Timber structures for the university of applied sciences center
A key milestone in the construction of the Graubünden University of Applied Sciences in Chur was reached on Wednesday: the successful hoisting of the steel lower chords marked the start of the erection of the large trusses in the west wing. To enable the extensive column-free spaces on the ground floor, truss support systems are being installed here along the two inner longitudinal axes; each spans six standard bays and extends over three storeys to make maximum use of the available structural height. This results in the remarkable overall dimensions of approx. 35 m in length and approx. 12.5 m in height. Vertical posts and top chords made of high-strength beech laminated veneer lumber, as well as steel diagonal bracing, complete the truss structure. The joint areas at the top chord are constructed using in-situ concrete.
The bottom chords installed on Wednesday are of steel construction with 550×800 box sections made from thick-walled sheets (t=30 mm) and meet the required fire resistance (R30) without cladding. The central segments are 27.5 m long and weigh 22 tonnes. The connections for the element beams (Peikko brackets) and in-situ concrete have already been prepared on the girders.
The drawings and the series of photos from the workshop not only illustrate the extraordinary dimensions but also reveal the ‘inner life’ of the lower chords, invisible from the outside. The force transmission of the tension diagonals (Æ180 mm, solid steel) takes place directly via solid steel cross-braces 600x600x140 (S690), which are integrated into the steel profile of the lower chords at the joints.
The truss bracing, until the large truss is fully erected, is carried out using HEB220 steel beams on the ground floor and in the first basement level. A lowering wedge is provided for each bracing beam to facilitate the dismantling.
