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

Seismic behaviour of steel storage pallet racking systems . 30the ratio between the maximum and the minimum distance between the pallet beamsin elevation is less than 2 (mass regularity)Down aisle directionRegularity in plan• Racks not braced or symmetrically braced in the down aisle direction in thefront and rear planes are stiffness regular in plan• Racks braced on the rear plane only in the down aisle direction are not stiffnessregular in planRegularity in elevation• Position of the pallet beamsThe rack can be regarded as mass regular if:the pallet beams are on the same level for the entire length of the blockANDthe ratio between the maximum and the minimum distance between the palletbeams in elevation is less than 2• Type of vertical bracingsRacks with vertical bracing continuous from the floor to the top load level arestiffness regular in elevation.Racks partially braced are not stiffness regular in elevationRules for the design of low dissipative structuresIn addition to general requirements related to materials, strength evaluation (for bothmembers and connections) as well as for bolt tightening, the following specific rulesare stated:1) If ductility factor q > 1.5 is assumed, members which contribute to the seismicresistance of the structure by working in compression or bending must be ofclass 1, 2 and 3 according to EC-3.2) If the structure is not regular in plan or elevation, q shall not exceed 1.50.3) K bracings, in which the tension diagonals intersection lies on a column, shouldnot be used in seismic zones.4) For bolted shear connections the shear strength of the bolts should be higherthan 1.20 times the bearing resistance.Structural systems withstanding the seismic actionThe seismic action can in general be studied separately in the down aisle directionand in the cross-aisle direction, and the lateral forces resisting systems can beuncoupled.