CASE STUDY | Archive Shelving Analysis

Precision have a long history in New Zealand manufacturing, dating back to 1921 and covering a broad range of products from car licence plates to milk tokens. Today, Precision are renowned as a focussed commercial steel storage provider.

Precision are part of the Dexion group and provide storage solutions such as custom designed cabinetry, steel filing and storage, retail shelving, library shelving, and mobile shelving units.

THE CHALLENGE

Precision had been awarded the contract for the design and supply of mobile shelving for Archives NZ‘s new building in Wellington. The building is 11 storeys high, and each floor is filled with rows of mobile archive shelving for storing important documents from land deeds to stormwater plans. Mobile archive shelving allows for the usage of each floor to be maximised while retaining easy access to documents.

The contract required the shelving supplied to comply with NZ engineering standards including appropriate seismic rating and be able to withstand lateral and longitudinal seismic loads of up to 1.5g. With significant shelving payloads, this meant that the thin-walled sheet metal shelving needed to be assessed and reinforced to provide adequate strength to withstand a 1 in 100-year earthquake event. Adding to the challenge, the shelving needed to be mobile while being protected from tipping under earthquake loading. The work had come at a time where Precision’s design team were fully engaged with other projects and were in need of support to meet the deadlines set by their customer.

Caliber were engaged to assist with the design of the locking mechanism, and assess the design of the full shelving system against the relevant NZ standards (including NZS 3404 & AS/NZS 4600).

THE SOLUTION

Caliber worked alongside Aurecon and a 3rd party certifying engineer to assess, revise and validate the design as fit for purpose. Each element in the load path in both the lateral and longitudinal seismic loading directions was evaluated, which given the complexity of the design resulted in a large number of calculations being required.

As the shelving is a non-structural element, with a design that is very different from structural steelwork typically used in construction, Caliber were in a position to add value to a certifying structural engineer by leveraging combined mechanical design, calculations, CAD and FEA capability. Caliber’s involvement provided the heavy lifting to carrying out the calculations, with the certifying engineer engaged for guidance, design reviews and final sign off. Quickly alternating between calculations and design modifications in CAD allowed for fast iteration of the design based on analysis findings, improving productivity. FEA was leveraged to assess the mechanical strength of complex parts that were difficult to analyse by hand. In addition, FEA was used to assess the buckling strength of the shelving, including shapes that are challenging to assess with other approaches, such as formed sheet metal and bead rolled panels.

The final shelving design was subjected to physical testing, where it passed with flying colours in front of a panel of key stakeholders. The shelving was also subjected to loading above the design limit, which confirmed the accuracy of safety factors used – and was a rare opportunity to discover the true accuracy of the analysis work.