1st Croatian Conference on Earthquake Engineering 1CroCEE 2021

In a large number of seismic-prone regions, the reinforced concrete frames of the buildings are filled with masonry and in this way, a composite constructive composition is created whose behaviour can be hardly predicted and modelled, which leads to flaws in the design regulations. Masonry infill is often presented as a non-constructive element and often is not included in the analyses, which creates a problem, a constructed building, in reality, can have different dynamic characteristics from the project ones, and thus different seismic behaviour than predicted. Therefore, the aim of this paper is to investigate how buildings behave in seismic activities when the masonry infill is included in the model and calculations.
A comprehensive comparative analysis has been performed involving linear and nonlinear-Pushover static analyses and the obtained results from hypothetical models with 5 and 8 floors, with and without modelling the infill, according to the Macedonian regulations and according to Eurocodes were compared. For modelling the infill, the recommendations according to FEMA 356 for macro-modelling were used, where the masonry is modelled with an equivalent diagonal strut. From the conducted analyses, it can be generally concluded that the masonry infill has a very favourable effect on the behaviour of the buildings when it is evenly distributed. Although the ductility of the building decreased, however, the initial rigidity is substantially increased (almost 2 times in the presented paper). It can be freely recommended that when we have such a case of evenly and regularly distributed masonry infill, it should be included in the analysis as the first line of defence in overcoming seismic forces. In the model ЕКopen 1-st story, it can be seen that the infill has a negative impact on the overall behaviour with a tendency to form a soft story on the ground floor.