Partially and non-destructive testing of 40 concrete bridges

This paper discusses the use of information collected from long-term bridge inspection records held by bridge owners and the carrying out of partially and non-destructive testing on a representative sample of bridges. In order to develop deterioration models for concrete structures in the Greater London area, work was carried out on the basis of the inspection and repair records of a large number of bridges owned by London Underground and Railtrack (formerly British Rail). A computer database of defect histories consisting of more than 2500 observations extending over 60 years taken from in excess of 400 bridges was collected and collated. This database was called the ‘field data’. Analysis of the field data will provide deterioration rates from one condition state to more severe condition states as observed by bridge inspectors during their regular inspections. To establish a measure of the quality of construction, cores and dust samples from 40 bridges have already been collected, together with data in relation to carbonation, reinforcement cover, Schmidt hammer readings and visual observations as to the condition of each element of each bridge. The rates of deterioration were found to vary considerably but seem to be showing reasonable correlation with the general quality of construction and the degree of exposure experienced by the element over its life. This latter condition may well have changed during the element's lifetime, which makes this correlation particularly difficult to predict.