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Seizmička analiza armiranobetonskih mostova u krivini
The subject of this thesis is seismic analysis of reinforced concrete bridges curved in plane. This study was made in a probabilistic framework. Probabilistic seismic demand analysis and probabilistic seismic damage analysis were conducted. An estimate of seismic vulnerability of bridges curved in plane was performed, with particular reference to define bridge fragility curve parameters as a function of the bridge subtended angle.
In order to generate the probabilistic seismic demand model (PSDM) for analysed bridges, investigation of known earthquake intensity measures (IMs) regard to their efficiency and proficiency was conducted. A total number of 16 IMs and and 3 engineering demand parameters (EDP) were considered. Bridge bent skewness were considered also. 18 nonlinear 3D models were generated and 2736 non- linear dynamic analysis were performed. Conclusions were made regard to the most appropriate IMs that should be used in PSDM for curved bridges. Modifications in calculating of IMs, which contribute to more reliable PSDM, were proposed. Derived relationships EDP-IM can be used to evaluate bridge response (column drift ratio) for various intensities of seismic excitation. The analysis of the modal response of structures and the results of non-linear static analysis were conducted and it was concluded that decrease of radius of curvature leads to increase of stiffness of the structure. Also, it was concluded that increasing the skew angle and reduction of the radius of curvature leads to increase in vulnerability of bridge demand.
Fragility curves were generated using results derived from two methods: the capacity spectrum method (CSM) and a non-linear dynamic analysis (NDA). These analyzes were conducted for bridges with two-column bents with circular cross section. Total number of 1140 CSM and 570 NDA were carried out in this part of the study. 4 damage states were defined in accordance with EN 1998-3. Values of damage index on the onset of considered damage states were calculated and fragility curves were derived. Influence of the distance from the fault on bridge vulnerability were investigated. Regression analysis was performed in order to define bridge fragility curve parameters as a function of the bridge subtended angle. It was shown that increase of radius of curvature increases the fragility of bridge for all analysed limit states. Derived functional relationship of median PGA values on bridge subtended angle and average dispersion can be used in the design of bridges and roads even in early conceptual phase. It is fact that existing hazard tools do not provide relevant information so this functional dependence can be implemented. Recommendations that should be applied in engineering practice, seismic analysis and design of curved and skew bridges were presented.