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.