Verification in situ of the behaviour of a new 3-span concrete integral road bridge

In replacing an existing concrete tunnel construction of the railway line from Brussels to the Belgian coast crossing the road from Brussels to Ninove, a new concrete integral bridge has been designed. The new bridge passing over 4 tracks has 3 spans of respectively 18.1, 18.3 and 25.7 m and is built over the existing tunnel. Due to the very skew crossing angle of about 45 degrees, the bridge was made integral avoiding expansion joints in the construction. The superstructure consists of rectangular continuous reinforced concrete beams and a slab on top of the beams. The foundations of the outer abutments consist of bored piles and were made from the upper level of the road, making the foundation or abutments stiffer than what could be expected in normal cases of integral bridges. Up till now, there is no experience in such skew and stiff constructions. The paper describes the design of the bridge and its construction method. During construction of the first phases, soil pressure transducers as well as strain gauge measurements on the concrete beams were installed to monitor pressure and strain measurements for a long period in verifying the design and the behavior of the bridge. The paper describes the first results in the long period of monitoring the construction. Especially the comparison of the increasing soil pressure after the abutment walls is put in relation to the increasing compression stresses in the concrete beams of the superstructure.