Estimates of the useful lifetime of bridges using a generated database

The useful lifetime, or lifespan, of a bridge is an important parameter in its economic evaluation and sustainability assessments. There is little lifetime data in the public domain for UK bridges. Current sources of lifetime data are reviewed. To look at UK age data, a sample of bridges was taken and analysed: 123 bridges currently spanning the River Thames from Cricklade in the west to Dartford in the east and 124 bridges previously spanning the river but now removed, these helping define the lifetime rather than age. The methodology used for collecting, collating and analysing the database and its accuracy is outlined. The methodology included the use of artificial intelligence, which needed significant checking to be useful. Best estimates of age, design working life and useful lifetime of a bridge were determined to be 131, 57 and 127 years respectively. The data was used to help identify the most important parameters, which – in approximate order of importance – are material, form, articulation, owner, condition, use, economic conditions, size and location. Significant interaction between these factors was noted. It is recommended that, for lifecycle assessments, the useful lifetime should be used. It is also recommended that more masonry arch structures should be built as these clearly have longer useful lifetimes.