Concrete Bridge Assessment Program


Failure Mechanisms

In order to perform a yield-line analysis, it is necessary to postulate a possible failure mechanism that must form in order for the bridge to collapse.

The COBRAS Program has a built in library of 27 failure mechanisms. These have been chosen to reflect the mechanisms that have been observed in lab tests and full-scale tests.

6 way Fan Mechanism (exagerated) (7KB)

This diagram shows a mechanism in which the bridge which has collapsed on one side, leaving the other side of the bridge undamaged. Analysing this mechanism by hand would be very tedious and prone to error.

All 27 Failure mechanisms (33KB)

This diagram shows all 27 failure mechanisms currently supported by the program. For any given bridge and loading, only one will give the lowest posible factor of safety. With COBRAS you can try all of the likely ones quickly and easily. When the worst case mechanisms have been determined, the user can iterate those mechanisms with a smaller step size to look for the worst case position for those mechanisms.

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