6. Conclusion
It was the intention of the survey to try to establish some common practices in the design, specification and fabrication of simple and/or semi-rigid structural steel connections in the UK. This has been achieved and the information obtained has been quantified and presented within this paper. The importance of this information being published is such that it will not only help to bridge the gap between the academic research community and industry, when considering future research on such structural connections, but also provide a useful practical insight to the community within the steel construction industry as a whole. From the survey results, the following points can be inferred: - Steel box sections (SHS’s & RHS’s) are not commonly used as primary columns on construction projects. A total of 88% of the respondents have encountered their use on projects 25% of the time or less. - On projects where tubular box sections are the primary columns, the preferred method of connecting an incoming open section to them is a fin plate connection. - If a ‘blind’ connection is absolutely necessary, the survey indicated that Hollo-bolts were the preferred fastener to use (as opposed to Blind Bolts). The preferred choice for connecting an open section beam to an open section column was overall highlighted as a full depth end plate (39% of the survey population), followed by a partial depth end plate (29% of the survey population) and then a fin plate (20% of the survey population). A portion of the survey respondents (10%) also indicated that their choice of connection between open sections would be scenario dependent. The remaining 2% of the respondents indicated their preferred method of connecting open sections would be to use web cleats (now withdrawn as standard connections). Stainless steel bolts are rarely used on construction projects, 49% of the survey respondents stated that they have never encountered their use on construction projects and 38% stated that they had only encountered them up to 5% of the time. These points will help devise a full scale testing programme in which standardised details from the Green Book will be subjected to a range of dynamic tests. The purpose of this testing is to propose a design methodology for the standard connection details that can be used to calculate the dynamic capacity of such connections with greater confidence than simply applying dynamic increase factors. Currently, only the static design capacity is catered for within the Green Book. Static tensile capacities of the standard connections are provided and are used to satisfy the tying requirements set out in Approved Document A [17]. These capacities and the concept of ‘tying’ provide a safety net against collapse but overlook the dynamic nature of a progressive collapse. Inertia, rapid rotational force and any strain rate effects that could be encountered during a collapse event are not considered by the Green Book. It is the intention of the overall PhD study mentioned to output peer reviewed research findings that can be used to progress the development of the standard connection dynamic capacities with due consideration to structural and material dynamic behaviour.
