ENGINEERS ON London's controversial 180m tall Swiss Re building are gearing up for a complex dimensional monitoring exercise after the first of the massive A-frame structural elements arrived on site last week.
Weighing up to 11t each, the 360 steel circular hollow section A-frames will have to be precisely located during erection and allowance made for a tortuous and progressive set of deflections as increasing loads from the floors and cladding are added.
Structural engineer Arup's design team has to analyse and predict the shortening and expansion of the structure under load and monitor the external diagrid frame as construction proceeds.
Main contractor is Skanska, with the 8,400t of structural steel supplied by jv fabricator Victor Buyck-Hollandia.
At the ceremony marking the arrival of the first structural section, project architect Lord Foster dismissed concerns about the need for extra structural protection for the tower following last month's World Trade Center disasters.
'No design changes were required as the codes are already quite specific, ' he said.