Influence of buckling of longitudinal reinforcement in columns on seismic response of existing reinforced concrete bridgesAnžlin, Andrej (Avtor) Isaković, Tatjana (Mentor) building environmentcivil engineeringthesisbuckling of the longitudinal reinforcementeffective confinementbridge columnssubstandard transverse reinforcementI- shaped columnsrectangular columnsseismic strengtheningExperimental and analytical studies of the influence of buckling in longitudinal reinforcement on the seismic response of existing reinforced-concrete bridge columns were performed. Based on the results of previous tests of typical I-shaped bridge piers, new cyclic tests of rectangular columns were performed. The impact of inappropriate seismic detailing and of the concrete cover on the achieved drifts and load-carrying capacity, as well as on the buckling of bars, were analysed. After the literature review data about 63 experimental tests of RC columns were assembled, in which the collapse of the element was mainly controlled by the buckling of bars. All these tests were included in a newly established ‘buckling’ database. Using the latter, new empirical equation for the estimation of the post-capping stiffness of rectangular columns was introduced. All columns from the ‘buckling’ database were analysed with the existing macro models which are typically used in seismic engineering. It was concluded that, in the case of rectangular RC columns with inadequate seismic detailing, the principal assumptions regarding their behaviour are often not fulfilled. A new procedure for the evaluation of the effect of inappropriate hook angles of the lateral reinforcement and of bar buckling on confinement effectiveness was derived. It is based on the results of numerous detailed FE analyses of concrete columns with different reinforcement detailing configurations. Experimental tests of strengthened RC columns were also performed. At first, the efficiency of the strengthening of a typical I-shaped bridge pier with substandard reinforcement was investigated using CFRP wrap. It was concluded that, due to the unfavourable aspect ratio of the section flanges, conventional strengthening methods are rather ineffective. Improved strengthening of substandard rectangular column was therefore investigated, the column being jacketed with pre-stressed CFRP fibres. In this way the deformation capacity of the columns was increased by more than 70%. The behaviour of the strengthened columns was analysed with similar numerical models as the previously described columns. For RC members of this type some modifications of the existing numerical models were also proposed.[IA. Anžlin]20172017-06-05 12:26:06Doktorsko delo/naloga92515sl