What should be considered in bridge performance?
The performance of a bridge is evaluated by considering the following factors:
- Reliability: The probability that the bridge remains suitable for its purpose over its service life. This is a complementary measurement to the probability of structural failure, operational failure, or serviceability failure.
- Availability (operation continuity): The proportion of time the bridge is operational. It originates from maintenance works (e.g. additional travel time due to an imposed traffic regime on the bridge).
- Safety: Related to minimization or elimination of potential harm to people during the service life of a bridge.
When determining how a bridge should behave, there are several aspects to consider that are conditional on any proposed solution. Analyzing the structure type, its usage, criticality, and the impact of non-operation is necessary. In this regard, two concepts must be considered:
- Robustness: the ability of a structure to resist events such as fire, explosion, impact or the consequences of human error, without being damaged to an extent disproportionate to the original cause’.
- Resilience: The ability of an infrastructure or physical asset to recover quickly from a disruption, possibly in a new configuration or network structure.
It is necessary to design more robust structures if the interruption of service results in damage that cannot be assumed (critical infrastructure) despite the extra expense involved. There is the option of designing a robust bridge by improving its condition, but redundant and capable of withstanding extraordinary actions (low, medium or high intensity) or a resilient bridge, one that is prepared to deal with disruptions, damage, and recovery processes that are acceptable despite disruptions and damage.
In the event that an interruption of service for a reasonable time does not result in disproportionate adverse effects (non-critical infrastructure), it is advisable to design a resilient structure, so that the service can be temporarily reduced, but the recovery time is relatively short.
Shortly, a resilient design may be acceptable if the cost of repairs is not so high or if the service can be temporarily suspended. Alternatively, a robust structural solution should be designed which ensures adequate performance, with low chances of operational disruption.
