Ultimate strength and failure modes of short-to -medium span composite bridges. A desk study

The purposes of this study were to: a) identify gaps in existing knowledge; b) identify areas where existing knowledge had not been exploited fully; and c) consider procedures of assessing the ability of existing bridges to carry loads grater than those for which they were designed. In order to do this a critical review of the literature was carried out. Areas where this knowledge is not taken fully into account in BS5400 (see IRRD 235662, 235663, 263232, 282725, 264406, 245610, 249424, 267691, 268353) were identified. It was found that current serviceability had more influence on design than was implied in the wording of the task, and so additional knowledge relevant to these criteria were included. Situations in which failure could occur such as dead loading, wind loads, and highway live loads were discussed. Comments were also made on the design and overall capacity of three bridges built to BS5400 standards by Johnson (see IRRD 286789). The conclusion was that the capacity in each case was probably limited to criteria of serviceability or of repetitive loading. Recomendations for further research on bridge decks were made.