Innovation In Structural Investigation


Investigative specialist, GBG, has installed and tested a replacement suspension system for water polo nets at Bedford Modern School. The old system, which dated back more than twenty years, had been used to winch the water polo nets above the School’s swimming pool when they were not in use and to support one of the nets during matches

Stephen Kemp from GBG’s office in Watford commented: “Initially, we were commissioned to inspect and test the old system. Our preliminary inspection indicated that the ropes were looking well-worn, and that we would recommend replacement. It was not possible to inspect the fixings due to their height from the poolside, but after twenty years, it was likely that there had been some deterioration in the warm corrosive atmosphere. The lack of conventional access meant that realistically it would not be economical to test the existing system before partial replacement, and that it would still be necessary to repeat the test on the new system. The most cost-effective and safe approach was to replace the entire suspension system and just test once.”

Installing and testing the new system was less straightforward than might be imagined. Water polo nets are relatively rare in the UK, and there are no published loading or testing standards for this type of installation. According to Stephen Kemp: “our approach was to go back to basic engineering principles. Under normal usage the loadings are minimal. The main challenge was to cater for use by boisterous players”.

GBG’s engineers assumed a working load of 300 kg. This would ensure that the new system could support the weight of three or four competitors who might hang, albeit briefly, on the net during the course of a game. The system was tested using a digital reading load link attached to the bottom block of the tackle and the water in the pool as the test load. The fixing points on the roof were observed throughout the course of the testing to check for any deformation.

There were representatives from the School present during the entire GBG activity, which resulted in a valuable working partnership to achieve a safe and secure teaching environment.

GBG has recommended that the new system should be periodically assessed, to include regular checking of the fixings, inspecting the ropes and load testing.

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