Reliability of existing structures

Structures that have been in service for some time have been load tested ei ther by the in service load or, in some circumstances, by a proof load. The ir successful survival is evidence that their load-carrying capacity, over and above the dead load, is greater than the applied load. This information can be used to update their reliability. The reliability updating analysis can be carried out based on efficient reliability updating methods. Results of analysis show that the increase in reliability of a service-prov en structure is strongly influenced by the Value of maximum load already su stained. This increase implies that a less stringent strength requirement f or a service-proven structure than for a new structure should allowed for t he same safety level. A graphic representation of the relationship between the updated reliability index, maximum applied load, and reliability index before service is suggested for possible applications.