Generating customized housing plan layouts in computer environment using tunnel form structures

Flexibility is featured as a key concept of the housing stock in Turkey in order to adapt to the changing needs of households. Flexibility in housing production became an issue in the 20th century due to the specific modalities of production adopted. Flexibility became a difficult problem area because unlike in single houses, the users of these houses are not identified and they are variable, therefore it is unpredictable to foresee the interventions that the houses will undergo in time (İlhan, 2008). Yürekli (1983) discusses the notion of flexibility under two headings; design flexibility, and usage flexibility. In design flexibility, decisions about the planning and space organization (layout) are considered in the design and construction phase (Yürekli, 1983). In addition to Yürekli, Deniz (1999) suggested the notion of production flexibility -within the scope of the design flexibility- as another type of flexibility depending on the particular characteristics of the building and construction system. A design which can have unlimited flexibility for all types of users would increase the initial cost. Therefore if the borders of the flexibility are delineated during the planning and design process, it will reduce the initial investment significantly. Thus, predetermination of flexibility in housing would allow the designer, to foresee the potential of the changes in the future. Unique and individualized design and production before 20th century was replaced by mass production in the areas of housing production and architecture as in many other areas. From this perspective, mass customization is combining positive aspects of mass production with individual design in the best way possible. Mass customization produces alternatives while supporting flexibility. Thus, with pre-defined framework and rules can be applied in various orders and products can be formed. Also with the use of computational design technology, it is possible to calculate and see the alternatives in computer environment and foster economical and feasible production. Thus was born the concept of developing a design strategy and method, instead of individual designs solutions (Akipek and İnceoğlu, 2007). In other words, instead of designing a product, the rule sets and a variety of design input parameters are defined to design product group(s). For this reason, the information required to design the products needs to be defined clearly as well as the rules and rule sets. Furthermore with tests and feedbacks, rules can be changed and design can be developed or altered. In the case of housing, (as opposed to mass housing), a more individualized mass production is needed. Customized mass housing may respond the problems better but even in mass customization, the unpredictability of the future or change of needs must be taken into consideration. In addition, a more flexible methodology can be used in order to be able to respond the unforeseen needs. In the scope of this study an expert system (FPL_Gen – Floor Plan Layout Generator) is developed and designed in order to create plan layouts of apartment blocks. Three different topics/themes are discussed in order to generate the new housing solutions. While flexibility and mass customization emerges as the concepts for accurate solutions, open building approach is utilized as the major approach to create realistic and implementable layouts and postpone the final decision making to the household - final user. Pursuing the generation of FPL_Gen tool, structured interviews are held with various architects and engineer in order to test the tool and to discuss the aforementioned themes and methodology. In the suggested prototype, creating plan layout alternatives responding the requirements of various users is aimed. In other words, flexible plan layout alternatives in different sizes and positions are created for not pre-defined users. The prototype is designed and developed in computer environment aiming to respond to the defined parameters and constraints rapidly. To draw the borders of the flexibility and support alternative production, an open building approach is selected. As it is known, open building approach is a multidisciplinary approach applied in building design. Kendall and Teicher (2000, p. 4), define open building approach in two parts 1) support (the durable part of the building), and 2) infill (the changeable part of the building). The main idea is to create the support; the stable part of the building and to delay the infill process (the construction of partition walls). The support consists of the structural system, as well as the mechanical systems, which constitute the unchangeable part, and the infill is changeable and the user-responsive part, which may be determined or altered for each individual household (Kendall and Teicher, 2000, p. 33). Even though various plan schemes and mass configurations may be selected for the prototype, rectangular plan scheme is selected. The main reason for this decision is to use a basic shape so that the products and alternatives can easily be tracked. FPL_Gen generates rectangular blocks based on the architectural decisions, data (embedded in the tool), and the initial input (width, depth, number of floors, percentage for each type-selected by the user). In order to create the support (base - core and structural system), basic design decisions are made and various calculations are performed about the structural system, space organization, and service areas. After support decisions are finalized, the main frame for infill is determined. After this point, the architect can manipulate the design, re-generate it, or use it as a base and modify it manually. The detail and design on the infill part is assumed to be finalized by the household - the final user. In order to select the structural system, TOKİ (MHDA - Mass Housing Development Administration) and the houses designed / constructed by TOKİ are analyzed. TOKI tried to solve the housing problem by building mass houses -housing blocks (mostly medium and high-rise apartment buildings)- with solid infrastructure and most of the time created typical plan schemes which overlooks contextual features, climatic or cultural needs. Tunnel form construction system is the most common construction method in housing projects in Turkey which TOKİ is the biggest housing supplier. Tunnel form system is a prefabricated, fast, and economic system used in housing projects. Using tunnel form system helped to limit the size of the structural system and it is an applicable solution in Turkey. The modular and repetitive use of tunnel formwork can be altered and in order to design various alternatives with different width and depth sizes. In the prototype, the size of overall mass, the desired floor number and the percentage of apartment types are entered as initial input. Based on the overall size and floor numbers, core size and the required circulation area are calculated. Depending on the size the core and overall area of the mass, core is positioned on the corner, edge or in the middle of the mass. After initial values are set, the size and the position of the core is determined and in case of multiple alternatives, one is chosen randomly. The core and structural system creates the support part in the prototype which is called base. After the core is determined, structural system is randomly created to finalize the base. The structural system in turn, determines the sizes of the rooms and floor schemes are determined based on the initial percentages. It is possible to create various floor plan alternatives for the same structural system as well as creating various structural system alternatives with the same initial input. Prototype's outputs are plan schemes and their dimensions as well as their numeric list (room and house square footages) for each floor and overall building. With this organization the durable frame -the support- will be the center part of the plan with the bearing walls enable the infill to be planned freely and to be altered in case of need. Infill encourages flexibility and adaptability, while it also promotes mass customization. The flexibility is based on the possibility of generating numerous houses with the same structural system. The decisions are made, main elements and constraints are defined (for example, the size of the rooms, the size of the cores, the size of the bearing walls and their relations with each other etc. are all calculated) and embedded in the tool using the houses designed in Turkey as cases. Interviews with architects and engineers from engineering and architectural firms have been conducted with the aim of testing the prototype. In the process of sample selection, architecture and construction firms designing or constructing are preferred so that they can represent a wider group of people. Interviews are conducted with the founders of the firms or with senior professionals (architects mostly). First; the general profile of the participants are categorized. After that, the evaluation of the prototype and comments are explained briefly. Suggestions and comments of the participants (engineers and architects) are very valuable to improve the prototype, the approach and how to interpret the architectural knowledge. Although the firms design or produce (various) housing complexes in different scales for different income groups, the prototype has received positive response by all participants. Square footage calculations received positive feedback and suggestions about future additions such as useful area calculations, or percentages from regulations are also made. Working with such a tool has also received positive feedbacks, even though the participants wanted to manipulate different data or add / remove some features. In other words, instead of a generic tool, participants sought for a tool that could be modified based on their own architectural needs, knowledge and style. FPL-Gen generates flexible and mass customized plan layouts while it uses the structural system as a constraint. It is also promising to see that developing the prototype is also possible by manipulating the code. Changing the initial assumptions, or decisions, with feedbacks and various interventions the scope of the prototype may differ widely. And in the further phases other features and panels can also be added.