Development of friction-damped seismic fuses for steel storage racks

Abstract

This paper describes a study [1] on the behaviour and design of drive-in racks with fuses installed to reduce seismically imposed internal actions. Two different cross-aisle framing systems were tested using various earthquake signals and magnitudes. The first system featured cross-aisle frames fully braced from top to bottom using diagonal braces. In the second system, the cross-aisle frames were braced from the top down to the level of the first pallet runner. In the former system, the rack structure was found to be very stiff and hence, it attracted high base shear action causing severe damage to the uprights, braces and connections. The latter system was found to be significantly more flexible, attracting much lower base shears. However, due to the inherent flexibility of the latter system, second order effects due to excessive sway could cause instability especially when spatial plastic hinges develop in the uprights. Based on the outcomes of the study, a new bracing mechanism has been developed to improve the seismic behaviour of steel storage racks using friction-damped seismic fuses. This paper presents the new bracing system with integrated seismic fuses including tests of the components of the fuses. Full-scale tests of complete 3-bay drive-in racks are also presented featuring tests in the elastic range to determine the natural frequencies of the two systems and destructive tests of fully loaded racks subject to common earthquake time histories of increasing magnitude. The paper also discusses the opportunity the seismic fuses present to substantially enhance the seismic performance of steel storage racks.