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 [email protected], b [email protected], c [email protected]
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.
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