Repair and reconstruction of engineering structures - Assessment and Refurbishment of Steel Structures - page 328

moving of pipeline of TGP II was begun using the pulling devices. The supports for the
pipeline on the both sides of the bridge were gradually released from the crown of the
arch. In two places (Figure 6.167) pipeline TGP II was moved in small steps into its new
position by means of hydraulic presses, with the horizontal loading increasing by 20.0 kN
increments.
Figure 6.167 Locations on the crown
of the arch where the separating device
were fixed
Because such rectification work on a pipeline in operation that had not previously been
done in Slovakia, it was necessary to monitor the pipeline stresses at each loading stage.
In the preparatory work a tensiometric monitoring system was installed on pipeline TGP
II. Stresses were checked by this system during depressurizing, rectification and returning
to full operation. The whole procedure was controlled so that the pipe was in a flexible
condition at every moment in the separation to ensure the resulting stresses kept to a
minimum.
The maximum measured input stresses immediately after completion of three
separation cycles was 62.17 MPa. On the theoretical assumptions that the pipes would
behave rigidly, stresses up to 110 MPa were expected. With pipelines TGP I and TGP II,
which were originally tight together at the crown of the arch, the gradual separation
created a gap with a minimum width of 229 mm (Figure 6.168) at the crown of the arch.
In the horizontal movement there was an elastic distribution of stresses due to
longitudinal movement towards the linear sections of the pipelines at both ends of the
bridge. Therefore up to a horizontal separation of 229 mm was reached, significant
additional longitudinal stresses had not developed. At that value for the horizontal