A free-form timber gridshell canopy standing on a paved plaza in front of a glass building, its tree-like column of timber battens spreading into a wide roof, joined by colourful 3D-printed nodes and casting a net of shadows on the ground

Academic Project

CanTreelever

Timber Battens and 3D-Printed Nodes

Year: June 2023
Classification: Academic Project
Status: Course project, 4480 Contemporary Building and Structural Systems
Location: Izmir, Türkiye
Designer: Gökalp Kalfa & Zehra Çelik
Team: Gökalp Kalfa
Zehra Çelik (opens in a new tab)
Emirhan Duğral
Ece Hepmutlu
Elif Kır
Berkin Değirmenci
Zeynep Diker
Bengisu Şengün
Murat Şen
Ecenaz Adıgüzel
Işıl Sezer
Consultants: TutorMauricio Morales-Beltran (opens in a new tab)

Our aim in this project was to design, fabricate and assemble a free-form gridshell within a single twelve-week course. The structure combines timber battens with 3D-printed connections, a hybrid technique that makes free-form structures possible with standard building materials and ordinary 3D printers. It also had to be designed for disassembly.

Students first explored the design through digital and physical form-finding, then each presented a proposal. The project to be built was chosen by a vote among the students and developed further by the whole class. Structural and fabrication limits, including a cap of 110 nodes, shaped the final canopy.

Nodes and Fabrication

The students then designed the 103 connection nodes, weighing 3D-printing parameters such as filament (PLA+), print time, infill and orientation. The aim was to make the nodes as strong as possible and easy to assemble with the timber pieces, so some were designed as a single piece and others in two pieces, with holes for screws and cables.

The printing followed the assembly sequence. The column, the supporting part, was built first. Once it was ready, the nodes for the canopy were designed and printed; with the canopy's smaller bar sections, these printed faster. The last nodes to be designed and printed were those joining the canopy to the column, which were also the last to be assembled. The timber battens were cut, the column and the canopy were built separately, and the two were joined in the final stage.

Learning from Failure

Shortly after it was installed outdoors, the structure was brought down by a strong wind. The evaluation that followed found that one of the column nodes had been overstressed and broke, causing the whole structure to lose stability. The column nodes were redesigned for greater strength and printed in PETG, and cables were added for stability. The second version performed very well in strength and stability, but high summer temperatures made the nodes soften and melt, leading to large deflections of the canopy.

The final prototype is a proof of concept for hybrid fabrication as a way to build temporary structures in architectural education. The process of design, production, assembly and disassembly, and its failures, was later published in Learning from Failure.

Assembly

Construction Process

01 / 07

Timber battens joined by red, blue and white 3D-printed nodes into a hexagon on a tiled floor. — 01Step 1: creating the hexagons.

Students fixing vertical timber battens into the nodes of a hexagon on the floor. — 02Step 2: adding vertical elements to the hexagons.

Students assembling the base and the top of the column as two separate timber frames in a university lobby. — 03Step 3: building the base and the top separately.

The finished tapering timber column with red, white and teal nodes standing on the plaza outside. — 04Step 4: varnishing and joining the entire column.

Students on the plaza connecting the Voronoi pieces of the canopy on a temporary timber frame. — 05Step 5: connecting the Voronoi pieces on the frame.

The canopy raised on a timber frame at night, with students on ladders placing the column underneath. — 06Step 6: raising the canopy on the frame and placing the column under it.

Students at night joining the column to the canopy before removing the temporary supports. — 07Step 7: connecting the column and canopy and removing the supports.

Photographs

01 / 03

View from above of the gridshell on the paved plaza between curved benches, its Voronoi canopy casting a matching net of shadows on the ground. — 01The canopy and its shadow seen from above.

The finished gridshell on the plaza in front of the university building, a tapering column of timber battens spreading into a wide Voronoi canopy with colourful nodes. — 02The finished canopy on the plaza.

Close-up of a blue and yellow 3D-printed node joining several timber battens, with a cable and smaller nodes behind. — 03A 3D-printed node joining the timber battens.

Diagrams

01 / 04

Diagram of the two phases, the Voronoi canopy lowered onto the tapering hexagonal column, with a connection point detail showing a red 3D-printed node with screws and four timber battens. — 01Phase 1, the column, and phase 2, the canopy, with a connection point.

Top view of the timber Voronoi canopy over the hexagonal column, with its shadow drawn in blue beneath. — 02Top view.

Side view of the gridshell, a tapering column spreading into a wide canopy, with a sketched human figure for scale. — 03Side view, with a figure for scale.

Exploded render of a two-piece 3D-printed node in dark brown, labelled 27U and 27B, with the top plate lifted above the base that holds four timber battens. — 04A two-piece node, with the top plate lifted off its base.