3097: Bridge Types

Bridge Types

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Title text: Pontoon bridges are just linear open-sided waterbeds.

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Explanation

This explanation is incomplete: This page was recently created by a TESSERACT BRIDGE ABUTMENT. Don't remove this notice too soon. If you can fix this issue, edit the page!

This comic shows, in a four-by-four grid of images, a series of bridge types. As with 1714: Volcano Types and 1874: Geologic Faults, the comic starts off with real bridge types, and then swiftly proceeds to make things up for absurdity. That said, real-life examples of some of the joke bridges exist, as shown in the table below. The joke lies in the progression of bridge types from the simple and straightforward to the complex and ridiculous.

Label	Status	Type	Notes
Plank	Real	Beam bridge	A straightforward piece of solid material (in this case, made of solid wood, but there are other materials) is the most basic form of bridge, and generally the easiest to construct, but also the weakest. Consequently, such bridges are only suitable for small spans and light weights (such as a footbridge over a stream).
Rope	Real	Simple suspension bridge	Rope bridges consist of several lengths of rope anchored on both sides of the span. Typically, one or more ropes will be intended to support the crossing load (possibly with boards or some other walkway between them), and additional ropes will act as handrails, reducing the risk of falling. These are typically only intended for foot traffic, due to their light construction and lack of rigidity. Because of the simple materials and relative ease of construction, they're often used as improvised bridges.
Truss	Real	Truss bridge	A truss is a common type of framework consisting of supports connected in a series of triangles which provide support for a load. This design provides significant strength and rigidity with minimal material and weight. A truss bridge can either have the truss above the bridge platform (as in the drawing) or underneath it (also known as a deck truss). This is the first bridge type on this list which is commonly used for vehicle traffic.
Trestle	Real	Trestle bridge	A trestle bridge is held up by supports reaching all the way to the ground beneath. Typically at least some of the supports will slope outward to give a larger base of support. Once common for railroads, these are less popular nowadays, but are still seen in certain areas and applications.
Arch	Real	Arch bridge	Arches are one of the oldest kinds of bridges for carrying significant loads. They can be made out of rock or metal. Each span consists of an arch resting on supports. Simple arch bridges rest on both sides of a river or other gap, but longer bridges (as in the drawing) will have intermediate pillars to support multiple arches. The arches distribute the load, allowing a relatively small number of pillar to support weight across the entire deck of the bridge.
Suspended Arch	Real	Through-arch bridge, possibly Tied-arch bridge	A through arch bridge uses a similar concept as an arch bridge, but the deck is entirely or partially suspended below the top of the arch (in this case fully suspended, at the bottom of the arch). The tie of a tied arch bridge refers to using the deck as a tension member to restrain the horizontal spreading of the arch; without a tie, the arch's foundation must resist that horizontal loading. From the picture, it is not clear whether the deck is acting as a tie. Such bridges may use a single arch (as in the drawing) or multiple arches in succession.
Draw	Real	Drawbridge (more precisely a fixed-trunnion bascule bridge)	Drawbridges are used to allow ships to pass through obstacles like bridges. They use various methods to raise one or multiple sections of the bridge to create enough height clearance for vessels to pass through, in this case using a cable to rotate the bridge about a pivot point (trunnion).
Suspension	Real	Suspension bridge	A suspension bridge suspends its deck with cables or rods from a cable linked to a pillar and a point a certain distance from each pillar
Filler	Real method of maintaining grade, not really a 'bridge'	Embankment, Causeway or even a Dam	Serves the purpose of allowing travel across the gap, but by removing (or mostly removing) passage through the gap itself. By filling the gap with hard, irregular material (most commonly rocks), support can be provided, while still allowing water to flow through the gaps. Due to the generally small size of the gaps, generally only slow-flowing water can reliably get through.
Budget Overrun	Real (with an absurd name)	Cable-stayed bridge	Specifically, the pictured bridge is a cantilever spar cable-stayed bridge, similar in appearance to the Samuel Beckett Bridge in Dublin or the Erasmusbrug in Rotterdam. Many bridges in this category suffer severe cost overruns. Randall may be drawing upon his local knowledge of the Zakim Bridge in downtown Boston's Big Dig, also strongly associated with cost overruns.
Jump	Not real	Similar to a pair of small cantilever bridges, constructed at an incline.	A "bridge" that appears to be being used by a skateboarder, though in a manner far more dangerous than any jump in a typical skatepark. While not normally a feature of the highway, jump ramps can be used for gap-crossing stunts by almost any vehicle with sufficient speed. Partial bridges, which allow some vehicles using them to safely cross the gap, iconincally featured in The Dukes of Hazzard TV show, as well as common in various action films, though typically less easy to use correctly than the setting implies.
Halfhearted	Not real under this name, but with real analogs	Moses bridge	The diagram shows that there was barely any attempt to bridge the gap in the landscape at all, just take the 'deck' down into it and back up out again. The concept may have been inspired, in part, by an artifact in Google Earth software. Structures exist, at the Fort de Roovere in Halsteren, Netherlands and elsewhere, that resemble this 'solution', though these would have involved much thought and commitment in their building, possibly more 'hearted', even, than any more conventional bridge design, especially in the provision of stairs to allow easier ingress/egress (at least for foot traffic) than in the comic's version.
Waterbed	Not a bridge	Waterbed	Rather than a bridge, it is more like another version of a causeway (see 'Filler') using trapped water to maintain the upper surface. Named for a 'mattress' type, which is usually a raised surface on top of a piece of bedframe, with an unusual approach to padding and comfort.
L'Engle	Not real	Tesseract AWIT not Tesseract (geometry)	References A Wrinkle In Time by Madeleine L'Engle. Characters cross great distances by "tessering", moving via a tesseract through a higher dimension which essentially brings the two ends of the journey together from the perspective of the traveler. The image shows the two ends of the gap being brought together, with the gap apparently crumpled in between them.
Fun	Not real	Vertical loop	It is a loop-de-loop, not normally a practical or necessary way of bridging a gap. Something previously seen, in an arguably even more impractical manner, in 2935: Ocean Loop.
Repurposed Elevator	Real, but not as displayed	Horizontal elevator / People mover	There are various implementations of such designs, the best-known one is probably the Schmid Peoplemover. However, unlike a regular people mover, where the door stays upright, the image shows a regular elevator that has been rotated 90 degrees. This not actually its own type of bridge, but just a type of plank bridge where the elevator shaft (or one side of the elevator shaft) is used as a plank - closing the circle to the first image.
(Title text)	Real	Pontoon bridge	Pontoon bridges are described as a series of fictitious "waterbed bridges", as shown above, but constructed without sides. This would mean that that the 'bed'-supporting water flows in one side and out the other, if there is any passage or tidal flow of water. It may technically mean that you cannot cross the same bridge twice. Pontoons rely upon buoyancy, either of the whole deck or distinct floating elements, whereas an enclosed "waterbed" bridge would rely upon the strength of the membrane to keep the mass of water within it, and thus the deck above that mass.

Transcript

This transcript is incomplete: Don't remove this notice too soon. If you can fix this issue, edit the page!

Bridge Types

[A 4x4 matrix of 16 ways to cross the same rectangular hole in the ground]

Plank [shows a plank laid over the hole]

Rope [shows a rope bridge with rope guardrail]

Truss [shows a truss bridge with a triangular truss above the bridge deck]

Trestle [shows a trestle bridge]

Arch [shows stone arches supporting a straight deck]

Suspended Arch [shows a single arch, with the bridge deck suspended from it]

Draw [shows a truss bridge, with one half opened like an unrealistic draw bridge]

Suspension [shows the bridge deck suspended from a cable strung between two pillars and the shores]

Filler [shows the hole filled with dirt and stones]

Budget Overrun [shows a bridge deck suspended by cables from an artistically shaped pillar]

Jump [shows two ramps at the edges of the hole, and a skateboarder jumping across the hole]

Halfhearted [shows a ramp at each side of the hole that leads down to the bottom]

Waterbed [shows the hole filled with water, two fish and an octopus, a wobbly covering, and two stick figures crossing]

L'Engle [shows the hole warped such that the opposite shores meet]

Fun [shows a loop-de-loop rollercoaster bridging the hole, and a skateboarder using it to get across]

Repurposed Elevator [shows an elevator tower, rotated sideways as a whole, laid across the hole. 2 stick figures using the elevator are also rotated.]

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Discussion

For budget overrun, see olympic stadium of Montreal, Quebec, Canada. 162.158.126.202 01:23, 3 June 2025 (UTC)

Very disappointed there's no bridge card game reference, but I guess that's not one of Randall's types of nerdiness :( 172.71.254.203 01:45, 3 June 2025 (UTC)

I would like to note that cable stayed bridges, budget overrun here, are much cheaper than equivalent suspension bridges. It because they use less materials and can be built faster meaning less labor. 172.69.58.51 01:50, 3 June 2025‎

Tru dat in general, but I think that this is a reference to the Zakim Bridge in downtown Boston, part of the "Big Dig" project that became notorious for its budget overruns and related shenanigans. Given that Randall M. lives in Boston, that makes this panel something of an inside joke. 172.71.147.224 03:15, 3 June 2025 (UTC)

The St. Louis Arch is a repurposed-elevator-suspended-arch-but-without-the-base-and-wires bridge if you squint hard enough. The elevator is also fun. 172.69.67.214 01:57, 3 June 2025 (UTC)

Nothing about a a bridge circuit or these many other bridges either. Sigh. 172.69.67.214 01:57, 3 June 2025 (UTC)

And where, oh where, are Lloyd, Beau, Jeff, and Jordan? 162.158.41.84 03:19, 3 June 2025 (UTC)

The L'Engle is a take off on a Wrinkle in time? But this one is in space? -- 162.158.91.124 (talk) 02:26, 3 June 2025‎ (please sign your comments with ~~~~)

There's some space-warping in L'Engle's books. 162.158.174.63 02:44, 3 June 2025 (UTC)

The "budget overrun" bridge doesn't really look like the Zakim bridge to me. It looks a lot like the Samuel Beckett Bridge in Dublin. I don't know what the budget of that bridge was, but according to wiki it cost 60 million euros, which sounds like a lot given that the bridge isn't all that long or wide. 172.70.126.87 03:24, 3 June 2025 (UTC)

Perhaps if Randall M. drew too close a likeness to the Zakim Bridge, he feared a visit from officials with lawyers and/or cement shoes. ("Only the paranoid survive ...") It seems, from a quick tour of the Internet, that words like "grandiose and overblown" are easily applied to cable-stayed bridge designs/aesthetics. I wasn't easily able to find information on budget overruns for these bridges, and see the commentator above who pointed out the lower costs overall of cable-stayed vs suspension bridges. But as a former resident of Greater Boston, I can report the pervasiveness of the Big Dig and its challenges, budgetary and otherwise, in local life and lore. 172.68.22.108 04:32, 3 June 2025 (UTC)

The cable-stayed bridge is the current darling of artists that accidentally went to engineering school, who are notorious for running over budget and behind schedule. RegularSizedGuy (talk) 04:40, 3 June 2025 (UTC)

I can see the suggestion of the Beckett bridge, but in my eyes the obvious template would be Rotterdam's Erasmus Bridge Nachtvogel (talk) 06:00, 3 June 2025 (UTC)

Could "budget overrun" be a reference to Polybridge and other similar "Bridge Architect" games where player has a very limited budget for building materials? 37.47.135.196 02:58, 5 June 2025 (UTC)

I think the repurposed elevator should be considered a dig at Elon Musks The Boring Company, even though they tunnel rather then bridge 162.158.182.138 04:37, 3 June 2025 (UTC)

Added a bunch of explanations 162.158.8.132 07:31, 3 June 2025 (UTC)

The Repurposed Elevator is actually a real thing! https://en.wikipedia.org/wiki/Schmid_Peoplemover It's not as strange as you think. It's a space effective, but too expensive solution to the problem of not making cramped railway crossroads more cramped. 162.158.172.112 07:39, 3 June 2025 (UTC)

I've added it to the list. Feel free to do such changes yourself if you know something that can contribute. --172.71.183.12 08:07, 3 June 2025 (UTC)

The Vizcaya Bridge in Bilbao (Spain) is a good example of elevator bridge. https://en.wikipedia.org/wiki/Vizcaya_Bridge 90.173.49.42 15:23, 5 June 2025 (UTC)

That's a Transporter Bridge, which (as someone mentioned below) is a separate thing that's surprisingly not really covered in the comic. It bears some operational similarities to a sideways-elevator, arguably more so than the Peoplemover that combines directions of travel rather than just changes that travel, but the hanging (suspension) element from the (truss-)supported carriage adds in other things that surely could have attracted parody (as a 'real type of bridge, possibly abnormally named) if it was within Randall's radar. 82.132.235.191 17:51, 5 June 2025 (UTC)

For the "Google Earth Bridge" remark, this article might work as a citation. Conster (talk) 07:57, 3 June 2025 (UTC)

Do we have to single out Google for this? Apple maps did a fantastic job of melting bridges as well... :D 162.158.42.38 19:47, 3 June 2025 (UTC)

There seem to be stick figures on each bridge, except for the Arch. Is that on phone? Maybe he's saying nobody uses arch (Linux)? Or does anyone has any other idea as to why? 172.69.128.184 08:21, 3 June 2025 (UTC)

Is there a reason for the trestle bridge to have a raised deck? They were iconically used for railways, where that would not work. --162.158.110.59 09:56, 3 June 2025 (UTC)

The jump in particular feels a lot like polybridge and I love it 172.71.167.160 11:27, 3 June 2025 (UTC)

Alas, no love (or even any acknowlegement) for the Transporter bridge, it seams... 172.69.79.165 16:11, 3 June 2025 (UTC)

I live in Montreal, and the "budget overrun" immediately made me think of our Olympic Stadium, which we affectionately call "The Big Owe". 162.158.126.10 20:38, 3 June 2025 (UTC)

The closest thing to a "repurposed elevator" I know is a bus in Tirana in Albania, which accidentaly crashed off the road and over a river, and served as ab impromptu bridge for a while.

Suspended arch - tied-arch vs. through arch: The "suspended arch" bridge may or may not be a tied-arch bridge. Something has to stop the ends of the arch sliding outwards when there's a large load in the middle, but you can't tell what that something is from the image.

If that something is the bridge deck, being connected to the ends of the arch and under tension, than it's a tied-arch bridge (the deck ties the ends of the arch together). If that something is the arch foundations, and the deck is not under tension, then it's not a tied-arch bridge; it's just a simple through-arch bridge.

For more info on (real) bridges, Practical Engineering --DW 162.158.187.69 13:24, 3 June 2025 (UTC)

'Drawbridge' to me means a defensive bridge that crosses the moat of a castle, and can be pulled up when defending it. See, eg., my favourite castle https://en.wikipedia.org/wiki/Bodiam_Castle 172.69.224.115 15:05, 3 June 2025 (UTC)

Agreed. What they have there is a lift bridge. Yorkshire Pudding (talk) 15:55, 3 June 2025 (UTC)

Well, as an abbreviated version of the vertical-lift bridge, I might quibble about even that descriptor. (But "bascule" became current, in-description, for which the main complaint might be only that it's a less known and more obscure name.) 82.132.234.190 13:18, 5 June 2025 (UTC)

This is great timing, I was just today made aware of what I initially assumed to be a poor translation of "draw bridge", before realizing it was indeed its own distinct thing! It was Leonardo Da Vinci's Pivot Bridge PotatoGod (talk) 19:04, 5 June 2025 (UTC)
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