P. Janssen, P. Loh, A. Raonic, M. A. Schnabel (eds.), Protocols, Flows and Glitches, Proceedings of the22nd International Conference of the Association for Computer-Aided Architectural Design Research in
Asia (CAADRIA) 2017, Paper 109 (Preprint). © 2017, The Association for Computer-Aided Architectural
Design Research in Asia (CAADRIA), Hong Kong.

BAMBOO CONCRETE SHELLSAn Adaptable Construction Method Using Onsite Materials in a RemoteLocation

NAOKI IMANISHI1 , SHINICHIRO HINOKI2 ,MIZUKI MURAOKA3 , RAN TATEYAMA4 , YUICHI ABE5 ,HOTTA KENSUKE6 and YASUSHI IKEDA7
1,2,3,4,5,6,7Keio University, Japan
1,2,3,4,5,6,7{t13120ni|t12745sh|t13932mm|ran1005|kamex|kensuke|yasushi}@sfc.keio.ac.jp

Abstract. This paper proposes an on site construction support systemwith digital techniques, to solve the issue of logistical inconvenience on
remote islands, where industrialized construction methods are absent.
Transporting heavy machines are costly and difficult in the rural area
isolated from cities. In addition, sourcing materials produced outside
implies a heavy ecological footprint, so construction materials be betterto be locally produced. The design has to consider the use of local materials as well as structural strength. As a case study, Kuchinoerabu island
in Japan is chosen as the site. The shell is made by concrete reinforcedby bamboo readily harvest-able in wild. Through the study, several technical issues are revealed: bamboo differs individually in material properties, unskilled labor frequently makes mistakes, the concrete placingin 3-dimensional surface is difficult to construct. The system proposes
the following functions. 1) Synchronizing data between CAD and materialized part. 2) Checking errors between the target and produced part.
3) Inputting material characteristics on site. 4) To make structural analysis, and reflects its execution. These functions minimize the margin oferror, and encourage unskilled labor to work accurately.
Keywords. Bamboo; natural material; digital construction.

1. Background and Social Problems
There are social issues when one attempts to construct buildings on isolatedislands.The first problem is following; in remote places, especially rural area,

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N. IMANISHI ET AL.

there are few advanced construction devices, as well as heavy machineries.
Skilled labourers to operate general or specific devices for construction work
are also missing. The second issue is the difficulty of transporting materials.
Since the 20th century, factory made standardized/industrialized parts are usedfrom design to construction. But on the other hand, in remote island there arefew production bases, thus, the logistics becomes difficult. Shipping is expensive and would put a heavy burden on the site environment.Thirdly, an environmental adapting building is required ; Kuchinoerabu-island is set as thesite, where there are extreme weather conditions such as fierce wind in typhoonseasons. The structure has to be structurally robust and utilizes local materials. In order to ensure the effectiveness of the proposed system, the building
experiment was done in Kuchinoerabu-island. Located far away from Tokyo,
reaching the site takes 1.5 hours on plane and twice transfers on ship. The
place is known to have had extraordinary environmental conditions, including
a volcanic eruption.
2. Bamboo Reinforced Concrete Shell by Digital Construction SystemIn this section, referring from existing research (Yamamoto et al. 2010), general idea of this building are explained.

Figure 1. Bamboo reinforced concrete shell.

2.1. WHY BAMBOO REINFORCED CONCRETE SHELL ?

The project of bamboo reinforced concrete shell (figure 1) explores the topic
of shell structure and its construction method, while in ordinary constructions
steel are used as reinforcements. This project is the answer for three social
issues raised above. Solution 1) Effortless construction.This surfacing by steel
trowel method is much more effortless than form construction method, because
it is able to reduce time to make form by sandwiching wooden panels. The

BAMBOO CONCRETE SHELLS

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required technique of this concrete placing method is relatively difficult forunskilled labors but can be reduced by using the proposed system. Solution 2)
Low environmental impact. For the purpose of alleviating the environmental
burden, the proposal attempts not to bring in external materials. So the wildbamboos that grow luxuriantly there are chosen for reinforcement for concrete.
Fecundity of bamboo is very high, so that a wild bamboo forest can expand
quickly. Appropriate consumption rate of the bamboo can bring positive effectfor vegetation in there. Solution 3) High structural performance to respond towindy weather on the island, weight and strength of the material are required.
The proposal employs concrete as the structure, instead of using only weaving
bamboo straps. In addition, the unique character of bamboo straps of bending
toughness in normal direction of annual ring because of fiber direction, hasinspired the design to become a curved surface rather than a box-like form. In
order to answer these requirement , a hypothetical design proposal is suggested
and tested on that island (Inoue et al. 2009).
2.2. PROBLEMS WHEN CONSTRUCTING THE SHELL

When executing three solutions revealed that ‘errors’ would be the serious issue. The problem of solution 1; the human hand work may cause various errors,
when bamboo felling and timber-rizing it, when worker making foundations,when a worker weaving it by handcrafting errors, when plastering with handtrowel.The problem of solution 2; because of using local material, it can not be
guarantee uniform materials. So each bamboo strip slightly differ from others,
that induct errors inevitably. The problem of solution 3; there are no parts division based on architectural idea, such as wall, ceiling in shell structure. So that
this smooth surface does not have singular point, it may able to says structurally
better. However, to materialize three dimensional surface into reality without
guidance is hard for human. Thus, deviation between desired shell and realizedshell would occur. As above, three solutions surely makes ‘errors’. In order tosolve this problems, the design and build system is proposed here. That system
has divided into two parts supplementally ; first is pre-construction method tomake a CAD model which has allowance range, second is during-construction
method checking data with digital devices.
2.3. HOW TO SUPPORT WITH DIGITAL CONSTRUCTION SYSTEM

The concrete system is explained below.The aim of this system is to designa construction system that guarantees a building’s construction quality eventhe subject (worker/machine, or those hybrid system) creates a discrepancy between the finished outcome and the original design, but that gap still lays withinthe possible allowance. The construction is considered “complete” when theworker corrects this misalignment created by unexpected site circumstancesand decisions through adjustment informed by the system, whereas in conventional constructions, completion is defined as almost perfect material realization of building as designed in drawings, which often led to inferior quality asa result of this unrealistic management methodology (figure 2). As a method-

4N. IMANISHI ET AL.

ology of this, 1) pre-adaptability and 2) post-adaptability, and 3) those hybrid
adaptability are assumed. The first method is referring to the design processthat is before conduct materialize (construction). The idea that the objective
data (geometry) originally contains the approvable range. The second method
is mainly work on construction steps. That is have been taking difference during construction steps, then operate somehow to recover towards original object (can be geometry) next part, following way; one may have to break andrebuild the previous part, or other is modify next part for recovering to original
with admitting existing part. Thirdly, those hybrid method that are take difference then make new target(can be a geometry, can be an objective function)
based on those conditions. In this method, materialized part is going to giveup, then re-calculate in next step, which allows multiple possibility.

Figure 2. Digital construction support system.

3. Digital Construction Technology
In this section, concrete methods for digital design and construction are introduced. These includes how to make building construction with using data, butalso relates to digital design too.
3.1. PARAMETRIC MODELINGThe margins for construction of the bamboo-reinforced concrete shell are considered and parametric parts are determined. This parametric model offers
pre-adaptability for the precision of the construction process. The actual parameters (figure 3) are: 1;Diameter of the base circle 2;Location and diameterof the inner circle 3;Range of an inflation of the base torus geometry 4;Theused portion of the base torus (angle) 5.Locations and shapes of the holes.

BAMBOO CONCRETE SHELLS

5Figure 3. Parametric 3d model

The surface of shell is surrounded by curved edges, which is called edge
arches here. Each edge arch is made from two bamboo timber, start from theground. The construction process starts from installing these edge arches. The
length between point A and point B (figure 4) is calculated automatically. Thus
the required material length can be seen immediately, then able to search frombunch of different material mountain.

Figure 4. Automated calculations for the length of the edge arches.

On the torus structure, appropriate distribution of the bamboo (figure 5) isradial as in the (a). In order to verify this, (b) was made with the split bam-6N. IMANISHI ET AL.

boo whose width is same for the actual construction. From this experiment, it
turned out that the concentrically twisted geometry is not suitable for bamboo.
However, the radial geometry was successfully constructed. In the case of (c)bamboo breaks when the angle between the bamboo and the shell is too big,whereas in the case of (d) the bamboo’s elasticity is utilized as the bamboo ismore in parallel direction with the shell (Yamamoto et al. 2010). However, inorder to create a stable shell, the bamboos have to be crossed. When creating
a concentrical geometry, the bamboo became perpendicular the surface of theshell on the upper part. Hence, this distribution of the bamboo is problematic.
The curvature of geometry was calculated (e) on the 3d model and determined
60 degrees that is one of optimal angle(f) (Brink et al. 1996).

Figure 5. Design of donut-shaped bamboo geometry.

3.2. LASER RANGE FINDER

In order to check the errors, a laser rangefinder is deployed to conduct measurement accurately throughout construction and feedback is given to the parametric model. The measured data is stored in an Excel file which would beloaded to the 3d modeling software. As the geometry is a curved surface, alaser rangefinder is chosen among other options for measuring the shape. If
the geometry is a cube, for example, the more points have to be measured. Plus,some points are unmeasurable from a certain spot. On the other hand, a curved
surface requires fewer points to be measured. Besides, in this concrete shell,
no points is hidden by itself. Thus, using laser rangefinder is reasonable.
3.3. AUGMENTED REALITY

AR technology is used for guiding the mesh geometry when the bamboos arewoven. Unity and Vuforia are used. AR marker is made with Vuforia. InUnity, the marker and 3d models are related and checked through Android
tablet during the construction process. AR played a role as a balancer of themesh direction. Even if the actual shape deviates from the originally designed
model, it can guide the direction of the mesh.

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74. Experiments
In this section, two experiments are shown below. One is done without proposed system, other is done with proposed system.
4.1. EXPERIMENT1

The construction period is 6 days. The total number of construction workers
is 4 people. The location is within the premises of Keio university, Kanagawa,Japan, not on the island (figure 6). There was also a secondary purpose to determine the construction procedure of the concrete shell to be built for Experiment
2. First, the position of foundations of building was determined with a laser
rangefinder fitting to the digital 3D model. After that, the building was built
not using digital technology but just by hand manually. The bamboo weavingphase was completed as scheduled. However, there was a problem with thenumber of supports and the height of edge arch. The number of supports was
not considered in the construction process of Experiment 1. Moreover, a serious problem arose as an error on the edge of the arch was found.The edge
arch was about 10cm lower than the 3D model.As the shell became lower by
10 cm, it seems that the shell approached a planer shape from the curved shape,
and the weight of the concrete was directly applied in the vertical direction andbuckled (figure 7). (Terai et al. 2010)

Figure 6. Construction process & Buckling

Figure 7. Error of edge arch

8N. IMANISHI ET AL.

4.2. EXPERIMENT2

In experiment 2, a post-adaptability system was adopted in addition to the preadaptability 3D model of Experiment 1. The system has the ability to check up
building information during construction. The Construction period was from
8/4 to 8/14, for a total of 12 days, the location was Kuchinoerabu island. The
construction process was divided into two terms. The number of construction
workers was three for the first term, four for the second term and eight for casting concrete. The size of the bamboo reinforced concrete shell was designed
to be twice as large as Experiment 1.
4.2.1. First Term
AR shows the position of each part in the target premise. The number of bamboo calculated in 3d model analysis was 113, with diameters from 4.0 to 5.0cm. Each bamboo was cut into four in order to make use of the characteristicsof bamboo. It also approached the streak width (2.0 - 3.0 cm) of the geometry of the shell set on the 3D model. The position of the foundation was doneby using a laser rangefinder.Bamboos were sorted out matching with the edge
arch. Round bamboos were adopted in Experiment 1, sometimes there was nowell-matched bamboo. On the 3D model the bamboo’s thickness of the edge
was set to 5 ˜ 6 cm. Therefore, in Experiment 2, The divided bamboos wereoverlapped to make their thickness closer to the 3D model edge arch.Concreteof the foundation part was cast. The degree of Z axis direction (height direction) deviation of the constructed edge arch from that on the digital model wasmeasured with a laser rangefinder (figure 8). As a result, the edge actually constructed was about 5 cm lower. It was ½ degree of the error at Experiment 1,and the error can be amended by increasing the number of supports to support
the shell at construction, we considered it within the allowable range.

Figure 8. First term construction process.

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94.2.2. Second Term
When building bamboo strings, AR was used as mesh guidance. The positionof the edge support was measured with a laser range finder. Wire mesh fastened concrete to prevent concrete falling when casting concrete. Wire mesh
was kept open with a gap of about 2 cm. Supports building was divided into
two stages so as not to interfere with the work of assembling bamboo and thework of fastening the wire mesh. The support of the first step (until finishingand attaching the wire mesh to the bamboo shell) would be simple. Increase
support in the second step (when bamboo shell concrete is cast). Cast concreteand dry it.The composition of concrete was 1 portion of cement, 2 portionsof sand, and 0.3 portion of water. In addition, the amount of concrete wascalculated based on the 3D model analysis and optimized to reduced weighton the shell. The thickness of shell on the digital model was 50mm, the actual constructed one varies from 50mm 70mm in different areas. Its curvatureshape error was reduced. It passed the load vector test. One month after casting concrete, the load vector test 150 kg weight on the top of shell have tested
again the intensity of shell structure was checked (figure 9).Now the structureis exposed as permanence experiment.

Figure 9. Second term construction process.

5. Conclusion and Prospect
In conclusion, towards the idea of ‘Digital Construction’, one of the useful
benefits of digital technology in onsite construction is increased adaptability.
Under this hypothesis, the result of Experiment 1 clearly demonstrates failurein the collapse caused by ‘buckling’. Here, the proposed system was not used,
so the assumed reasons of failure can be seen as the hypothesis of this system.
That is the many site circumstances were not reflected in the design. On theother hand, in Experiment 2, the information (here the materialized geometry)is continuously taken from the site and updated to the digital model by using
the proposed system. Manual, low-skill requiring shell structure construction
is made possible by the system. (structural strength to be examined). While,
as byproduct of this method, the allowance would be other key of parametricmodeling when designer/constructor work together using this system. In another word, the allowance implies a number of possibilities within a tolerable
range. Precisely speaking, if the margin of error is properly set, the model (ge-10N. IMANISHI ET AL.

ometry in this case) can move. The implication of this project is that there aretwo sets of keywords for digital construction in remote locations (figure 10).
One is about parts quality, unique parts instead of standardized-product aspect
in. The other is about the use of a guiding system, from primitive usage like answering predetermined quests such as Jigsaw Puzzle, to much more advanced
usage like reacting to ad-hoc conditional change, car navigation system is anexample.

Figure 10. The adaptability of digital technology increases the possibility of digitalconstruction

Currently, the research is being conducted to attempt making those shellstructure suitable for human habitation. Hence, the required architectural performance (structural strength for practice, environmental performance etc.),
and architectural functions (toilet, kitchen, bedroom, living room etc) has tobe pre-determined as objectives. Especially in architectural scale, the mean
to divide inner space and outdoor space is yet to be studied, the notion of asemi-outdoor space is also attractive, as called Engawa in traditional Japaneseintermediate space. On the other hand, on an urban scale, this proposal may
have novel potential. That is how multiple shells can make grouping on site
and it must be reviewed from the social aspect perspective, because this projectis ongoing at the volcanic island.
References
Brink, F.E. and Rush, P.J.:
1996, Bamboo Reinforced Concrete Construction, U. S. Naval Civil Engineering Laboratory, Hueneme, California,
http://www.romanconcrete.com/docs/bamboo1966/BambooReinforcedConcreteFeb1966.htm.
Inoue, S., Matsutomi, K. and Kawakubo, H.: 2009, A Study on the Mechanical Properties ofBamboo, Otemae journal, 10, 43-52.
Terai, M. and Minami, K.: 2010, A basic research of adherability and flexibility of concrete thatreinforced by bamboo, the Japan Concrete Institute, vol. 32, 1183-1188.
Yamamoto, M., Murakami, K., Takeda, K. and Shimoda, S.: 2012, Flexural performance ofbamboo reinforced concrete beams using bamboo as main reinforcements and stirrups, AIJ
Kyusyu Japan.