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Myths about construction
- deepsun 4y ago> Most construction projects are bid using a set of drawings and a book of specifications that include all the detail necessary to build them. I wish we'd have that in software development (hard to say "engineering" here).
- clintonb 4y agoYou can have this, if you practice waterfall. Just wait a few months for a product manager and designer to determine every last detail. I've experienced this, and it's not my ideal working condition.
- jaclaz 4y agoThe 4 points in the article are all well detailed/explained, but he has a few parts that are either missing or represent theory much more than practice (on a site titled practical engineering). >Will you build a bridge that’s inexpensive, but will have to be replaced in 25 years, or will you spend twice the money for more concrete and more steel to make it last for 50? Of course the second (which is what is actually usually done) the issue being that in real world after 50/60/70/80 years the bridge won't be replaced/repaired . > Most construction projects are bid using a set of drawings and a book of specifications that include all the detail necessary to build them. An engineer, architect, or both has gone to great lengths to draw and specify exactly what a contractor should build, often to the tiniest details about products, testing, and procedures. You can see for yourself; just google your city or state, plus “standard specifications,” and scroll through what you find to get a sense of how detailed contract documents can be. We go to that level of detail in defining the project before construction so that it can be let for bidding with the confidence that an owner will end up with essentially the same product at the end of construction, no matter which contractor wins the job. This is pure theory/wishful thinking, the regulations/norms/specifications are a needed thing (and a good one), but projects in reality (non-trivial ones) are largely "vague" or however not detailed enough (there are exceptions, of course, but while the project does make an even enough bidding ground it usually fails to properly detail the construction). It is of course a compromise of sort, making a good project would simply cost too much and take too much time. The assumption here is that all the architects and/or engineers are omniscient, competent, honest and have all the time in the world to think about the project and an unlimited budget. >But, the lowest bidder model is still used around the world because it generally rewards efficient use of public funds. No, the lowest bidder model is still used around the world because it is the simplest way to assign a contract without (the public manager) being responsible of the decision to award it to company A instead of company B.
- brudgers 4y agoExperienced design teams know what the unknowns are. The same is true with experienced builders. And experienced owners. Hence everyone at their umpteenth rodeo knows that the low bidder has a list of change orders developed while preparing the bid. And everyone knows how the owner will react. And everyone knows how good or bad the plans are. Almost inevitably, the plans are good enough, which is all that's needed.
- jaclaz 4y agoThere are usually three outcomes: 1) the builder changes are accepted at the same cost AND they are actually same or better than project 2) the builder changes are accepted at an extra cost AND they are actually same or better than project AND the construction goes over budget 3) the builder changes are not accepted, the project is (hopefully) executed as designed BUT the builder losing money will not complete it (or not complete it in time) with daily bickering on site AND an endless trail in Courts No, the plans - generally speaking - are not good enough.
- brudgers 4y ago[ US standard practice based ] A change order always changes the cost of the work. “Change order” and “cost of the work” are terms defined in the contact (often by reference) and come with implementation protocols. Once a person has been around the block a few times, they usually realize that the plans are not the construction, the design brief is not what the owner actually wants, and the contractor doesn’t build everything right. And the whole thing is about working together to get the building built in a way that favors getting the next project.
- jaclaz 4y ago>Once a person has been around the block a few times, they usually realize that the plans are not the construction, the design brief is not what the owner actually wants, and the contractor doesn’t build everything right. Exactly.
- 4y ago
- brudgers 4y agoThe reason construction workers stand around is because construction is a job-shop scheduling problem. [1] Hence, the optimum schedule is NP-Hard. The simplest solution to job-shop scheduling is to have slack in the system. See https://www.johndcook.com/blog/2008/10/21/what-happens-when-you-add-a-new-teller/ https://www.johndcook.com/blog/2008/10/21/what-happens-when-... [1] The contractor has other commitments. Each subcontractor has other commitments. Each material supplier has other commitments. It's true all the way down to the turtles being dug out of the ground. Having people waiting around for work to do, means that work can be done when it can be done. If the people aren't there waiting around, they are off at another site doing something that can be done for a few hours/days/weeks/months.
- eru 4y agoNP-hard problems are solved in practice all the time. The average instance of most NP-hard problems in pretty tractable. However, you are right that if you can get a bit of slack, you can get much more robustness and simplicity. But that observation about slack giving you robustness against perturbations applies even in scheduling (or flow) problems that we can solve in P. (To be fair to your position: the situation in continuous problems is not quite as bad as in discrete problems. I think the stiffness of some underlying matrix might give you an idea of how bad it is in the continuous problem (for some formulations where that makes sense).) https://en.wikipedia.org/wiki/Stiffness_matrix https://en.wikipedia.org/wiki/Stiffness_matrix
- deleted 4y ago[deleted]
- blt 4y ago> The average instance of most NP-hard problems [is] pretty tractable. I don't think the "average" and "most" in this claim make sense. If we could solve NP-complete problems efficiently, we would suddenly want to solve a lot of NP-complete problem instances that we currently do not even attempt.
- deanCommie 4y ago
- hristov 4y agoSo I read the last paragraph .... and I am thinking this must be the guy that designed the great millenium leaning tower of San Frencisco. "Civil engineers don’t always have the luxury of founding structures on the most stable of subgrades, so we’ve come up with foundations that keep structures secure on sand, silt, clay, and even floating on water. When the rain comes down, and the streams rise, and the winds blow and beat against our structures, they almost always remain standing no matter what the geology is below." Yep. "Almost always!"
- wodenokoto 4y agoI've noticed more than a few documentary style youtubers create a blog post with basically the script of the video. Is this for SEO purposes, or is it some sort of plan B in case of Youtube takedowns or is it an attempt to build an on-platform following? I like watching practical engineering, but I don't like reading video scripts, so while I understand that not everyone have their own preferences, I'm not really sure who this is for.
- japanuspus 4y agoI think they are just being nice to people like myself who much prefer to skim a wall of text than sit through a video of someone talking.
- dj_mc_merlin 4y agoDifferent strokes for different folks. I like watching practical engineering, but I'd rather just read his script quickly than have him narrate it.
- lamnk 4y agoYes, it is for SEO purposes and to build your own branding presence, and to be less dependant of other major platforms, in this case Youtube. 1. He probably already wrote a script for his video before production. 2. Speech-to-text is quite good and cheap nowadays. So, why not?
- ghaff 4y ago>Speech-to-text is quite good and cheap nowadays. So, why not? It's gotten comparatively good. But my experience with podcasts was that if I wanted a professional transcript I'd put online--as opposed to this is the general gist of the thing that's better than nothing, possibly just for my own reference--I'd get it done by a person. Wasn't worth my time to do the extensive editing that would be required to polish it.
- h2odragon 4y agoSatellite internet user: Video is effectively non-existent for me. Many hosts won't even attempt to serve connections at the "throttled" speeds we get.
- innocentoldguy 4y agoFoundations do not have to go to bedrock but they do need to be poured on tightly compacted dirt or the building can eventually sink and crack as the loose soil gives under the weight of the structure. If you watch a lot of home builders nowadays, they don't bother compacting, which is why people tend to have settling issues and cracking in their brand new homes after a few years. Another issue is pouring a foundation on clay because it will move whether it is compacted or not because it is around 40% water by nature.
- throwaway0a5e 4y agoThey don't bother doing more than a token effort at compacting because unless you have really crappy soil the foundation is likely strong enough to spread the load to enough soil to bear the weight without cracking. If foundations didn't need to do that job they'd have a lot less if any rebar. Basically the way they do it is cheaper and good enough.
- engineer_22 4y agoIt's not that simple. Even pile foundations don't always go to bedrock. In fact, most of the load bearing strength of a driven pile is in the friction along the length of the shaft, and the end-bearing capacity is a fraction of that. (It's intuitive if you recognize the surface area of the end of the pile is much smaller than the surface area of the sides of the pile) Soil calculations treat the soil almost as if it is a highly viscous fluid. In regards to settling - all structures settle. It is the structural engineer's job to design a structure that anticipates settling and mitigates strain in the rest of the structure. Clay is interesting, because it has a property called consolidation. If the clay is overconsolidated, that means the overburden pressure in the past is higher than the pressure on the soil now. If a clay is overconsolidated, it settles a lot less.
- TonyBagODonuts 4y agoLowest bidder is exactly how bids are won in my industry. The money is then made by RFIs and ECOs during construction. Petro/chem industry.
- isk517 4y agoThings work the exact same way in the prefab steel building construction industry.
- toolslive 4y agoI think the problem with "Roman concrete was better" is that archaeologists don't know about construction neither. You can see that as well when they estimate the duration of the construction for pyramids, or when they state 20 men were needed to move some block/stone/whatever around. A sleight tool like a pulley or a sled decimates the amount of manpower needed. Our ancestors might not have had our technology and knowledge, but they were as smart as we are.
- timbit42 4y agoDecimate means to reduce by 10%. A pulley or sled more than decimates the amount of manpower needed.
- toolslive 4y agoOxford dictionary: decimate: verb - 1.kill, destroy, or remove a large proportion of. "the inhabitants of the country had been decimated" drastically reduce the strength or effectiveness of (something). "public transport has been decimated" - 2.(historical) kill one in every ten of (a group of people, originally a mutinous Roman legion) as a punishment for the whole group. "the man who is to determine whether it be necessary to decimate a large body of mutineers" Sorry, I'm not a native speaker, I wanted to say: effort*=0.1. Thx for pointing this out.
- loudmax 4y agoFans of the Practical Engineering who would like to support the channel should consider pre-ordering a copy of Grady Hillhouse's book "Engineering in Plain Sight": https://practical.engineering/book https://practical.engineering/book
- smnscu 4y agoHere's one website I found that ships to the UK: https://www.bookdepository.com/Engineering-Plain-Sight-Grady-Hillhouse/9781718502321 https://www.bookdepository.com/Engineering-Plain-Sight-Grady...
- varjag 4y ago> If those construction workers stepped into any office building, they might see you hanging around the water cooler talking about your favorite YouTube channels and start a rumor that office workers are so lazy. Hell, am an office worker and would agree!
- throwaway23234 4y agohurry up and... wait
- kloch 4y ago> That’s why engineering exists in the first place. With an unlimited budget, my 2-year-old could design a bridge that carries monster trucks over the English channel for a million years. I'd like to see the math on this one. A million years is a lot of weather (including tropical storms that sometimes reach England), wars, meteors, earthquakes, climate variation, but especially a million years of weather. I suppose if you truly had an unlimited budget you could build it thousands of feet tall out of gold plated titanium mined from the moon.
- Cerium 4y agoUnlimited budget? A million years? That 2-year old is probably going to fill in the channel.
- woevdbz 4y agoWrt "people standing around", software is the same. You look at what it takes to ship a one-line change in any nontrivial, well-engineered website or app, compare the textual code change with all the work that goes in waiting for the compiler, code review, writing and running unit tests, integration tests, running release QA tests, testing in prod, and final release, and you got a lot of apparent overhead "waiting around". One difference is perhaps that the work is more amenable to automation and adding machines to replace humans, but even that (as in construction) has its limits.
- AtlasBarfed 4y agoMy #1 frustration with road construction: You effing barreled/cordoned off 8 miles of road but you're working on about .1 mile of it for a day? I would LOVE to hear the justification for that. While I'm loathe to credit accounting and economics for things considering how they've basically underpinned our societal direction towards environmental destruction, the issue is fundamentally misaligned incentives. Flat bid basically optimizes for monetary extraction of the "ownership class" from the government, and labor and the actual project are just annoying costs. Features + schedule + cost optimization would come from incenting labor and management. If workers got paid salary + a huge bonus for schedule then things would get a lot more efficient. Just look at your typical big enterprise, it's basically an authoritarian boondoggle, with only very long-range economic realities ever intruding, and the organizations themselves use monopolies to avoid those. It's these big hierarchies, with people carving out sub-domains and knife fighting over budgets. What probably should happen is internal competition: if you have several datacenters, let them compete against cloud offerings and other internal datacenters for customers. Don't organize them to a central org. Road construction may not be vanilla cookie cutter, but it should be a well known problem at this time, and frankly it should be an embarrassing parallel one. YOu have the route set down, you have the plan in place, you have the 8 miles of barrels done, you have phases (tear up, clear out, re-grade, pave) that can be pipelined. You can have teams do it in parallel in separate parts of the road to compete for incentives. But... that's not the point. The elephant in the room is that this is government revenue extraction, corruption in the guise of stimulus, and really, if we were totally efficient in road construction, we'd just have overbuilt the roads and sprawled even worse in the US. People hate on Musk, but look at the infrastructure his companies produced: Tesla has a national charging network, what, a half-decade and counting before anyone else? SpaceX has a nutso cheaper space launch capability (if starship even approaches its targets)? If Boring Company does the same for tunneling per their stated goals, it would be a trifecta. The first two really aren't magic by some modern day wizard. Tesla is about changing the world for the better with EVs, Musk probably gets crazy overwork from his staff with just that core missions. SpaceX is about getting humanity to the stars. Again, Musk doesn't have to whip people to get productivity, the mission and goal are the drivers: awesome cool space projects. I also recall a story from decades ago about an all-in-one road builder that would dig up, break down asphault, regrade, and then lay down the asphalt all in one package, and it would crawl along. It never got adopted because it would make things too cheap. Or maybe some labor/unions killed it. This was pre-internet, so it was probably an old wives tale, or maybe it required a nuclear reactor. I can't find it in google, which heavily favors recent stories. The lack of low-level robotics, specialized equipment, and other similar things after 20 years of gigahertz processors and robotics in manufacturing seems to point to industry resistance to productivity enhancement, which one would expect from a business that is fundamentally corrupt. At CES I've seen multiple strength-enhancement exoframes, and this was 8-10 years ago. It is insane to me that these aren't in extensive use and undergoing active economies of scale and year-on-year improvement. It's simply too easy and satisfying for the elite class to have manual laborers do pure manual labor, enhancing their relative perceived position in the great pecking order or America's class system.
- isk517 4y agoDon't know how things are done in Texas but I know in Alberta and BC most construction projects have a prequalification stage so while the lowest bid usually gets the job everyone that bids has already demonstrated they are capable of handling said project.