Prof. Ing. Carlo Andrea Castiglioni Seismic Behaviour of Steel ...

Seismic behaviour of steel storage pallet racking systems . 28Combination of the horizontal components of the seismic actionIn general the components of the seismic action shall be considered as actingsimultaneously, and their combination components may be accounted for as follows.Method 1• the structural response to each horizontal component shall be evaluatedseparately• the maximum value of the effect of each action on the structure due to the twohorizontal components of the seismic action is estimated by the square root ofthe squared responses to each horizontal component.Method 2As an alternative to the above method, the action effect on the structure due to thetwo horizontal components of the seismic action may be computed using the twofollowing combinations:a) E Edx “+” 0.30×E Edyb) 0.30×E Edx “+” E Edywhere“+” implies “to be combined with”E Edx = action effects due to the application of the seismic action along the horizontalaxis x of the structureE Edy = action effects due to the application of the same seismic action along theorthogonal horizontal axis y of the structureThe sign of each component in the above combinations shall be taken as the mostunfavourable for the effect under consideration. When the regularity criteria arefulfilled and the lateral resisting systems are separated for the two principaldirections, the seismic action may be assumed to act separately along the two mainorthogonal horizontal axes of the structure.Combination of the vertical component of the seismic actionIn case the horizontal components of the seismic action are also relevant for thoseelements that are affected by the vertical seismic action, the following three