The development of section 5, concrete, of the NAASRA bridge design specification 1988

The draft bridge design specification in limit state format has been made available to the state road authorities for trial designs in January 1988. The concrete section of the specification has been prepared in close cooperation with the Standards Association of Australia. The Australian standard AS 3600 (1988) published in march 1988 and section 5 of the draft NAASRA specification are not only compatible but with some minor exceptions also similar in format. Aspects of the new concrete design specification are outlined. Major changes to the specification occur with the change to limit state format and the integration of reinforced, partially prestressed and prestressed concrete into one section. Requirements for durability are substantially amplified with exposure classified according to atmospheric conditions and special conditions or structural application and requirements given for different classifications. Material properties have been rearranged into one section. They are based primarily on tests and ranges of error are given. Serviceability limit states for both reinforced and prestressed concrete are considerably liberalised, and generous redistribution allowances are now available at the strength ultimate limit state. The design of columns has been completely changed and is now based on the moment magnifier effect (a).