Form TBE-POL-01 · Edition 2026/09 · This document is provided in small type in the tradition of documents that nobody reads, so that it may be read by those who do.
Plain-language summary, offered without prejudice to the 47 Articles that follow: TheBridgeEng.com is a free, non-commercial reference site made by one bridge engineer in his spare time. You may use what he made. You may not blame him for what you do with it. The bridge data comes mostly from Wikipedia, Wikidata and Wikimedia Commons; the videos come from YouTube; the calculators produce preliminary estimates that are not a design. If you print something, a dialog will ask you to acknowledge this. That is the whole Policy. Everything below is the same thing, at length.
1.1 WHEREAS TheBridgeEng.com (the “Site”) exists because its author, Beomsoo Park (the “Author”), a practising bridge engineer, wanted a place where the things he kept looking up were already looked up; and
1.2 WHEREAS the Author has, over a career of more than twenty-five years spanning Korea, the Philippines, Türkiye and the United Arab Emirates, accumulated a quantity of bridge engineering notes, calculators, sketches, opinions and photographs that exceeded the capacity of any single hard drive to remain organised; and
1.3 WHEREAS the Site is offered free of charge, without advertising, without subscription, without a newsletter that you did not ask for, and without any expectation of return other than the faint hope that a bridge somewhere will be slightly better because somebody checked a number; and
1.4 WHEREAS a free thing given in good faith should not become a lawsuit;
1.5 NOW, THEREFORE, in consideration of the mutual covenants set out below (the Author’s covenant being to keep the Site running and yours being to read this paragraph), the parties agree as follows.
2.1 In this Policy, unless the context otherwise requires:
2.2 Headings are for convenience and do not affect interpretation, except Article 12, whose heading is also a warning.
2.3 Words in the singular include the plural; words importing the masculine include every gender; words importing bridges include viaducts, footbridges, aqueducts and, when the Author is feeling generous, culverts over 6 metres.
2.4 Where this Policy is translated, the English text prevails, except where it is wrong, where common sense prevails.
3.1 The Site is a personal, non-commercial reference. It is not a consultancy, not a journal, not a standards body, not an accredited course, not a software product with a support desk, and not a substitute for the person in your office who has actually built one of these.
3.2 The Author maintains the Site in the evenings and at weekends, in the time not taken by a full-time job, a family, and a commute. Updates therefore arrive irregularly and occasionally in the wrong order.
3.3 Nothing on the Site constitutes professional engineering advice in any jurisdiction. Where the Site says a thing is “typical”, “usual”, “common practice” or “what everybody does”, it means that it was typical, usual, common or universal on the projects the Author happened to see, which is a smaller number of projects than the phrase implies.
3.4 The Site does not know your bridge. It has never seen your ground investigation, your traffic count, your client, your budget, your approvals authority, or your contractor’s idea of a launching nose. Anything it tells you was written before it met you.
4.1 Every calculator on the Site (Section properties, Beam analyzer, Frame & truss, Spread footing, Anchor bolt, Budget estimator, FCM cycle, Girder depth, Span recommender, Expansion joint, Bearing pad, Post-tensioning loss, Method selector, Abutment sizer, Stay-cable catenary, Distribution factor, HL-93 envelope, Load rating, Pile capacity, Development length, Pier column, Prestress losses, Wind load, Scour depth, RC beam, and any calculator added after this sentence was written) produces preliminary, indicative, order-of-magnitude figures intended for feasibility, concept comparison, teaching, checking somebody else’s number for gross error, and winning arguments at lunch.
4.2 An Estimate is not a Design. A Design is produced by a qualified engineer who has read the governing code in the current edition, the project specification, the geotechnical report, the hydraulic study and the client’s brief, and who signs it. The Site signs nothing.
4.3 The calculators implement simplified methods. They assume linear elastic behaviour where real structures crack and creep, uniform soils where real ground is layered and surprising, symmetric loads where real trucks park on the edge, and code factors from a particular edition of a particular code that may not be the one You are bound by. Where two codes disagree the Site has usually followed one of them and said which; where it has not said which, assume it followed the one You were not expecting.
4.4 You shall not: (a) submit an Estimate as a Design; (b) submit an Estimate as an independent check of a Design; (c) attach an Estimate to a tender, a claim, an expert report, a variation order, an insurance notification, a court filing, a thesis, or a LinkedIn argument as if it settled anything; (d) show an Estimate to a client without the word “preliminary” appearing at least once per page, in a font no smaller than the number itself.
4.5 The Budget estimator in particular estimates budgets in the way that a weather forecast estimates weather. Construction cost depends on the market, the year, the contractor, the ground, the access, the season, the currency, the client, the mood of the steel mill, and events that have not happened yet. A budget from the Site is a starting point for a conversation and an ending point for nothing.
4.6 The Span recommender recommends. It does not decide. The Method selector selects among the methods it knows about, which are the ones the Author has met. If your contractor proposes a method the Site has never heard of, the contractor may well be right.
5.1 The Bridge Game (“the Game”) simulates the design and construction of a bridge on a randomly generated site using a simplified engine written by the Author. A grade awarded by the Game, including the grade “A”, is not a professional qualification, a licence, a certificate, a chartership, a continuing professional development credit, a job offer, or evidence of anything except that You played the Game.
5.2 The Game’s site conditions, events, costs, durations, floods, punch-throughs, base heaves, barge downtime, rail possessions and environmental permits are generated for instruction and entertainment. Any resemblance to a real project, a real client, a real river or a real permit officer is coincidental, except where it is inspired by experience, in which case the names have been changed to protect the Author.
5.3 The cartoon figure in the Game and in the Dialog is a caricature of the Author drawn with his consent. It is not a photograph of the Author at work, although the expression is accurate.
5.4 Scores may be verified server-side. Scores may also be lost when the Author changes the engine. The Author is sorry about this in advance.
6.1 Wikipedia, Wikidata and Wikimedia Commons. The Bridges atlas, the Rankings, the Failures library, the span data quoted in the Book and elsewhere, and the photographs shown with them are drawn from Wikipedia, Wikidata and Wikimedia Commons, projects of the Wikimedia Foundation and their volunteer contributors. Text and data are used under the Creative Commons Attribution-ShareAlike licence (CC BY-SA) and the CC0 dedication that apply to those projects; each photograph is used under the licence declared on its own Commons file page, which the Site displays beside the photograph together with the author credit, and links to. The Site does not claim any of it as its own. The Site does not modify the photographs beyond scaling. Where the Site’s automated checks found no free, credited photograph of adequate quality that could be tied to a bridge, that bridge is not shown rather than shown wrongly.
6.2 Data from those projects is as good as the volunteer who last edited it. Spans have been checked against the article text; years, types and coordinates are taken as found. If You find a bridge in the wrong country, with the wrong span, or with a photograph of a different bridge, the fault is in the pipeline and the Author would like to hear about it. A correction on Wikidata itself helps everybody.
6.3 YouTube. The Media pages list videos found through the YouTube Data API and show them through YouTube’s own embedded player. The Site stores only titles, channel names, identifiers, thumbnails and publication dates, refreshed periodically as the YouTube API Terms of Service require; it does not host, copy, download or re-encode any video. Playing a video on the Site is playing it on YouTube, subject to YouTube’s Terms of Service and Google’s Privacy Policy. The Author does not endorse the videos, their creators, their comments sections, or the advertisements YouTube may show before them.
6.4 Other sources. Daily briefs and field notes synthesise linked sources (news reports, official statements, technical papers, standards) in the Author’s own words and link to them; they do not reproduce them. Where a quotation appears it is short and attributed. The Bridge Data section is an index of links to documents published by others; the documents belong to their publishers.
6.5 Third-Party Data is provided under the licences of its respective owners and not under Article 7. If You reuse a Commons photograph You must comply with its own licence (usually: credit the photographer, state the licence, share alike where required). The Site’s credit line beside each photograph is there to make that easy.
7.1 Subject to this Article, the Author grants You a worldwide, royalty-free, non-exclusive, perpetual licence to copy, reproduce, adapt, translate, print (Article 12 applying), teach from, present, embed, quote and otherwise use the Materials, for any purpose, commercial or not.
7.2 In return the Author asks, and does not require, that You: (a) credit “TheBridgeEng.com” where practicable; (b) do not present a Material as your own original work in a context where that matters; (c) do not use the Author’s name, face, caricature or the Site’s name to imply that he endorses your product, your design, your bridge, your company, your candidacy or your argument; and (d) tell him, because he likes to know where things end up.
7.3 The licence in 7.1 is granted AS IS. Responsibility for any use You make of the Materials, including any consequence of relying on them, adapting them, misreading them, misquoting them, applying them to a case they do not fit, or forwarding them to someone who does any of the foregoing, rests with You and not with the Author. This is the sentence this Policy exists for. It is repeated in Articles 8, 12 and 33 in case You skipped to the end.
7.4 The licence does not extend to Third-Party Data (Article 6), to the Author’s name and likeness except as shown on the Site, to any trade mark of any third party appearing incidentally, or to any content on the Site that is marked as belonging to somebody else.
7.5 The Author may withdraw a specific Material from the Site at any time; copies You already made stay licensed.
8.1 THE SITE, THE MATERIALS, THE ESTIMATES AND THE THIRD-PARTY DATA ARE PROVIDED “AS IS” AND “AS AVAILABLE”, WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED, STATUTORY OR OTHERWISE, INCLUDING WITHOUT LIMITATION ANY WARRANTY OF ACCURACY, COMPLETENESS, CURRENCY, MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, NON-INFRINGEMENT, UNINTERRUPTED AVAILABILITY, OR FREEDOM FROM ERRORS, TYPOS, ROUNDING, UNIT CONFUSION, OFF-BY-ONE MISTAKES, STALE CACHES, OR OPINIONS THE AUTHOR HAS SINCE CHANGED.
8.2 In particular, the Author does not warrant that: (a) any Estimate is correct; (b) any Estimate is conservative; (c) any two Estimates are consistent with each other; (d) any bridge in the atlas is where the map says it is; (e) any video is still online; (f) any method in the guide is permitted where You are; (g) any diagram is to scale; (h) the Site will work in your browser, on your phone, behind your corporate proxy, or in the year You are reading this.
8.3 Some jurisdictions do not allow the exclusion of certain warranties. In those jurisdictions the exclusions above apply to the fullest extent permitted, and the Author apologises to the jurisdiction.
9.1 TO THE FULLEST EXTENT PERMITTED BY LAW, THE AUTHOR SHALL NOT BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL, EXEMPLARY OR PUNITIVE DAMAGES, OR FOR ANY LOSS OF PROFIT, REVENUE, DATA, GOODWILL, TENDER, CONTRACT, REPUTATION, SLEEP, OR FACE, ARISING OUT OF OR IN CONNECTION WITH THE SITE, THE MATERIALS, ANY ESTIMATE, ANY PRINTOUT, ANY THIRD-PARTY DATA, OR THIS POLICY, HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, EVEN IF THE AUTHOR HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES, AND EVEN IF THE AUTHOR WAS THE ONE WHO SUGGESTED THE SITE TO YOU.
9.2 If, notwithstanding 9.1, the Author is found liable for anything, his total aggregate liability to You for all claims in any twelve-month period shall not exceed the total amount You paid to use the Site in that period, which is zero, plus one (1) cup of coffee if You are in the same city, to be redeemed in person.
9.3 Nothing in this Policy excludes liability that cannot be excluded by law, including liability for death or personal injury caused by negligence, or for fraud. The Author has no intention of committing either, and would point out that he has no control over what You build.
10.1 You are responsible for: (a) checking every Estimate against the governing code, the project documents and your own judgement before it influences anything real; (b) engaging a qualified engineer, licensed where the bridge is, for any Design; (c) complying with the licences of any Third-Party Data You reuse; (d) your own equipment, browser, printer, paper, toner and eyesight; (e) anyone You give a Printout to; (f) reading the Dialog before pressing the button.
10.2 You shall not use the Site to: (a) attack, overload or scrape it in a manner that costs the Author money; (b) submit false scores to the Game (the server checks, and the Author is petty about this); (c) upload anything unlawful, where uploading is possible; (d) claim the Author reviewed, approved, checked or knows about your bridge.
11.1 You agree to indemnify and hold harmless the Author from and against any claim, demand, loss, liability, cost or expense (including reasonable legal fees and unreasonable amounts of the Author’s evening time) arising out of your use of the Site, your reliance on any Estimate, your Printouts, your reuse of Materials or Third-Party Data, or your breach of this Policy.
11.2 The Author will not actually enforce 11.1 against a student who used the Beam analyzer for homework and got a B. The Author was a student too.
12.1 When You attempt to print any page of the Site, whether by a Print button or by the keyboard shortcut, the Site shall first display the Dialog: a window bearing the Author’s caricature, a short statement to the effect that the Author bears no responsibility for what You are about to print or for what You do with it, and two buttons.
12.2 Pressing the button that agrees confirms that You have read Article 4, Article 7.3, Article 8 and Article 9, or at least that You would have if You had had time, and that the Printout is your Printout. The page then prints in the ordinary way.
12.3 Pressing the other button, the Escape key, or the background closes the Dialog and nothing is printed. This outcome is also acceptable to the Author.
12.4 The Dialog is decorative in law and serious in intent. Its absence (for example, because a browser blocked the script, because You printed from the browser menu, because You photographed the screen, or because You copied the number into an email by hand) does not make the Author responsible for the Printout. Article 7.3 applies whether or not the Author’s face was involved.
12.5 A Printout is a snapshot. The Site changes. A number printed in March may differ from the number on the screen in April because a bug was fixed, a code edition changed, or the Author changed his mind. Date your Printouts.
13.1 The Site does not require an account, does not ask for your name, e-mail, employer or telephone, does not show advertising, and does not sell, rent or trade anything about You. What it does measure is set out in 13.2.
13.2 The Site measures its own traffic in two ways. Cloudflare Web Analytics counts page views at the edge without cookies. Google Analytics 4 (measurement ID G-4E0LVDG5VB) runs in your browser, sets first-party cookies (the _ga family) to tell one visit from the next, and reports pages viewed, approximate location derived from a truncated IP address, browser and device type to Google, under Google’s own privacy policy; the Author sees aggregate reports, not individuals, and has not enabled advertising features. If You would rather not be counted, a content blocker, your browser’s tracking-protection setting, or Google’s opt-out browser add-on all work, and the Site behaves identically without it. The Site is served through Cloudflare, whose edge servers see your requests in the ordinary way that any web host does.
13.3 Your browser’s local storage may hold the state of the Game, your calculator inputs, your preferred units, whether You dismissed a banner, and whether the Site is installed as an app. That data lives in your browser and never leaves it unless You submit a Game score, in which case the score, the seed and the name You typed are sent so they can be verified and listed. You may clear all of it with your browser’s site-data controls, after which the Site will greet You as a stranger.
13.4 Embedded YouTube players and links to third-party sites are governed by those sites’ policies. The Author cannot see what You do there and does not want to.
14.1 The Site may be unavailable, slow, cached, partially updated, or mid-deployment at any time. The service worker may show You a page from last Tuesday while the network catches up; a hard refresh (Ctrl+F5) usually resolves this and, in the Author’s experience, most other things.
14.2 The Author may change, move, rename, redesign, retire, or accidentally roll back any part of the Site without notice. Bookmarks are held at your own risk. The Construction Methods guide in particular has changed its menu location twice in one week and may do so again.
14.3 The Author may amend this Policy. The revision date appears in the bar at the top. Continued use after a revision is acceptance of it, in the traditional legal fiction.
15.1 The Site contains errors. The Author does not know which ones, or he would have fixed them. If You find one — a wrong unit, a wrong factor, a wrong bridge, a wrong year, a diagram that shows soft clay in water-blue, a launching nose on the wrong end — please say so through the contact link. Corrections are made in the evenings and announced nowhere.
15.2 Feedback becomes the Author’s to use for improving the Site, without obligation to credit, reply, or agree.
16.1 “TheBridgeEng”, the logo, the ink painting of the bridge, the cartoon likeness, the Game engine and the Materials are the Author’s. Wikipedia, Wikidata and Wikimedia Commons are trademarks of the Wikimedia Foundation. YouTube is a trademark of Google LLC. Cloudflare is a trademark of Cloudflare, Inc. AASHTO, Eurocode, KDS, BS, JIS, ASTM and the names of every other code and standard mentioned on the Site belong to their respective bodies, none of which has reviewed or endorsed the Site, and one of which might be displeased at how often it is cited.
16.2 If You believe something on the Site infringes your rights, write to the Author with enough detail to find it, and he will take it down or fix the credit, usually the same evening.
17.1 The Author lives in one jurisdiction, works in a second, was trained in a third, and the servers are wherever Cloudflare put them. Any dispute shall first be attempted to be resolved by e-mail, then by a phone call, then by coffee (Article 9.2), and only then by whatever court has jurisdiction over a free website, if one can be found that wants it.
17.2 If any provision of this Policy is held invalid, the remainder continues in force, and the invalid provision is deemed replaced by a valid one that says the same thing more carefully.
17.3 This Policy is the entire agreement about the Site and supersedes every earlier note, footer, tooltip, banner and README that said something similar in fewer words.
18.1 Use of the Site does not create an engineer-client relationship, a duty of care specific to You, a fiduciary relationship, a partnership, an employment relationship, a joint venture, a mentorship, or a friendship, although the last is not excluded if You write.
18.2 The Author does not accept engagements through the Site. If You need a bridge engineer, You need one who can visit the site, and probably one who is licensed where it is.
19.1 The Site works in SI units unless a calculator says otherwise. Where imperial units appear (HL-93, some American bridge data), they appear because the source did. Conversions are performed by computer and are correct to more decimal places than the input deserved. A pound is a force where the code says so and a mass where it does not, and the Author has stopped arguing about it.
19.2 “Span” in the atlas and Rankings means the main span measured between supports, as far as the source allowed that to be determined; total length is a different number and is often the one in the headline.
20.1 A bridge’s year on the Site is the year it opened where known, otherwise the year it was completed, otherwise the year construction began, otherwise the year somebody on Wikidata thought was right. Roman bridges are dated to the nearest emperor.
21.1 The ink painting behind the home page depicts an inverted-Y pylon of a cable-stayed bridge with mountains, a pine tree and, at the edge, a small house. It was made for the Site in the manner of East Asian ink-wash painting. The bridge in it is not a real bridge, has not been designed, has no drawings, has not been checked for wind, and would need a wider deck. It is there to be looked at, faintly, while You read; if You find yourself looking at it instead of reading, the Author has made it fainter twice already and can do so again.
21.2 The calligraphy in the original painting gives the Author’s name and his profession — bridge engineer — which is the most accurate statement on the Site.
22.1 The Author tries to keep the Site usable with a keyboard, with a screen reader, on a phone, and on the office monitor whose colours were last calibrated in 2014. This Policy is an exception: it is deliberately small. A larger version is available by pressing Ctrl and + a few times, which the Author encourages, and which does not void anything.
23.1 You may link to any page of the Site without asking. You may not frame the Site inside a page that charges for it, or inside a page that suggests the Site is yours.
23.2 The Site links outward liberally. An outward link is a pointer, not an endorsement, a guarantee that the page still exists, or a promise that it says today what it said when the Author read it.
24.1 The Site is not directed at children, but a child who wants to know why the cables on a cable-stayed bridge get steeper near the pylon is welcome, and the answer is in the Book.
25.1 The Author is not responsible for failure to update, host or maintain the Site caused by events beyond his reasonable control, including acts of God, acts of Cloudflare, acts of the Wikimedia API rate limiter, power failures, undersea cable damage (a bridge-adjacent topic he follows with interest), strikes, pandemics, a Windows update, a new baby in the building, or a deadline at work.
26.1 Reserved. Insurance policies always have reserved articles, and the Author did not want the Site to feel left out. These Articles may be filled in a later edition with provisions about the Failures library (which describes real events in which people died and which is written with that in mind), the Rankings (which change when a longer bridge opens, usually in China), and the Data section (which indexes other people’s documents and takes them down on request).
33.1 For the avoidance of doubt, and because it is the point: You may use what the Author made. What You do with it is on You. The data is mostly Wikipedia’s and Wikimedia Commons’; the videos are YouTube’s; the numbers are estimates; the grade is a game; the face in the Dialog is asking You to remember all this before You print.
34.1 The Author is a bridge engineer. He has been one for more than twenty-five years, which he mentions not as a credential but as an explanation for the tone of Article 4.
35.1 He began in Korea, where the first bridge he worked on taught him that the drawing is not the bridge, the bridge is not the drawing, and the ground is not the borehole. He has since worked on and around bridges in the Philippines, in Türkiye, and in the United Arab Emirates, on the design side, the construction side, and lately the owner’s side, which is the side that asks why both of the other sides are late.
36.1 His particular interest is cable-supported bridges — cable-stayed, suspension, extradosed, and the arches that borrow from them — and the things that make them behave: cable geometry, construction-stage analysis, balanced-cantilever erection, and the way wind treats a deck that was drawn in still air. He has spent an unreasonable fraction of his life thinking about how a stay cable’s length is set on site and why it never quite matches the number in the report.
37.1 He keeps a list of bridges he wants to stand under before he stops travelling. The Bridges atlas began as that list and got out of hand.
38.1 He writes in Korean and in English and considers neither of his versions of this Policy final. He reads more bridge papers than is healthy and watches launching videos the way other people watch football.
39.1 He built the Site because the reference he wanted did not exist: one place with the span tables, the quick calculators, the erection methods with pictures, the failures with their real causes, the atlas of what has actually been built, and the sequence animations, all free, all linked, none behind a login. He built it in the evenings with the help of tools that did not exist when he started his career and that he regards with the same mixture of gratitude and suspicion he reserves for a new contractor.
40.1 He believes that a bridge is the most honest kind of structure, because everyone can see whether it stands. He believes that most bridge failures are failures of attention rather than of knowledge. He believes preliminary estimates are more dangerous than no estimate when they are printed on good paper, which is why the Dialog exists.
41.1 He is a member of the professional bodies one would expect and lists them on LinkedIn, where he also posts the daily briefs and the occasional forensic write-up of a collapse, in both languages, at an hour that his family regards as unreasonable.
42.1 He has opinions about integral abutments, about the correct number of decimals in a span, about form travellers, about the word “iconic”, and about whether a deck should ever be launched over a live railway without a possession. Some of these opinions are on the Site. The rest are available over coffee (Article 9.2).
43.1 He can be reached through the contact link in the footer. He replies to corrections faster than to compliments and to compliments faster than to invoices.
44.1 He would like the Site to outlast the enthusiasm that started it, and this Policy is part of that: a free thing survives longer when everyone understands what it is.
45.1 He thanks the volunteers of Wikipedia, Wikidata and Wikimedia Commons, without whom the atlas would be a list of names; the people who film bridge construction and put it on YouTube; the colleagues on three continents who taught him what is on these pages; and You, for reading this far, which almost nobody does.
46.1 He is, in the painting, the name on the left.
47.1 By using the Site, printing from it, playing the Game, reusing a Material, or reading this sentence, You accept this Policy. By closing this window You accept it too, but more efficiently.
This Policy was drafted in the style of documents printed in 6-point type on the reverse of an insurance schedule, out of affection for the genre. It is nevertheless meant: the disclaimers, the licence in Article 7, the data attributions in Article 6 and the privacy statement in Article 13 describe how the Site actually works. If any part of it is unclear, the short summary at the top governs. If the summary is unclear, write to the Author.