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Duygu Yenerim1, and Wei Yan2 Department of Architecture, Texas A&M University, College Station, Texas, United States of America
Abstract – Parametricism has come to scene as an important style in both architectural design and construction where conventional Computer-Aided Design (CAD) tool has become substandard. Building Information Modeling (BIM) is a recent object-based parametric modeling tool for exploring the relationship between the geometric and non-geometric components of the model. The aim of this research is to explore the capabilities of BIM in achieving variety and flexibility in design extending from architectural to urban scale. This study proposes a method by using User Interface (UI) and Application Programming Interface (API) tools of BIM to generate a complex roof structure as a parametric family. This project demonstrates a dynamic variety in architectural scale. We hypothesized that if a function calculating the roof length is defined using a variety of inputs, it can later be applied to urban scale by utilizing a database of the inputs. Keywords: Parametric Variety, Parametric Modeling, Building Information Modeling, Application Programming Interface, Architectural Design, Urban Design
between components that determine both geometric and non geometric properties of a model . Building Information Modeling (BIM) is a recent tool for object-based parametric modeling which means that instead of designing each instance such as walls or windows, the designer identifies an object family and its parameters including angles, dimensions and other properties helping it to relate to other objects. Creating a variety in typology is the second important concern taken into consideration as a design problem; it has started off with Modernity and Minimal Dwelling in 1920s by embracing the concept of flexibility along with variety . Owing to the parametric relationships, designers not only can achieve the concept of variety in a continuous and dynamic way, but they can also create flexibility from small scale interiors and architectural designs to a larger scale . Object-oriented modeling of BIM and parametric variety as an inclusive concept, which encompasses flexibility and adaptability, structures the framework of the discussion. The purpose of this research is to pursue the capabilities of BIM in achieving variety and flexibility spanning from architectural to urban scale. In order to do so, we performed an experiment in architectural scale by modeling a building complex through using BIM technology. This complex is composed of three buildings with six different S-shaped roofs. These roofs are different from each other but they share the same parameters. Radius and curvic lengths of the arcs are changing from one roof to the other. Therefore, the roof is the component that ensures the dynamic variety according to the changing floor dimensions beneath. The aim is to build a model which can adjust itself according to the change in floor dimensions. This method is experimented in architectural scale and explored if it can be applied to urban scale. We hypothesized that if a function calculating the roof length is defined using a variety of inputs, it can later be applied to urban scale by utilizing a database of the inputs. The expected outcome is to be beneficial for larger scale designers. This research is important because the process of creating a variety in a larger scale is time consuming and the solutions may not always be successful. For instance, for settlement design, one of the major problems that architects come across frequently is creating a variety in houses. Every dweller has different needs and expectations; therefore they want their houses to be unique. Using BIM parametric
Architects, planners, designers, and engineers who have a role in designing and implementing physical constructs have come to believe that diagrams play an important role in representing design thinking and managing collaboration among them . In architecture, drawings mostly represent the design decisions on building form, spatial configurations, orientation, materials, and users, and the relationship among buildings, environments, and people. Computer-Aided Design (CAD) is a conventional design tool that produces drawings by creating lines, arcs and other geometric shapes. However, in order to make any changes in design, CAD requires performing changes on each related component in the drawings. This may affect time spent on design and construction . In recent years, parametricism has become an important style in architectural design and construction. Today, parametric design technology has come to a stage where conventional CAD tools not only has been losing its power but also has become substandard. The idea of parametric design and thinking is seeking and exploring for relationships
1 Moreover. However.1 The capabilities of BIM-based parametric modeling In traditional design and drawing system which includes both pencil and CAD-based applications. parametric model refers to the medium that is utilized to establish variation of geometrical components of objects whereas parametric design is the design action by utilizing parametric models . Due to its capability of adapting the model to the changes performed by users. The National Building Information Modeling Standard (NBIMS) committee 1 BIM design tool is currently used for architectural scale.2 Parametric modeling for continuous and systematic variety Variety is an important concept in architecture. BIM is essential for object-based parametric modeling which was first developed in 1980s . Ability of automatically updating the objects comes from the parametrically defined interface between object and user which is called object based modeling . it is easy to create a model of a building. Object-oriented design embraces the design around objects and methods together . This has been a concern starting from the era of modernism. Parametric model and parametric design are overlapping terms that denote a slight difference in their meanings.modeling User Interface (UI) and Application Programming Interface (API) tools will shorten the process of design and offer endless solutions. whereas it is difficult to make adjustments or changes to the models [10. It was defined as “an instance of populated data model of buildings that contains multi-disciplinary data specific to a particular building [through its lifecycle. Especially in housing design. parametric modeling is starting to be used in urban scale as well. the building should provide an opportunity to offer a choice of selection from a variety of configuration and layout . designer needs to update all drawings individually: plans.3 Parametric modeling in urban scale 2. Parametric modeling also allows having control over an object. They designed the urban fabric of Kartal-Pendik in Istanbul in 2006. The design includes buildings.]” .9]. If the length of a wall is changed. Zaha Hadid Architects apply parametric design into both architectural and urban scales (Figure 01). something which differs or varies from others of the same class or kind.8. or condition. This is the main difference between BIM design applications and CAD systems. Besides its benefits in design. (4)financial data. . a kind or sort” . (3)geospatial data.14]. Parametricism has been the recent movement in architecture and there are studies showing that parametric design has a theory underneath. using BIM is an accurate way of documenting and implementing big chunks of data on individual buildings to relevant stakeholders. (7)sustainers data. (5)specifier data. thereby. elevations. pedestrian and vehicle path systems. Integrating parametric design thinking into design process results in flexible solutions with endless and continuous potential of forms [7. A single building can be replicated in a continuous and systematic variety by creating BIM parametric family in UI and integrating API tool to generate a function between parametric family objects. the idea of parametric modeling refers to creating models which are clearly defined by its parameters. 13]. the end product of design generated with predefined parameters are established successfully . According to Robert Woodbury. For instance. Turkey by Zaha Hadid Architects . The purpose of this research was to investigate BIM technology in parametric design and its capabilities in achieving variety spanning from architectural to urban scale. (2)legal data. integrating algorithms in parametric modeling enables to deal with more complex forms and leads a variety in object geometry . 2 Background 2. quality. 2. (6)environmentalist data. The term refers to “[a] different form of some thing. Patrik Schumacher defines the term as “the great new style after modernism” . The model was generated in Autodesk® Maya® and the end product includes the exterior geometry of buildings. sections. states that BIM can incorporate eight data sets: (1) designer data. BIM is a very effective environment for designers to create objects which can vary based on changing specifics of the model. Figure 01: Kartal-Pendik Masterplan in Istanbul. and (8)owner/occupier data [3. and the 3D model.
category. the roof is the component that provides parametric variety in the design of the building geometry through changing design decisions on values of its parameters: angles and radii of arcs. In this study. and (b) have similar formal representation in the project [19. In other words. double flush. The method that we experimented in this project consists of two levels: (1) creating the roof as a BIM parametric family by math functions in UI and (2) establishing an algorithm between floors and the roof structure by API functions. BIM tool Autodesk® Revit® 2011 was used to model an architectural project. double sliding door families. we started off with creating the roof as a family. 𝑅2 𝑂𝑓𝑓𝑠𝑒𝑡 = 𝑅2 − 80 𝑐𝑚 𝑅1 𝑂𝑓𝑓𝑠𝑒𝑡 = 𝑅1 + 80 𝑐𝑚 𝑅1 + 𝑅2 = 𝑅2 𝑂𝑓𝑓𝑠𝑒𝑡 = 𝑅2 − 80𝑐𝑚 𝑅1 𝑂𝑓𝑓𝑠𝑒𝑡 = 𝑅1 + 80𝑐𝑚 𝑅1 + 𝑅2 = (𝑋1 − 𝑋2)2 + (𝑌1 − 𝑌2)2 𝑋1 + 𝑋2 2 + 𝑌1 + 𝑌2 2 (1) (2) (3) 𝐴2 + 𝐵2 𝑙2 = 2. 3. an external database was used in order to set constraints and control these changes such as dimensional information on how to make adjustments to the model in order to obtain various and flexible end products.1 Roof as a BIM parametric family In Autodesk® Revit®. double panel. Each building in the complex has two different S-shaped roofs. no matter what their radii are. Parametric modeling was tested to achieve numerous geometric forms along with its structural columns. 3 Methods and implementations In this research. In this project. By using the math function. This study of the roof shapes was done through varying curvature. ( ) 360° (4) (5) Figure 02: Diagrammatic drawing of a S-shape roof and its parametric rules. the value of the radius of the circle on the right (R2) changes automatically. it was followed up with defining the coordinates and drawing the two arcs tangent to each other in the Generic Model family template along with fixing their centers. length and width of the two arcs. 𝑅1. For instance. after experimenting the proposed method and tools in architectural scale. Each S-shaped roof consists of two arcs. In order to create roof as a parametric family in Autodesk® Revit® (Figure 02). family and type are three terms that constitute the basis of modeling by defining objects and their hierarchy in a project. Coordinates of center points and radii were added as parameters. the radius and length of these two arcs are changing. we suggested that BIM could be a beneficial tool for larger scale projects as it provides enough detail. length. door. the roof structure is created as a parametric family from scratch. and for each roof. information and variety in building scale. and width. by plugging in different values to the origins of the circles or the radius of the circle on the left (R1). Figure 03: Changing the length of the arcs (upper figure) and varying the shape of the roof (lower figure) . ( ) 360° 𝐴1 + 𝐵1 𝑙1 = 2. In addition. floor. Pythagorean Theorem. However. 𝑅2. It contains all the parametric information about the building allowing it to reflect any changes applied by the designer. The term family is used for a set of objects under a category that (a) possess same properties which are called family parameters. The external database for this research was designed in Microsoft® Excel® and the interaction between BIM and MS Excel was coded using Microsoft® Visual C#. single sliding. 𝜋. These door families possess similar parameters which enable users to create a variety of different types in one family. the major problem in this level was how to constrain these two arcs in order to keep them tangent to each other. furniture or beams. window.20]. Category refers to the main group of elements such as a wall. double glass.In this research paper. we made the radii and the coordinates of the center point of arcs dependant on each other (Figure 02 and 03). 𝜋. a door category dwells several door families such as single flush. roof.
The challenging part of this project was that the length of the roof was actually the arc lengths not the projection on the X axis (Figure 04). BIMbased modeling allowed for adaptation to the overall design for any changes occurred in any components and fast creation of variety in building design. 3. no matter what the dimensions of the floors were (Figure 04). Since angles more than 45° are not appropriate for a roof design in this project. UI provides an . Basic algorithm was developed to find the appropriate length of the roof by referring to the database. and shows the length increase or decrease according to the selected angle for each arc. If the code was successful. even with the constraints and the database table. This database includes angles of each arc. two separate codes were created. any change on the length of the floor could reflect proper change in the length of the roof. which contains the pre-calculated length values and their corresponding angles. Revit® API allows us handle this limitation using MS Visual C#. two constraints were applied to the arc angles in order to limit the values to any degree between 0° and 45°. Base case arc angles were fixed at 5° for ARC2 and 10° for ARC1 in the project. all length values in the Excel table were tested by the program with the use of a loop function. we identified two angles for each arc and added them as parameters. To find the appropriate roof angle.2 API for creating the relation between Roof and Floor To overcome this challenge. 4 Findings and discussion Although there are other methods used in both architectural and urban design. we performed experiments on the length of projected roof on the X axis and prepared a database with different arc angles (Table 02). However. Therefore. which were to be run based on the direction of the change on the floor (Figure 04 and Table 02). we moved to the next step which was to constitute algorithmic relationships between object families. This was the limitation of this parametric roof family. Consequently. When the change was applied. given a floor length. These two abilities of parametric modeling are the innovations in design. These two constraints are that angle of arc cannot get (1) any value larger than 45 and (2) any negative value. Table 01: Parametric variables of parametric roof family In order to create a correlation between the roof and the floor length. what has been missing from achieving parametric variety for more complex forms. This step allowed us to get a variety of roof structures (Table 01). changing the length of the roof by modifying the length of the floor would not give the right solution unless the angles were set up properly. Table 02: Excel Sheet for the external database of the roof angle-length relations The roof structure was designed parametrically in order to easily create/design indefinite varieties of buildings with this roof. To be more flexible on the shape of the roofs. Figure 04: Diagrammatic drawing of the function between roof and floor. part of the roof on the other side of the floor and its arc angle were kept constant. However. whereas the other part of the roof was modified. the challenge was that we were not able to make adjustments on the roof at the project level. there were still infinite number of solutions for the angles. Autodesk® Revit® as a parametric BIM tool offers two options in modeling: (1) User Interface (UI) and (2) Application Programming Interface (API).The offset value of each circle showed the thickness of the roof and they were also defined by the value of one of the radii (R1). The change on the value of the angle had an impact on the length of the arcs.
it can later be applied to urban scale by utilizing a database of inputs. length. (2) the size of buildings. The significance of this research is that the potential applicability of this method to urban scale. we used API tool to overcome this limitation. and (4) inhabitant preferences can also be added. However. dividing or multiplying spaces. Therefore. Residents of the houses have different needs and requirements thereby. It is possible to create roof and floor parametric models from scratch by using API but it would be time consuming. the findings demonstrate that BIM-based parametric modeling of an architectural project provided fast creation of continuous variety in design form. Existing roof on the left and modified roof after running the Code 1on the right and In Lower figure. variety in houses are needed. integrating UI and API is more feasible to develop parametric BIM models: (1) designing complex geometries in UI and (2) applying complex calculations and algorithms in API. First. We picked a geometric shape which was challenging due to its relation with the floor (Figure 05). A single family house may be designed parametrically integrating powerful programming methods for adding or removing rooms. However. and can be designed successfully in a significantly short time period. Figure 05: In Upper Figure. the shape of the roof and the floor caused problems while linking their length parameters. Future work BIM parametric design and API applications are very powerful in architectural scale and may be adapted to urban scale. This application has several potential limitations due to the existing tools. other parametric design software only allows designers to consider urban sphere. Autodesk® Revit® does not allow us to label it under the roof category. as a limitation. To overcome this limitation. and width. However. One of the major benefits of BIM-based urban design is that exterior shapes of buildings are designed together with their interior spaces. more functions and more spatial complexity come to the stage. we parametrically modeled an architectural project to test if we could achieve a continuous variety on design form. Existing roof on the left and modified roof after running the Code 2on the right. industrial. Second.environment for user interactive geometry and prototype design. commercial. Larger the scale. we implemented a set of experiments on the projection of s-shaped roof on X axis and developed a database that links angles of the roof (ARC1_ANGLE_A and ARC2_ANGLE_B) and expected projection on the X axis. In other words. UI did not allow linking two or more different objects: roof and floor. created roof is a massing model which ends up with typological variety by changing the values of its parameters. informal settlements are one of the major challenges for developing countries and the United States has experienced this through the settlements developed along the US – Mexico border called the Colonias. Therefore. 6 The hypothesis was that if a function calculating the roof length is defined using a variety of inputs such as length of floors. 5 Conclusions In this research. A roof of a building complex is used as a case study that provides parametric variety in the design geometry form of the building through changing design decisions on values of its angles and radii of arcs. This adaption requires more relationships to be defined between different components to achieve enough level of variety in buildings. the number of parameters and codes for urban scale modeling can be much larger. Future work can be to apply this method to a larger scale design. (3) the lot of buildings. Parametric modeling is a useful tool to achieve that kind of complexity in design problems. since the parametric roof family was modeled by utilizing Generic Model family template under mass category. For instance. New parameters can be utilized and played with according to (1) the function of buildings such as residential. but not focus on individual buildings. . through BIM designers can deal with the individual building scale together with the urban scale with other tools. A great percentage of these houses are substandard and need to be redesigned. The method that we experimented on this project consists of two levels: (1) creating the roof as a BIM parametric family by math functions and (2) establishing an algorithm between floors and the roof structure by API programming. Therefore. Overall. This method suits this goal.
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