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

Seismic behaviour of steel storage pallet racking systems . 36Safety VerificationsUltimate limit stateThe safety against collapse (ultimate limit state) under the seismic design situation isconsidered to be fulfilled if the following are met.The design values of actions shall be combined using the following formula:Σ γ GA G k “+” γ QA Σ ψ 2,i Q k,i “+” γ I A E,dwhere“+” implies “to be combined with”Σ implies “the combined effects of”G k = characteristic value of the permanent action (dead load)Q k,i = characteristic value of a typical variable actionA E,d = design value of the seismic action for the reference return periodγ GA = partial safety factor for permanent actions = 1.0γ QA = partial safety factor for variable actions = 1.0ψ 2,i = partial reduction coefficient for variable actions:ψ 2,1 = 1.0 for the pallet loadψ 2,2 = 1.0 for floor loads on storage areasψ 2,3 = 0.5 for passage floor and walkwaysγ I = importance factorServiceability limit stateDamage limitation requirementThe requirement for limiting damage (serviceability limit state) is consideredsatisfied if the response of the rack remains in the elastic field under the seismicaction having a larger probability of occurrence than the design seismic actioncorresponding to the “no collapse requirement” (See prEN 1998-1)Pallet slidingThe pallet sliding on the beams must be assessed under a seismic action calculatedwith the behavior factor q=1 and ground acceleration reduced by factor E D1 .The ratio between the horizontal seismic force and the pallet weight, or between theacceleration at rack level and the acceleration of gravity g, must be less than thefriction coefficient of the pallet on the beams.If the sliding of the pallet occurs, devices must be installed in order to prevent thefalling of the pallets.