevnost pa omogoča rutinsko uporabo na običajnih osebnih računalnikih ter preprosto vključevanje v inženirsko prakso. This doctoral dissertation presents a novel numerical framework for the fire analysis of post-tensioned concrete beams with curved tendons. The framework consists of three sequential steps: (i) analysis of fire development in the vicinity of the structure, (ii) hygro-thermal analysis of the cross-section, and (iii) mechanical analysis in which the reinforced concrete beam and the prestressing tendons are represented as separate interacting components, allowing their mechanical response and potential failure to be assessed individually. The core contribution lies in the formulation and implementation of a highly efficient model for the structural deformation analysis (step iii), for which a new beam-type finite element formulation is proposed. Unlike 2D or 3D finite element models commonly used in the literature, this approach significantly reduces the number of degrees of freedom and thus the computational cost, while retaining high accuracy. Additional numerical efficiency is achieved by selecting strains as the interpolated unknowns, which prevents numerical locking often encountered in displacement-based formulations. By adopting exact material nonlinearity (enabling implicit or explicit consideration of transient and creep deformations) while linearizing the structural kinematics, the model gains further robustness. These features collectively enable efficient analysis of larger structural systems, rather than being limited to individual members. Validation against experimental studies confirms the model’s accuracy and numerical stability, while its low computational demand supports routine use on standard personal computers and facilitates its integration into engineering practice. prednapeti beton ukrivljen kabel naknadno prednapenjanje numerični model metoda končnih elementov prostorske linijske konstrukcije požarna obtežba prestressed concrete curved tendon post-tensioning numerical model finite element model simply-supported beam continuous beam fire load true false false Slovenski jezik Angleški jezik Doktorsko delo/naloga 2025-12-20 08:45:22 2025-12-20 08:45:44 2025-12-30 03:49:54 0000-00-00 00:00:00 2025 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 1970-01-01 178698 20554.pdf 20554.pdf 1 D9299CAD72124592F295F0637A769691 75edc880b376af27501f843b5e549f37a4e7680d1f520499ac826afbb350ea75 72f59e6e-dd77-11f0-9328-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=224281 Fakulteta za gradbeništvo in geodezijo 0 0 0