Review of strength behaviour of circular concrete filled steel tubes under monotonic pure bending

The existing literature concerning the flexural strength of circular concrete-filled steel tubes (CFSTs) has been reviewed in this paper. Using a much-expanded database of published flexural tests than considered in previous review studies, the applicability and conservativeness of four commonly used design standards to assess the flexural capacity of circular CFSTs have been substantiated through this review. This was verified to be the case irrespective of the type of concrete used for infilling the steel tubes of the circular CFST. Reliability analyses performed based on 219 circular CFST flexural tests obtained from the literature provided confirmation that the capacity factors stated for steel and concrete in AS/NZS 2327 provide an adequate reliability level for structural design. The calibrated capacity factors for the target reliability index exceeded the values given in the standard thereby confirming the conservatism of the code. In addition, it was ascertained that the slenderness limits specified for compact behaviour in the design standards were significantly conservative. Further bending tests on larger diameter tubes with thinner walls and higher steel strengths are needed to establish the actual limits. Further testing is also needed to ascertain the effect of the steel tube fabrication method on the flexural capacity of circular CFSTs.