Investigation into Seismic Behavior of Reinforced Concrete Frames with Subsequently Added Floors and Modeling of Connecting Joints

Abstract

The size of the population and the need for residential spaces are increasing. One possible solution is to add new floors to existing buildings. The positive aspects of such a solution with respect to its socio-economic impact and impact on the environment is that large amounts of carbon dioxide release will be avoided, waste and its treatment will be reduced, and agricultural land and green spaces will be preserved. However, adding floors to existing structures might be structurally challenging, especially in terms of the behavior under seismic actions. This paper presents a numerical study of a reinforced concrete frame in an old building to which new floors are subsequently added. The analysis shows that the frame does not behave as a whole with the old part of the structure, nor does it behave the same as if it were made with rigid joints compared to additional ones connected using hinge joints. The change from the corner (knee) joint to the external joint has its own effect on the distribution of internal forces in the structure as a whole and in the joint in particular.