Joints in frame structures do not function simply as pinned or rigid. Rather, these two categories represent extremes in a spectrum of behaviour. The concept of semi-rigid and partial strength joint properties has been the object of research in steel construction, in composite construction and, more recently, in concrete frames and timber frames have made many advances.

Few studies, however, have addressed more than one material at a time. A conspicuous exception is the COST C1 Project, which has generated much interest throughout Europe. The project is distinguished by its concern with all main structural materials. In the Istanbul Colloquium Report, some findings from the COST C1 Project are presented by André Colson, France, Chairman of the Project. The conversion of Eurocode 4 into a European standard is an opportunity for David Anderson, UK, Convenor of the Project Team, to outline the present draft rules. The 35 contributions to the Istanbul Colloquium Report come from 14 European countries and Japan. They also cover many areas not linked via the COST network. The Colloquium Report thus presents the state-of-the-art in Europe. Contributions are grouped under the themes:

• Experimental Results on Joint Characteristics
  
• Effect of Joint Actions on Frames
  
• Tests and Analysis of Frames
  
• Modelling of Connection Behaviour
  
• Design of Connections
  
• Design of Frames