DOWN-AISLE SEISMIC BEHAVIOUR OF DRIVE-IN STEEL STORAGE RACKS

Abstract

Steel storage racks are extensively used as an essential element in warehouses, manufacturing facilities and distribution/logistic centres throughout the world as an economic and efficient way of storing goods. With the advancement of technology and increase in production volume, more efficient, engineered and mechanized ways are introduced for storing goods. Two main types of storage racks are used in industry depending on their intended application and space requirements. These are selective racks and drive-in racks. Selective racks are one or two pallets deep with aisles between rows of racks which allow for flexible access. Drive-in racks are typically 3 to 7 pallets deep and are used when space utilization is a priority while accessibility to a particular pallet is not. The structural behaviour of steel storage racks is significantly different to regular steel structures. Racks are freestanding and act as structures in their own right, supporting mainly gravity loads, placement and impact forces and potentially, seismic forces. They are more likely to carry the full design live load many times in their design life. Drive-in racks use spine bracing at the rear and plan bracing at the top to transfer horizontal forces to the ground and ensure overall stability in the down-aisle direction. This eccentric bracing configuration results in pronounced 3D behaviour in which down-aisle motion triggers movement in the perpendicular crossaisle direction This thesis investigates the three-dimensional response of steel storage drive-in racks under down-aisle seismic excitation. A uni-axial seismic testing facility was developed to test full scale, three-bay wide and three-story high, fully loaded drive-in rack subassembly using real earthquake time histories, in both down-aisle and crossaisle directions. Dynamic properties of drive-in racks with different spine bracing configurations were obtained from experimental investigations. Down-aisle seismic response of drive-in racks with different spine bracing configurations are presented and based on the experimentally obtained results, an optimum bracing configuration is suggested.