Partial safety factor for reinforcement

In 1994 a proposal was published in the Structural Engineer [1] that the partial safety factor for reinforcement be reduced from 1.15 to 1.05. This was accepted and incorporated in BS8110 [2]. A change was subsequently made to the specified characteristic strength of reinforcement, changing it from 460 N/mm2 to 500 N/mm2. As a temporary measure until data was available on the characteristics of the new specification, the partial safety factor was changed back to 1.15. This study uses new, and very thorough, data obtained from CARES on current reinforcement properties to re-examine the requirements for a suitable partial safety factor for current reinforcement production.The reliability approach is first considered using the previous data. The approach is then applied using the new data and a new factor is suggested. The practical implications and the alternative of deriving factors from experience are then considered.The quantitative study is carried out on sections subjected to pure flexure although implications for other aspects are also considered. It is concluded that the partial safety factor of 1.15 is unnecessarily high and the value of 1.05 is justified.The paper was first drafted by Professor Beeby who died shortly afterwards and before responding to comments by the second author. Because a change in the basis of reinforcement standards discussed below was not considered in the first draft, most of the analysis reported was by the second author.