ARCH653:Building Information Modeling in Architecture: Project 1: Parametric AT&T Stadium

Parametric Design of AT&T stadium

by Azeemuddin

About the Project

AT&T Stadium, formerly known as Cowboys Stadium, is a city-owned 85,000-seat capacity stadium with a retractable roof in Arlington, Texas, United States. The maximum capacity of the stadium with standing room is 105,000. It marks the largest stadium in the NFL in terms of seating capacity. It was completed and opened to public in May 2009.

A pair of nearly 300 ft (91 m)-tall arches spans the length of the stadium dome of 1290 ft, anchored to the ground at each end is what makes this stadium a structural antique. Adding to that it has a Retractable roof which can make the ambiance inside the stadium indoor or outdoors as and when required. With two glass doors which apparently are the biggest in the world is another of many exquisite features of this eye pleasing structure.

Photo credits: Rockwall ISD

Its an worthwhile experience to watch a football game here and the credits go to HKS Inc, who are the Architects of AT&T Stadium. The Retractable roof was designed by Walter P Moore. There is a clerestory window which provides way for the sunlight to enter the stadium. This window surrounding the stadium gives the feeling that the dome is floating. The features mentioned above are few of those which drove me to design the skeleton of the stadium using Revit Architecture. I was puzzled to notice the control that Revit provides in maneuvering the external skeleton and I was proved correct after actually putting all of the components in place after given the ability to control the size and shape using Parameters in Revit. The external facade of the stadium changes with the daylight and that is something which we will keep aside for time being and we can attend to that later in this Course using Dynamo.

Getting into the details of the methodology adopted to set the parameters, unlike any other stadium, which can be created by sweeping the exterior facade and the interior seating would not suffice the modeling of AT&T stadium as there are many other exquisite features which compelled the creating different parametric families and load them in a Giant family linking the individual families together para-metrically

The individual families that were created were.

Two Arches

Exterior face wall.

Sliding doors

Retractable roof

Dome

Window

Seating

Giant Family

Lets discuss in detail how the above families were created and how can they be controlled by using parametric equations.

1. Two Arches:

Two half ellipses were drawn as reference lines in two different planes parallel to each other. The dimension between the two planes was parametric and which would ultimately define the width of the stadium. Later, a reference point was hosted on the elliptical lines and rectangular cross-section, length and breath of which were parametrically driven, was drawn and swept all along the reference line. This was the easiest!!! Curtain panels resembling a structural truss were created and loaded into the Arch family as shown below.

Fig 1: Arch family with curtain panels

Fig 2: Curtain Panel for Arch family

2. Exterior Face-Wall

The exterior wall of the stadium comprises of half elliptical conceptual mass whose thickness, height and the extremes of the ellipse(semi-minor axis) are parametric. The ellipse controlling the mass of the face wall changes with periphery of the dome, see below for dome family, and for the better control over the ellipse, use of spline over 5 reference points was adopted. Three points para-metrically driving the ellipse would cause irregularities. Hence 5 points with a spline was a better idea. So the five points can be parametric if 'a' and 'b' are known.

Fig 3: Basic idea for parameters

Fig 4: Face-wall conceptual mass

Fig 5: parametric Equations for Face wall

3. Sliding glass doors

Apparently, AT&T stadium has the biggest glass sliding doors in the world. So, to miss on that would be in just. However, sliding doors were create in a generic family template and

by extrusion.

Fig 6: Plan view and Reference planes for Sliding doors

Fig 7: Parametric equations of the door.

4. Retractable roof

Another exquisite feature of AT&T stadium is the Retractable roof which opens and closes when required. The complication in creating a mass roof which opens and closes as and when required is that the elevation of the stadium is elliptical; the radius of curvature changes along the ellipse. Adding to that, with change in the stadium dimensions the ellipse would change as well. Icing on a cake!! The solution to the above problem was to create explicit ellipse point family. What is explicit ellipse point family?? Its a point family which defines a point of the ellipse. An ellipse or a part of an ellipse can be created by plotting consecutive point families and joining them using adaptive component. Following the idea, a point family was created as follows

Fig 8:Explicit Point family

Fig 9: Parameters dialog box for point family

As in above dialog box, we can notice a parameter 'n' which defines the point on the ellipse. For example, if n=9, then the point would be at (0,b) co-ordinate, where b is the length of semi minor axis of the ellipse. Moving on, three point families were uploaded in a conceptual mass family with consecutive points (say n=9,8,7). Then an adaptive component using three reference points was created and uploaded in the mass family which consisted of 3 points on ellipse.

Fig 10: Adaptive component for Retractable roof

Fig 11: Adaptive component placed on 3 consecutive elliptical points

With change in the parameter 'n' as shown in the dialog box above, the roof can be moved accordingly.

5. Dome

The Dome of AT&T stadium is the most enticing ones in the market. Its just so eye pleasing. The plan view of the dome is in the shape of 'American' Football. The dome rests upon the two arches and at a certain height. The height of the arches and the base height of the dome are the determining factors for the shape of the dome. The basic idea to contour the dome is shown below.

Fig 12: Basic idea of dome elevation design

Four Reference ellipses were used to create a form of the dome with the inclined ellipses are used to change the end angle of the dome.

Fig 13: Reference lines for dome family

Fig 14: 3D view of Dome

Fig 15: Elevation view of the Dome

1. 6. Window

In between the Dome and Face walls there is a window which is the only source of natural ventilation and sunlight. The window was created using half ellipses on two reference planes inclined to each other and curtain panels were inserted.

Fig 16: Window with Curtain Panels

7. Seating

For the stadium seating, sweep along a rectangle with curved corners was used.

Fig 17: Seating elevation(Reference lines)

Fig 18: 3D seating sweep

8. Stadium family(Giant Family)

All of the 7 individual families where uploaded into a Giant family and the individual family parameters were linked with each other to a family parameter of the Giant family.

Few of the links provided are as follows.