Archive for the 'architecture' Category

Iconic Structures of Indiana: Lucas Oil Stadium


If you have been in Indianapolis recently, or perhaps seen the Indianapolis Colts on TV this year, then you have likely seen the latest edition to the Indy skyline: Lucas Oil Stadium.

I love this stadium.

Exterior Construction Photo (by hyku)

Lucas Oil Products bought the naming rights for USD$121M

September 2008 – The Stadium is now open for business

My appreciation for this structure has nothing to do with the game of football or the events inside, I just totally love the way it was conceived, designed, and built. HKS was the Architect and Walter P. Moore was the Engineer of Record. The structure was finished in August of 2008 and has already been used for one full season of American Football and for many other conventions and events. It replaced the innovative RCA dome (or Hoosier dome) used as the Colts stadium since 1984. The RCA dome stood alongside its finished replacement for a few months before being imploded in December of 2008.

A last view to the old RCA Dome

I’ll leave it to other critics (try Circles and Squares or DIG-B) to decide the merits of the architecture of the stadium, I am only writing this post to discuss the structural system and design of a few key elements I find interesting. Also, I strongly recommend anyone who is interested in this stadium to review most of the documents on the IndyStar stadium page. They have some great photo galleries (like this one, but view in reverse order) and a great time-lapse video that shows construction from groundbreaking to completion (see below, I recommend muting and going full-screen).

As you can see from the video, this is a huge structure and it took a long time to complete it. It’s most famous feature is the retractable roof. A lot of stadiums these days have retractable roofs, but Indy’s stadium is the first with a gable roof system that splits lengthwise. It also has sliding end-zone panels that reveal downtown Indy just to the northeast. Beyond that, it’s a pretty typical football stadium, seating 63,000+ spectators on precast stadium risers. It also has all of the standard “jumbo-tron” equipment and luxury suites that modern stadiums use. But let’s discuss the shell and roof of the stadium because that’s what appeals most to me.

So what makes the Lucas Oil Stadium an achievement worthy of celebration? Why do I think it’s the best modern “dome” stadium? Partially I think it’s just a feeling, but I’ve got some good substantive reasons, too:

  • The overall form pays tribute to the massive sports arenas of the region such as the Hinkle Fieldhouse at Butler University
  • The material choice reflects the common materials used in downtown Indianapolis
  • The structural system uses enormous portal frames similar to the large industrial buildings throughout downtown

It all comes down to context. The building isn’t removed from the city surrounding it either by form, material choice, or structural system. Everything just seems to fit. That was the one complaint about the RCA dome, it appeared as though an alien spaceship had landed in the midwest. I fear the Dallas Cowboy New Stadium went down the alien path, however. It is unique in its own way, but mostly Dallas just needed something BIG. (aside: I grew up in Texas; yes everything is bigger; no don’t mess with us) The bigness was very important when both Dallas and Indy were competing for 2011 Superbowl. Dallas won out because more fans = more money.

I actually prefer smaller stadiums. Both Heinz Field in Pittsburgh (USD$281M) and the Columbus Crew Stadium (USD$28M) are regional stadiums that have successfully met the requirements of their tenants. The smaller stadium size allows fans to get very close to the action, and lowers tickets costs and maintenance. Having attended games at all of these locations, and being caught in thunderstorms, heavy snow, and hot sun, I can say that Lucas Oil Stadium’s (USD$720M) famous roof was well worth the effort. The Lucas Oil Stadium stayed with the small stadium formula but optimized the fan experience.

To be honest, a good stadium design hasn’t changed much in the past 2000 years. The Roman Colosseum could seat 50,000 spectators. This structure used earth-moving processes and concrete construction similar to today’s efforts. The complex system of trap-doors and ability to convert to a lake for water battles are pretty notable. The structure had a lot of versatility built-in. Architectural historians are pretty sure the stadium even had a retractable fabric roof, either supported from poles or using catenary action in an inverted dome sytem. Throw in the advanced plumbing system, beer and bread vendors, and free admission (yes, free) and you might even think our designs have regressed.

Cross Section of the Flavian Amphitheatre (Colosseum)

Cross Section of the Lucas Oil Stadium

But there is a huge difference between the Lucas Oil Stadium and a simple outdoor stadium (modern or ancient). Lucas Oil Stadium gives the power to completely control the weather element. During nice weather, the stadium is open at the top and side. During extreme weather events or hot/cold seasons, the stadium can be closed up and operated as a conditioned space. This doesn’t matter as much for a simple game like football which should be played outdoor as much as possible, but for other events like RV shows, Final Four basketball games, or high school band competitions it is essential. The real benefit here is certainty. Indy can guarantee that large events can be hosted anytime of the year without worry. The added bonus of holding the event in a sports stadium lends a certain amount of clout to the event as well. This gives a huge advantage in securing conventions and events. Versatility is the key here, and it only costs money.

Enclosing a volume such as Lucas Oil Stadium is no easy task. The wind force on such a large surface area can build up to incredible levels. There are no floor diaphragms to help distribute the loads evenly around the building. The brick facade and sensitive roof mechanisms demand a very stiff frame, as any movements can cause cracking or throw off the alignment of the retractable roof system. This is where the experience of Walter P. Moore as a company is tremendously important. The structural system concept was based on previous successful methods, but also different from any previous system because of the unique roof configuration.

If you refer to the photo above you can see the most important piece of structure: the Supertruss. There are two of these above each sideline in the North-South direction, and they support a large percentage of the roof loading. The supertrusses are essentially portal frames, which means they resist moment at the transition from vertical to horizontal. This behavior is in contrast with a typical post & beam system which allows the beam ends to rotate freely. The advantage of using the portal frame is a much stiffer structural member; the penalty is dealing with the insanely large forces that develop inside the member. I recall a Walter P. Moore designer telling me that the moment in Reliant Stadium supercolumns were being measured in “kip-miles”, I would assume a similar situation would occur in the Lucas Oil Stadium.

The Supertrusses develop internal forces using truss behavior, with top and bottom chords, diagonal web members, and gusset plates tying everything together. I don’t know the dimensions of the members used, but the weight of even a single gusset plate on one of LOS’s supertrusses is probably heavier than a typical truss used in one of my projects. The supertrusses are massive in every sense of the word.

Here you can see the supertruss as it connects to the foundation system. I should probably point out that major projects like the LOS stadium can have well past 50% of the structural cost in foundation costs. In this particular case, the civil engineers had to account for underground utilities including a new pedestrian tunnel linking to the convention center in addition to all sorts of wastewater, electrical, and telecom trunk lines. Just locating all these services is a major task unto itself. Accommodating them or building around them certainly adds a challenge to the already difficult situation. In the case of the LOS, one entire corner of the building had to supported by an underground bridge across an existing CSO line.

When you look at Lucas Oil Stadium, try to visualize a huge network of piers, concrete pads, and a huge mass of soil supporting all the weight. Buildings don’t just sit on the ground, they interact with them and become part of the earth. Just like the root system of a tree, a building is truly part of the subsurface environment. But referring back to the photo of the supertruss base connection, I can’t tell you how thrilled I was to see they left this part exposed. Here is the exact location where most of the weight and wind force is transferred into the foundation. It is an incredibly important structural relationship, and I am glad they celebrated it.

I have included a few shots of the supertruss as it continues up the levels and transitions to a horizontal member. I am so glad they left this portion exposed, these components are usually hidden behind walls and gypsum, so it quite special to see it. It really is a great representation of the strength of the building. Next up is the minor trusses. They aren’t “supertrusses”, but they aren’t so bad, either.

Steel framing under construction

You can see the truss poking out at roof level

The smaller trusses intersecting at right angles to the supertrusses serve a few purposes. First, they carry the wind loads down to the framing in the other direction. Next, they prevent buckling of the supertrusses. Finally, they provide a rail for the roof to travel along and set the gabled roof profile. Most importantly, though, they look pretty cool. There are five of these trusses in the East-West direction. You can see them on the inside of the building or poking out from the top of the walls.

Going back to the construction video, you can see several phases of construction. The first is the foundation and earthwork. The playing surface of the stadium was lowered a few stories for some practical reasons. The stadium seating starts first, and then the first supertruss (west side) starts going up. The temporary erection structures for the supertruss are large enough to be considered a separate project, I would imagine. As time progresses, the gable trusses are installed in pieces. The other supertruss (east side) goes up, and the gable trusses are finished. About this time, you can see the cladding being applied. This isn’t fake brickwork or metal panels painted brick red (well, not very many at least). The masons assembled brickwork into large panels which were then lifted and set into place. I thought that part was pretty clever too, it sped things up and kept the masons safely on the ground.

The final parts of the video show the roofing, windows, and finishes being installed. The finish installation is a pretty rapid process compared to the overall project, but it probably is the most rewarding for the builders. Up until that point, everyone is really operating on faith that the designers knew what they were doing, so seeing the actual product assembled and functioning takes a lot of stress off of everyone involved. And besides, it’s pretty freakin sweet just to see the biggest operable window in the city opening up.

Sliding Window Photo (by hyku)

East side entry lobby – insert huge fan pun joke here

I also wanted to show some photos of the general interior. The huge fans were a great touch, they really push the whole industrial feeling of the space, and they certainly get the job done. I wish they had more stairwells or escalators, but most spectators will get to their seats using a really long ramp system. It’s wacky and kind of boring, definitely the biggest missed opportunity of the design.

Makes a person wonder… where the hell am I, and where am I going?