A temporary strain gauge system was used to measure tendon tension during the landing of the pre-compressor module and the primary result was the difference in load before and after the operation.
Figure 1 shows the strain measured at one of the tendons and the step change in load during the module landing is clear. Two dynamic cycles are observed during touchdown and the dynamic stresses in the tendon after installation of the module are clearly visible.
In 2003 Fugro installed a permanent Structural and Environmental Monitoring System (SEMS) on the same platform to measure wind and wave conditions and the jacket response. The comprehensive system records data from accelerometers and strain gauges at various locations on the platform topsides in order to validate the design case for the structure and provide information towards its on-going structural integrity and maintenance.
Extensive modal analysis of measured vibration was carried out by Fugro prior to the addition of the module. The tension monitoring system will be incorporated into the existing SEMS to undertake verification of the design performance on an on-going basis.
Fugro has more than 25 years’ experience of measurements on jackets, flare stacks, bridges and other structural elements. Measurements are typically performed for design verification, evaluation of ageing structures or integrity monitoring.