1st Croatian Conference on Earthquake Engineering 1CroCEE 2021

With the increase of the population in densely populated areas, the lack of living space leads to an increase of need for upgrades to existing buildings. The problem related to upgrades is of greater importance in seismically active areas, especially in older buildings designed according to old codes. Depending on the type of upgrade, it may affect the existing structure differently, but on the other hand, the existing structure affects the upgrade as well. In the paper first a short review of achievements in the world regarding this problem has been discussed and then the activities conducted in IZIIS related to the investigation of the influence of different material upgrade systems on the integral structural behaviour have been briefly described. This comparative investigation has been performed by conducting a total of 177 dynamic tests on the 5x5 m shaking-table at the IZIIS Laboratory, using harmonics, synthetic and real earthquake records as input in one horizontal direction. Elastic tests with low level of excitation without occurrence of damages and plastic deformations have been conducted first and then capacity tests have been performed up to the failure of the models. The various upgrade systems were constructed of steel frame, light- frame timber, cross-laminated wooden panels and composite systems of wood and glass. The first two floors represented the existing reinforced concrete, and the third floor was the upgrade system which was changed during all the tests. The main purpose of the investigation was to investigate the behavior of this kind of upgrades systems subjected to seismic loadings and their applicability in seismic prone areas. Important output regarding the National annex parameters needed for Eurocode design has been also expected from this investigation. This investigation will be realized within the frame of а part of the doctoral thesis that is to be proposed.