Inspection of “post-tensioned” reinforced concrete beams on the roofs of two buildings of the German School Athens: The Sports Hall and the Auditorium.

These buildings were built in 1968 with large spans on their roof slabs of about 20.00m scale.

So after about 40 years of their construction, it was decided to control their behavior under vertical loads.

It was difficult to investigate non-destructively the condition of the tendons of the “post-tensioned” beams, along their whole length, as they had to be examined for their degree of corrosion, to ensure their connectivity through the grout and the adequacy, the integrity and function of their anchorages.

Experimental testing of the behavior of the “post-tensioned” beams was implemented.

Test loadings in the central areas of both roofs’ beam-grids took place and the “load-deflection” ratio measurements for comparison with the calculated values.

On the roofs of the buildings, two temporary formwork tanks with PVC watertight film inside them, were constructed and were gradually filled with 240tn water.

At the same time, measurements with precise instruments were performed by expert scientists, carving out the corresponding curves.

The behavior of the beams was found to be approximately as expected, slightly more rigid, stiff and therefore it was concluded that the roof-diaphragms were still safe.