The Task Group has been active since February 1992 and published in 1993 Bulletin 218, a first collection of individual contributions. Now the final synthesis report in part 1 of this Bulletin summarises research results and strives to give a harmonised view on the topic. It suggests proposals that by and large endorse the CEB-FIP Model Code 1990. Further research needs are identified. The individual contributions in part 2 of this Bulletin report on research performed since 1993 within the framework of the Task Group. Although extensively discussed within the group, the papers express the individual views of their authors, all of them being members of the Task Group.