University of Kansas School of Architecture and Design

Challenging the mass timber status quo, our structural engineers posed the question: could the structural frame be 100% wood with no steel connection hardware or fasteners? Full-scale connection prototyping (with a resulting full-scale mockup, pictured here) and a deep dive into pure timber engineering ensued.

Further sustainable material choices including low-carbon concrete, dry floor build-ups, non-conventional façade materials, and gypsum alternatives throughout the building complement broad sustainability goals and create pause for thought for future users of the space.

CLT Bearing Walls and Concrete Substructure

The reinforced concrete substructure consists of partial basement and service tunnel supported by shallow foundations. Concrete volumes were reduced wherever possible to support sustainability targets, alongside low-carbon mix designs. The CLT core walls are gravity bearing only and do not form part of the lateral force resisting system.

CLT panels up to 40ft long frame the stair and elevator shafts and are designed to achieve the required 2hr fire resistance rating. The remaining walls in the core do not require a rating.

Gravity Framing

The gravity structure consists of a glulam post-and-beam frame, with primary girders spanning from the CLT core out to the perimeter columns, supporting 1-way spanning mass timber panels.

The girders create a distinctive “X” shape in plan, matching the aesthetic of the “mega-X”  bracing system. The MEP systems have been carefully coordinated with the glulam structure. A 12” deep x 30” wide notch is provided at the interior support, providing a home for the primary duct.

Stair Tube

The stair tube is a significant architectural and structural component of the building, connecting all 6 floors as it circulates around the core. The tube provides both a feature stair on the exposed top level and a rated egress on the enclosed bottom level. The stair is utilized to support the floor framing, acting as a truss or deep beam spanning diagonally across the building.

Given that it is an egress, the stair tube has a 2-hour fire resistance rating (FRR).

“Mega-X” Braced Frame Optimization             

The timber braced frame lateral system, designed as a “Mega-X” shape in each elevation, was optimized using two methods. First, a topological optimization was performed to understand the overall flow of forces. This was followed by a multi-objective optimization to find the most efficient brace arrangement, ensuring lateral drift limits were satisfied while minimizing glulam volume.

100% Timber Connections in Braced Frame

The connections in the “Mega-X” braced framed are detailed as all timber joints, with no steel or engineered timber screws, inspired by traditional Japanese joinery. The braces are particularly complex, with optimized saw-tooth geometry used to transfer both tension and compression forces into the beams, columns, and braces. Critically, the joints are primarily tight-fit, requiring a high degree of precision and accuracy in detailing and fabrication.

Full-Scale Mockup

Our engineers were challenged to imagine a mass timber structure with no steel connections or fasteners – all wood. This resulting full-scale structural mockup uses an exterior Glulam diagrid achieved with 100% wood connections.

For the project, we had the opportunity to create this mockup of the larger building featuring part of the Glulam diagrid, the architecturally expressive “Hero Node”, and a section of the L2 floor plate.

Notably, the diagrid connections are designed as all-wood, inspired by traditional Japanese joinery, and requiring a high-level of precision in detailing and fabrication. Our structural design was entirely modeled in Branch 3D (our in-house parametric structural design software), fabricated in our shop by master carpenters, and erected in just 8 hours.