CAADRIA2018
Adaptable Design-Construction Method for Remote-Location
Experiment with Reverse-Engineering System to expand the possibilities of natural materials with Bamboo
concrete shell as a case study
NAOKI IMANISHI1,HISAYUKI OGIHARA2,
CHEDDADI MOHAMMED AQIL3,KENSUKE HOTTA4 and YASUSHI IKEDA5 1,2,3,4,5,Keio University ,Kanagawa,Japan
1,3,4,5{naokiti|aqil|kensuke| yasushi}@sfc.keio.ac.jp 2,Ogiis@keio.jp

Abstract
In this paper, the aim is to develop a construction system that utilizes digital technology whichmeasures the completed shape and checks its degree of safety. This is because in the case of
conventional construction, it is assumed that drawing and structure are consistent by using advanced
construction techniques. However, it cannot always be assumed that there are correct composition
parts and advanced construction techniques in all geographical areas. Under such conditions, andthrough the use of digital technology, it can be easier to integrate the errors that occurred while thestructure is being built as part of the construction process rather than to try to make the structure
consistent with the original design.

1.Introduction
In this paper, the place where the infrastructure is not sufficient is defined as the 'Remote-Location'.
In the case of on-site construction, there is usually a difficulty concerning delivery access andtransportation. For example, overall costs do typically increase due to the high costs of transporting
workers, materials and construction heavy machinery. On the other hand, the transport anddissemination of digital technology is easy. As such, when establishing this system, it is expected that
construction capabilities will increase. In addition to this, in conventional construction work, thedesign is decided in advance, and it is difficult to change it during the course of construction.
However, when this construction system is used, it becomes possible to perform construction by
allowing errors that occur during construction to be part of the building up process. By using digitaltechnologies, we expect to develop construction techniques that are easy and affordable, andadditionally, certain accuracy is guaranteed in the outcome. Thus, this can enable the possibility ofbuilding various architectural forms even in remote areas that are characterized with theaforementioned constraints. In order to pursue these possibilities, research has been carried onfollowing the paper of CAADRIA2017 (Naoki et al 2017).

2.Achievement of previous ‘Bamboo Concrete Shells’ (Naoki et al 2017)
The following points can be cited as the result of CAADRIA2017's paper. As a result the discovery
of a form that is easy to elevate with the use of bamboo. Bamboo is easier to make than curved lines
than straight lines. The realization of a geometric model adapted to the characteristics of bamboo. The
geodesic direction is good. The shape of the structure can be finalized considering sunlight andsurrounding environment on site. Because the created model was a parametric model. Althoughsignificance of the construction system could prove, it stayed at the stage of measuring the shape, anda feedback system between construction site and 3D model was not established between the"measuring" and the "checking with the model" parts. In conclusion, regarding the concept of 'Digital

Construction', one of the useful benefits of digital technology when used for onsite construction isincreased adaptability. In another word, the adaptability of digital technology increases the possibilityof digital construction. In response to the conclusion of last year, the research to make this feedback
system more practical was conducted.

3.Practical thinking in construction system of 'Bamboo Concrete shells'
3-1. Concept of construction methodology
One concept was drawn from the efforts of last year. That is 'Reverse-Engineering System'. Thissystem is not conventional Reverse-Engineering. First, a 3D model, adaptable 3D model, that can
integrate the construction situation is prepared. Next, the real shape to be built is measured with alaser range finder. The measured data is feed backed to the adaptable 3D model, and the current shapeof the structure is generated. This flow of construction is defined as the 'Reverse-Engineering System'.
By using the Reverse-Engineering system, natural materials will be easier to use. Even natural
materials that have been avoided due to individual differences can ensure a certain resistance bychecking the shape that was built. The next chapter is the content of the development of theReverse-Engineering System.

3-2. Technics and measurement of the shell form.
The following diagram(figure.1) is basic concept of Reverse-Engineering System.

figure1:Reverse-Engineering system diagram
This system uses the laser range finder and Excel to measure the target point coordinate data. Next, usingrhinoceros and grasshopper, the measurement data is recreated on the adaptable 3D model and analyzed.
The point coordinate data measured by the laser range finder can be connected by interpolating the curve
In this way, the bamboo shape is recreated on the adaptable 3D model. That is, if there are many points tobe measured, it will be accurate as the reproduction of the shape.
However, if the number of measurement points is excessive, it will make construction rather difficult. It
is necessary to clarify the following two points.
1) In order to grasp the general shape of the shell, what part of the bamboo should be measured?
2) How many points must be measured for the bamboo shape selected in 1) to be reproduced on the 3Dmodel? Regarding 1), this geometry is a structure, ridge arch, that forms a shell which is radially divided

from the shell top. Next, the shape is roughly determined by the arch, edge ​arch, which becomes the
opening of the shell. Furthermore, a rhombus grid is constructed so as to draw the geodesic direction
between the arches (figure 2). In addition, the edge arch has a rib arch to increase the overall strength andprevent rainwater from flowing into the shell.In other words, the ridge arch and the edge arch create thegeneral shape of the shell (figure 2).

Figure 2:Bamboo Concrete Shell geometry, Ridge arch, Edge arch and Measurement study result of bamboo ​arch(2), it was verified whether the reproducibility would be high by measuring at least the number of points.
The arch was divided into 3 points, 5 points, 7 points, 9 points, 11 points. Then the measurement of thebamboo arch was performed in each different case(figure 2).
When connecting 11 points, highly reproducible curves are reproduced. The curve was compared with 9,
7, 5, 3 points respectively reproduced curves. A difference of maximum 12mm at 9 points, a difference of
maximum 20 mm at 7 points, a difference of 26mm at maximum at 5 points, a difference of 138 mm at
maximum at 3 points. From this result, it was found that the difference is increased by 3 points. Since it
was found that there was no difference to 9 or 7 or 5 points, it was decided as the number of points tomeasure 5 points that are not troublesome.(Figure 3).However, this result is considered to change thelength of each arch depending on the size of the structure.

3-3. Link adaptable 3D model and construction process.
The construction process consists of the positioning of the foundation, the edge arch, the installation of
the ridge arch, the creation of a rhombus grid, the setting of a rib arch and the concrete casting. The
adaptable 3D model created by grasshopper is also created by the same on-site construction process.
Therefore, making measurement and confirmation easier. By linking it with construction, the adaptable
3D model incorporating the construction information shows the shape that can be finally formed.
Therefore, measurement with a laser range finder is also performed for each construction step. By making
the adaptable 3D model like it was shown above, implementing the Reverse-Engineering System will beeasy. Next, advantages and disadvantages of the 'geometry that facilitates Reverse-Engineering' which
can be confirmed are listed at this stage (Seturo et al 2009).
Advantages: 1) Makes it easier to feed back the laser measurements and the information obtained thereby
onto the adaptable 3D model. 2) The construction process is easy and accessible. 3) The method of fillingwith the rhombus grid between the ridge arch reduces the risk of encountering problems because thebamboo is arranged in the geodesic direction.
Disadvantage: Comparatively, it was easier to change last year's 3D model's shape (Naoki et al 2017)
according to the on-site conditions. However, this year's adaptable 3D model has no relation between

edge arch and ridge arch, not on the same curved surface. Therefore, parameters such as the size of theedge arch and the ridge arch and the inclination position must be arbitrarily adjusted.

4.Verification experiment in 2017

Figure3:Bamboo Concrete Shell 2017​ and Construction process
Last year, it was a construction method that could cope with the site's environment, but this year an experiment
was conducted to decide what kind of construction process is best for dealing with natural materials used forconstruction. In August 2017 the construction of a dome-shaped bamboo concrete shell with a height of 2 meter
was performed (Figure 3). The site was the same as last year, at Kuchierabu-Island, which is located in the southof Japan.
The construction period was about 2 weeks, the work was done with a minimum of 2 people, and a maximumof 10 people cooperating at once. For the outline of the shell, the required number of round bamboo is 125,preliminary is 20, and cast concrete is 0.9m3 (Figure 3).

This experiment was aimed at comparing the two methods.
・How to bring the constructed model closer to the 3D model ? (Conventional way in general public)(Bui Trong et al 2010)
・How to bring the 3D model closer to constructed model ?(This concept is Reverse-Engineering
System)4-1.How to bring constructed model closer to 3Dmodel ?
The length of the bamboo for arch and the position of the installation point, the start point and the end
point of the bamboo, on the ground are fixed, and the curvature of the bamboo is controlled by the
support. Position the support and cut the supporting bamboo to a predetermined length. Fix the archbamboo at the top of the supports bamboo. In this way, bending of the bamboo is realized as shown inthe design.
4-2.How to bring the 3D model closer to constructed model ?

The length of the bamboo for arch, the installation point on the ground, the start point to the end
point of the bamboo, shall be fixed. The shape of the arch is left to the natural curvature of thebamboo. The measure with a laser range finder is done at the same time as the construction process. In
order to improve the accuracy, it is done multiple times, not only once. Details are described in thefollowing flowchart (Figure 4).

Figure 4:Measurement flowchart
In the above order, it is possible to grasp the shape of what was constructed. And the size andposition of the bamboo to be used in the next process are predicted.

5.Experiment result / Assessment
5-1. Result and Assessment of 4-1
In the method of bringing the constructed model closer to the 3D model, bamboo breakage andtwisting has occurred. When construction is done ignoring those characteristics of bamboo, the curve
required on the 3D model is not reproduced. Because the curvature which can not be reproduced withbamboo and the direction the bamboo wants to bend naturally influence (figure 5).

Figure5:Forced the bamboo closer to the model.
In order to reproduce the curve more than now, it is necessary to select each bamboo. Increase thecurvature indication by support or indicate the curvature in another way. The indication of bamboo

curvature by the support carried out in this experiment had a lot of time loss, which is a laborious
work. In the method of bringing the model closer to constructed model, this process can be omitted
and the flow of construction is made smooth.

5-2. Result and Assessment of 4-2

FIgure 6: Surface creation process and Comparison of three models

In the method of bringing the 3D model closer to the constructed model, measurement could be donesmoothly because the measurement point was fixed. Since it was linked with construction, the timingof measurement was easy to understand. On the other hand, there are two problems to be considered.
The first problem is that it is not possible to create a rhombus grid between each arch. In detail, fromthe information of the measured ridge arch and edge arch, it is not possible to predict the completedrhombus grid in the process of creating the next mesh. The configuration of the geometry linked withthe construction process has led to easier measurement. However, there is also a problem in feedbacking the measurement results to the 3D model. From the information of the ridge arch and the edge
arch, there is a problem with the method of reproducing the curved surface between the arches. At thetime of this experiment, the ridge arch division line was increased, and the surface was created (Figure
6).
However, connecting the point coordinate data of the measured ridge arch resulted in a twisted curve.
When practicing how to paste the surface as described above, such curve data caused an error on the
3D model. When connecting the measured point coordinate data, the following two points are
considered as causes of the twisted curve. 1) It is a material with a structure that bamboo itself twists.
2) Manual error in measuring bamboo will occur. Therefore, the 3D model that can tolerate such twistand error is necessary.
Next problem is that the difference between pre-designed shape and result is so huge. By giving
priority to the bending of natural bamboo, measurements were made on how much error it has withthe 3D model. Experiment: How much is the difference between the 3D model and the actual
structure? Result: The shell after the concrete casting was measured by 502 points with the back sideand the front side by laser range finder. Using that data, a highly reproducible "measurement resultmodel" was created (Figure 6). It was thought that a deviation of 350mm occurred before casting theconcrete and then deviated further by 49mm due to creep reduction, resulting in a total deviation of
399 mm.
Even with the concept of ​Reverse-Engineering, it is a problem that there is a 'huge' difference inprediction and result. As for the reason, it seems that it is because there is no information such as thedirection in which bamboo naturally bends when creating a curve in pre-designed 3D model. A curveis an arbitrary curve connecting points with each other by an interpolate curve. Because of catenary
curve similar to actual bamboo curve. If this curve was supposed to be a catenary curve, the overall
shape approached the actual bamboo curve (Figure 9). In other words, by clarifying the tendency ofthe bending direction of bamboo and by providing this information in the pre-designed 3D model, it
becomes possible to make the prediction closer to the result. Furthermore, even when predicting theshape to be created in the next construction process, by providing the bamboo characteristics in the
pre-designed 3D model, it becomes a shape close to the actual structure.

6.Conclusion
In conclusion, there are still two problems to be dealt with. 1) Information of bamboo characteristics
are essential to the adaptable 3D model. 2) The model that can tolerate with bamboo twist and error isnecessary. However, in a construction that uses natural materials with physical properties that cannot
be changed, a Reverse-Engineering System that allows what is already made is less labor-intensive
when compared to conventional construction methods, thus leading to facilitation in the process ofconstruction.

7.Consideration
In order to bring constructed model to the adaptable 3D model, it is necessary to grasp the characteristics ofnatural materials and to add information of it to the adaptable 3D model. However, it must grasp thecharacteristics of bamboo which bamboo not only draws naturally, but also difficult to measure with a laser
range finder. One of them is 'tensile strength'. Bamboo concrete shell such as reinforced concrete, expects
bamboo to have tensile strength. Therefore, it is necessary to test, digitize, and evaluate how much tensile
strength can be expected for bamboo, Ryukyu bamboo, to use (Francis et al 1966, Masakazu et al 2010).
Therefore, bamboo strength test is being conducted. Divide four pieces of bamboos, pull it from both ends, andprepare a device to check the broken load. Currently, the test is continued and the results are collected. From theresults, it is beginning to turn out that the strength of bamboo is very fluctuating. In other words, through anexperiment that brings the 3D model closer to the constructed model, the result that was obtained is that 'theshape to be built can be grasped for the first time at the site'--1). At the same time, because there are individual
differences in bamboo, it is necessary to assume that 'it is possible to grasp physical properties for the first timeat the stage of collecting bamboo'--2).

8.Prospect

Figure 7: New Measurement flowchart
By considering both 1) and 2) that were described above, it is possible to calculate the structure in real time.
The result of the structural calculation can be expected not only to grasp the current structure but also to assist in
the correction of the structure. The creation of 'Bamboo Building Information Modeling' - making it possible tohandle information on physical properties and the shape of bamboo as a model is also a goal in the future.
Therefore, a new reverse engineering system is proposed.(Figure 7)
1.Increase accuracy of Predesigned 3D model
It is necessary to increase the accuracy of the prediction of the predesigned 3D model (5-2. Result andAssessment of 4-2). However, it is difficult to predict a complete form. There are two kinds of information (1)that must be grasped from the design stage and information (2) that can not be grasped in advance.
(1) The required number of bamboo, the amount of concrete, the shell thickness, the bamboo material length, thefoundation position.
(2) Errors caused by the variation of the original bamboo during construction.
Although it is desirable to create a model that can predict accurately, variations due to natural properties of thematerials (variations in the bending of bamboo) will certainly come out. By making simple measurements of theerror at each construction stage and grasping the construction situation, it is possible to proceed with safe andaccurate construction while correcting the trajectory iteratively. Therefore, in order to improve the accuracy ofthe prediction, it is thought that it is necessary to understand the degree of variation of bamboo and narrow therange of prediction on the Pre designed 3D model in order to improve the accuracy. Actually dividing the cases
into different lengths of 1 m, 2 m, 3 m, changing the widths of both ends to create curves, and collecting data ofvariations using a laser rangefinder (Figure 8).

Figure 8:Bamboo bending test and 3D scan test
2.Improvement of shell measurement method
It is also necessary to improve the shell measurement method. Although the shape after concrete casting wasmeasured by the laser rangefinder, the number of measurement points was 502, which was very troublesome.
Therefore, a measuring method using a laser rangefinder and 3D scanning (iSence, Canvas, Roomchapture) was
proposed. The 3D scan makes it possible to measure the shape of the actually constructed shell, which isnecessary for structural analysis, faster and easier than the laser rangefinder.
However, 3D scanning also has problems. The Shell was measured using three kinds of scan applications:
iSence, Canvas, Roomchapture. The rough shape and the thickness of the shell were much easier to measurethan the laser rangefinder, but since the 3D model is formed by mesh data, it is difficult to grasp the detailed
surface irregularities and the shape of the curve . In order to improve the measurement precision, it is primordial
to research scan sensors and measurement devices for scanning methods (Figure 8).
・Structural analysis by Karamba
In this part we will describe the structural analysis methodology for the shell (Figure 9). We measure the current
physical conditions by enumerating the load conditions assumed for this shell, such as net-weight, wind load,lateral load, etc. After setting up the previously mentioned load conditions, we proceed by performing thestructural analysis by using Karamba, FEM analysis, etc. for each load condition (Shigeru et al 1980, Hiroshi etal 1995). Based on the result, the weak part of the shell becomes known to us. By taking into account theseinformations, it is then necessary to consider whether reinforcement by a rib and a method to open a hole can beapplied to the weak part of the shell in order to disperse the force.

Figure 9:Structural analysis methodology for the shell
Finally, when establishing a method to grasp the current shape of the structure and grasping the physicalproperties of bamboo used as building material, the possibility of the idea of ​site-oriented construction instead of
conventional design-oriented construction is expected to widen.

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