Verification of thermal restraint of a railways trough structure by long-term monitoring

At the central railway station of Berlin a trough structure was erected to extend the tracks from the underground station to ground level. The trough is subjected to high ground water pressure. Safety against up-lift called for the coupling of the trough with the underwater concrete slab and the back-anchorage of the structure by piles. Such coupling leads to high restraint due to hydration of the concrete and the ambient weather. Analysis required assumptions regarding the interaction between the trough and the impeding substructure, as well as the stipulation of load-independent design actions based on meteorological studies. The owner decided to install a long-term monitoring system in order to verify the thermal and mechanical response of the structure. However, the main goal of monitoring is the improvement of specifications for design and tender of future structures with comparable complexity. The program and the monitoring techniques will be described, and specific results will be reported. Preliminary conclusions are drawn.