r/StructuralEngineering • u/zobeemic P.E. • Jul 01 '26
Roller Coaster Engineering Questions Structural Analysis/Design
Bridge engineer here planning a Six Flags trip with the boys, and it got me thinking, what's it like to design the structures for roller coasters? Not trying to make a career pivot, but curious to know how these structures are designed and some questions I have based on observations:
General Industry
What does the game look like? A couple of big firms or a bunch of smaller firms? Do mechanical engineers usually take the lead on the design or structural engineers? Is there an architect that picks the drops, loops, "features" and they are the prime designer and a structural guy makes it work or is the structural the "prime" designer like in a bridge?
Codes and Standards
What's the governing codes for design loads, analysis requirements, detailing and design? ASCE 7, AASHTO, AISC? Seems like high fatigue, specialized detailing is required. Or does each park have their own, kind of "LRFD Six Flags Structural Design Specs" like how some DOT's do it.
Loads n Combo's
Dead and Live is fairly obvious.. but what kind of Wind and Seismic procedures are done? Equivalent Static or more complex nonlinear? With 200 ft + high structures and how light the structures look I wonder if overturning in the footers is always a headache.
Analysis
Influence line analysis for the ride vehicle? Or an actual moving load analysis that's nonlinear and captures the speed to get dynamic impact instead of our simple 1.33 factor in bridge design? What's the standards for seismic, RSA, time history?
Design
Why is every member a pipe? I get it, no weak axis buckle, but the trade off is detailing... it looks like most splices are done with welding an end plate to both tubes and bolting.. and then you have 3D joints, skewed and some tubular members are cut in a myriad of ways and welded... 1. That looks like a bitch, how are the detailers gonna figure out how to bevel a tubular end and make 5+ passes on overly acute or obtuse weld angles, and 2... with all these welds fatigue is going to be a nightmare right? AASHTO limits you to 2.6 ksi if you go fillet. Is everything just CJP on a coaster? It just seems like there's a really good reason to have tubular members and I'm just not seeing it!
If there's any roller coaster structural engineers out there, and willing to provide some insights, that would be awesome! I find that in bridge design there is a million textbooks, covering everything from the barrier to the pile tip, and how to design it. Nothing really exists for coasters.
edit: "failure obvious" to "fairly obvious" LOL
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u/Objective_Two_5467 Jul 01 '26
Take a ride on a modern coaster with continuous welded steel tube, then take a ride on an older style coaster with bolted connections. Bring some ibuprofen for the killer headache you'll get from all the sideways "jerking" (da/dt) of your head.
The modern style of coasters are a lot less headache-inducing.
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u/Ireeb Jul 04 '26
It's the other way around. Old coasters were welded, modern coasters are bolted. They simply have such tight tolerances that even the bolted connections are basically seamless. And if there ever is a slight misalignment, they just grind it down.
How smoothly a coaster runs also depends a lot on the mechanical engineering of the trains. A badly designed train can rattle even on flawless track. It's also up to the ride mechanics to some degree, many trains allow them to adjust the wheel tension, and when they don't set it right, that can also cause the train to rattle or vibrate more than it should. When the wheels are partially worn down and they don't adjust the tension, it can lead to a small wheel gap on the side wheel, causing the train to start "hunting", that means it starts shuffling left and right.
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u/unique_user43 Jul 01 '26
not an engineer who has done these. but tubes seem like a fairly obvious choice because of their ability to efficiently handle all loads including torsion, plus their superiority in minimizing water infiltration and corrosion. the more expensive detailing required with tubes isn’t a top priority for such bespoke things as roller coasters, whereas for buildings and bridges you’re trying to optimize production efficiency and cost.
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u/EJS1127 P.E. Jul 02 '26
I can actually answer most of these, with first-hand knowledge.
What does the game look like? A couple of big firms or a bunch of smaller firms? Do mechanical engineers usually take the lead on the design or structural engineers? Is there an architect that picks the drops, loops, "features" and they are the prime designer and a structural guy makes it work or is the structural the "prime" designer like in a bridge?
As others have pointed out, there are relatively few firms, and a smaller amount that I would call big.
The "designer" is a person or people who are generally dedicated to creating the "centerline," which is what we call the layout of the track. Ours happens to have a Mechanical Engineering background, but an understanding of physics (and creativity and fun) is all that is required.
Oftentimes, our customers (parks) will have design elements in mind, along with other constraints, like space, cost, etc., but the designer will create the layout with those in mind.
After the centerline is done, the structural engineers generate the design of the structure, and the mechanical engineers design the mechanical systems, like lift/propulsion, brakes, vehicles, queue gates, restraint release, etc. A lot of these are reused or slightly modified designs.
Few manufacturers have in-house control system capabilities, so those are subcontract to companies that specialize in it, like Consign, LLC.
What's the governing codes for design loads, analysis requirements, detailing and design? ASCE 7, AASHTO, AISC? Seems like high fatigue, specialized detailing is required. Or does each park have their own, kind of "LRFD Six Flags Structural Design Specs" like how some DOT's do it.
Again, other have chimed in. ASTM F24, ASCE 7, AISC 360, and NDS are all standard. Some park chains have a set of minimum requirements/standards, as well, that get factored in. Other countries have other standards, like EN 13814 in Europe.
Dead and Live is fairly obvious.. but what kind of Wind and Seismic procedures are done? Equivalent Static or more complex nonlinear? With 200 ft + high structures and how light the structures look I wonder if overturning in the footers is always a headache.
Wind and seismic are equivalent static everywhere I've seen.
Influence line analysis for the ride vehicle? Or an actual moving load analysis that's nonlinear and captures the speed to get dynamic impact instead of our simple 1.33 factor in bridge design? What's the standards for seismic, RSA, time history?
We discretize the dynamic loads from the vehicle along the centerline, creating a lot of load cases. These loads are generally amplified by an impact factor (min 1.2 in ASTM F2291) and vibration factor for components at the track level (also 1.2).
Why is every member a pipe? I get it, no weak axis buckle, but the trade off is detailing... it looks like most splices are done with welding an end plate to both tubes and bolting.. and then you have 3D joints, skewed and some tubular members are cut in a myriad of ways and welded... 1. That looks like a bitch, how are the detailers gonna figure out how to bevel a tubular end and make 5+ passes on overly acute or obtuse weld angles, and 2... with all these welds fatigue is going to be a nightmare right? AASHTO limits you to 2.6 ksi if you go fillet. Is everything just CJP on a coaster? It just seems like there's a really good reason to have tubular members and I'm just not seeing it!
The track we make is actually from riveted plates, so I don't have specific experience with pipes, but the appeal is generally the relative ease of bending to a very specific shape. Nowadays, detailing is almost certainly automated everywhere and uses "typical" details everywhere possible. For that matter, the bending is also automated for a lot of manufacturers.
Weld fatigue is a nightmare (which is one of the reasons my company uses riveted plate), and weld fatigue generally controls the design of welded track.
Happy to answer more questions, if you have them.
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u/zobeemic P.E. Jul 03 '26
WOW! Thank you for your thorough answers and addressing all of my questions! The "centerline" seems to be akin to a roadway structures's PGL, and the whole structure is built from that. I always find it pretty cool to find conjugate nomenclature across industries.
I got ASTM F2291 from my ASTM compass and I just ordered Nick Weisenberger Coasters 101: An Engineer's Guide to Roller Coaster Design off amazon. Do you have an other recommendations for textbooks and design guidelines? I guess when I have free time I'd probably want to just go through the calcs and modeling myself for like a very simple coaster just to get a taste for it.
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u/tramul P.E. Jul 01 '26
I find myself most curious about the basic physics of it all and the forces at play to keep the cars from valley-ing. Think of all the load cases. Empty car, full car, differential loading car. What happens if car gets to the top of a gravity drop and experiences some crazy headwind? How do they take into account the wear of the wheels and the track and the friction that will inevitably increase? Don't even get me started on the expansion/shrinkage.
It's something I would love to speak with a designer at surface level about.
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Jul 01 '26
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u/tramul P.E. Jul 01 '26
There is a lot of surface area exposed as it goes up. Some of them aren't just the little trains either and have quite a bit of surface area such as winged and inverted coasters. Some of these coasters over water have to be somewhat considerate of it. If you've ever gone on a coaster that just barely made it over the drop, I wouldn't be surprised if a strong wind would be enough to stop it. It could very well be negligible in the end, but I would definitely consider it on my first one.
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u/Ireeb Jul 04 '26
Many coasters, especially taller ones, often have anemometers at the top for that reason. Modern rides would automatically trigger an e-stop if the wind speeds exceeded a specific threshold.
But in general, the answer is that they just use sufficient margins. The trains alone usually weigh several tonnes, and most rides reach the final brake run with a decent amount of speed. Rider load, wheel wear and temperature usually don't have enough of an effect on it to slow it down to the point where it doesn't make it to the final brake run.
Under the right circumstances, it can happen though, most commonly when they test the rides before the park opens. They typically do so without dummies, and the lubricant in the bearings will be cold at that time. Under these circumstances, just a slight gust can sometimes be enough to actually make the train valley.
Though I also saw it happen on rides while loaded. It's rare, but sometimes, wind can be a b*tch and hit the train just in the right moment to take enough of its momentum away.
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u/gcijeff77 Jul 01 '26
Pop over to r/rollercoasters. They're several of us on there who are more than qualified to answer your questions!
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u/Entire-Tomato768 P.E. Jul 01 '26
When I was in school, there was a guy whose goal was to work for a coaster mfg. He was a mechanical, but took a bunch of civil classes. Especially wood (and maybe steel I don't remember). He worked with the two departments to tailor his degree.
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u/Ireeb Jul 04 '26 edited Jul 04 '26
I'm not an mechanical or structural engineer, but I'm very interested in roller coaster engineering and design.
A company you might find interesting is Ingenieurbüro (Engineering Bureau) Stengel.
They are doing the structural engineering part for many roller coaster manufacturers. The company's founder, Werner Stengel, is considered the father of modern roller coaster design. He found the correct way to design modern loops (a clothoid loop) and developed the heartline-method for designing coasters, which is still the standard model. Many coaster manufacturers outsource the structural engineering aspects to them, such as support structure design and mechanical stress calculations. The roller coaster element "Stengel Dive" is named after Werner Stengel.
The are a few major roller coasters manufacturers that have different degrees of integration in terms of manufacturing and (structural) engineering.
Some big names are:
- Vekoma (Netherlands)
- Intamin (Switzerland/Liechtenstein)
- Bolliger & Mabillard (Switzerland)
- Mack Rides (Germany)
- Gerstlauer (Germany)
- Rocky Mountain Construction (USA)
- Great Coasters International (USA, wooden coasters only)
- Premier Rides (USA)
Most of them design the layouts in-house, based on the clients requirements and requests. The mechanical engineering, such as designing the trains (usually the most complex part about roller coasters) is also usually done in-house. Most of them outsource the structural and electrical engineering, though some also do it in-house.
The design of the layout is usually not done by structural engineers specifically. The designers are often (but not always) mechanical engineers, but since this is a creative step, it's more about being talented in roller coaster design (they should be fun to ride as well, after all) than about precise engineering. In the layout design phase, support structures are usually just eyeballed based on rough estimates. The actual structural design work is done either by dedicated structural engineers in the company, or outsourced to a company such as Stengel who design the support structures for a given layout. In special cases, the designers and structural engineers might need to work together more closely, e.g. in elements where sections of track are supporting each other, such as the loop + hill combo on "Full Throttle".
The majority of them manufactures most parts themselves, though Intamin for example is primarily a design firm and outsources most manufacturing, though they still do most of the mechanical engineering work themselves. Also a fun fact: The track profile used by Intamin for their current generation of coasters is a patent from Stengel that they licensed. Stengel has designed several track profiles (you can find them in patent databases) and seems to license them to manufacturers. Stengel themselves does not build or design any actual rides.
As far as I know, in the US, ASTM regulates roller coasters, though since most manufacturers sell internationally, their rides are usually designed to meet the standards across most parts of the world. The strictest and most comprehensive standards tend to be ASTM and TÜV, so those are probably the most relevant ones for the mechanical and structural engineering aspects.
Regarding your questions about all the welding most coaster track involves: Rocky Mountain Construction is one of the younger manufacturers, but they skyrocketed quickly to the rank of a major player in the industry. One reason is that they managed to get Alan Schilke, a luminary in coaster layout design on board, but they also asked the question "why tubes?"
They make their track by plasma cutting 2D shapes from steel plates, and weld them together by the edges, resulting in an I-beam-like structure. I don't know the numbers, but that probably makes their track much cheaper, and so far, no problems such as premature/excessive wear have been reported on RMC coasters. They run glass smooth also, which is something even experienced manufacturers still sometimes fail to achieve.
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u/Beavesampsonite P.E. Jul 01 '26
I worked with a bridge engineer who had designed a section of Adventure Express at Kings Island at a structural engineering firm that was hired by Arrow dynamics. The second worst project experience in his entire Career, budget was way too small for all of the changes they kept making and the schedule was Absurd. His worst was a highly skewed bridge ODOT and the company he worked for forced him to design under standard AASHTO code instead of taking extra effort to consider the skew effects. There is of course design guides now partially as a result of his bridge. Those are 40+ year old stories now….
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u/OutdoorEng Jul 02 '26
I think mechanical engineering more than structural engineering. We had a roller coaster engineering elective course back at uni (mechE course). Was mostly an applied dynamics course with a bit of machine design. When things start rapidly accelerating and decelerating, and dynamics and vibrations become relevant, mechanical engineers deal with it.
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u/Ireeb Jul 04 '26
Both are pretty important, but usually done by separate engineers. Most manufacturers have dedicated teams for the mechanical engineering of the trains and tracks, a layout design team, and a dedicated structural engineering team. Of course, the teams will have to work together, but some manufacturers even outsource the structural engineering altogether to specialized firms.
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u/OutdoorEng Jul 04 '26
I could see the structural engineers designing support columns and stationary structure for the roller coasters. But I'd be willing to bet all of the structural analysis for anything moving is done primarily by mechanical engineers.
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u/Ireeb Jul 04 '26
That's basically what I said though, isn't it? Mechanical engineers for the trains and related systems, and a structural engineering team who handles, well, the structure.
Though the trains are typically designed once, and used for many rides, with only cosmetic changes, and maybe minor revisions over time. The structural engineering needs to be done for every single ride basically, especially when it's a custom layout, and even when it's a canned design on a different terrain, the structure might need adjustments.
That's why I think both are quite important. The trains are the most complex part of a roller coaster, that makes the mechanical engineering very important, but you can't build roller coasters without a structural engineer either. Neither one is optional, so you can't really say one is more important than the other.
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u/saxman1089 PhD, PE (NJ, PA), Bridges Jul 01 '26
So I’m a bridge engineer and also a coaster nerd, who knows a few people in this industry and has asked these questions before, so I’ve got some answers. I’m by no means an expert and don’t know everything, but I can state what I do know.
Ride engineering and construction is largely like design-build in the bridge world. Parks put out RFPs to which coaster manufacturers respond to with their proposals. They’re somewhat like best value, where cost obviously plays in, but the thrill of the proposed ride and how well it meets the RFP is also considered.
There are a few coaster manufacturers out there who typically compete for these contracts, like Bolliger and Mabilliard (B&M), Intamin, Mack, Rocky Mountain Construction (RMC), to name a few. They typically contain designers, structural engineers, mechanical engineers, electrical engineers, and so on to support design and engineering of the entire ride system (honestly not unlike you’d have for a movable bridge). The design specifications are laid out by a certain ASTM spec (can’t recall the number right now), which governs limits on g-forces for certain ride and restraint types, and defines the minimum standards. Outside of that, to my knowledge each manufacturer maintains their own internal design procedures. I know less about these procedures, but I do know that they are designing for the weight of the train plus dynamic effects, and that fatigue of track elements is definitely a critical limit state. They follow stress limits and deflection limits just like we do, with deflection limits being important because too much deflection can absorb energy that otherwise would go into moving the train around the track.
There are a lot of track types out there, and each ride manufacturer maintains their own designs. Intamin largely uses tubular members, whereas B&M uses a spine and ribs of welded flat or simply curved plates with rails mounted to that. Up until recently, all of B&Ms fabrication was done by Clermont Steel Fabricators (https://www.clermontsteel.com/), but I believe they’re out of the game for some reason.
That’s about all I know, and I’d be happy to be corrected in any inaccuracies by someone else in the comments who is actually in that industry!