Structural Design and Development for CNC-Milled Based Wood Construction

.fabfield structural design and development for CNC-milled based wood construction

Aloysius Kevin Gunawan/4502396 The version of this thesis has been shortened in order to protect COLOPHON confidential data provided by company ECOnnect involved in this research. For more information regarding non-disclosed items Report P5 please contact ir. PMM Stoutjesdijk at [email protected] Master Thesis

Title FabField : Structural Design and Development for CNC-milled Based Wood Construction

University Technical University of Delft Faculty of Architecture & the Built Environment Master Building Technolofy

Tutors Dr. Ing. Marcel Bilow Ir. Peter Eigenraam Ir. Pieter Stoutjesdijk

External Examinator Henri van Bennekom

Date 06-07-2016

Student Aloysius Kevin (Kevin) Gunawan 4502396 [email protected] 01 RESEARCH 6

Research framework 7 Environmental problem 8 Adaptability problem 8 Efficiency problem 9 IFD building 10 Flexible structure 13

02 PRECEDENT STUDY 16

PO-Lab 18 Building system 20

03 PROBLEM STATEMENT 28

Original Hypothesis 28 Calculation 34 Problem Statement 35

04 METHODOLOGY 38 table of contents Methodology sequence 42 05 CONCEPT DEVELOPMENT 46

Weight 48 Matrix 49 00 Wall to wall connection 50 Wall to wall connection calculation 50 Design alternatives 53 Floor to floor connection 64 Floor to floor connection calculation 64 Design alternatives 65 Design concept 72

06 DESIGN 74

Design proposal 75

07 PROTOTYPE 78

Floor, wall blocks, and beam 80 Assembly 82 Remarks 83

08 CONCLUSION & RECOMMENDATION 84

Conclusion 85 Future recommendation 87

09 BIBLIOGRAPHY 88

10 APPENDICES 90 Research//RESE FrameworkARCH FRAMEWORK

ENVIRONMENTAL ADAPTABILITY EFFICIENCY PROBLEM PROBLEM PROBLEM

CONCLUSION

The needs for IFD BUILDING

INDUSTRIAL FLEXIBLE DEMOUNTABLE

research PROBLEM

The needs for dynamic STRUCTURAL calculation 01

LITERATURE RESEARCH

IFD Buildings references

Structural calculation of the references

Dynamic structural calculation + interface references

TECHNICAL BASIS

Parametric Design Structural Design Digital Product Manufacturing Development Grasshopper Flexible structure CNC Milling Industrial Karamba OSB Structure Flexible Rhino Demountable

Figure 1 (own illust.) : Research framework 1. Environmental Problem Following today’s trends of fast-cycling market changes, Satisfying user requirements depends on the supplied it becomes very difficult to predict future scenarios for quality of the building. If user requirements are expect- In 2010, more than half of the world’s population are liv- share of embodied energy in a building is going to play ed to increase over time, the importance of improve- ing in man-made environments and this statistic will still a significant role as the percentage of embodied energy ment of the level of functionality in the initial building grow rapidly. Meanwhile, the emissions of carbon diox- compared to the total energy balance is rising (Mumma, design is tantamount. The supplied functionality is, ide - which causes global warming - are expected to in- 1995). therefore, larger and the decrease may be less substan- crease up to 45% - 90% and the total energy consumption tial (see figure 5). User requirements change during the by 2005 will have doubled (UN estimates). Recent studies The impact of the amount of energy needed for building, lifespan of a building. People roughly spend 80% of their also stated that the construction industry is the greatest maintaining and demolishing a building is well illustrat- time inside buildings; logically the user always looks for consumer of world’s natural resources and energy (40% ed by an analysis by Ding (2007)of 20 Australian schools. the solution that meets his/her demands best.

of worldwide energy consumption), as well as the great- According to this analysis, the amount of energy needed Figure 3: The pulse of change in dwellings (Rigo, 1999) est dumper of waste. for building maintaining and demolishing those is about the use of buildings. Recent research done by one of the 3. Efficiency Problem the same as 37 years of energy to operate a school. This biggest housing corporations in Amsterdam illustrates Currently, reducing the energy consumption of the build- includes heating, cooling and electricity use. Problems of conventional construction method is: that the recurrence of changing sequences in dwellings ing industry is a crucial issue. The conventional focus in is increasing. Dwellings whose design life is 50 years be- reduction effort in Quality x Scope = Cost x Time gin to change within three years. On average, the whole the operational en- 2. Adaptability problem ergy consumption, dwelling is transformed within 25 years (Figure 3). Buildings should be able to adapt to different life phases In automotive, shipbuilding, and aircraft : e.g. smart HVAC and of their users and to maintain building standards since The types and terms of change in user requirements in lighting system or PV Quality x Scope > Cost x Time human behavior does not remain constant. the use of buildings are characterized and illustrated in panels integrated in figure 4 .They are defined with the help of related- re building envelopes It seems to easy to dismiss the manufacturing industries search projects executed by Hek et al. (2004), Dobbel- to generate ener- for having no relevance for architecture. (Kieran & Tim- If these requirements cannot be met within the context of steen (2004) and Post et al. (2006). This shows that users gy. However, energy berlake, 2004) inhabited spaces, these spaces are abandoned. This, for tend to change their preferences throughout the year, reduction potential example, is the problem with social housing in the Neth- which shows the needs of adaptability aspect in their lies in the initial part erlands. Decision-making on construction of dwellings dwellings. of the design itself: 3.1. Current Situation material choices, was based on the short-term view of the current state of manufacturing pro- housing, and not on a long-term survey of users’ needs and market conditions. Nowadays, architect is excluded from the making processes, and end-of cess. Yet back then, architects, engineers, and con- life possibilities. Therefore, most apartment blocks are demolished be- tractors were all the same person. Architect worked as “master builder” who controlled the whole design and The conventional cause of their inability to adapt to new requirements. It has been recently reported that demolition contractors making process. Since then, design and construction building industry are treated as two independent products. This results has a limited under- in the Netherlands expect to demolish hundreds of thou- Figure 2 : Dominant linear model of life cycle of sands of apartment blocks in the coming decade. This will in a conflict in between these two phases which ended materials and components (Durmisevic, 2006) standing of building with lots of “waste” , e.g. incomplete and inaccurate de- efficiency. Buildings result in the creation of 25 million tonnes of waste materials each year. Recent changes in technologies and soci- signs, conflicts between design and construction, lack of are always conceived as fixed and permanent structures buildable designs. Designers struggle with, and usually although they may be subject to transformation. Conse- ety, coupled with changes in the lives of users, dynamic market activities, and environmental awareness, justi- ignore, the production conditions in which their designs quently, most of the building structures need to be bro- will be implemented. (Sarhan & Fox, 2013) ken down, in order to be changed, adapted, upgraded, or fy the need for new planning approaches that focus on buildings as economic and sustainable solutions during replaced. The material flow is one-directional, starting To conclude, these waste are caused mostly by the seg- from material extraction, and ending with landfill (dis- their whole life cycle. Conventional building cannot facilitate such demands. regation between roles . The architect has been sepa- posal of waste by burying it underground). This will re- rated from the contractor and the materials scientist is sult in huge waste production and material consumption. Apartments were built to minimum standards to satis- not on a par with the product engineer. This results in Figure 4 : Types of change of user requirements (Dobbelsteen, 2004) problems in communication between all disciplines. fy basic needs. The development of housing projects to- 1.1. Embodied energy day has a similar strategy. Although energy and acous- tic performance has improved, spatial performance has Buildings can be seen as complex combinations of var- remained at a very low level, since the spatial system is 2.2. Effect to user CONCLUSION: ious materials of which each contributes to a building’s unable to transform from one use pattern to another. total amount of embodied energy. Besides the energy Environmental : the needs of recyclable material and required to extract and process the raw materials into The main problem facing building transformation today low emissive construction process. components and the energy needed for the transport is the fact that in the past, developers, architects and Adaptability : the needs of demountable system. and installation of the components, the energy involved builders visualized their buildings as being permanent, Efficiency : the needs of integration of roles and design in maintaining, removing and recycling or disposing can and did not make provisions for future changes. “waste” reduction. also be seen as part of the total amount of embodied energy related to a building. Based on the conclusion from aforementioned aspects, As the operating energy of buildings is declining, the it is concluded that the conventional building needs to move forward to IFD(Industrial, Flexible, and Demount- able) model.

Figure 5 : Relation between functional performance and time. (Gijsberg et al., 2009)

/// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 8 ///////// /// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 9 ///////// 2.2. Product flexibility 1. Industrial The building industry is inefficient due to errors and 2. Flexible Conventionally, the technical and functional service life unstructured process. To deliver better quality and cost of a modern building is approximately 50 years. Yet, today buildings with an benefits, the conventional process – which segregates Flexibility can be defined in different ways. In this area every role – needs to be more integrated. age of 15 years are de- it is defined as: ‘Flexibility is a property of a building or molished to give way building product which makes it possible to make ad- Integrative method is started in industrial construction, to new construction. justments in order to respond on (changing) demands The average func- which uses prefabricated components that are sys- and wishes’ SEV (2007). tem-built in factory controlled conditions. Using pre- tional service life of a building is becom- fabrication principles can result in benefits on quality, Flexibility can be separated in two phases of the build- time, and cost. ing shorter and this ing life cycle: forces the return on 1. Process flexibility : flexibility during the building pro- investments to come Costs Prefabricated buildings are more efficient than cess traditional on-site construction. In theory, costs during more quickly. In or- 2. Product flexibility : Flexibility during the use phase of der to extend the life the building process depend on material, labour, and the building time. By reducing only 1 aspect, the overall cost will be cycle of the building reduced. and its components, 2.1. Process flexibility the building should be designed focusing on Material : reduction of on-site material waste due to Process flexibility can be regarded as freedom of design over-ordering. the building as an eco- for user. The essential part of it is that users have pos- nomic and sustainable sibilities to decide the look or size of the building. Yet, solution for a desired Labour : more efficient and error-free building process fabrication or industrialization create some concern for on site. use strategy over time. user that it will occur a monotonous effect. The fear for This means that the mass production of prefabrication gives it a bad reputa- Time : faster building process. unit of design analysis tion, that standardization creates uniformity in lifestyle. is not the building it is

the use of the building Figure 9: Interdependency between technical and spatial flexibility (Durmisevic,2006) Yet, the process flexibility of the automotive industry over time. can be integrated into the building industry. Not every Figure 8: Functional, technical, and economic life- client can order an unique car, but the tools and meth- time (De Jong, 1997) Having this in mind De ods that are used to produce the car could be automated Jong explored the re- Indicators of spatial flexibility can be defined as : to produce more customized products with small in- lationship between functional, technical, and economic • Extendibility (enlargement of the space), crease in cost per unit. life cycle shown, in Figure 8. • Partitioning (rearrangement of space units), • Multi-functionality (rearrangement within space Functional life-time : change of tenant units), and

• Functional mutation (mutation from one function to Technical life-time : every tenant change, re-invest- another). ments is necessary & required performance level is in-

creasing On the other hand, the technical life-time is related to Figure 6 : Conventional vs Prefabrication time comparison (Smith, 2010) the technical flexibility. Economic life-time : time span which the building meets the return on the investment criteria (revenue - income, Figure 6 shows the difference of construction time be- Technical flexibility indicators : expenditure - expenses) tween conventional method and prefabrication method, • Accessibility, possibly creating 50% time saving over the whole con- • replaceability, Functional life span is related to the use of the building struction. Yet, prefabrication is a lifecycle investment. It • reconfiguring, and while the technical life span is determined by its tech- has a high initial cost, but the prefabricated product can • separation. provide higher value on the long term. nical state. The service life of the building is a result of the balance between supply (technical– life span) and demand (functional life span. Figure 7 : LEGO. (source : google.com) The figure shows that there is natural interdependency between technical flexibility and spatial flexibility This implies that the economic life span ends when the and they cannot be isolated from each other. Every Modular design functional requirements are not met by the technical Quality change within the space has consequences for the tech- specifications. This causes economic action such as in- nical systems of the building, and vice versa. vestment in replacement of components, or investment On site construction still highly depends on craftsman- Modular design is a design technique that has the po- in demolition of structure. ship skills, where prefabrication process with auto- tential to improve the process flexibility in the building In conclusion, to fulfill the flexibility aspect from a mated process will increase the precision of each com- building, the construction system needs to be segregat- industry. In principal, the small modular components Therefore, based on the lifetime, one can differenti- ponents. Products from the factory will have a better ed based on the trends of modifications. The systems could be assembled together into a complex product in ate type of flexibility in a building. Functional life time, quality since the assembly takes place in an controlled which are modified more often needs to be independent a different way, such as Lego (figure 7). This will lead to which changes more often is related to spatial flexibility. and automated environment, diminishing the chance of than the ones which are not. possibility of mass customization despite all the modu- inaccuracy caused by human errors. lar components are manufactured in large standardized series.

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Figure 12: Hierarchical levels in building.(Durmisevic, 2006) Figure 10: Building layers according to Brand. (Brand, 1995) According to such a definition of building structure, the hierarchical levels of building composition/decomposition can be defined as: • The building level represents the arrangement of systems, which are carriers of main building functions (load bear- The prefabricated components are mostly designed ing construction, enclosure, partitioning, and servicing), to ease the installation yet it lacks the ability to be de- mounted. As already been mentioned in the Environ- • The system level represents the arrangement of components, which are carriers of the system functions (bearing, ment part, demolition processes directly account for finishing, insulation, reflection etc.) - the sub functions of the building. 90% of waste production within the building sector and • The component level represents the arrangement of elements and materials, which are carriers of component func- approximately 50% of the embodied energy of a building tions, being sub-functions of the system (Durmisevic, 2006). One of the reason of the demolition process is that the construction is not designed to be The relationship between these levels will conclude in different levels of flexibility. demountable. In some cases, some already attempted to disassemble existing building that are not designed for disassembly. Eventually, this results in time-consuming and labor intensive activities.

Designing for disassembly can improve the end-of-life cycle of a building. According to Durmisevic(2006) flexible building and design for disassembly can be the way out for diminishing aforementioned environment problem. The aim of sustainable design should be a design of Figure 13: Static configuration (Durmisevic, 2006) transformable building structures made of components Static configurations (figure 13) are characterized by maximal integration and dependency between building com- assembled in a systematic order, for achieving the pos- ponents, and is caused by: (i) Material levels that do not correspond to independent building functions, (ii) hierarchy sibility of maintenance and replacement. of assembly not related to component service life and expected time to obsolescence, (iii)complex relational patterns By analyzing the different lifecycles of different compo- presenting High levels of dependency between elements (iii) application of sequential assembly sequences, (iv) design Figure 11: Assembly sequences of components (Durmisevic, 2006) nents in a building, one can categorize each components of integral joint types (components are shaped in such a way that bringing them together forms a joint), and (v) use of into independent categories based on the lifecycle. Fig- chemical connections. ure 10 shows one example from Brand, who categorize building components into several levels. The thicker Such structures do not have the potential for functional, technical, and physical decomposition, which define the lines shows higher level of life cycle. Therefore, for in- potential for a structure to be transformed. They define a category of non-transformable structures Traditionally, stance, skin and space plan should have demountable building elements are closely related to one another, with no respect to the different functions and life cycles they may aspects compared to the structure. have. This creates maximum integration at joints. Such traditional buildings often have a great dependency between the load bearing structure, façade, partitioning walls, and installations, due to their closed hierarchical assembly. By differentiating each category, the components could be assembled using different hierarchies, for example : Such buildings usually end up being demolished. showed in figure 11.

Demountable buildings will create enormous advantag- es for construction, for instance :

Environmental benefits • Reduction in waste • Conservation of natural resources

Economic benefits • Easier to adapt to new requirements • Reduction in maintenance costs

/// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 12 //////////// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 13 ///////// Overview of the structure based on the hierarchical levels :

Figure 14: Partly decomposable structures (Durmisevic, 2006) Partly decomposable structures (figure 14) are dependent design strategy in which the hierarchy of fixed and flexible elements is adjusted accordingly. Fixed elements are elements with high levels of flexibility that allow spatial and functional changes, and high durability. Flexible elements are elements frequently exposed to change.Flexibility of such structures is restricted to the designed capacity of fixed elements and the type of flexibility strategically cho- sen. Such structures are partially decomposable because fixed parts of the structure are not designed for functional, technical, and physical decomposition.

Figure 16: Overview of flexible structures. (Durmisevic, 2006) Several types which are used generally for total transformable structures are:

Figure 15: Dynamic structure (Durmisevic, 2006)

Dynamic configurations (figure 15), as opposed to static configurations, have open assemblies with independent sub-assemblies that represent independent functions. Main characteristics of dynamic configurations are (i) Separa- tion of material levels, which correspond to independent building functions, (ii) creation of open hierarchy of distinct sub-assemblies, (iii) use of accessory joint types that require additional parts to form the joint between components, (iv) application of parallel instead of sequential assembly/disassembly processes, and (v) use of mechanical connections in place of chemical connections. Such building configurations provide the precondition for independence and exchangeability of building components, and accordingly, their reuse, reconfiguration, or recycling through functional, technical, and physical decomposition

Figure 17: General types of transformable structures. ( SEDA, 2006)

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As already been explained thoroughly in the previous researchers and students to build their research in 1 to 1 chapter, the building industry is responsible for the scale. It will be used to investigate and test digital produc- environmental impact of the industrial sector. To di- tion technologies such as CNC-milled wood connections, minish the impact, one should shift the conventional effect of file to factory production, material use, building way of building to IFD (Industrial, Flexible, and De- process, and many more aspect that relates to the next in- mountable) in a sustainable way, or so to say, energy dustrial revolution that will change construction world. efficient. The actual process of maximizing energy efficiency in building industry revolves mainly on -re The nature of its modular and open to dissassemble will ducing the operational energy consumption, and less allow the building to be updated and upgraded with in- on embodied energy of the building itself. Now, a 4TU novative ideas, both from students and researchers. The Lighthouse project is trying to improve the field of low- assembly system, using modular OSB blocks, is aimed to ering the embodied energy - named PD-Lab (Product maximize the efficiency of building with reducing errors Development Lab) or PO-Lab (Product Onwikelling) in and a low-labour construction process. Even untrained Dutch, which has been built in Faculty of Architecture construction workers should be able to assemble the in TU Delft on 2017. building.

It uses the digital technologies to develop a modular Due to its nature of digital fabrication, everything starts building system, which is based on standardized com- from file to factory. It allows the user to easily have their ponents to configure affordable and fast buildings. It own custom preferences by configuring standardized Figure 19 : FabField scheme. (van Veen, 2016) responds to the progressive awareness and require- components in different variations. One can choose stan- ments amoing government and costumers. This build- dard component to configure a relatively cheap building Project Goals ing system tries to improve sustainibility aspect in area that can be upgraded later on, regards for the dissassembly of construction by focusing on reducing the embodied aspect. Based on the strategy of improving energy efficiency, it Fast and easy construction energy and considering the environmental impact of is important to set goals in scale of the entire life cycle, the overall life cycle. PO-Lab became a basis for The New Makers’ product starting from choosing a right material, producing effi- The building system aims to be fast and easy to build. named FabField (http://www.fabfield.com/) , focusing ciently to reduce waste, minimizing the energy use, and Practical translation of the aim is the system needs The objective of this project (figure 18) is to provide more in commercial usage of the blocks to create a struc- designing for disassembly and material recycle. to be able to construct with a minimum of 2 people, a platform to test and prototype innovative ideas for ture, which system is depicted in figure 19. without the use of heavy machinery or cranes. This will the building industry. This platform will encourage To conclude, the main goals of PO-Lab are : heavily reduce the amount of expenses for workers. • Sustainable material production and transport • Resource efficient production • Fast and easy construction Durable Constructions • Durable constructions • Dissasembly, reuse and recycling strategies By making the components modular, user is able to configure it as they want. Everyone can create a build- Sustainable material, production, ing to their own desires and demands. In order to fit and transport the need of the costumer fully, it is extremely important to ensure that the building system is adaptable yet Digital technologies significantly reduces the transport safe. The structure component needs to be durable and distances, both before and after the production process. still allowing flexibility. The material for building will be harvested locally instead being shipped from one point to the other. Instead Strategies for disassembly, reuse, of products, the digital data of the design can be distrib- and recycling uted over the world in order to produce it wherever it is necessary. This will reduce the amount of wasted CO2 Most of building in the world will not suit requirements due to transportation. after certain usage time. Instead of demolishing it, the building needs to be disassembled back into compo- Resource efficient products nents. The use of standardized building compoents will allow the disassembled components to be reused, such Digital manufacturing production, specifically CNC fab- as Lego blocks. It opens up the possibility to build a rication, can create products with high accuracy and house out of used components which reduces the em- very little residual products. CNC-based product will bodied energy of new materials. If the component’s also be well controlled in a closed environment. In prin- lifespan completely ends, the component can be recy- cipal, this will result in high quality building products cled back into ecological cycle. with little waste material.

Figure 18 : POLab goals. (4tu.nl)

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The building system is made from 3 main components which size can vary based on the requirements. The base of the building is made up of a floor and a beam element with protruding notches on the sides. Onto these notches, the wall element can be placed and fastened using 16 bolts (8 top and 8 bottom) in each element. The bolts are fastened from the outside, protruding through the notches to pre-embedded nuts in the wall component. For assembling the second floor, the process on the ground floor is repeated by placing the beam element and floors on top of the wall. To finish, the roof elements are placed against each other and fastened on the connection to the wall using bolts.

All the blocks are made from 18 mm OSB plate and all the components weigh under 50 kg (maximum weight that can be carried by 2 people in construction)

The roof size is 300 x 250 mm, with varying slope from 0, 30, 45, and 60 degrees.

The wall size is 600 mm x 250 mm, with varying length of 2.4 m, 2.7 m or 3 m

The floor size is 300 mm x 250 mm, with varying length of 2.4 m to 4.8 m.

Figure 20 : PO-Lab components (van der Knaap, 2016) Figure 21 : PO-Lab section and plan (own illust.)

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B A

Figure 22 : PO-Lab beam connection between wall and floor blocks (own illust.)

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Figure 23 : PO-Lab floor blocks (own illust.) Figure 24 : PO-Lab wall blocks (own illust.)

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Figure 24 : PO-Lab beam connection of wall blocks and roof blocks (own illust.) Figure 25 : PO-Lab roof blocks (own illust.)

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In the early phase of PO-Lab design, there were 3 options The selected alternative is ALL FIXED connections of stability system : all hinged connections, fixed on the since the criteria - freedom of design, adaptability, bottom, and all-fixed. and ergonomics, are all optimized with this situation. Furthermore, a simple FE Model is developed to com- The arguments that led into the selection are : prehend the force that is happening in the members. As can be seen in the image, the maximum moment is

ALL HINGED CONNECTION

Reduction of design freedom. (Inability to create open-facade or large openings on the floor without additional load-bearing component)

No complex connections due to zero moment on the connec- Figure 26 : All hinged connection tions. precedent study (own illust.)

FIXED ON THE BOTTOM 03 More freedom of design due to stability in its plane without secondary stability element. Figure 29 : Moments in the structure. (van der Knaap, 2016) Bottom connections have to bear nearly all the forces, which ends in more complex detail. happening on the bottom part ; 3.1 kNm and 4,6 kNm, respectively. Therefore, the connections were developed to bear the moment. Figure 27 : Fixed on the bottom Different connections on - bot (own illust.) tom and top which leads to complications in building ease. The moment is translated into formula :

M=F(force) * a(distance)

ALL FIXED Tensile strength inside the connection Mmax inside : 3.1 kNm Maximum design freedom A : 300 mm (width of the block) = 0.3 m since all connections can bear F = M/a = 3.1/0.3 = 10.33 kN multiple forces. Divided over 2 connections : 5.17 kN per joint

Same detail for every connec- Tensile strength outside the connection tion. Mmax outside : 4.6 kNm A : 300 mm = 0.3 m Leads to oversizing of connec- F = M/a = 4.6 / 0.3 = 15.33 kN tions where there are no open- Divided over 2 connections : 7.67 kN per joint Figure 28 : All fixed connection ings or open facade. (own illust.) In conclusion, each wall to floor need to bear 15.33 kN. A

A : M10 Bolts B : Nuts C : Notches with hole The connections consists 4 notches, which will be tighten by bolt and nuts. Basic calculation shows that 4 bolts are capable for handling the moment :

M10 bolt compression on OSB = area * max. stress area = 628 mm2 628 * 3.5 = 2.2 kN so 7.7/2.2 = 3.5 (4 connections needed)

As can be seen in the image, the connections are made in form of notches. On each blocks, nuts are pre-inserted in the production phase. Afterwards, the bolts will penetrate the components through a hole to reach the nuts. Lastly, the bolt can be tighten easily from outside, clamping all the layers of components - creating a fixed C connection.

Figure 31 : Force in the details(van der Knaap, 2016)

The images clearly depicts the structural hypothesis ; that the connections will transfer the lateral load into axial C loads. Two notches, 300 mm apart, will convert the moment into tension and compression. A The largest moment - in the face that exposed to the wind load, will create compression force in the inside part and tension on the outside part. The tension is transferred from the outer notch into the large beam - using hook-like mechanism. The beam is connected to the foundation. Furthermore, the compression force is barred by floor elements.

On the other hand, the moment that occurs on the other side of the wall will create compression on the beam and tension on the inside bolts. The elaborated 2 moments are the expected force that will occur in the connections due to horizontal load. As can be seen, the critical point of this detail is the tensile strength of the notch against the bolt. B

Figure 30 : Details of wall to floor connection(van der Knaap, 2016) C

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Since the previous analysis has concluded that the criti- To get more accurate result for the structural behavior, cal point of the joint is the tensile strength of the notch, more elaborated test with full scale mock up is execut- a material test was executed to verify the argument. ed. The figure shows different setup, one for tension, and the other one for compression test. In this way, The height of the notches and the location of the holes predicted moments for both direction can be simulated. for the bolt are derived from the CNC-limitation that limits the milling process only on one side. To optimize the notch in structural capacities, the only variables are Result : • Thickness of notch The tension test collapsed at the moment of 2.1 kNm and • Type of bolt the compression test failed at 3.1 kNm. • Type of material

Therefore, the set-up for the test is aimed to conclude Compression Tension a reliable conclusion about the most optimized solution from available 3 variables.

1. A tensile test to measure the required force to pull M10 bolt out of notch - to achieve a value as standard of comparison to forthcoming tests. 2. Tensile test using M12 bolt to determine the advantage of bigger diameter connection. 3. Tensile test with different material, which is birch- wood.

Results

It shows that M12 bolt is not necessarily stronger compared to M10 bolt in 18 mm OSB. The lowest maximum tensile strength of M10 and M12 are respectively 3731 N and 3705 N - which does not differ much. Therefore, it is concluded that M12 is not a suitable solution.

The birch wood definitely adds up the strength of the notch, to minimum of 7.5 kN

The test shows that the bolt and notch is the critical point. The failure happens due to the failure of material, and the connection of the plates. The construction creep will only exarcebate this problem.

Figure 32 : Test samples(van der Knaap, 2016) Figure 33 : Test result(van der Knaap, 2016)

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For receiving the building permit of PD-Lab in TU Delft ground, a professional structural calculation was performed by Luning BV. The calculation method will be explained shortly to give some insight and references for the project.

Luning did not use full-overview model of the structure. Instead, they analyze the behavior of each member separately and calculate the stability in the end phase.

Boundary Conditions

Permanent load Figure 37 : Force irregularity in the structure(own illust.) Roof & wall element : 0.73 kN/m2 Floor element : 0.60 kN/m2 Irregularity of forces Loads 2 Wind loads : 0.65 kN/m The problem in the structure comes from the stability. Snow loads : 0.70 kN/m2 As can be seen in the image, half of the plan has beam that connects point A and B. On the other half, the Figure 34 : Full overview model of the structure(own illust.) load transfer relies heavily on the edge beam and roof 1. Floor Element blocks, which makes it as crucial point of the construction. Therefore, the same calculation which was used to assess the floor beam is executed to test whether the edge beam can withstand the forces. Luning calculated the floor beam with only the live load input. The image above shows the loads that occur on the beam (permanent load from the roof blocks and wind load) and The floor beam is separated into 3 different the necessary reaction forces to ascertain the stability. components : upper rib, skin core, and lower Furthermore, the result shows that the beam is in the edge of breaking (73% of the material due to axial stress and rib. 89% due to shear stress) – especially due to shear stress. Based on the ULS check, maximum stress that occur in the beam only uses 34 % of the material strength (on skincore). Connection strength

Figure 35 : Floor element (Luning BV, 2016) To function well as a structural component, all the box / block that are made from plates component need to have a reliable 2. Roof Element fixed connections. The method that was used for PO-Lab (adhesive and nail gun) is considered unstable by Luning, due to The calculation of the roof blocks is neglected the unreliability character of the adhesive. Adhesive needs to since the roof blocks already have bigger di- be verified and certified by authority to be considered capable mension compared to floor blocks - which are to be used in construction. able to withstand live load. Hence, roof blocks are assumed to be strong enough to withstand wind load that is significantly smaller to live load.

Figure 36 : Roof element (Luning BV, 2016) Figure 37 : Plate to plate connection(own illust.)

3. Wall Element Fixed joints

The wall is calculated as 2 column – since the Based on the methodology, the ideal connections for the side parts have to deal with forces in 2 direc- construction is all fixed (except roof to roof connection). tion (Z & Y) whereas the front part only has Yet, in reality, creating fixed joints only using wood and to withstand the force on Z direction. Subse- bolts is a difficult task due to its anisotropic characteristic: quently, the wall is calculated in buckling mode by exposing 2 thin columns (18 x 214 mm) with • Preferable load is compression parallel to grain. Figure 37 : Wall element (Luning BV, 2016) wind load and permanent load. In the end, the • Wood needs to take on load spread over its surface. calculation concludes that the buckling load factor of the wall component is only 0.22. • Tension perpendicular to grain is not desirable(may cause splits). Initial stress and deflection check concludes that the blocks are able to withstand the determined load. • Hygroscopic behavior which ends in varying dimension due to water absorption.

Figure 38 : Fixed connection(own illust.)

/// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 34 //////////// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 35 ///////// Therefore, to create a fixed joint, the intersection of 2 components - in this case column and beam - needs to have enormous height to counter the occuring moment. Not only the height, the load concentration must be spread into bigger area. Therefore, using only 1 or 2 connections are not desirable.

In the other situation, if the construction requires fewer connections, wood connections needs to be strength- ened by steel plates inside the connection to counter the tension force and spreading it to bigger area.

Figure 41 : Lateral loads. (own illust.) Main problem of the construction system comes from the lateral load. The occurring load will be separated into 2 axis, x and y. Since the connection cannot accommodate the occurring bending moment caused by the lateral force, the force will be transferred into the blocks, as shown below.

Figure 39 : Example of fixed connection(Moment Resisting Timber Connection lecture)

In conclusion, the existing PO-Lab connection will hardly function as a fixed connection. All the connections completely relies on 4 connections of 10 mm bolts.

Simple calculation can show how the fixed joint would not function well :

Maximum moment : 4.6 kNm a : 200 mm (in reality) = 0.2 m F = M/a = 4.6 / 0.2 = 23 kN

Divided into 2 connections : 11.5 kN Figure 42 : Force path. (own illust.)

After safety factor of 0.4 (friction coefficient between The image shows that the lateral force from x-axis steel and wood) = 8.05 kN create significant problem compared to y-axis, due to these reasons: Based on the tensile test, the average maximum shear • Bigger contact area, which results in bigger force. strength of 18 mm OSB inserted with M10 bolt is 3,9 kN. • The irregularity of the plan creates eccentric flow Therefore, we can conclude that the connection will of force towards the left part that ignites rotation not be capable of functioning as fixed joint. In addition, movement. the tension and compression that were done by van der Knaap will also not be relevant - since the force will not To conclude, the main force flow will be carried by occur in the reality. The force will spread to the mem- the stacks of wall blocks. Yet, since they don’t have bers instead of to the connection, thus creating an al- any connections to each other (only the top and most-hinged behavior for the connection. bottom are clamped together via beam that doesn’t have big contact area). Eventually, the force will make the blocks deform (depicted in the image).

Figure 43 : Predicted deformation. (own illust.)

Figure 40 : Physical test result. (van der Knaap, 2016)

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The methodology is aimed to solve aforementioned structural problem by design decision. It is divided into two main parts, one focuses on structural analysis and calculation, and the remaining focuses on filtering multiple design alternatives to solve the structural problem, based on specific requirements.

The structural part pursues in finding a structural solution for different articulation which can be made by user using FabField system. Therefore, the structural problem needs to be translated into a structural value - which will be used as a parameter and a base for developing the necessary structural problems. In behalf of the development of parametric model, it is possible to generate structural solution, each tailored for different design and articulation methodology from different users. Yet, to start, the research will focus on PD-Lab structure.

Furthermore, the second part is adapting the methodology which has been developed by Jeroen van Veen and Nick van 04 der Knaap for creating the components for PD-Lab. The method is developed to provide a helping hand for decision making during development of any kind of components for a modular, CNC fabricated building system, on the basis of predefined criteria. This methodology shifts the role of an architects. Architects need to be capable to develop, desig, engineer and manufacture the building system - from the initial development to end of life decision. The first part of the methodology will lay path for this second part by be- coming one of the criterias.

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Figure 45 : Methodology (own illust.)

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The methodology is divided into 2 parts, structural an analytical approach, borrowed from product develop- (point A to point C) and design (point D to F). All the ment industry. The points will be elaborated shortly, to give phases will be explained and elaborated individually the background on how it works. in particular paragraphs. D1. Design problems A. PD-Lab The methodology starts with a specific design task for a PD-Lab will be the starting point for solving structur- project, whether it is connection details, facade details, al problem in a bigger scope - FabField. In this point, building services, or any design task can be derived. Due the boundary conditions are set : to the complexity of a particular design task since it has • Structural loads (wind, live loads, etc.) to fulfill multiple aspects - such as from point of view of Figure 46 : Weighting systems (van Veen, 2016) • Material environmental energy, manufacturing, and user ergonom- D4. Weight • Weight and dimension of structure system ics - criterias need to be generated systematically in order In this particular problem, which is structural, it allows to • Construction system to make an equal comparison between design alternatives The demands of costumer can be integrated into the create a prototype that can tested against the existing the that are aimed to solve the design problems. criteria by ranking them to the priority the user gives design to fully validate the problem and solution. By setting up the boundary conditions, the scope of to a specific criteria. This can be done by individual- the research is determined clearly. D2. Criteria ly compare all the criteria to each other, which will G. Comparison shows the rank of importance in between all the cri- B. Problem Statement Depending on the project, the criteria can be specified dif- teria. The prototypes can be assessed based on the result of ferently. In the initial phase, one should identify the main structural test, either compression, shear, or tension to An in-depth analysis to find any structural related aims of the design. To give an example, there are multi- By doing this for all the criteria, there can be division validate the effect of structural components, compared to problem is executed. In this particular research, writ- ple aspects in construction that can be criterias : material, of importance : important (weight 3), less important the existing component. er is working together with Luning BV (part of ABT production process, transportation, assembly, end-of-life, (weight 2), and relatively unimportant (weight 1). group) who calculated the PD-Lab structure based on costs, etc. H. Final Design regulations. D5. Alternatives D3. Aim The test from the comparison phase will validate the pre- To simplify, the analysis of the problem can be started In this point, all the design alternatives to solve the dicted structural behavior which is going to be the basis based on SLS (Service Limit State) and ULS (Ultimate From specific criterias, there will be particular aims to problem is reviewed, based on the criteria. The most of final design selection. Selected sub-solutions will be fit Limit State). Based on Eurocode, SLS assess the con- reach the goal. The aim specificies in what amount a de- favourable alternative can be found by scoring the together in the system in the end. struction by the limit of deflection and ULS assess the sign solution is convenient to an ambition. The higher a concepts to the criteria and multiplying this by the material breakage due to overstressing. Anything that solution scores for an aim, the more suitable the solution is weight. The sum of these scores will give a most suit- Future Projection relates to reducing the required value of ULS and SLS to be used in the eventual design. First, the ambition from able concept solution. below the standard can be considered as a structural the criterias gets a specific description. Next, the specific Future projection will be elaborated further on chapter 08 problem. design task defines an aim in what amount the ambition E. Concepts (Recommendation) needs to be fulfiilled. This can be linked to a score : a design C. Structural Value or idea can score from 1 to 4 - the higher the score, the bet- Combining promising alternatives will result in a con- ter the design satisfies the aim. cept proposal. It is probable that combination which Furthermore, the problem needs to validated using receives the highest score does not combine well in calculation. The calculation should create an output reality. Yet, in this step, there will already be the most of structural value (force in kN, moment in kNm, or sensible alternatives to solve the design problem in other possible outputs) that can be used as a mini- point A. mum value which should be fulfilled by the output of the same calculation applied to improved design. F. Prototyping

To simplify, the aim of this step is to find : The benefit of using CAD/CAM is that it can accelerate the verification or validation process. By using rapid New value from improved design > value from exist- It is important to consider different views of involved par- prototyping technologies, scale models can be made ing design ties in the process and their influence on the design when very efficiently. setting up the criterias. It is also critical to take into account It should be valid that if the new value surpasses the user requirements as users are the most decisive party in With prototypes, problems will become more visible. old value, the structural problem is considered solved. product design. However, user’s point of view can conflict By making multiple iterations this can become a cy- with demands of the manufacturer or environmental point clic process. If a specific problem is noticed, one can D. Alternatives of view. In order to define universal criteria which incor- return to the concept phase to solve this problem. The porate different needs and requirements, it is essential to other benefit of prototyping is that one can reaches This is the the point where the research shifts from build a knowledge in area of different parties - user, manu- a full-working prototype, the drawing data can im- structural methodology to design methodology. This- facturer, and environment. mediately be applied for the production of the actual spart consists multiple layer of complexity, to create design.

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This methodological approach provides designers a framework to develop their products based on a specific set of criteria. The analytical methodology is divided into seven different stages; a. design problems b. criteria c. alternative selection d. concept comparison e. concept proposal f. prototyping and testing g. sub-solutions h. final design

In all different design cases, the methodology comes to the assessment of an design solution to the related requirements. The method can be used to generate design options and draft recommendations and to justify the final design on a quantitative basis. The approach is systematically because by making of combinations and multiple different solutions, a concept design to the problem can be created (shown in Fig- ure 47)using a structured and analytical method.

Figure 47 : Methodology for selecting design alternative (van Veen, 2016)

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Based on the problem statement, the design task is to develop a connection for the blocks so they can act together as a shear component. In conclusion, there are 2 components from the structure that need to be solved.

Wall to wall

05concept development

Floor to floor

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The different criteria have a varying importance on the with a high sum of importance receive a high weight and design. This can, on its turn, vary for another design visa versa. To translate the score into a weight the amount problem. Therefore weights are introduced. Criteria can of criteria can be divided by three. With a total of 23 cri- have a weight of 1, 2,3 or 4. This weights are determined teria In this case values from 1-3 receive weight one, 4-6 Wall to wall by following the methodology described before. shows weight two, 7 -9 weight three, and 10 -13 weight four. In the process of the weight valuation from the set crite- the case a criteria scores a value 0, one has to rethink its ria. In the scheme criteria are valued 0 or 1. Criteria are importance in the design. The designer can choose to do compared one to one in terms of importance. Is a criteria not included this criteria. more important than another, it gets the value 1. If it is or less importance it gets the value 0. This can be done for all criteria and results in a sum of importance. Criteria

TOPIC CRITERIA WEIGHT Weight Dimension Process time time Milling components of Amount Foolproof ergonomics Installation Building speed Maintenance reusability / Adaptability distribution Stress Freedom of design Aesthetics Weight 1 1 1 1 1 1 1 1 1 0 0 1 Dimension 0 1 1 1 1 1 1 1 1 1 1 1 Process time 0 0 1 0 0 0 0 0 1 0 0 1 BOUNDARY CONDITIONS STRENGTH Milling time 0 0 0 0 1 0 0 0 0 0 0 1 Amount of components 0 0 1 1 1 1 1 1 1 1 0 1 Foolproof 0 0 1 0 0 1 1 0 0 0 0 1 WEIGHT Installation ergonomics 0 0 1 1 0 0 1 1 0 0 0 0 TRANSPORT Building speed 0 0 1 1 0 0 0 1 0 0 0 1 DIMENSION Maintenance 0 0 1 1 0 1 0 0 1 0 0 0 Adaptability 0 0 0 1 0 1 1 1 0 0 0 1 Stress distribution 1 0 1 1 0 1 1 1 1 1 1 1 Freedom of design 1 0 1 1 1 1 1 1 1 1 0 1 PROCESS TIME Aesthetics 0 0 0 0 0 0 1 0 1 0 0 0 PRODUCTION MILLING TIME Figure 48 : Wall to wall matrix (own illust.)

AMOUNT OF COMPONENTS Floor to floor

FOOLPROOF ASSEMBLY INSTALLATION ERGONOMICS

BUILDING SPEED

MAINTENANCE Weight Dimension Process time Milling time components of Amount Foolproof ergonomics Installation Building speed Maintenance reusability / Adaptability distribution Stress design of Freedom Aesthetics END OF LIFE Weight 1 1 1 1 1 1 1 1 1 0 0 1 ADAPTABILITY Dimension 0 1 1 1 1 1 1 1 1 0 0 1 Process time 0 0 1 0 0 0 0 1 1 0 0 0 Milling time 0 0 0 0 1 0 0 0 0 0 0 0 Amount of components 0 0 1 1 1 1 1 1 1 1 0 0 STRUCTURE STRESS DISTRIBUTION Foolproof 0 0 1 0 0 1 1 0 0 0 0 0 Installation ergonomics 0 0 1 1 0 0 1 1 0 0 0 0 Building speed 0 0 1 1 0 0 0 1 0 0 0 0 Maintenance 0 0 0 1 0 1 0 0 1 0 0 0 FREEDOM OF DESIGN Adaptability 0 0 0 1 0 1 1 1 0 0 0 0 DESIGN QUALITY Stress distribution 1 1 1 1 0 1 1 1 1 1 1 1 AESTHETICS Freedom of design 1 1 1 1 1 1 1 1 1 1 0 1 Aesthetics 0 0 1 1 1 1 1 1 1 0 0 0

Figure 47 : Weight and criteria (own illust.) Figure 49 : Floor to floor matrix (own illust.)

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The important initial phase is to find boundary condi- reaction force will be 4 kN. As can be seen above, 4 blocks reduce the wind force tions - a value in unit that can be compared to conclude Furthermore, the reaction force from the connection is By loading the blocks with wind force as point load, the closer to 0. This calculation is then translated into para- whether a solution will work or not. As already been de- derived from the tensile test result from van der Knaap’s block will deflect in rotation, revolving around the corner metric model in Grasshopper. scribed in the Chapter 03, the existing structure system thesis. As shown in the image, the average maximum ten- point. is vulnerable to lateral force due to inability of the blocks sile stress from 6 tests on 18 mm thick OSB is 4 kN. PARAMETRIC MODEL to transfer the load as a whole. Wind force - self weight < 0 A parametric model is made to analyze the effect of blocks First, a verification of the Fw*h - 1/2l(Fb+Fr) < 0 weight to react to the lateral force. User can change the initial assumption needs 31.65*2.7 - 0.3(0.5+0.5+0.5) - 4< 0 input of height, weight, and the amount of blocks. to be done. 80.75 knM < 0 29.9 kN < 0 (NOT CAPABLE TO WITHSTAND THE WIND) The script is giving an output that the necessary amount of blocks to withstand the wind force is 7 blocks. All the The calculation shows that wind force is reduced by self combined reaction forces and self-weight of 7 blocks Initial assumption : the weight, from 31.65 kN to 29.9 kN - by the weight of 1 block. managed to reduce the wind force into zero (total reac- blocks will work togeth- To see the effect of the weight further, a second iteration tion forces creates 40 kN in total. er to react to the lateral is executed.

load(1), using the friction Figure 52 : Physical test sample (van der Knaap, 2016) Next step is to finding a way to connect the blocks - us force from the next block ing friction so they can function as a shear wall. Figure 55 (2), their own mass (3), Each wall component is connected to 4 notches (2 notch- clearly representes the behavior of wall blocks below the and the moment from the es on each floor component), meaning each wall compo- necessary amount. connection (4). nent will have 16 kN of reaction forces.

Figure 50 : Occuring forces in wall blocks The friction force (2) also Thus, one can conclude that the two forces that will hold (own illust.) will only work in the state the walls from deforming is normal force from their mass when a block totally leans on the next block, ideally on (2) and reaction forces from the component (4). an angled position. Yet, if a block is already in an angled position, logically it will already surpasses the limit of deflection. Calculation Setup

Limit of deflection : h/500 = 2700/500 = 5.4 mm The initial phase is establishing all the known variable into hand calculation. First, the lateral force which occurs The necessary angle to reach the limit of deflection is 0.12 are calculated : 3 degrees - which means it can barely tilt to activate the Wind force : 0,65 kN/m 3 Figure 55 : Deflection of 4 wall blocks (own illust.) friction force. Facade: 1.5 m * 6 m (0.8 + 0.5) * 0,65 kN/m = 7.60 kN Roof : (1.04 + 1.21) kN/m * 6 m = 13.50 kN To prevent this deflection, the blocks need to be connect- Ftotal = (7.60 kN + 13.5 kN) * safety factor of 1.5 = 31.65 kN ed. The scheme below shows the desired behavior of the blocks. The blocks should be able to rotate as a whole.

1 BLOCK Figure 54 : Forces in 4 wall blocks (own illust.) This expectation puts another variable in the calculation.

Fw (wind) = 31.65 kN 4 BLOCKS Fr (roof) = 50 kg * 9.8 m/s = 0.5 kN Fw*h - (Fr+Fb+Fb)(3.5l + 2.5l + 1.5l + 0.5l) - (4/4 * Fr * l1 + Fb (beam) = 1/2 (only half of 3/4*Fr*l2 + 2/4*Fr*l3 + 1/4*Fr*L4) < 0 the weight) * 2 (2 wall blocks per wall component) * 50 kg the reaction forces is gradually reduced based on the * 9.8 m/s2 = 0.5 kN number of the blocks due to different magnitude. The Fb (block) = 50 kg * 9.8 m/s closer it is to the point of rotation, less reaction force =0.5 kN occurs. l (length) = 0.6 m h (height) = 2.7 m 31.65 * 2.7 - (0.5+0.5+0.5)(2.1+1.5+0.9+0.3) - (4*2.4 + Reaction forces (R1 & R2) = 3/4*4*1.8 + 2/4*4*1.2 + 1/4*4*0.6)< 0 16 kN Due to uncertainty of the 85.45 - 7.2 - 18 < 0 value , a safety factor of 4 will 60.25 kNm < 0 be applied, hence the total 22.3 kN < 0 Figure 53 : Forces in 1 wall block (own illust.) Figure 51 : Tensile test result. (van der Knaap, 2016) Figure 56 : Deflection after connection is applied (own illust.)

/// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 50 //////////// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 51 ///////// Ff (shear force) is the necessary force that connect one Design Alternatives block to the other. Figure 56 shows that Ff1 is the biggest shear force , since it has to carry all the mass of the Wall-to-Wall Connection remaining blocks. Hence an overestimation can be concluded to assume that friction force in this critical point will be able to clamp all the blocks together as shear wall. Not only carrying the weight of the blocks, the shear force also needs to be able to maintain the support reactions.

The necessary friction force to connect the walls comes A1 :3344122212113 Steel Bracing 68 from reaction friction force to carry all the mass of necessary amount of wall blocks (7). The parametric model gives the result of minimum 25.47 kN of friction force - spread on wall and roof blocks.

To conclude, the connections needs to fulfill 25.5 kN to A2 :4 Butterfly4 1 3442Joint 3142 44 105 assure that all the blocks will be connected together as shear wall.

For calculating the necessary amount of components, this formula will apply : output 344 3344 2442 42 110 Minimum friction force = n(amount) * Shear capacity * A3 : Steel Bolts coefficient of friction

A4 :112 Wood Plate 4131 4114 14 63

number of blocks A5 :441 Wood Dowels 1143 3442 41 99

reaction force : wind force mi- nus all reaction A6 :224 Steel Plates 2121 1234 44 83 forces necessary friction force

A7 :444 Smart Connection 3444 3431 44 115

A8 :224 Steel Rod 3343 4121 22 78

Figure 57 : Grasshopper code for the calculation (own illust.)

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Figure 59 : Steel bracing components(simpson.fr) A few benefits by using steel bracing are quick assembly/ Figure 63: Butterfly joint (source: Google.com) dissassembly, lightweight, and good strength. On the other Butterfly joint, or dovetail key, is a well-known method hand, steel bracing is an one-time solution ing if there is to connect 2 wood plates. The block needs to be rede- an adjustment in design, new steel bracing should be or- signed, basically by adding the “keyhole” in between. dered, tailored to the necessary length. Moreover, if there The benefits of using this method is the ability to create is a scenario where the user needs to change or maintain a a smooth surface. wall block, everything needs to be removed and reinstalled Yet, the assemble/disassemble method requires a lot of again. The other drawback is the force distribution. The force since the dovetail key needs to be hammered into force is concentrated on the corners, resulting in needs of the slot. details that needs big area and depth. CALCULATION CALCULATION

The calculation method for steel bracing does not use fric- Figure 60: Steel bracing (own illust.) The strength of the connection depends on the shear ca- tion force method. It focuses more on the tensile forces pacity of the material and the area of the section. Since caused by wind. the required shear stress to keep all the blocks together is already determined (25.4 kN), one can also determine Figure 64: Butterfly joint (own illust.) Total wind force in horizontal axis : 31.65 kN the amount of necessary connections .Wood to wood Total wind force in vertical axis : 31.65 x 3/3.6 m = 26.4 KN friction coefficient also need to be considered.

2 2 Diagonal force : √(26.4 + 31.65 ) = 41.20 kN Wood type Shear capacity (N/mm2) Key width (mm) Coefficient friction Necessary amount OSB 6.5 100 0.375 6 Based on catalogue from Simpson Strongtie (simpson. OSB 6.5 200 0.375 3 fr), 2 of type FPIx40/2/25 ( with maximum tensile force of OSB 6.5 300 0.375 2 22.69kN) is able transfer the tensile load on the wall. Plywood 9.5 100 0.375 4 Plywood 9.5 200 0.375 2 22.7 * 2 = 45.4 kN > 41.2 kN Plywood 9.5 300 0.375 2

Figure 61: Corner details of steel bracing(Luning BV, 2016)

ASSEMBLY

Assembly is generally quick and easy. The fastening function (5) will assure the wall components to be clamped together.

Figure 62: Assembly method of steel bracing. (simpsons.fr)

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By nailing wood plate on top of all the blocks, it will create a shear wall – traditional method for maintaining lateral force in lightweight wood construction. Yet, this method has many drawbacks : big dimension which makes it hard to carry and install, not allowing any freedom of design, and difficult installation by less than 3 people. Also, freedom of design is hard to achieve since every adjustment need a new plate. On the other hand, the wood plate creates a clean finish.

CALCULATION Wood plate is effective for creating enormous shear force with low thickness. As can be seen in the calculation, only with 12 mm of MDF it can create 307.8 kN of shear force, surpassing the required amount of 25 kN. The following problem will be massive amount of screws to connect the plates on the blocks. Moreover, not only the massive amount, the screws will leave a permanent holes on the finishing.

Figure 67:Wood plate connection(own illust.)

Figure 65: Assembly method of steel bolts(own illust.) Figure 66: Steel bolts connection(own illust.) Material Thickness (mm) Shear capacity (N/mm2) Shear force (kN) MDF 12 9.5 307.8 This method is using market-ready bolts and nuts. As shown in the figure, the assembly and dissassembly method is OSB 18 6.5 315.9 relatively easy and quick. The torque wrench in the end will assure all the blocks clamped together by compression.

The drawback of this method is the notches for the bolt that has to be considered - the blocks need to be redesigned, as the connection will change. The extra space that is created between the notches can be integrated for insulation, services, or also with the facade system.

CALCULATION Friction coefficent : metal to wood The value that is used for calculation is tension instead of shear capacity. Due to the fastening mechanism, the bolt is pretensioned to create friction force on the blocks surface.

Property class Tension capacity Friction Bolt Size Amount (BS EN ISO 3506) (kN) coefficient M10 80 20.9 0.4 4 M12 80 30.3 0.4 3 M16 80 37.8 0.4 2

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One other known method for spreading the tension load is using perforated steel plates with multiple screws on the surface. It has benefit of allowing flexible design and smooth finishing.On the contrary, the drawbacks will be slow assembly and disassembly due to high amount of screws. Re- garding finishing, the thickness of the plate should be milled so in the end smooth finishing can be feasible. However, the screws needs minimum thickness of 30 mm to perform on the determined strength, which is hardly achievable in the existing design of wall blocks.

CALCULATION

Steel plates calculation is based from man-

ual from its manufacturer, Rothoblaas. Figure 70 : Steel plate connection(own illust.) There are 2 calculations that needs to be made : for the steel plate and the screw. PLATE Figure 68 : Wood dowels assembly method(own illust.) Figure 69 : Wood dowels connection(own illust.) Ideally, the perfect condition is : Thickness (mm) Width (mm) Maximum shear capacity (kN) 60 20 Wood dowels connection uses the same principal as butterfly connection, which relies on the shear capacity and the Tensile strength of plate > Friction force 1.5 mm 80 26.7 area of the connection. Yet this type of connection (wedge connection) allows using bigger area of shear components Shear capacity of nails > Tensile strength of 40 17.8 2 mm - there are market ready products of wood tenon ( shown in calculation) made from pinewood, varying from 38 x 88 plate 60 26.7 mm to 100 x 100 mm. Based on the required shear force of 25.6 SCREW The drawbacks are more multiple small pieces and difficulty for dissassemble. The later issue is the same as butterly kN, there are few selections that is suitable. joint, since it needs much force to locked into position by hammeringm it also needs the same force to release it. The For each plate, it will require approximately Diameter (mm) Minimum depth (mm) Maximum shear capacity (kN) other drawback will be unsmooth surface caused by the notches. 15 screw each to assure the connection of 4 30 2.02 the plates CALCULATION

The calculations are made using ready-market products and 2 materials that are used for butterfly joint (OSB & Ply- wood) for comparison. It is also important to pay attention to the thickness of the wedges. The thinner it is, the harder it is to be hammered into position. OPTION A7 : Smart Connection

Shear capacity Key width Thickness Wood type Friction coefficient Amount (N/mm2) (mm) (mm) This method uses ready-market cam lock and nuts for furni- Fernwood 6.5 38 89 0.375 4 ture and it allows connections with clean finishing and best Fernwood 6.5 38 140 0.375 2 ergonomics for assembly/disassembly. Yet this method re- Fernwood 6.5 50 50 0.375 5 quires more thickness so it can get embedded inside the Fernwood 9.5 50 75 0.375 2 blocks. Therefore, some redesigning is necessary. Fernwood 9.5 75 125 0.375 1 Fernwood 9.5 100 100 0.375 1 In this case, AVB 4 Slim needs at least 12.5 mm thickness OSB 6.5 200 18 0.375 3 of surface, so the original OSB thickness of 18mm is viable. Plywood 9.5 200 18 0.375 2

Figure 71 :Hafele AVB4 Slim(Hafele.com)

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For the shear force, the same calculation for bolt applies. Yet for the desired lateral force bearing behavior as truss structure tension will create the need of extra detail on the corner parts. Figure 72 :Hafele AVB4 Slim assembly method(Hafele.com) The figure depicts the difference between bolt system and steel rod system. In steel rod system, the CALCULATION force is concentrated in the edge, with limit of compression force of 11 kN. On the other hand, bolt sys- Due to inavailability of technical information, the shear tem has better force distribution. strength will be calculated from the steel pipe with 7mm diameter (can be seen in the scheme above). Figure 76 : Forces in steel rod connection(own illust.)

UTS (Ultimate Tensile Strength) of stainless : 0.52 kN/mm2 Area of connection : 38.48 mm2 Therefore, shear capacity is 0.52 * 38.48 = 20 kN 20 kN * 0.4 (wood to steel factor) = 8 kN

To fulfill the necessary friction force, there needs to be 4 connections.

Yet, since this component is developed for furniture, it is still uncertain whether it will function in building scale, therefore the strength is considered unknown. Figure 73 : Smart connection(own illust.)

OPTION A8 : Steel Rod

Figure 74 : Steel rod(source : google.com)

This method uses the same detail as steel bolts yet instead of bolts it uses steel rods, which allows continuous support throughout the walls. The aim is to combine the mechanism of bracing (option A1) and bolt (option A3). Each rod, with length of 600 mm, is connected to each other using bolt connector.

This method has good strength, quick assembly-disassembly, and freedom of design. Figure 75 : Steel rod connection(own illust.)

CALCULATION

For the shear force, the same calculation for bolt applies. Yet the consequence of using the rod as singular tensile member will create a concentrated stress on the end parts - which possibly require different and more complex details than the rest.

/// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 60 //////////// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 61 ///////// Wall to Wall Connection

As can be seen in the graph, for wall to wall connection, the most valuable criterias are : weight & dimension (related to the possibility that it can be installed with 2 people, which is one of characteristic of FabField), stress distribution (concentrated in few points or spread in balance), and freedom of design (possibility of design alteration). The secondary criteria is the amount of component, which is heavily related with the connections strength and building speed.

These are the three best alternatives of wall to wall connection, based on aforementioned criterias and structural calculation.

3344122212113 68

STEEL BOLT CONNECTION 110 2 x M10 bolts for wall to wall 2 x M10 bolts for roof to roof 4 4 1 3442 3142 44 105

344 3344 2442 42 110 BUTTERFLY JOINT 105 2 x 200 mm width key for wall to wall 2 x 200 mm width key for roof to roof

112 4131 4114 14 63

WOOD WEDGE 441 1143 3442 41 99 99 2 X 38 X 89 mm wedge for wall to wall 2 x 38 x 89 mm wedge for floor to floor

224 2121 1234 44 83

444 3444 3431 44 115

224 3343 4121 22 78

Figure 77 : Score for wall to wall connection(own illust.)

/// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 62 //////////// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 63 ///////// Floor to Floor Connection Design Alternatives Floor-to-Floor Connection STRENGTH WEIGHT DIMENSION TIME PROCESS MILLING TIME AMOUNT OF COMPONENTS FOOLPROOF ERGONOMICS INSTALLATION BUILDING SPEED MAINTENANCE ADAPTABILITY DISTRIBUTION STRESS FREEDOM OF DESIGN AESTHETICS

B1 : 4Butterfly4 1 3Joint4 4 2 3 1 4 2 4 4 104

Figure 78 : Floor blocks deflection(own illust.) Figure 81 : Floor blocks forces after the connections(own illust.) To ensure the stability system of the construction, the The calculation setup will be based also in finding neces- floor also needs to act as shear floor or diaphragm floor. sary shear force to keep the blocks connected. 3 4 4 3 3 4 4 1 4 4 2 4 1 96 The image above depicts the hypothesis of occuring de- B2 : Steel Bolts flection due to no connection between the floor blocks. Wind force : 0.65 kN/m2 The lateral loads - the wind force that exposed to roof 0.65*(3.4 (roof height) + 1.45 (half of the wall)) = 3.125 kN/m 1 1 2 4 1 3 1 4 1 1 4 1 4 61 Width of 1 floor block : 0.3 m B3 : Wood Plate

V1 : 1 * 3.125 * 0.3 = 0.93 kN V2 : 2 * 3.125 * 0.3 = 1.88 kN V3 : 3 * 3.125 * 0.3 = 2.79 kN V4 : 4 * 3.125 * 0.3 = 3.75 kN B4 : 2Steel2 Plate4 2 1 4 1 1 2 3 4 4 4 86 This example shows a calculation for row of 5 floor blocks. The closer it is to the shear wall, the bigger shear force that is needed to hold the wall together. In principal, block number 4 has to carry all the load from block 1,2, and 3. B5 : 4Smart4 4 Connections3 4 4 4 3 4 3 1 4 4 108 Figure 79 : Lateral load area(own illust.) Furthermore, the calculation is parametrized in Grass- hopper, linked with wall calculation. User can change the and half of the wall height - are predicted to dislocate amount of floor blocks, and the output will be the value the floor from each other, especially in the irregular plan of necessary shear force that will conclude in number of such as in PO-Lab. structural components to connect the floor elements. B6 : 2Steel2 Rod4 3 3 4 3 1 1 2 1 2 1 67 As already been explained in the previous chapter, the Floor to floor connections will apply the same choices configuration of the floor is and criterias as wall to wall connection. However, 2 as- not ideal as a shear compo- pects will be more emphasized : nent. Instead of covering the • Foolproof : related to the installation ergonomics perimeter from 1 shear wall from the bottom to other shear wall (in this part. Gravity adds case the glass wall), it stops extra difficulty for in the middle of the plan, heavy components. creating a cantilever-like • Aesthetics : Differ- behavior. ent with walls, floor

Figure 80 : Ideal shear wall and diaphragm floor(own illust.) inquires smooth surface, especially on the top part.

Figure 82 : Floor connection assembly(own illust.)

/// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 64 //////////// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 65 ///////// OPTION B1 : Butterfly Joint OPTION B3 : Wood Plate

Main benefit of using this method is creating smooth surface. which fits the requirement for the floor and Wood plate will create smooth surface yet it requires a lot quick assembly. of time to assemble / disassemble and reduces freedom of desig n aspect. Different design will require different -di CALCULATION mension of plate. Moreover, the drawback of dimension and weight will also reduce the installation ergonomic. The calculation is executed for PO-Lab plan - 7 floor blocks connected to only 1 shear wall. CALCULATION The calculation from wall to wall connection is still valid for this connection.

Figure 83 : Butterfly joint floor connection(own illust.) Material Thickness (mm) Shear capacity (N/mm2) Shear force (kN) Figure 85 : Wood plate floor connection(own Wood type Shear capacity (N/mm2) Key width (mm) Coefficient friction Necessary amount MDF 12 9.5 307.8 illust.) OSB 6.5 100 0.375 3 OSB 18 6.5 315.9 OSB 6.5 200 0.375 2 OSB 6.5 300 0.375 1 Plywood 9.5 100 0.375 2 Plywood 9.5 200 0.375 1 Plywood 9.5 300 0.375 1

OPTION B2 : Steel Bolt OPTION B4 : Steel Plate

To create a smooth surface on top, the side of the blocks Steel plate also has the benefit of smooth surface (required with notches should be facing down - and integrated thickness need to be milled in the wood). On the other with mechanical parts and ceiling. Installation ergo- hand, a lot of fastener components are necessary. nomics from the bottom is still possible since torque wrench does not need enormous movement and energy, compared to hammering the wood wedges, for instance.

CALCULATION CALCULATION The calculation is executed for PO-Lab plan - 7 floor Different type is used for floor due to smaller force. blocks connected to only 1 shear wall.

Figure 86 : Steel plate floor connection(own illust.) Figure 84 : Steel bolts floor connection(own illust.)

Property class Tension capacity Friction Plate size Tensile strength Fasteners Friction coefficient Amount of Amount of Bolt Size Amount (BS EN ISO 3506) (kN) coefficient (mm) (kN) shear strength (kN) fasteners plate M10 80 20.9 0.4 2 60x1000 16 2.96 kN 0.4 8 1 M12 80 30.3 0.4 1 M16 80 37.8 0.4 1

/// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 66 //////////// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 67 ///////// OPTION B5 : Smart Connection STRENGTH WEIGHT DIMENSION TIME PROCESS MILLING TIME AMOUNT OF COMPONENTS FOOLPROOF ERGONOMICS INSTALLATION BUILDING SPEED MAINTENANCE ADAPTABILITY DISTRIBUTION STRESS FREEDOM OF DESIGN AESTHETICS

4 4 1 3 4 4 2 3 1 4 2 4 4 104

Figure 87 :Smart floor to floor connection(own illust.)

Smart connection allows smooth surface and easy assembly / disassembly.

CALCULATION 3 4 4 3 3 4 4 1 4 4 2 4 1 96

Based on the wall calculation, each connection has 8 kN of shear capacity. To counter the occuring shear force in the floor (10 kN), 2 connections are needed.

1 1 2 4 1 3 1 4 1 1 4 1 4 61

OPTION B6 : Steel Rods

2 2 4 2 1 4 1 1 2 3 4 4 4 86

Steel rod system will create uneven surface caused by the notches. The installation of the steel rods requires the notches to be in the upper part. After all the steel rods are installed , the notches can be covered by wooden plate, to 4 4 4 3 4 4 4 3 4 3 1 4 4 108 create smooth finishing. Thus, it will extend the installation time.

CALCULATION 2 2 4 3 3 4 3 1 1 2 1 2 1 67 The same calculation from bolt is valid to be applied in this component. Figure 88 :Steel rod floor connections(own illust.)

Property class Tension capacity Friction Bolt Size Amount (BS EN ISO 3506) (kN) coefficient M10 80 20.9 0.4 2 M12 80 30.3 0.4 1 M16 80 37.8 0.4 1

/// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 68 //////////// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 69 ///////// Floor to Floor Connection

The same criteria from wall to wall connection is applied to floor to floor connection, yet there is a slight difference in the weight. The aesthetics, or finishing quality is valued higher in floor to floor connection since floor requires smooth surface.

In conclusion, these are three best alternatives for connecting the floors :

Butterfly Joint 104 2 x 200 mm width OSB key

Steel Bolt Connection 96 2 x M10 bolt (possible on the bottom surface)

Steel Rod 67 2 x 10 mm steel rod (on the top surface) Wooden plates for cover

/// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 70 //////////// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 71 ///////// A. Wall to wall A1 A2 A3 A4 A5 A6 A7 A8

B. Floor to floor B1 B2 B3 B4 B5 B6

Figure 89 :Design concept(own illust.)

/// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 72 //////////// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 73 ///////// Design Proposal

Using the conclusion from the previous chapter, more in-depth detail design is executed for the alternatives which generated best score - bolts for wall to wall connection and butterfly joint for floor to floor connection.

The detail is integrated in existing connections that are made by Nick van der Knaap (2016) for PO-Lab project.

06design

Figure 90 :Design concept visualization(own illust.)

/// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 74 //////////// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 75 ///////// Exploded Axonometry

Bolt 120 mm Based on AISC (American Institute of 60 mm M10 bolt and nuts Steel Construction) ANSI 360 table, the minimum distance of steel bolt to the edge is 1.5 x diameter of the hole. Yet, since the requirement is aimed for steel construction, safety factor is applied. De- rived from the table, the minimum distance is 15 mm, yet safety factor of 4 is applied in the design. In conclusion, the distance from the hole is 60 mm.

The type of bolt that is used is M10 bolt with length of 50 mm.

100 x 200 mm butterfly joint

200 mm 300 mm 600 mm

Butterfly Joint

Based on calculation from previous chapter, the butterfly joint is 200 mm in the direction that is prone to shear stress and 100 mm in the other direction.

Figure 92 :Plan and section(own illust.) Figure 91 :Exploded axonometry of the concept(own illust.)

/// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 76 //////////// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 77 ///////// 07prototype The process of transferring the drawing to the CNC machine is started by drawing the 2D curves using Rhinoceros. Different layers will be used to separate different functions, such as pocket and contour. Moreover, the drawings will be imported into CamLab program where one should assign each functions to different layers. The program will automatically generate a G-code, a language for CNC-milling machine.

The preparation does not only happen in computer, one should also put the drill bits in place. and set it into the right height.

Floor Blocks

Since the focus of the prototype is in the detailing of the connection, the floor blocks is cut to 600 mm in length. The pieces is derived from the 3D model shown in previous chapter. As shown in figure 93, all the pieces should be fit in 1250 x 5000 mm.

The butterfly joint has to have tolerance of 0,2 mm to fit easily in the slot.

Milling time : 50 mins

Figure 93 : Floor blocks CNC drawing(own illust.)

Wall Blocks and Beam

The wall height is also reduced to 600 mm.

Milling time : 40 mins

Figure 94 : Wall blocks and beam CNC drawing(own illust.)

Figure 95 : Prototype of floor and wall blocks(own illust.)

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Figure 97 : Defects in the production(own illust.)

Another remarks regarding the prototyping session : • The important remark regarding setting the tool’s height before the production. Figure 97 shows the effect of drill that did not start in the right height - in this case, too close to the surface. Since the drill does not reach the Figure 96 : Connections in the prototype(own illust.) necessary speed to go through the material, it creates fire from friction. • In CNC-milling based product, one should pay attention to the location of holding parts. Holding parts are auto- The assembly of the pieces are easily executed. The only matically generated by the program so the finished pieces would not go off the CNC table due to the torque force occuring problem is that the deviation of the thickness of of the drill. The most right picture clearly shows the effect of wrongly placed holding parts. The piece moved OSB which varies from 17.5 mm to 18.3 mm. It affected the around due to the drill force and ended up having a huge defect. parts which are made from several layer of OSB - such as bottom part of wall blocks.

Eventually, some treatment such as sanding is still necessary to adjust the different thickness of the -compo nents. This took more time compared to the assembly itself.

Another occuring problem is that the existing connection of the plates has not enough friction area to clamp everything together (especially bottom part of floor blocks). Some parts still need to be screwed to each other.

Other than aforementioned minor defect, both connections works perfectly.

/// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 82 //////////// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 83 ///////// Conclusion

Methodology is beneficial to have multiple parties in order to make considerable decisions. In this research, the method- The PO-Lab design methodology from Nick van der Knaap ology successfully providing designers a framework for and Jeroen van Veen (2016) has proven itself in this re- developing their products while integrating multiple search, not only as methodological approach - but also point of views. It divides specific design task into small- as open system that can be integrated with different vari- er aspects that are easier and faster to evaluate. ables, in this case : structural behavior. The criterias and weight are open to adjustment relative to the project goals which explains why strength and stress distribution are on Structural Components the top of the criteria. The whole methodology process managed to generate As the top priority of the selection, strength variable is also open-end solutions to solve the structural problem. complex to derive. First task is to find comparable value - There are multiple solutions solving same problem, in form of critical stress, moment, or force value that can which has their own benefit and drawbacks. Designer be acknowledged as a basis value that is comparable and can choose which solution fits different design, by their relevant to the design solution which allows the designer own circumstances. to decide whether the structural component works or not. To start, one should analyze the system extensively to ad- In all likehood, the determining criteria for the designer dress the structural problem, or one force type which the will be cost - which is still neglected in this research, system is prone to. due to its complexity. Costs are intermingling in differ- conclusion & future ent aspects. One can have an expensive ready market In the scope of this project, the value is derived using 1 spe- solution, but the solution can also cut the costs of as- cific case : PO-Lab, which shape is very straightforward. sembly time and production time (labour worker cost). The extensive challenge is only caused by the opening on recommendation the ceiling that triggers the irregularity of force flow. Af- In conclusion, the methodology succeeded in generat- 08 ter in-depth analysis of the existing system, the problem ing structural solution for this particular system - that was found. The system is prone to lateral load and causing can be used as a basis for further development using domino-like deflections, which is exacerbated by the fail- different system and configuration. ure of the joints to act as fixed joints.

By addressing the problem, one can find the comparable value. Different calculations and assumptions were made Prototype in the beginning, yet it all revolves around the same hypothesis : the friction force between the blocks. The con- The rapid prototyping method is also proved beneficial clusion is - if the lateral force is bigger than the friction to develop a design. Due to the shortage of time, it is force, the deflection will happen. This argument was the only possible to prototype 2 solutions. The amount of whole basis of the calculations and design development. time to create the prototype is relatively short, around 1,5 hours of milling time. This is really beneficial to dis- In this point, the design methodology was started simulta- cover the problems in real scale, quickly. nously. Multiple solution was generated, using the research of common CNC-based joints, market-ready products, The deviation of material thicknesses and tolerance are and traditional lateral load bearing structure. The chal- mainly the problem which occured in the prototyping lenge is translating the behavior of each alternative into session. Yet, the speed of CNC-milling will allow the aforementioned friction force. For instance, bolts-based designer to find and fix the problem quickly to create alternative and screw-based alternative creates friction a fully working prototype that perfectly resembles the force betwen the blocks in totally different way. Bolts cre- real product. ate the friction force from the compressive strength that keeps the blocks together. On the other hand, screws create the force by the shaer capacity of the element. There- FabField fore, each solution needs to be analyzed in-depth, that will relate to the strength criteria of the design development. PO-Lab is starting point of FabField. It clearly rep- After deriving friction force from each analysis and com- resents the intentions which is trying to solve the rele- paring it with the minimum comparable value, one can vant problem of the construction industry. derive the necessary amount of each component - that will become another important input for assembly and pro- • Sustainable material production and digital data duction aspect in the design methodology. The more com- transport which reduces the carbon energy for ponent is needed, the more time is needed for production transports. and assembly. • Resource efficient production using CNC-milling. By pre-assembling elements into components in These aspects - production, assembly, etc. - are integrat- controlled area, the process will reduce the waste ed in the design methodology. Yet, one has the freedom to production. subjectively set the weight for those aspects. Therefore, it • Fast and easy construction due to standardized and

/// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 84 //////////// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 85 ///////// prefabricated components. This will reduce the amount Future Recommendation of time for constructing and builder cost. • Demountable and recyclable components allows the maintenance to be done easily. Not only maintenance, Structural Test components can be fully recycled when the building is not functional anymore. To fully validate the argument of this thesis, a further It is interesting to see if there is a possibility to design physical test should be executed. The test can be applied floor blocks that can be connected to create bigger These aspects promises design freedom. And FabField is aim- for the existing condition and the improved condition to span, that also expand the possibilities of the function ing for that. Once it become commercial, people could create really conclude that the proposed design is solving the ex- of the system. their own design using these standardized components. Yet, isting problem. these create uncertainities. The developed structural component is relevant for PO-Lab configuration, yet there still are extensive possibilities for different configurations with - dif Parametric Model ferent structural problems.

Therefore, this research is aimed to be the baby step, as first solutions to one problem - which methodology can be applied for different cases in FabField.

The findings from the previous researches can be used Fixed Joint as an input for a parametric model, where the model can simultaneously suggest structural components The existing detail is still regarded as spring connection while the user create their own design. Therefore, study (between fixed and hinged connection). The problem with about limitations of the configurations and the struc- spring connection is stability if its own plane. This kind of tural components need to be done in the first place. connections always needs extra structural measure, such as shear wall or bracings. Not only stopping there, the model also can contain geometrical information of the blocks and structur- This condition also reduces the freedom of design due to al components, that automatically generate the CNC inability to create open facades and large opening in the drawing. Furthermore, the model also can contain the floor. Therefore, a research to create fixed joint for Fab- nesting code, which already exists in the industry, that Field, followed by a structural test, will be huge leap in the automatically set the most efficient nesting configura- level of freedom of design. tion in certain area. The parametric model should be embedded to the web- site (fabfield.com) to become more UI-friendly. Different Configurations

The nature of FabField is allowing the user to create their own design. Therefore, different cases can be explored to accomodate the structural stability of those different forms - such as 2 levels or widespan structures. Now, the maximum span of a floor blocks is 4800 mm (due to the maximum milling area of the machine ), which also limit the maximum width of the construction.

/// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 86 //////////// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 87 ///////// Melgar, E. R. (2011). Integrating Physics into the Design Pro- Flexibility and Buildability to Facilitate Evolution, cess, (September), 1–46. (January 2010).

Jones, G. P., Connor, J. J., Supervisor, T., Clune, R., Reader, Stoutjesdijk, P. (2013). Digital Design & Fabrication for T., & Nepf, H. (2013). Interoperable Software for Parametric Ultimate Challenges. Structural Analysis and Optimization by.

Van der Knaap, N. (2016). PO-LAB : In Detail. Vischer, L. (2015). Shaping CNC-Cut Plywood Struc- tures. Van Veen, J. (2016). PD _ LAB. Vogler, A. (2015). The House as a System. IOS Press BV. DURMISEVIC, E. (2006). Transformable Building Struc- tures.

Geraedts, R. P., Cuperus, Y., & Shing, K. (2011). Timeless Flexible Building: Matching demand and supply in flexible housing. International A4D Conference, (November).

Carbon, R., & Naab, M. (2016). Architectural Design for Flexibility and Buildability to Facilitate Evolution, (January 2010).

Brad, G., & Ciarimboli, N. (2005). Design for Disassemblyin bibliography the built environment: a guide to closed-loop design and building. 09 Timberlake, J. (n.d.). Quality Assurance, Quality Control. Gijsbers, R., Lichtenberg, J., & Erkelens, P. (2009). A new approach to flexibility-in-use: adaptability of structural elements. SASBE 09, 3rd CIB International Conference on Smart and Sustainable Built Environments, 1–8. Retrieved from http://alexandria.tue.nl/campusonly/Metis231178.pdf

Menges, A., Sheil, B. O. B., Glynn, R., & Skavara, M. (n.d.). FABRICATE 2017.

European Union. (2011). Eurocode EN-1990 (Basis of structural design), 1(2004).

McKenzie, W. M. C. (2013). Examples in Structural Analysis, Second Edition. Retrieved from https://books.google.com/ books?id=K6CNAgAAQBAJ&pgis=1

Robeller, C. (2014). Snap-fit Joints : CNC fabricated , integrated mechanical attachment for structural wood panels. Acadia, 189–198.

Sebera, V., & Šimek, M. (2010). Finite elementanalysis of dovetail joint made with the use of CNC technology. Acta Universitatis Agriculturae et Silviculturae Mende- lianae Brunensis, 58(5), 321–328. https://doi.org/10.11118/ actaun201058050321

Smith, R. E. (2011). Prefab Architecture: A Guide to Modular Design and Construction. John Wiley & Sons, Inc. https:// doi.org/10.1017/CBO9781107415324.004

Hvam, L., Mortensen, N. H., Thuesen, C., & Haug, A. (2013). Mass Customisation and Personalisation in Architecture and Construction. Mass Customisation and Personalisa- tion in Architecture and Construction, 67–77. https://doi. org/10.4324/9780203437735

Carbon, R., & Naab, M. (2016). Architectural Design for

/// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 88 //////////// FabField-structural design and development for CNC-milled based wood construction ///////////////////////////////////////////////////// 89 ///////// Appendix A : Structural Calculation from Luning BV

10appendices

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