The Post-Tensioned, Prestressed Ketton Stone Perimeter Frame of The Queen's Building, Emmanuel Colle

Hipped rafters Two more contributors have reverted to this much-discussed topic. Stuart Marchant writes from London SW18: I have been following the recent correspondence with interest and studying my own roof I fail to understand how Alasdair Beal(1 June 1999) infers that purlins greatly reduce the triangulation forces. The purlins in the roofs that I have seen are generally perpendicular to the rafters with inclined props. These will induce an axial load in the rafter in much the same way as a ridge board, although of a slightly reduced magnitude, resulting in an outward thrust at the wallplate.

Immediate Past President, ladies and gentlemen, members and guests of the Institution, it is both a great honour and a great pleasure to take office as President: when I started out on my professional career, it would have been inconceivable to imagine that, 30 years after graduation, I would have been elected to lead my chosen profession. I say this without any false modesty, and I have no doubts at all that the same sentiments would apply to any of my predecessors. It is doubly exciting for me to serve over the Millennium, not because of the symbolic significance of the date itself, but because of the large number of high quality, exciting projects that are being constructed or completed at this time which, I believe, will add significantly to the public perception of structural engineering (Fig 1). J.R. Roberts I had decided more than a year ago to focus some of my

Mr P. L. Campbell (Past President) In 1973, not long after the M & S structure was constructed, I was asked by the editor of New Scientist to write an article about the inherent dangers of demolishing ‘special’ structures (pre- and post-tensioned structures, nuclear and offshore installations, etc.), if full information concerning the original design were not available. I believe that such structures should have a plaque stating that they are ‘special’, and full design information should be retained in a central repository in perpetuity for reference by future generations. On the face of it this building had well-grouted tendons, space around it, a useful basement area, and a configuration that suggests to me that demolition using explosives was an obvious option. Was this considered and, if so, why was it rejected?