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Potresni odziv armiranobetonskih mostov s pomanjkljivo prečno armaturo stebrov : magistrsko delo
Janevski, Antonio (Author), Gams, Matija (Mentor) More about this mentor... This link opens in a new window, Isaković, Tatjana (Co-mentor)

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Abstract
V nalogi smo analizirali potresni odziv armiranobetonskih mostov s pomanjkljivo prečno armaturo stebrov. V večini novejših mostov v Sloveniji je strižna armatura določena tako kot je zahtevano v standardu Evrokod 8/2, preostali dve funkciji prečne armature: a) objetje betonskega jedra in b) preprečevanje uklona vzdolžne armature, pa nista vedno ustrezno obravnavani. Količina prečne armature je v kritičnih področjih dostikrat premajhna, razdalja med podprtimi palicami vzdolžne armature pa prevelika. Stremena so pogosto neustrezno oblikovana in izvedena brez primernih kljuk. Vse to lahko povzroči razpad betonskega jedra in uklon vzdolžnih armaturnih palic, kar zmanjšuje razpoložljivo duktilnost stebrov (sposobnost sipanja potresne energije), oziroma deformabilnost konstrukcije. Nalogo smo razdelili na dva delovna sklopa: 1) v prvem delu smo analizirali vpliv pomanjkljive prečne armature na ciklični odziv stebrov, ki so bili eksperimentalno preizkušeni v okviru doktorske naloge Anžlin (2017); 2) v drugem delu smo analizirali vpliv pomanjkljive prečne armature na odziv značilnega viadukta. Vse analize v prvem sklopu naloge smo izvedli, ne da bi poznali rezultate eksperimentov. V prvem delu naloge smo vse obravnavne stebre modelirali s standardnim Gibersonovim modelom s koncentrirano plastifikacijo. Odziv nelinearnih vzmeti smo opisali s Takedovimi histereznimi pravili. Ovojnice histerez smo določili s semi-empiričnimi in parametrično-empiričnimi metodami, ki jih vsebujeta standarda Evrokod 8/2 in Evrokod 8/3. Z vsemi upoštevanimi metodami smo dobili podobne ovojnice histerez, z eno pomembno izjemo, vrednosti za mejni zasuk stebrov so se namreč precej razlikovale. Tiste, ki so bile določene s parametrično-empirični postopkom, so bile v večini obravnavnih stebrov najmanjše in so se zelo dobro ujemale z rezultati eksperimentov. V obravnavnih stebrih je pomanjkljiva prečna armatura zmanjšala deformacijsko kapaciteto stebrov. Spremenila je tudi način porušitve stebrov. V večini stebrov s pomanjkljivo prečno armaturo so se vzdolžne palice globalno uklonile. V stebrih s standardno prečno armaturo je porušitev nastopila, ko so se vzdolžne palice pretrgale. V drugem delu naloge smo primerjali potresni odziv značilnega viadukta, kjer so bili stebri v enem primeru armirani s standardno, v drugem pa z nestandardno prečno armaturo. S primerjavo rezultatov teh analiz smo ugotovili, da pomanjkljiva prečna armatura ni imela bistvenega pomena na nosilnost konstrukcije in potresni odziv konstrukcije, preden je stekla armatura v stebrih. Bistveno pa je vplivala na deformacijsko kapaciteto viadukta. Deformacijska kapaciteta viadukta, ki smo jo definirali kot maksimalni pomik, pri katerem se poruši prvi steber, je bila v primeru standardne prečne armature večja.

Language:Slovenian
Keywords:potresno inženirstvo, pomanjkljiva prečna armatura, analiza moment ukrivljenost, ciklični odziv, poenostavljena nelinearna analiza, N2 metoda, OpenSees
Work type:Master's thesis/paper (mb22)
Tipology:2.09 - Master's Thesis
Organization:FGG - Faculty of Civil and Geodetic Engineering
Year:2019
Publisher:[A. Janevski]
UDC:624.042.7:624.21(497.4)(043.3)
COBISS.SI-ID:8883809 Link is opened in a new window
Views:56
Downloads:30
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Secondary language

Language:English
Title:Seismic response of reinforced concrete bridges with substandard columns’ lateral reinforcement : master thesis
Abstract:
In this thesis, we present an analysis of seismic response of reinforced concrete bridges with substandard lateral reinforcement of columns. Most of the bridges, that were built in Slovenia in the near past have shear reinforcement according to standard Eurocode 8/2, however the other two functions of lateral reinforcement, which are: a) confinement of the concrete core; b) preventing buckling of the longitudinal reinforcement, are not always adequately satisfied. In such cases, the amount of lateral reinforcement in critical areas of the section is mostly inappropriate, while distance between the supported bars of the longitudinal reinforcement is too large. Stirrups are often inadequately designed and constructed without suitable hooks. All of this can lead to the collapse of the concrete core and buckling of the longitudinal reinforcement, which reduces the ductility of columns (the ability to absorb energy), or the deformability of the structure. The thesis was divided in two parts: 1) Cyclic response of columns with inadequate lateral reinforcement detailing, which were experimentally tested in the framework of doctoral thesis Anžlin (2017), was analysed in the first part; 2) Influence of inadequate lateral reinforcement details on the response of a characteristic viaduct was examined in the second part. All of the analyses that were performed in first part were done without knowing the results of the experiments. In the first part of thesis, considered columns were modelled using the Giberson material model with lumped plasticity. The response of nonlinear springs was described with the Takeda hysteresis rules. Hysteresis envelopes were determined using semi-empirical and parametric-empirical methods according to Eurocode 8/2 and Eurocode 8/3. With all of the considered methods, similar hysteresis envelopes were obtained, with one notable exception. The values for the ultimate rotation of the columns varied considerably. Those determined by the parametric-empirical procedure were the smallest in most of the considered columns and were in good agreement with the results of the experiments. Inadequate lateral reinforcement of column specimens showed a reduced deformation capacity of columns. They also change the way of failure, in most columns with inadequate lateral reinforcement, a global buckling of longitudinal bars was obtained. In columns with appropriate lateral reinforcement, the failure occurred due to the rupture of longitudinal bars. In the second part of thesis, comparison of seismic response of typical viaduct, in which one case considered columns with standard, and in the other substandard lateral reinforcement, was made. It was observed, that inadequate lateral reinforcement did not have a significant impact on capacity and response of structure before yielding of column longitudinal reinforcement. However, it significantly affected the deformation capacity of the viaduct. The deformation capacity of the viaduct, which was defined as the maximum displacement at which the first column collapses, was higher in the case of standard lateral reinforcement.

Keywords:earthquake engineering, deficient lateral reinforcement, moment curvature analysis, cyclic response, simplified non-linear analysis, N2 method, OpenSees

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