Steel Buildings in Europe

Part 4: Detailed Design of Portal Frames 4 - 74 The practical application of this recommendation is to calculate H NHF as 1/200 of the vertical reaction at the base of the column. In combinations including wind actions, H NHF should still be calculated as 1/200 of the vertical reaction at the base. In calculating  NHF only the notional lateral forces, H NHF , are applied to the frame. Base stiffness may be included in the analysis (as described in Section 3.4). L h H H NHF NHF NHF NHF   3 1 Ed Ed 2 N N 1 Frame dimensions 2 ULS analysis, and N Ed in rafter 3 Sway analysis, under H NHF alone Figure B.1 Calculation of  cr  cr can then be calculated as: NHF cr 200   h  The lowest value of  cr for any column is taken for the frame as a whole.  cr,s,est can then be calculated as: cr cr,R max Ed cr,s,est 0,8 1                     N N where: cr,R max Ed         N N is the maximum ratio in any rafter Ed N is the axial force in rafter at ULS (see Figure B.1) 2 r 2 cr,R L EI N   is the Euler load of the rafter for the full span of the rafter pair (assumed pinned).