An alert over tension cables and rod connectors commonly used in bridges and roofing structure has been issued by the Standing Committee of Structural Safety (Scoss) following a string of failures.
Scoss said it had received a number of reports reagrding failure of connecters of high strength steel cables at loads well below the intended design capacity. It added that it has also seen a number of reports where the cables and rods where discovered to be “substandard” either during construction or once in service.
The alert is aimed at clients, designers and contractors of steel tension structures to raise awareness of the issue. Scoss wanted to highlight that failure of one steel section could trigger a chain reaction causing progressive collapse.
According to Scoss, the problem may arise because tension rods and their connectors are usually sold as proprietary products, which are accepted into the design based on generic information provided by the manufacturer, rather than by verification against the specific performance requirements of a project.
Reasons for failure
- Issues with the material quality and dimensional accuracy of components manufactured by casting (defects and lack of toughness), compounded by inadequate or misleading records.
- A lack of understanding of the behaviour of pinned joints in service.
- Misalignment, both in the connection to a gusset or fin plate and in the geometrical accuracy in the holes bored in the forks of the connector and the degree of tolerance required.
The Scoss report can be found here.