CONSTRUCTION, BUILDING STRUCTURES
Helsinki University first floor was redesigned to have a glass front instead of a former load-bearing stone wall. To enable the change, the second floor needed to be reinforced with specially designed Vierendeel truss that could be hidden behind the front wall and it's openings could be aligned with existing windows to preserve the historic appearance. Such trusses do not have the usual triangular voids seen in a pin–joint truss bridge, rather employing rectangular openings and rigid connections in the elements, which (unlike a conventional truss) must also resist substantial bending forces. The truss weighted 22t in total needed to be lifted in three parts and assembled inside. Also the liftings needed to be done during the night in order not to disturb the traffic in old town. The truss as pull in place with two cranes through windows, jack up with with 360t lifting power hydraulic press and welded in place. The Truss also holds in place the ceiling of the first floor.