Investigation of equivalent diagonal strut approach in an rc buildings by using ambient vibration measurements

The method commonly used in studies investigating how effective the equivalent diagonal strut approach is in real buildings; Determining the dynamic characteristics of the building by ambient vibration measurements and composing a numerical model of the building using these data. In the composed numerical model, infill walls are defined with the equivalent diagonal strut approach, and various investigations are made. Fundamental building periods determined by ambient vibration measurement are taken as reference and material properties are updated; The periods and mode shapes of the numerical model are tried to be matched with the fundamental building periods and mode shapes determined by ambient vibration measurement. When the existing studies in the literature are examined; it is seen that this process is generally carried out by ambient vibration measurements conducted in completed buildings or even in the buildings that its residents are settled. Composing a numerical model of a fully finished or even an inhabited building and calibrating this model according to the ambient vibration measurement results can be extremely difficult, even impossible, as it requires determining more than one parameter at the same time. In this study, in order to overcome this problem, ambient vibration measurements were carried out in a five-story reinforced concrete building, first in the bare frame stage, and then when the infill walls were built but not yet plastered. The natural periods and mode shapes of the building were determined. The created numerical models were calibrated with the measurement results and the elasticity modulus of the concrete and unplastered infill wall were determined respectively. In the investigated building, the infill walls inside the reinforced concrete frames were determined and defined in the numerical model, in which these walls were defined as rigid bodies attached to the reinforced concrete frame, and the numerical model with the equivalent diagonal strut approach were compared in terms of period values and mode shapes. It was observed that the torsional period of the equivalent diagonal strut model was 21% longer, the x-direction translational period was 9% and the y-direction translational period was 11% longer. Besides, numerical models were composed using different formulas suggested in the literature for the equivalent diagonal strut width, these numerical models were compared with each other in terms of period and mode shapes, and the results were found to be very close to each other.