Usage of continuous steel truss in multistorey shopping centre frame
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Jatkuvan teräsristikon käyttö monikerroksisessa kauppakeskusrungossa
Rautaruukki Construction is developing a new frame system for shopping centres. This Master of Science Thesis is part of the project. The frame system is based on continuous steel trusses and composite steel columns. Floors are typically hollow core slabs. The structural characteristics of shopping centre buildings were researched by examining executed targets in Finland, Sweden and Norway. In analyzed frames the first two storeys are typically parking levels. Above parking levels are hypermarket and commercial levels. On the roof is a technical level. All floor to floor heights and clearances were defined by target reviews. In the parking levels the columns grid is 17,0 x 5,4 m2 and in the upper levels 17,0 x 10,8 m2. The height of steel trusses is determined by optimizing consumptions of steel and required stiffness and also by ensuring adequate routing space for HVACE-utilities. Loads are determined by usage of levels and by Eurocodes. Four static frame models were analyzed. The static function of the frame and critical loads were clarified. The largest loads 5-10 kN/m2 were applied on hypermarket and commercial levels and 2,5 kN/m2 was applied on parking levels. The research exhibited that the size of columns was determined by N-M resistance not the sway-factor αcr. The factor αcr is in all researched frame models over 10 so frames are non-sway. Using continuous steel trusses instead of one-bay trusses the circular section of middle columns is about 50 - 100 mm larger. The frame of the shopping centre must be adaptable and configurable. Structural elements that limit the use of space, such as shear walls, bracings and struts, should be avoided or minimized in order to improve the efficiency of the space. In all analyzed frame models the stiffness of the continuous steel truss – composite column -system guaranteed the stability in the direction of frame. The stability in opposite direction was not been checked in this research but it is normally carried out by steel bracings. Topics for future research could be among other things optimizing of continuous steel truss, development of joints between continuous trusses and columns and development of dimension tools for unbraced frame.