PRINCIPAL INVESTIGATORS: Skidmore Owings & Merril, Tsz Yan Ng, Wes Mcgee.
LOCATION: Chicago Architecture Biennial, The Available City, South Shore Chicago, IL
SPLAM, SPatial-LAMinated timber (SLT) reconsiders the conventional use of nominal framing systems, mainly with 2X4s, to design an engineered structure that uses about 46% less material compared to typical CLT structures of the same loading capacity. The SPLAM timber pavilion is a demonstration of this system, as part of the 2021 Chicago Architecture Biennial Exhibition The Available City. The project is a collaboration with Skidmore Owings & Merrill (SOM) and Epic Academy, where the project will remain after the exhibition as a flexible outdoor classroom for the South Shore public high school.
The collaboration focuses on timber as a renewal resource with a low carbon footprint. Instead of mass timber, the choice of using 2X4s highlights the opportunity to use shorter growth pine trees that are more rapidly renewable then larger solid sawn species (translating to lower carbon-footprint) and expands the typical use of 2X4s beyond framing for single-family homes. Structural topology optimization allows for the design to place members only where it is needed relative to the loading paths. Leveraging advanced milling fabrication processes for the 2X4s, traditional joinery methods such as scarf joints, previously reserved for mass timber construction, are now extended to smaller dimensional members. This enables material efficiency by being able to string shorter off-cuts that might have been previously considered as waste into usable elements for the SPLAM system. The project employs only two joint types, the scarf joint for end-to-end connection, and an overlap joint for cross-orientation layering for sectional thickness. Slab thickness are reduced from 22 inches to 17 inches compared to traditional framing structures, enabling higher floor-to-ceiling heights or for multi-level structures, can translate to an extra floor. The simplicity of the system enabled pre-fabrication and some preassembly of all 912 members off-site with a one-week on-site assembly by a three to four-person crew. To account for inconsistency of 2X4s, a self-centering pneumatic gripping jig was developed to aid the milling process. Physical stress-testing (tension and loading) of joint prototypes provided the data necessary for the engineered system.
Kendall McCaugherty © Hall+Merrick Photographers, © David Burk / SOM, Tsz Yan Ng, Diagrams: SOM