2nd Croatian Conference on Earthquake Engineering 2CroCEE

Recent seismic activity in Croatia has caused significant damage to a large number of old masonry buildings. Since the post-earthquake condition and mechanical properties are not known, on-site experimental testing is an important segment of the maintenance and repair of old masonry buildings. In this paper, the results of testing the mechanical properties and dynamic parameters on the damaged maisonette building of Gymazium Sisak are presented. In order to confirm the experimental results, a numerical analysis of the building was performed. The results of the natural frequencies of the numerical model compared to the experimental results were not satisfactory. Therefore, the model was updated through a whole series of iterations: modification of the boundary conditions, modelling of partition walls, modelling of the damage and modification of the global stiffness of the structure. In relation to the initial numerical model, no significant differences in the frequencies of the structure were obtained by changing the boundary conditions of the numerical model. Then the comparison between the numerical model with the modelled partitions and the numerical model with the input mass of the partitions was started. The result was a higher frequency of the models with modelled partitions as the stiffness of the structure increased. In subsequent iterations, structural damage was added to the numerical model. The damage was first modelled by reducing the elastic modulus of the damaged parts of the building, but the results of the frequencies were not satisfactory. Then, damage modelling was started by reducing the elastic modulus of the finite elements along the cracks. In the end, the global stiffness was additionally reduced for this model. Based on the mentioned assumptions introduced in the global numerical model, satisfactory results were obtained for the natural frequencies of the structure compared to the real behaviour of the structure.