The post-tensioned roof trusses of industrial halls from 1960-1980, of which there are an estimated 10,000 in the Czech Republic, pose a serious risk. A common problem with these structures is the inadequate grouting of the channels with the prestressing reinforcement, which leads to leakage and subsequent corrosion of the reinforcement. This problem has been the cause of at least four accidents, the most recent of which occurred in northern Bohemia in December 2023 and in western Bohemia in March 2024.
The most commonly diagnosed truss types include SPP 6-18/6, SPP 12-18/6 on 18 m spans and SPP 9-24/6, SPP 14-24/6 on 24 m spans. These structures differ in the arrangement of the diagonals and the routing of the prestressing cables, with the extreme diagonals being found to be at greatest risk of corrosion. For the lower flange, perfect grouting of the channels was observed in 70% of cases.
Diagnosis is made by endoscopic examination of the prestressing reinforcement, with mild corrosion (grade 2) being the most common. Critical damage (grade 5) has been found exceptionally, but never reaching the highest grade (6).
The failures were generally initiated by reinforcement failure in the anchorage areas. Future research will therefore focus on these critical parts of the structure, especially at the extreme diagonals.
Authors. Vladislav Bureš, Ph.D.; Ing. Petr Mynarčík, Ph.D.; Ing. David Čítek, Ph.D.; Ing. Arnošt Hlaváček; Ing. Karel Čapek