Frames

Abstract

The calculation of the absorbed energy i.e. the area of the hysteretic loop for rods of circular and square hollow sections (CHS and SHS) has been worked out. The limiting points of the hysteretic loop have been determined on the basis of experimental results published in the literature.

A square symmetric portal frame with four horizontal beams and four columns, carrying a silo is designed for vertical and seismic loads. Design rules of Eurocodes 3 and 8 are used. X-bracing is applied, in which the compressive member absorbs the energy by a hysteretic cycle with overall buckling. The cost function for the braced portal frame is expressed in function of unknown dimensions of beams, columns and braces.

The beams and columns are constructed from SHS profiles. All joints are fully welded. The design constraints are formulated for beams and columns on stress, overall buckling and admissible sway for unbraced frame. This sway has two main components: the sway of the vertical frames and the deformation of the beam due to bending in horizontal plane. The constraint on slenderness of braces is also important.