Seismic Performance of Reinforced Concrete Frames with Added Floors: Emphasizing the Influence of Structural Joints in the Context of Sustainable Vertical Extensions

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. This research examines the seismic behavior of reinforced concrete frame structures that have undergone vertical extensions by adding extra floors. The primary focus is on the joints that connect these extensions to the existing structure and the appropriate modeling of these joints. 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. It is noted that in structural analyses, the connection between an existing structure and a vertical extension is often considered rigid, yet in practice, these joints may behave differently. 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. Compared to demolishing and rebuilding, vertical extension is considered environmentally friendly, reducing the financial costs, environmental pollution, and waste generation.