Testing Center at Federal Institute for Materials Research and Testing, Germany (P05-0980)
Herbert Wiggenhauser, Federal Institute for Materials Research and Testing, Germany

Two box girder bridges in the course of A23 Südosttangente in Vienna have been evaluated in a joint research project between Magistrat Wien and BAM. The tendon ducts inside the walls of the box girders had to be located non-destructively. Additonally, the ducts had to be inspected for any indications of grouting defects and compaction faults in the concrete should be identified. All measurements had to be carried out without traffic disruption. The bridges have been built in the eighties, the two investigated bridges were constructed using two kinds of post-tensioning systems (VSL 5-12, DYWIDAG St85/105). The first bridge has bundles of 8-10 ducts with a diameter of 80 mm. The tendons consist of 12 strands (100 m2 cross section). The second structure has 30 ducts with 40 mm diameter in six layers in the investigated area. Each duct has one bar with 32 mm diameter inside. The thickness of the box girder side walls is 50 cm, their height appr. 180 cm. The test program consisted of a combination of radar, ultrasound pulse echo and impact-echo. Measurements were carried out on large areas to get a representative picture of the structure. At the first bridge one side wall was tested along a length of 10 m, the second area was over 4 m long. Initially, measurements were planed only at one bridge but the test program was extended after ungrouted ducts were located (through drilling) at the second bridge nearby. Radar was used to locate the ducts, the acoustical methods were used to test the grouting condition inside the metal ducts. Measurements were carried out using a scanner system which has been developed at BAM. It carries out automatic measurements with the NDT methods on a chosen grid. 3D-SAFT reconstruction of ultrasonic data requires measurements in a very dense grid with a step width of 20 mm for optimum results. The test concept, the actual test situation and the results of the duct inspection are presented.