Building of indoor Sports Hall, of the German School of Athens, built in 1968 from reinforced concrete.

It consists of a ground floor building, with spans of approximately 20.00 m and of 6.00m height and a basement at a section of the plan view.

The ground floor roof consists of post-tensioned beams and reinforced concrete slab.

The aim was to control the seismic behavior of the building and to strengthen it if required.

During the inspection, it was found that the shear walls were adequate to bear-up the entire seismic load in the transverse direction.

In the longitudinal direction, the building is greatly deformed to a potential earthquake due to the lack of shear walls, which could result in a failure of the “short” columns on the facades.

The method of strengthening suggested and implemented was to add L-shaped reinforced concrete walls to the building’s exterior, on both sides, without any interference with the interior of the sports hall.

With the right foundation of the new shear walls and their full attachment to the existing load-bearing body, the building becomes more rigid and the deformations are reduced.

The new shear walls were fixed on the existing reinforced concrete walls with from-side-to-side, steel rods, along their full height, in order to achieve full cooperation of existing and new elements.

They, also, had their own new foundations constructed, at the same level and fully connected to the existing ones.

After the hardening of the cast-in-situ reinforced concrete walls, the rods have been post-tensioned.

An “extrusion” test and a “nut” strength test were carried out.

The project was completed in a short period of time, only with external interventions and complete restoration of the facades’ decorative elements.