Bamboo Pavilion in São Sebastião, Brazil

Project · São Sebastião, SPArchitecture and structural design

The pavilion nave: bamboo bundles opening into arches under the roof, with the valley behind — The nave: the bundles open into arches and the valley appears between them.

From the middle of the pavilion, the mountains seen between the bamboo bundles — From the middle of the pavilion, the mountains framed by the bundles.

The whole bamboo structure, without the roof, on the floor — The whole structure, before the roof: arches, trusses, rings and gridshell.

The bamboo weave seen from below: arched trusses and the gridshell mesh — The weave seen from below: arched trusses and the gridshell mesh.

Bamboo bundles fanning down to the concrete floor — The bundles fan down to the concrete floor.

The tip of the roof over the bundles, with the valley and the mountains — The tip of the roof, over the valley.

The pavilion seen from the slope, with the undulating roof over the light floor — From the slope: the roof resting on the light floor.

A light roof between the forest and the sea.

Trussed arches, rings and a gridshell, with continuous culms from the ground to the ridge.

The pavilion grew from a simple question: how much bamboo does it take to cover a large open span, at the edge of the Atlantic Forest, without losing lightness? The form was found through pressure, like a membrane filling with air, and then translated into trussed arches, rings and a gridshell mesh.

Architecture and structure were designed together. The bundles fan down to 28 steel bases, the low eave, at 2.40 m, shelters from sun and rain, and the ridge rises to 6 m. That is 556 m² of shade over culms of 10 and 12 cm.

Wind and structureFig. 01 to 03

The wind passes through the roof.

Longitudinal section, north wind of 4.7 m/s at 10 m height.

The air speeds up over the ridge and drops again beyond it. Underneath, it keeps flowing between the bundles, more slowly: at 1.5 m above the ground the breeze falls on average from 3.2 to 2.4 m/s.

Fig. 01 — CFD streamlines (OpenFOAM, k-ε) in the longitudinal section, with the wind from the climate assessment of the north coast; north, where the wind comes from, is on the left. Hover to see the air move.

wind speed (m/s) · by quantiles03,84,54,85,1

White model of the structure: under the nave, looking towards the valley — **Fig. 02** — *Under the nave, looking towards the valley.*

White model of the structure: the weave seen from below — **Fig. 03** — *From the bottom up: truss, rings and gridshell. Rhino model.*

“Spanning almost 12 m with culms of 10 and 12 cm, without a single extra culm.”

The challenge: the smallest possible section.

The aim was slenderness. Each version of the structure removed culms and reduced diameters down to the limit ISO 22156 accepts, in all eight wind directions. The result is 13.4 t of bamboo for 556 m² of roof.

The culms run continuously, with staggered splices every 6 m, and the bamboo never touches the ground: each bundle rests in steel cups on a concrete neck.

Structural analysisFig. 04

One culm per member.

The analysis model has the geometry of the building.

In Karamba3D, each culm is a member, with its own diameter and position, and each element is checked in the eight wind directions. Under self-weight and wet piassava, the roof deflects less than 1 cm; under the most unfavourable wind, 1.4 cm.

In most of the structure, weight governs. Wind decides at the tips and at the eave, and each direction finds its own elements.

Fig. 04 — Karamba3D member model, one culm per member: the wind direction governing each element and the internal forces under the north-east wind, the one with the greatest deflection.