Types of pallet racking systems

Pallet racking systems are usually categorised from a functional perspective and include the following types:

• Selective pallet racking: the most common type of pallet racking system. Provides accessibility to all products at all times and is important for quick turnover. There are two structural forms:
  • Roll formed: the horizontal load beams are held in place by mounting clips that locate in ‘tear-drop’ shaped holes in the vertical columns. Allows quick adjustment to different heights to accommodate various load sizes
  • Structural: similar to roll formed pallet systems except the horizontal load beams are attached to the uprights with bolts and have much greater load-bearing capacity. Structural pallet racking can be designed into the structure of the building itself, creating a rack-supported building

• Double deep racking: a variation on selective racking in which the pallets are stored two deep from the aisle
• Drive-in and drive-through racking: are storage rack configurations that allow the forklift to drive directly into the lane of stacked rows (called a bay). Drive-in systems have a bay entry at only one end, while drive-through systems have entry/exit at both ends
• Push-back pallet rack systems: are designed around the principle of organising space by depth rather than width. Each bay can be up to six pallets deep, with pallets commonly stored on wheeled carts running on rails. Push-back racks are a LIFO (last in, first out) storage system
• Compact mobilised pallet racks: have rows of pallet racks mounted on heavy duty rolling carriages running on floor tracks. Bays can be opened up as needed for access
• Cantilever racking: is ideal for storing long products that require no obstruction at the pick face. The system comprises cantilever beams supported off columns at the back side of the storage space.

Double deep racking system. Courtesy Dematic.

Standards and design

Australian Standard AS 4084:2012 ‘Steel storage racking’ applies to the design of steel storage racking systems. The 2012 revision to this Standard introduced significant updating of the analysis provisions, allowing the design to be based on analysis types including:

• Linear (elastic) analysis (LA)
• Linear buckling analysis (LBA)
• Geometric nonlinear analysis (GNA)
• Geometric and material nonlinear analysis with imperfections (GMNIA).

GMNIA, often referred to as 'advanced analysis', incorporates the dominant nonlinear effects and is capable of accurately predicting the behaviour and strength of structural steel frames. 

Two types of GMNIA are allowed in the Standard, namely the analysis of structural frames with compact cross sections (GMNIAc) and the analysis of frames with non-compact or slender cross sections (GMNIAs). GMNIAs should be based on a full discretisation of members into finite strips (the finite strip method) or finite elements. Provisions are included for the frame, member and cross section geometric imperfections to be incorporated into the structural model. 

Top) Advanced analysis of racking system. (Above) Testing of racking system. Courtesy University of Sydney.