Shear capacity of inverted-U reinforced concrete bridge beams

Existing reinforced concrete inverted-U beam bridges in Western Australia built using standard beams designed by Public Works Department between 1957 and 1969 were found to have reinforcement anchorage detail at supports not adequate when assessed using recent design standards. Tests were carried out on six full-size bridge beams recovered from a bridge scheduled for replacement to determine whether the deficient detailing adversely affects the shear capacities of these beams. These beams were the longest of the series designed in 1957. In addition, the mean shear strengths of the five bridge beams to AS 5100.5–2004 and to the most recent design standard AS 5100.5–2017 were determined and these were compared with their corresponding test values. It was found from testing that the detail does not affect the shear strength much. The predicted mean shear capacities using AS 5100.5–2017 were found to be more conservative than the corresponding values using AS 5100.5–2004. This suggests the likelihood of low load ratings for shear using the latest design standard (based on the Modified Compression Field Theory) for existing reinforced concrete bridges designed to previous standards.