Construction of mobile bamboo dome covered with textile canvas

Mario Augusto Seixas 1,2,a, José Luiz Mendes Ripper 2,b, Khosrow Ghavami 3,c

1 Bambutec Design; R. Senador Euzébio 30 / 402, Flamengo

CEP 22250-080, Rio de Janeiro - RJ, Brazil.

2 Arts & Design Department, PUC-Rio; R. Marquês de S. Vicente Gávea 225, Gávea,

CEP 22451-900, Rio de Janeiro - RJ, Brazil.

3 Civil Engineering Department, PUC-Rio, R. Marquês de S. Vicente Gávea 225,

Gávea, CEP 22451-900, Rio de Janeiro - RJ, Brazil.

a mario@bambutec.com.br, b ripper@puc-rio.br, c ghavami@puc-rio.br

Keywords: bamboo, structures, grid shells, textile canvas, scale models

Abstract

Domes and arched roofs are constructive forms used by mankind over centuries for housing and daily

life. In different places of the globe, domes with various social purposes uses local materials such as

wood, straw, raw clay and animal fibers. With the globalization and mass industry, dome shapes were

explored in its extreme constructive capabilities consuming industrial materials such as steel,

petroleum polymers and concrete which, despite its technological potential, were pollutants, heavy,

and expensive, causing high impact on soil and great energy consumption. Technical progress in this

direction, rather than spreading these structures, reduced its social scope, limiting it to certain fields of

knowledge. The present paper presents a self-standing bamboo dome built for an outdoor amphitheater

employing non-conventional technologies and materials. A form finding methodology from physical

scale models reproduced the characteristics of the land and could systematize the mounting plan. The

structural design was the result of working with these models that generated couplings suitable to the

local conditions and an innovative assembly engineering method employing modular arched grid

shells. The structure was built in stages through a system of lifts and supports powered by human

strength. It were used tree-support columns, bending arches, vault grid shells with bamboo species

Phyllostachys aurea and Phyllostachys pubescens, covered in acrylic textile canvas and tied up using

specialized polyester textile ropes moorings. The roof structure was installed in the hot and humid

tropical climate of Rio de Janeiro, Brazil.

1. Introduction

Shells and domes have been developed worldwide by humanity since ancient times for housing,

work and ceremony. In different primitive cultures, intuitive shelters have been made with indigenous

craftsman knowledge creating a vast range of construction types. These objects were adapted to the

physical and cultural conditions of these groups maintaining typical characteristics and regional

material solutions. Across the Southern Hemisphere, native vegetal-based cultures generated what

Berta Ribeiro so-called the “straw civilization” in South-America [1]. In the last centuries, with

industrialization and later with the mass industry, these techniques have been gradually replaced by

large scale techniques, accompanied by a huge loss of sociobiodiversity and vernacular lifestyles

where these groups traditionally does the maintenance of environment. The blind dissemination of

urbanization, pollutant processes and unlimited capital spread are causing serious social and

environmental problems and is one of the central causes of the world crisis. The use of non-

conventional materials in architecture and engineering is gaining ground toward a more balanced life

promoting health, social welfare, less impact on the environment and housing solutions integrated with nature. New achievements on Nocmat techniques for the construction sector are promoting new

applications of ancient culture combined with modern techniques. Across Latin-America we can see

the resumption of building types based on woods, bamboos, straw and raw earth. Nevertheless, we

know that the mere resumption of traditional processes of production are not sufficient for the current

demand, as the world population reaches a record of 7 billion people, with a high energy request on

energy, food, land and materials. In this sense, sectors of Puc-Rio and Bambutec group are working

together on development of lightweight bamboo structures. Systematic studies are conducted on

industrial design labs to aplly bamboo to useful objects and on structural engineering labs to

characterize the physical and mechanical properties of bamboo culms. Structural systems employing

the concepts of lightness, mobility, adaptability and resilience have been researched to develop design

and architecture objects from tensegrity and self-standing systems inspired by the observation of living

nature. Biology provides infinite number of solutions for construction. Seashells, plants and animals

contain complex information about nature, its structural behavior, dynamics, interaction and

adaptability to the earth surface. These living structures employs sophisticated materials: lignin,

muscles, membranes and bones are examples in nature that shape and material are inseparable. On

laboratory and field experiments were made with soap bubbles, membranes, vegetal-based textiles and

bamboo branches to understand natural patterns, and adapt them to construction (Fig. 1).

(a)

(b)

(c)

Figure 1: Living nature geometric organization.

(a) Experiment with soap bubbles. (b) Armadillo’s articulated body [2]. (c) Seashell.

2. Research background

On the early 90s, Puc-Rio proposes the first world bamboo spatial truss with steel point connections

called “structural tip” (Fig. 2). Mechanical tests were carried out with a truss structure prototype at

university laboratories [3]. Few years later a bamboo geodesic dome inspired by Buckminster Fuller

ideas was developed using similar point joints. Although interesting from a technological point of

view, the fabrication needed costly technical equipment, more expensive than the solutions available in

steel. Also bamboo culms conic geometry and its axial irregularities transferred a lot of tension to the

connections and bars, favoring the shear of the parts, especially during the assembly and disassembly

operations [4].

(a) (b) (c)

Figure 2: (a) 1st bamboo spatial structure developed at Puc-Rio with steel joints [3].

(b) Structural tip (c) Steel point connection dome developed at Puc-Rio.

An important achievement made at Puc-Rio was the application of Kenneth Snelson’s [5] tensegrity

invention to bamboo structures design. The principal innovation was that bamboo bars don’t converge

to one point anymore, simplifying fabrication and mounting processes. Also, the eccentric spin

connections were more able to transfer loads minimizing the fatigue of pieces, decreasing the

propagation of cracks on bamboo bars [4]. Employing vegetal rods, cables and membranes were

developed tips and moorings that worked in rigid and textile materials. Rigid bars and flexible

membranes worked together in tension and compression networks, favoring self-standing behavior,

generating structures without need of heavy foundations on the ground (Fig. 3).

(a)

(b)

(c)

Figure 3: Self-standing bamboo structures

(a) Bamboo tensegrity tent [6]. (b) Bamboo spin joint connections with straw, raw earth and castor oil

polymer composite. (c) Bamboo tensegrity geodesic dome.

2. Experimental models

This paper presents a part of ongoing research on deployable bamboo structures covered with textile

fabrics. It focuses on forming and building experimentally lightweight architectural prototypes applied

to the physical and social environment. The constructive system employs bamboo rods, textile tarps,

polyester ropes in tensioned systems. Technical features about these structures are the eccentric tied up

connections and the self-standing capability [7]. Spatial trusses, pantographic hinged shells and

specialized craftsman moorings were developed to connect bamboo culms allowing articulating and

locking of the pieces [8]. These structures are not achieved by static calculations, but they are found

with experimental models method. To this end was applied a methodology with physical models and

real scale prototypes, which are improved gradually [9] [10]. The roof project started from the

characteristics of a 300 m² sloping land at the banks of Rainha River, where it was built an outdoor

amphitheater at Puc-Rio university campus. To this end were proposed models using bamboo grid

shells with textile canvas which has ability to cover spaces due to the properties of pantographic

deployment and adaptability (Fig. 4). Using this principle were generated alternatives to cover

amphitheater. Design models were carried out to establish the composition of structure, modulation

and adaptation to local conditions. The maximum lengths to be overcome were of 14 x 19 meters.

(a) (b) (c)

Figure 4: (a) Fabrication of pantographic hinged shell prototype. (b) (c) Grid shell model.

Employing a 1:20 scale model of the amphitheater land were experimented compositions of grid

shells and arches to describe coverage geometries. The experiments took into consideration the aspects

of heat, prevailing winds, rain protection and incidence of local vegetation inspiring shelters with

spans appropriated to the tropical climate. A modular structure dome was proposed considering the

concrete amphitheater uneven ground, employing shells with different modelling forms. A custom-

made structure was developed using topography measurements of the land and surrounding vegetation.

Once registered, these markings were applied in 1:20 scale model for the mounting engineering

systematization, which consisted of a decisive aspect for the implementation of the structure. The

architecture should have sufficient mobility for the assembly of shells and beam arches on the ground,

its coupling and rotation to arrive at the final location on the structure, employing deployable lifting

towers. The physical scaled models enabled the generation of accurate information about the

fabrication formats, textile molds to be used and the whole movement that structure should go through

during the assembly processes (Fig. 5).

(a)

(b)

(c)

Figure 5: Experimental 1:20 scale models.

To support grid shells and textile acrylic canvas were developed bamboo bending arches with whole

Phyllostachys aurea culms. The composition of arches used bamboo rods tied up with textile craft

moorings. In order to win spans up to 19 meters was developed a truss-system to lock the deflection of

bamboo arches (Fig. 6 a). Frameworks were studied using bamboo bars, craftsman textile moorings

and tensioned steel ropes. It were developed 4 design models for vault grid shells and compound

arches in order to describe structure over the land geometry (Fig. 6 b). These arches were designed

with a coupling principle where the first mounted arch, structured with internal two-dimensional

trusses, receives the next arch to be tied up, creating an innovative framework system. Tests on

laboratory were made to establish the constructive methodology, the composition order of mounting

arches and the security capability for bending bamboo rods. The beam arches were able to be mounted

on the ground and coupled grid shells (Fig. 6 c).

(a)

(b)

(c)

Figure 6: (a) 16 meters compound arches studied. (b) 4 arches design models. (c) Mounting truss-

arches on the ground.

The form finding experiments allowed achieve the structure geometry. The dome employed 6 tree-

support columns on the ground. The structure had a self-standing behavior based on spatial trusses and

bending arches. The columns are distant 4 meters from each other in the longitudinal direction and are

distant approximately 12 meters in the transverse direction. The maximum span achieved was 19

meters and the minimum span was 13 meters. The structural behavior enables the shelter existence

without foundations, but with concrete anchors that fixed it on the ground. These anchors were

waterproofed and distant 50 cm from the ground level to protect the bamboo pieces of soil moisture.

The cover structure used 4 combined arched grid shells at different heights and angles describing the

spatial dome. The cover shells overlapped each other, generating rain protection and passage of air

(Fig. 7).

(a)

(b)

(c)

Figure 7: 1:50 scale model.

The studied assembly method predicted the elevation of the structure in stages. Each grid shell was

organized with beam arches and tree-support columns, functioning as independent modules. A system

of bamboo towers uplifted the modules with the aid of pulleys powered by human strength (Figs. 8a,

8b) until position it in situ, then the shell is anchored. Each next module was mounted employing the

previously built structure and the mobile set of elevators (Figs. 8c, 9a, 9c). Each structure module

described its own movement on space reaching its final location (Figs. 8d, 9b, 9d). Once in the final

position, the structure is locked using tied up longitudinal pieces, integrating it. The compose grid

shells were weighted on average 250 kg.

(a)

(b)

(c)

(d)

Figure 8: Assembly engineering steps. (a) (b) Grid shell number 1. (c) (d) Grid shell number 2.

(a)

(b)

(c)

(d)

Figure 9: Assembly engineering steps. (a) (b) Grid shell number 3. (c) (d) Grid shell number 4.

2. Experimental prototype

The structure was assembled in 25 working days. The assembly was performed by a team of 5

technicians in daily 8 working hours. The structure employed prefabricated pieces using tensioned

systems with support of lifts moved by human traction from bamboo towers, pulleys and textile ropes,

without using nails or screws. The structure weighed a total 1.4 ton, i.e. 7 kg per m², approximately 6

times lighter than a steel similar, putting this constructive type within the ultra lightweight structures.

Each concrete anchor weighed 0.5 ton. A simplified assembly method was developed, taking

advantage of the physical characteristics of the land, minimizing the demand for space in the operating

environment and the construction site, optimizing the space available for the construction without need

for heavy and expensive equipment. This method of clean and optimized use of space was developed

over 15 years of work on temporary structures within fast and efficient mounting [11]. Mechanisms

have been developed in order to facilitate the building processes and movement of these structures in

space, which demanded for innovative assembly methods, requiring many hours of study on models

and prototypes.

(a)

(b)

(c)

Figure 10: (a) Assembly of the first shell sector supported on elevators. (b) Lifting of the third shell

sector on elevators and over the previously installed structure. (c) Lifting and rotation the third shell

sector over the previously installed structure, until it is anchored.

Figure 11: 200 m² roof inside view of maximum 14 meters long and 19 meters wide.

Figure 12: Outdoor and indoor views of bamboo dome with self-tensioned grid shells covered with acrylic canvas.

(a)

(b)

Figure 16: (a) Coverage grid shells and beam arches (c) Tree support columns.

4. Conclusions

The construction was completed in November 2014 and showed good performance in the physical

environment. The bamboo dome had a self-standing structure within the combination of grid shells,

bending truss-arches and tree-support columns, which presented mechanical and structural stability.

The structure consumed approximately 50 times less energy than a similar on steel, weighed 1.4 ton

and employed treated bamboo culms, locally produced within a radius of 400 km from its

implementation. The main innovations was lightness, self-standing structural behavior, adaptability,

mobility and the use of green materials from Brazilian biodiversity with low environmental impact.

There were employed prefabricated building elements, installed on site with minimum electrical

machinery use, silent processes and low residual, without generating dust. The structure was fully

deployable, transportable and demountable. The bamboo species Phyllostachys aurea and

Phyllostachys pubescens presented potential for sustainability because its ecofriendly treatment

employing selection, cutting, smoking and drying of culms. Bamboo poles were waterproofed with

varnish and castor oil polyurethane polymer. The developed bending arches used whole bamboo culms

with a truss framework to lock the deflection of arches. It was tensioned by steel ropes and tied up with

craftsman textile polyester moorings, which is an accessible technique, previous opening the

construction of mobile bamboo domes in remote places with poor resources. The structure behavior of

beam arches was studied with scale models and prototypes that enabled improving gradually on

structural design. The adopted assembly engineering hypothesis developed in 1:20 scale model

employed an innovative construction method and introduced a new building typology located in the

field of ultra lightweight structures with great ecological potential. The mounting processes used

friendly construction elements like a set of lifts powered by human strength, bamboo scaffoldings,

pulleys and textile polyester ropes. Thus, the performance of the work does not depend on a

construction site but a mounting square, simplifying the building stages. The employed acrylic textile

canvas favored manufacturing by the local industrial park. The modelling of the acrylic tarps was

performed from physical models and molds without the need of computer programs. The adopted

textile solutions were resistant, appropriated to tropical climate and showed good resistance to

moisture, weighing approximately 350 g per square meter and tensile of 140 x 95 kgf/5cm. The

authors concluded that incentives will be needed in the supply chain over the next years for the

invention reach penetration in the American market. To this end, we anticipate the introduction of new

sealing elements using self-tensioned bamboo panels and straw fibers, introducing textile plant-based

waterproof tarps for external uses. The authors recommend the design and implementation of new

structures of this kind for pioneer application to the tropical climate, predicting the improvement of

new detailing, keeping characteristics of mobility and lightness, developed under this project. The

authors recommend testing bamboo domes covered with textile canvas in other states and countries,

for assessment of its functional behavior toward climatic factors and the monitoring of its durability,

collecting data as resistance to rain, wind, moisture and insolation.

5. Acknowledgements

The authors would like to thank, FAPERJ for the financial support of the research project. Our special

thanks are also to João Bina Machado Neto and Patrick Lopes Stoffel of the Bambutec Design company

for the active participation in the design and construction of the bamboo dome.

6. References

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Puc-Rio, 1998.

[4] J.L.M. Ripper, L.E. Moreira, M.F. Silva, J.V. Correia de Melo, L.A. Ripper. Puc-Rio Bamboo

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[5] Information on http://www.kennethsnelson.net

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2014. Brasília: Iass, 2014.

[8] M.A. Seixas, L.A. Ripper, K. Ghavami. Deployable Bamboo Structure for Sustainable

Architecture. Proceedings of the International Conference on Non-conventional Materials and

Technologies 2014. Pirassununga: Iac-Nocmat, 2014.

[9] L.E. Moreira, J.L.M. Ripper. O Jogo Das Formas: Lógica do Objeto Natural. Rio de Janeiro: Nau

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[11] Information on http://www.bambutec.com.br