Exhaustive Exploration of Modular Options to Inform Decision Making

Mohammed Mekawy1, Frank Petzold2 1,2Technical University of Munich [email protected] [email protected]

Europe is facing an increasing demand for new construction, which is pushing the industry away from traditional construction technology towards prefabrication and Mass-Customization. However, prefabrication-based construction requires a more efficient, better informed decision making process due to the increased difficulty of on-site variations. Furthermore, the lack of means to navigate the whole spectrum of solutions for a given design problem using traditional tools, and the absence of the manufacturer's input in the early phases of the project can present significant challenges for the efficiency of the design and construction process. As a way to face these challenges, this paper presents an approach, realized as an Autodesk Dynamo-for-Revit package called Box Module Generator (BMG), which enables the exhaustive generation of configurations for a given building based on a construction scheme that utilizes Box Prefabricates. The output can be sorted, dissected and explored by users in various ways and the building geometry can be generated automatically in a Building Information Modeling environment. This makes it possible for the projects' stakeholders to browse thousands of potential design alternatives, which would otherwise be very hard to explore manually, or using traditional parametric modelers.

Keywords: Prefabrication, Box Prefabricates, Design Tools, Design Automation, Building Information Modeling, Dynamo

INTRODUCTION turies, especially after World War II, to cover the post- Attempts at prefabricating building modules to pro- war housing needs in Europe (Huang et al., 2006). vide large amounts of well-constructed spaces date The need for high quality, speedy construction is still back at least to the Crimean war in 1854, when Isam- ubiquitous. Europe in general, and Germany with its bard Kingdom Brunel designed and built a 1,000 very buoyant labor market in particular, are facing a patient hospital in Renkioi using prefabricated tim- fast growing need for new construction. For exam- ber units that were shipped to be assembled on-site ple, to accommodate the increase in inhabitants in (Gibb, 1999). The trend of using prefabrication in Munich between 2011 and 2016 alone, 55,000 homes construction to minimize time and waste continued are needed simply to cover the gap in the supply of to rise during the eighteenth and nineteenth cen- housing units (Möbert, 2017). This highly challeng-

FABRICATION - MANUFACTURING - Volume 2 - eCAADe 35 | 107 ing environment demands more efficiency in design rooms or a group of rooms (Lewicki, 1966). These and construction, giving rise to the idea of Mass Cus- box modules are suitable for a lot of building types, tomization. can be repeated by stacking, and can be 95% deco- rated and fitted with the necessary equipment in fac- tory, reducing the work on-site to the assembly of the units and connecting them to services (Knaack, Figure 1 2012). This approach comes with a multitude of ben- Box modules in the efits: consistent quality because units are manufac- Pillerseetal social tured under factory conditions, Just-in-Time deliv- center in ery to construction site to decrease waste and pre- Fieberbrunn, vent material theft on-site, and time savings up to Austria assembled 50% in projects’ schedules (Gibb, 1999). An exam- on-site after being ple of such an approach is shown in Figure 1, where manufactured in 78 box modules acting as rooms for senior citizens factory (Kaufmann were installed in a social center in Fieberbrunn, Aus- Bausysteme, 2016). tria, complete with flooring, windows, doors, bath equipment and furnishings. Box Prefabricates can be constructed from steel, wood, or concrete; they can also be self-supported or installed on a supporting Mass Customization corresponds to technologies structure (Staib et al., 2008). They can thus be mass- and systems that are used to deliver goods and ser- customized to meet the individual needs of each vices in order to meet individual needs with enough project with different sizes, finishes, fittings, and with variety and customization and with mass production closed or open sides to fit both open plan and closed efficiency (Piroozfar and Piller, 2013). One of the rooms schemes (See Figure 2). key strategies for Mass Customization is modulariza- tion, whereby building are based on mod- ular components and subsystems that are prefabri- Figure 2 cated in parallel in a factory and afterwards assem- Different bled on the construction site to satisfy the individ- configurations from ual requirements for each (Huang et the box modules: a) al., 2006). Mass-Customization and prefabrication of- Closed from all fer significant advantages to the construction indus- sides b) Open from try including time saving in construction schedules, But the nature of design for prefabrication-based the long sides c) lower construction cost, tighter quality control, less construction differs from that of the traditional con- Open from the material waste, better sustainability, enhanced occu- struction because of the increased difficulty of on- narrow sides pational health and safety, lower manpower require- site variations to the design when using prefabri- ments, and a safer working environment (Tam et al., cated components (Maxwell, 2015). That means that 2007) (Rathnapala, 2009) (McGraw Hill Contruction, programming and design phases have to be more 2011). robust and better informed than in traditional con- One of the approaches to Mass Customization struction to minimize the possibility of last-minute and prefabrication is ”Box Prefabricates”. Building design changes. Furthermore, do not think designs that can afford a high of modulariza- about spaces or modules only in a three-dimensional tion are standardized into a group of box modules, paradigm. In addition to the length, width, and which are large prefabricates enclosing whole height of a space or a module, designers may also

108 | eCAADe 35 - FABRICATION - MANUFACTURING - Volume 2 Figure 3 consider orientation, cost, number of floors, and nat- The general ural lighting, among a group of parameters (n). De- framework of the signers have to navigate the full extent of varieties proposed tool of these n-dimensional spaces in order to make well- informed design decisions, a process that could be very daunting and labor intensive. Even in ordinary design problems, the architect may contemplate very few solutions like few needles in the haystack of all the configurations satisfying the boundary condi- tions of the design problem (Galle, 1981). While us- ing geometric parametric modelers can help design- ers, explore multiple design parameters more quickly and efficiently, they do not possess the ability to ex- plore the entire set of possible solutions, nor do they offer the rich data environment enabled by Building Information Modeling (BIM) platforms. The problem BACKGROUND can be further complicated by the lack of interac- Related work tion with prefabrication experts early on the design Retik and Warszawski (1994) presented a knowledge- project, leading to significant flows in project plan- based system that encapsulates prefabrication ex- ning, misinformed design decisions and unnecessary pertise for the automated detailed design of prefabri- rework. cated buildings. This system receives the preliminary By providing a platform that can generate an architectural design and then produces solutions for exhaustive list of all possible design configurations partitioning the building into modular components. and the outcomes of these configurations in a Huang and Krawczyk (2007) proposed a web-based rich BIM environment, stakeholders can make more design system that can generate design options for informed decisions with regard to prefabrication- modular houses based on the client’s needs, cap- based projects, and easily utilize the BIM models to tured via an online questionnaire. Diez et al. (2007) any (n) number of analyses necessary for a given presented an automatic modular construction soft- project. The intent of the research summarized here ware environment ”AUTMOD3” that offers two meth- is to provide a platform that enables the production ods of modular design; the architects can input ar- of this exhaustive list for a given project in a modular chitectural plans that can be processed to obtain construction scheme, with the scope being limited to the modules needed for a house design, or they can Box Prefabricates. The range of input parameters in- make the design from scratch using a catalogue of 3D tegrates the input from prefabricators, owners, and parametric modules. El-Zanfaly (2009) built a user in- the architects. The visual and numerical output can terface to produce alternatives for modular housing be sorted, filtered, and viewed in different ways that arrangements. Through the interface, the user can serve as a basis for the decision making process in the vary the design parameters and specify a number of early design stages and design brief. The aim of this alternatives. The system will then produce 3D alter- process is not to automate the design of the entire natives based on stochastic search. Kwiecinski et al. building with all details. Instead it serves as a way for (2016) proposed a design method based on shape stakeholders to rapidly assess hundreds or thousands grammars, focusing on light wood frame construc- of alternatives and extend the generated BIM models tion for the automatic generation of housing layouts to any analysis environment needed. according to the users’ requirements.

FABRICATION - MANUFACTURING - Volume 2 - eCAADe 35 | 109 Figure 4 The relationship between the processes run by BMG and the corresponding nodes

narios in earlier stages. While online services such as Figure 5 Autodesk Project Fractal (Autodesk, 2017) can fulfill The custom nodes this role partially, it operates on three-dimensional comprising the geometry only and cannot handle BIM models (at the BMG package date of writing).

Problem statement and objective The traditional manual approach or even geomet- ric parametric modelers may not present the whole spectrum of solutions for a given design problem. A building is not only judged by its appearance or architectural style; designing a building needs care- ful consideration to a number of parameters. The problem can be further complicated by the lack of proper communication between owners, archi- tects and construction experts from the early design stages. This becomes of special importance in projects based While these research efforts tried to tackle the exist- on Mass Customization and prefabrication because ing need for an automated design and communica- of the increased difficulty of on-site variations.This tion tool for prefabrication in design and construc- paper presents a tool that generates all the possible tion, none of them approached the field of Box pre- configurations of a building’s design that is based on fabricates. Additionally, most of the research focused Box Prefabricates, given input from the user regard- on a stage of the design process where the decision ing the maximum and minimum bounds of a set of for a prefabricated building has already been taken parameters and the number of variations allowed for with a very specific design outcome in mind. What is each parameter. The outcome can be sorted and dis- lacking is a platform that provides a comprehensive sected in a multitude of ways to enable the user to look on all the possible design scenarios, allowing the navigate the solution set and generate preliminary users to get feedback for the feasibility of these sce- BIM models (See Figure 3). The tool fulfils a necessary

110 | eCAADe 35 - FABRICATION - MANUFACTURING - Volume 2 communicative role in conveying the manufacturer’s “Custom Nodes”, which are tailored to help the de- requirements to the architect, who in turn can eas- signer generate, filter, sort, and visualize an exhaus- ily communicate the full spectrum of design possibil- tive set of solutions for projects based on Box Pre- ities to the owner during the programming and the fabricates. “Custom nodes” refer to reusable blocks early design phases in a rich BIM environment that of code, which can be utilized repeatedly by users can be extended to further types of analyses when across multiple projects for various project scenarios needed. (Das et al., 2016). Custom nodes can contain blocks of visual code as well as written IronpPython code, Figure 6 which is an implementation of the Python program- The input form of ming language that is tightly integrated with Mi- BMG crosoft’s .NET Framework. This enabled the authors to use Windows Forms, a graphical class library that is a part of the .Net Framework, to design a Graphical user interface (GUI) for BMG. The authors also used a custom Dynamo package called “Mandrill” by Konrad K. Sobon (Sobon, 2016) for parts of the GUI. The fol- lowing subsections explain the general workflow, the structure of the Dynamo library, user inputs, outputs, and the GUI of the tool.

General workflow and user inputs The general process starts with the input from ar- chitects, owners and manufacturers with regard to project requirements, local building regulations and construction limitations. For example the architect may acknowledge that the distance from the furthest point in any room and the stair should not be more than 35 m, which could decrease to 25m in high-rises (according to the building regulations in Germany: Musterbauordnung) (Stiftung et al., 2010). The man- ufacturer could determine that the maximum num- ber of floors is six, and the dimensions of the units could range from 3*5 to 6*20 m with heights rang- ing from 3.2 to 3.6 m (Staib et al., 2008), all depend- ing on the material used and transportation and lift- ing limitations. The owner may also have specific re- quirements for natural lighting, total guest capacity or other considerations. METHODOLOGY, AND WORK- The input parameters are then passed to the ex- FLOW haustive generator, which generates all the possible A prototype of the proposed tool was developed as combinations of the input parameters, calculates the an Autodesk Dynamo-for-Revit package called Box outputs, and presents them to the user where he Module Generator (BMG) consisting of a collection of would be able to slice or sort them and finally gen-

FABRICATION - MANUFACTURING - Volume 2 - eCAADe 35 | 111 Figure 7 The sorting and slicing view of BMG

erate the solutions he chooses as BIM models inside sified into GUI nodes, which aid the user in giving in- Revit. Figure 4 outlines the operations inside BMG puts and displaying/sorting outputs, and core nodes, and the corresponding Dynamo nodes. The input pa- which generate the solutions and the Revit geome- rameters include variable parameters (where a range try. The user can either use both sets of nodes to- of values is considered), which are the dimensions of gether or the core nodes separately just for generat- the box unit, number of floors, floor height, fenes- ing different configurations directly in Revit. tration dimensions, and outer building dimensions. The input also includes fixed parameters, which are Figure 8 corridor’s width, maximum distance between cores, The sorted results ground floor height, the ratio of the ground floor size view of BMG to the typical floor area, and the cost per square me- ter. The result provides information about the areas (individual unit, circulation, footprint, and built-up area), total building capacity, cost, window to wall ra- tio and total number of individual box units.

System components BMG is composed of a group of custom nodes com- prising a package inside Dynamo. An overview of BMG GUI Nodes. The first GUI node is the “Input pa- these nodes is shown in Figure 5. The nodes are clas- rameters” node, which initiates an input form asking

112 | eCAADe 35 - FABRICATION - MANUFACTURING - Volume 2 the users for a set of input parameters (See Figure 6). and with the lack of means to integrate the manufac- The input parameters are classified into fixed param- turer’s expertise in the early phases of the project, this eters, which will be constant throughout all the gen- can present significant challenges for the efficiency erated solutions, and variable parameters, where the of the design and decision making process. user has to input maximum and minimum bounds Figure 9 and number of variations for each parameter. Rendered views of Once the input parameters are given, the GUI trans- some of the models fers the user to the sorting and slicing view triggered generated by BMG by the “Sort and Slice” node (See Figure 7). This view in Revit enables the user to slice through the generated re- sults using a parallel coordinates graph and then ei- ther input the final parameters to generate a BIM model directly, or sort the results in an ascending or descending order by any of the input or output pa- rameters. If the user opts for the later, the tool will display the sorted results window (See Figure 8), trig- gered by the “Display Sorted results” node. In this window, the user can select any of the sorted set of parameters and generate the Revit geometry. BMG Core Nodes. The first of the two core nodes is the “Exhaustive Solution Generator” node, which performs a Cartesian product operation on the user inputs, the inputs are then passed to a Dynamo “code The objective of this research is to establish means block” which encapsulates the mathematical formu- to generate an exhaustive list of possible configura- las needed to calculate the outputs. After the user tions for a building design based on a modular con- decides on the parameters, the “Module Geometry in struction scheme in a rich BIM environment. This Revit” triggers Revit to render the desired BIM model. would enable project stakeholders to make more in- Both of the core nodes can be used separately from formed decisions and easily utilize the BIM models the other GUI nodes. Figure 9 shows a group of ren- to perform any further analyses necessary for a given dered views of the Revit models produced by BMG. project. The results of the current research establish a prototype of a decision support tool developed as CONCLUSION an Autodesk Dynamo-for-Revit package called Box The importance of Mass Customization and prefab- Module Generator (BMG). The tool attempts to ex- rication in the construction industry will continue to plore the entire solution space for a project, with grow, making use of the efficiency of factory con- the scope being limited to Box Prefabricates, given ditions to produce building elements in compact a set of simple input parameters that represent re- time schedules, with greater quality control and min- quirements of the local building regulations, stake- imal waste. However, programming and design for holders‘ vision, and the construction system limita- prefabrication-based construction need a better in- tions. Results are then presented to the users with formed decision making process due to the increased the ability to sort and slice the results to reach the difficulty of on-site variations. Combined with the desired solution. The approach is only generative lack of means to navigate the full extent of the solu- and does not attempt to perform optimization op- tion space for a given project using traditional tools, erations on the design. Instead, it offers suitable

FABRICATION - MANUFACTURING - Volume 2 - eCAADe 35 | 113 means to rapidly assess hundreds or even thousands 24(12), pp. 813-825 of possibilities and validate decisions during feasi- Gibb, AG 1999, Off-site fabrication, Whittles Publishing, bility studies, programming and early design stages. Latheronwheel Huang, Ch and Krawczyk, R 2007 ’A Choice Model of Con- Furthermore, Box Prefabricates are arranged in rec- sumer for Modular Houses’, Pre- tilinear stacked configurations to achieve maximum dicting the Future: Proceedings of the 25th eCAADe efficiency, so the research focuses on the possibilities Conference, Frankfurt am Main, Germany, pp. 679- of these rectilinear configurations. This research is 686 part of a wider investigation into the usage of com- Huang, Ch, Krawczyk, R and Schipporeit, G 2006 ’In- puter systems based on BIM to devise a decision sup- tegrating Mass Customization with Prefabricated Housing’, Computing in /Re-Thinking the port system for project stakeholders in early design Discourse: Proceedings of the the 2nd ASCAAD confer- stages to optimize project designs for prefabrication ence, Sharjah, United Arab Emirates requirements and to integrate the expertise of pre- Knaack, U 2012, Prefabricated systems: Principles of con- fabricators. While the scope of the current paper was struction, Birkhauser, Basel, Switzerland limited to Box Prefabricates in particular, the future Kwiecinski, K, Santos, F, de Almeida, A, Taborda, B direction of the research will focus on developing and Eloy, S 2016 ’Wood Mass-Customized Hous- ing - A dual implementation design strat- a BIM-based framework to help the architects opti- egy’, Complexity & Simplicity: Proceedings of the 34th mize building designs in early design stages in other eCAADe Conference, Oulu, Finland, pp. 349-358 fields of prefabrication-based construction. The aim Lewicki, B 1966, Building with large prefabricates, Elsevier, is to reduce misinterpretations and discrepancies be- Amsterdam [u.a.] tween architects’ design intent and requirements for Maxwell, DW 2015 ’Programming for prefab’, Living and prefabrication to reduce rework and ultimately to Learning: Research for a Better Built Environment: Pro- ceedings of the 49th International Conference of the speed up the process to face an ever increasing de- Architectural Science Association, Melbourne, Aus- mand for faster, more informed, and more efficient tralia, pp. 1018-1027 design and construction operations. Möbert, J 2017, Outlook on the German housing market in 2017, Deutsche Bank Research REFERENCES Piroozfar, PAE and Piller, FT (eds) 2013, Mass Customisa- tion and Personalisation in Architecture and Construc- McGraw-Hill Contruction, No initials 2011, Prefabrica- tion, Routledge, London : New York tion and modularization: Increasing productivity in Rathnapala, T 2009, Incorporating Prefabrication Pro- the construction industry, McGraw-Hill Contruction - cesses Into Building Information Modeling, Ph.D. The- SmartMarket Report sis, University of Wolverhampton Das, S, Day, C, Dewberry, M, Toulkeridou, V and Hauck, Retik, A and Warszawski, A 1994, ’Automated design A 2016 ’Automated Service Core Generator in Au- of prefabricated building’, Building and Environment, todesk Dynamo - Embedded Design Intelligence 29(4), pp. 421-436 aiding rapid generation of design options’, Complex- Staib, G, Dörrhöfer, A and Rosenthal, M 2008, Elemente ity & Simplicity: Proceedings of the 34th eCAADe Con- und Systeme: Modulares Bauen – Entwurf, Konstruk- ference, Oulu, Finland, pp. 217-226 tion, neue Technologien, Birkhäuser, Basel Diez, R, Padrón, V, Abderrahim, M and Balaguer, C 2007, Stiftung, W, Jocher, T and Loch, S 2010, Raumpilot Grund- ’AUTMOD3: The integration of design and planning lagen, Krämer, Karl Stgt, Stuttgart tools for automatic modular construction’, Interna- Tam, V, Tam, C, Zeng, S and Ng, W 2007, ’Towards adop- tional Journal of Advanced Robotic Systems, 4(4), pp. tion of prefabrication in construction’, Building and 457-468 Environment, 42(10), pp. 3642-3654 El-Zanfaly, D 2009 ’Design by Algorithms: A Generative [1] http://www.kaufmannbausysteme.at/file/de/modulb Design System for Modular Housing Arrangement’, au-2016.pdf Proceedings of the 13th SIGraDi conference, Brazil [2] http://archi-lab.net/mandrill-a-data-visualizat Galle, P 1981, ’An algorithm for exhaustive generation ion-for-dynamo/ of building floor plans’, Communications of the ACM, [3] https://home.fractal.live

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