BBI Warehouse

Entrant: 
Adam Hay / TimberSpan

Category: 
9. Hybrid building award

Photographed by: 
Adam Hay

TimberSpan was approached by BBI wood Products to design, supply and build a new distribution facility for their expanding business. The project brief was to provide a showcase building that represented their distribution philosophy of providing quality timber products along with demonstrating the potential for commercial timber structures in a predominantly steel dominated industry. The steel components are painted black to provide a nice contrast with the Pine and express the structure to a somewhat higher aesthetic level for an industrial building than is usual.

While a Timber/LVL solution was a nice to have, the advantage of the timber structure’s design offering no bird perches in the warehouse was deemed high priority, to prevent soiling of the high value stock and machinery inside. The building is 100.0m long and 45.0m clearspan with cantilevered canopy’s along both sides, resulting in a undercover roof area of approximately 6,500m2. On the front of the building is a 300m2 biophilic office design clad with Ply board and batten and fully lined with 12mm Birch ply.

Timber experts Potius Building Systems was chosen to provide the Structural design and drawings, working in conjunction with local consultants Strata Group for the Civil design and site inspections. To achieve the clearspan portal rafter both a box beam and solid LVL13 & LVL11 1220x225mm cross section rafters were considered. The solid LVL rafters were more cost efficient and were able to taper cantilever along both sides by 7.0m on the southern side and 8.0m on the northern side to offer further ‘under cover’ storage space. Rafter joints were positioned to maximise the available length of 12.0m LVL billets and position them at points near introflexion bending moments. The result was 60.0m long rafters that were fully machined CNC’d by Nelson Pine and delivered to site in a ‘ready to erect’ state.

Steel 610 UBs were chosen for the legs to minimise the impact into the working space inside the warehouse. This lent itself to having steel gussets, that protruded to the outside of the building (again to allow full height stacking to the underside of the knee inside) and connected to the LVL rafters with Spax screws. Longitudinal and roof bracing was achieved with Reidbrace. 8.33m bay spacing dictated 400x45 LVL8 purlins and 300x45 LVL11 girts, optimised for their cost/span ratio. The building was erected with a 120mm prechamber at the apex and 11mm column chamber towards the mid of the building to account for deadload deflections and creep.

Price wise the foundation ended up being cost neutral, however this structure ended up 12% more cost effective than either of the two steel quotes for the job. Several innovations contributed to the structural cost saving including: using lower grade LVL where appropriate for the rafters, purlins and girts, ensuring cost effective shapes and connections to minimise CNC time at Nelson Pine and swapping out steel gussets for LVL gussets along the rafter lengths.