THE DAMAGE OF THE TALL BUILDING AT PÉCS

Abstract

In the structure of the 24 storey tall building at Pécs constructed by IMS prestressed concrete skeleton system in 1975-78 significant corrosion damages occurred at the prestressing tendons of the column floor-slab joints because of the high chloride content of the joining mortar. After only 10 years of service 70 per cent of the prestressing tendons were severely corroded and almost 30 per cent of them failed. Because of loss of the prestressing force the interaction between the floors and columns of the floor-slab system and the stiffening system of the building was weakened. Especially the cantilever type facade structures have got in a disadvantageous state while at the crossings of the prestressing wires and the columns and at the anchorages of the cantilever beams there are ungrouted sections. Because of the decrease of the safety of the structure the building containing 250 flats was evacuated for the period of the strengthening works. The detailed examinations of the experts proved the necessity of the given measures and simultaneously worked out the basic theoretical ideas of the strengthening of the structure. The column - floor junction (the local reinforcement) has to assure the support of the floor-slabs at the columns; the interaction and mutual work of the floor system; the safe fastening of the cantilevers. From the different variants the method which applies for the support of floor-slabs reinforced concrete drops at the edge columns and steel collars at the internal ones seems to be the most advantageous. For t.he repair of the stiffening system (the global strengthening) it is necessary to hold together the floor-slab system. Advantageous is the method which does not require the alteration of the foundation structure. The detailed inspection showed that by the strengthening of the top bracing of the existing shear walls the rigidity of the building might be guaranteed. According to the examination carried out it can be stated that the strengthening is technically possible. The supervision of t he more than 300 000 square meter buildings constructed in Hungary by the IMS technology, the development of the methodology of corrosion exploration at damages and the improvement of the strengthening method were initiated with the inspection of the tall building at Pécs. The recognition of the corrosion at damages allowed to start the well organized strengthening works.