Six cylindrical concrete sewage tanks located in Dronfield, near Sheffield, required inspection in order to assess their structural condition. The tanks were constructed during the 1970s, and were beginning to exhibit signs of age.
In particular, the external post-tensioning was showing signs of relaxation. CCL was called in to investigate and provide an assessment of any necessary remedial action.
This involved load checking the unbonded monostrand post-tensioned tendons to assess residual loads. Using a monostrand jack, a lift-off test was carried out to monitor wedge release and determine the load in each tendon.