Abstract
Since few years ago only one typology of racks was used to store Grana cheese wheels for aging, which was designed focusing on the sole static behavior. Battened steel columns made by vertical tubes welded to horizontal angles were connected by means of wood boards supporting the wheels. In 2012, a strong earthquake occurred in Emilia Romagna (Italy) and a great number of these structures collapsed owing to the absence of checks for resistance against earthquakes. This catastrophic event plus the need to maximize the structural efficiency led to the development of a new typology of rack systems based on the use of cold-formed steel members. Owing to an extremely limited state-of-the-art on these modern cheese rack, design is carried out in agreement with the standard provisions calibrated and proposed for adjustable pallet racks, despite the non-negligible differences between these structural systems. The paper is focused on the comparison between the available seismic design approaches for cheese rack in order to highlight their main advantages and limits. In particular, among the four design approaches admitted in the European standards, the modal response spectrum analysis (MRSA) and the nonlinear time-history (NLTH) have been considered and the associated results compared in terms of maximum safety index of the members, global displacements and interstorey drifts. Research outcomes stress the differences associated with the considered approaches in terms of expected performance underlining the importance of an accurate definition of the behavior (q-) factor.
Highlights
In Italy, the dairy sector is recognized as one of the most impacting agricultural activities, with important economical revenues, having a relevant and growing role in the agri-food economic sector
Earthquakes occurred in May 2012 in Emilia Romagna (Italy) caused in few cases severe damages to grana warehouses [1], that progressively collapsed causing a domino effect leading to the loss/depreciation of several thousands of tons of grana cheese (Figure 1)
A study is currently in progress on cold-formed steel grana cheese racks, which started few months ago at Politecnico di Milano. It comprises of different phases: (i) experimental in-situ activities based on the modal identification techniques adopted to characterize Italian cheese frame typologies differing mainly for the number of bays and for the load levels; (ii) deep study of the seismic and monotonic behavior of the tested structures, which is the core of the present paper; (iii) definition of reliable design rules accounting for key features of both the old and new grana cheese racks
Summary
In Italy, the dairy sector is recognized as one of the most impacting agricultural activities, with important economical revenues, having a relevant and growing role in the agri-food economic sector. The longitudinal (down-aisle) direction, the geometry of the oldest and new type cheese rack is the same, differing only for the structural components and for the connection system between columns: in the modern systems the columns are connected one another via horizontal hollow circular tubes every 3–5 line of wood boards, realizing together with the X-type bracings located in few panels, a Buildings 2020, 10, 246 of 20 partially braced frame. A study is currently in progress on cold-formed steel grana cheese racks, which started few months ago at Politecnico di Milano It comprises of different phases: (i) experimental in-situ activities based on the modal identification techniques (currently in progress) adopted to characterize Italian cheese frame typologies differing mainly for the number of bays and for the load levels; (ii) deep study of the seismic and monotonic behavior of the tested structures, which is the core of the present paper;. Research outcomes stress the difference in terms of expected performance underlining the importance of an accurate definition of the behavior (q-) factor
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