Construction

* See also Primary_Construction 
* See also Columbia Construction (dubious)
* See also TechnicalDrawings (Diagrams)
: Environment ( Rapture Standard Pressure )
: Cement and Reinforcement (Concrete IS Your Friend)
: Defining_Rapture
: Design_Spec_index
: Rebar
: Ryanium
: Prefabricated Sections
: Monolithic Structure
: City Foundation
: Tunnel Boring and Constructs
: Utility_Distribution
: Transportation
: Buildings_and_Building_Blocks
: Decorations Of Rapture (Art_Deco)
: Wales_Brothers
: Interior Detailing 
: Viaducts
: Rapture IS A City
: Watertight Doors and Bulkheads
: Undersea Windows
: Having Too Many Very Tall Buildings IS Pointless/Impractical
: Utility_Stuff in Rapture
: Windows
: Streets
: Lighting
: Securis And Other Doors
: Sewers in Rapture
: Rapture City Layout
: Flexible_Game_Terrain_Design
: Buildings and Building Blocks
: Airlocks
: Rapture_Construction_Domes - Phase 1 Construction
: Repairs and Maintenance
: Lighthouse Island
: Rapture_Cityscape
: Geography
: UnderWater_Construction
split out the 'Too Tall_Buildings' stuff 
 "Skyscrapers were machines that made land pay, and were built ( like in New York City ) on some of the most expensive real estate in America." - A Famous Quote
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Planning And Building A Monumental City :
Not something just 'thrown together'. A whole Construction Process which had to be carefully Managed.
Planning - surveying and tracking at every step to have things fit cohesively.
Coordinated building efforts - so many things that can go wrong in a very difficult and dangerous environment. 
Huge efforts of Preparations so that the Construction Process could proceed.
Ryan had access to the Skill and Knowhow, and as an Industrialist had the Vision and Planning ability for organizing such a thing.
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That looks like WELDING being done there. If you are going to use pre-fabricated girders, then they should also be welded ( Technology available since before 1900 - if not 'rolled' in the mill up on The Surface ).
Ignorant Cliche game details is something to be avoided.
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How Would You Really Build Rapture : 
You are building something under the Sea where the outside water pressure at just 600 feet down is something around 280 lb per square inch ( that is 20 times the air pressure on YOU right now ). You are constructing a building structure that is meant to hold out all that water pressure. It would be (most practically) assembled 'building by building' in-place from prefabricated ferro-concrete sections, being linked together, embedded/anchored to the seafloor, sealed, and pumped dry, and then the interior details added. There would be thorough testing for water containment BEFORE the interior is installed and being readied for human habitation.
The structures would be designed to have sub-sections which can be emergency sealed independently. All of Rapture would be built to minimize the destruction by any single failure (leaks/breaches). That makes it simpler to find and repair initial and subsequent lesser leaks ( pressure integrity failure ).
There is great difficulty in doing construction IN water. Some pre-fab sections would be fully pre-manufactured/tested/proved on the surface - like Self-contained Airlocks systems. Windows, which have to handle extreme pressures, are heavily and carefully imbedded in the building sides - which would be easiest done ahead of time up above water. Pressure Door mechanisms likewise can be modularized and be ready to install with some confidence of their reliability. These door seal mechanisms have to all work completely immersed in water. Airlock-type arrangements would be required to allow personnel and equipment to pass inside any flooded section to do the work of emptying/clearing them of water -- work which would all have to be done in high pressure diving suits. 
Initial pumping out of the structures would require embedded pipes/valves/fittings pre-built into the building sections. Large pumps would be portable or connected centrally in clusters of buildings. This system would be planned to be later be used for utilities, but is needed first for the initial installation. 
Check/Cutoff Valves of various sorts would be integrated with all the pipes to fulfill the required operations ( and any later ones ). Air at slightly higher than Sea pressure would be fed in to force water from the sealed section's volume. Stopcocks will be open at the bottom allowing water to flow out quickly, and they will eventually be sealed off permanently. Large Pumps would drain/vacate the last of the water from the lower parts of the sealed compartment ( These sections would all have 'sumps' designed be to 'drain' naturally to handle the inevitable seepage ). The interiors would be cleaned out of debris and saltwater remnants at this point. For Pumping operations handling constant seepage, smaller local pumps would service the local collection sumps. 
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The initial underwater pressure sealing process should have been sufficiently redundant to disallow failure at this step ( a project should not be delayed by failures that could have been prevented ), as well as for decades afterwards. But nothing is perfect, and defects are always to be expected and thus planned for.
How do you find a leak while you are initially pumping out the section ? If it is a large leak you will not be able to vacate water below the point of the leak. Small leaks can be found by letting off the feed-in air pressure, pumping air out to lower the pressure and the water will flow in visibly at the failure point(s).
Fixing such leaks is not always straight-forward. Because of the thickness of the structural walls the path of the leak through the structure materials is not always apparent. Inspecting the outside wall when a leak is in progress may locate the exit points of the leak. The leak should be fixed from both the inside and outside to maximize the repair confidence. The cause of the defect should be found so that future material and processes can be amended to prevent future problems. Rapture would have gone thru an evolution in building methods, eliminating bad practices/problematic material, and substituting improvements ( for Ryan this also would bring cost effectiveness, because fixing things "after the fact" usually is far more expensive the correcting/preventing the problem ahead of time ). I would propose that one of Ryan's prior businesses had been UnderWater_Construction, so that the techniques and processes required for Rapture could have a long leadtime of development ( Money, Time, Expertise, Development ). 
The Wales_Brothers architects apparently (at least once) did not make enough allowances for potential defects and got a bad reputation for leaky building This may be a reference to architect Frank Lloyd Wright, whose design for more than one grand building was found to be terribly leaky. which lost them customers/clients to the point of bankruptcy. Grand designs are pointless if you drown while trying to appreciate them.
Special materials for sealing leaks were previously developed for the undersea structures built by Ryan Industry's Oil and Mining divisions ( offshore platforms and such ). High strength epoxies can be injected/pushed/drawn far into cracks to seal them. Cement/reinforced concrete can be reworked and patched. Extremely bad defects can have the modular section completely removed and replaced ( if detected before real permanency ). Irreparable sections may be sealed and bypassed so as not to have a whole building become a 'Write Off'. Bad Practices can be identified and abandoned.
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General Proof :
Let it be understood that quite fundamental things in-game shown ( WHAT THE PLAYER saw in the Game ) illustrate what the Place Rapture was -- FAR MORE than some dodgy/biased/twist-warped Audio Diaries, and self-serving monologues from Atlas, etc ... Yes, it is 'artists license', but implies substantiality for what was built there.
Rapture by the time of the game ( ~1960 - if not years after that in BS2 ) over 15 years old. SO much of it is shown to STILL be 'in one piece' ( not flooded, lights are still on, inhabitable, etc ... ). Thus, it could not have been Constructed in any slipshod way, and when built had effort put into making it solid enough to hold out the water and remain intact -- built with forethought to each of many potential failure points in Construction covered.
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==How Rapture Was NOT Built== 
Fan Proposal/Misconception : "Rapture would have been a small industrial mining, steel and construction town at first. This industrial site/town would have built the entire infrastructure needed as the city was built in large factory hangers with large airlocks to get the prefab sections onto the prepared seabed. The ocean floor mud could have been refined into concrete, as the mud would contain micro fossil carbonates etc. A power plant would have been one of the first things needed to be built, to supply power to the mines, mills, construction works and factories. It is highly unlikely that a whole city could be built on land and then sunk down into the ocean, even in prefab form."
Rapture's Buildings Built How ?? - Reality versus Magic Fiction :
A Building-making Factory 'On the Ocean floor' ?? IT has to be constructed first, and the buildings/sections are quite large. The Factory has to be even larger and capable to constructing many building chunks at once to meet the city construction schedule.
Underwater Steelworks ? - No, the right ores are not available locally. Fuel neither. All would be sourced on land.
Move millions of tons of Steel girders/structures from the Land ? - Rapture's buildings are not constructed like land Skyscrapers. Rapture's buildings are massive thick-walled pressure-proof structures. ( Think Rebar instead, AND most of it being delivered already embedded in prefabricated components )
Undersea Factories to Build Buildings ? - Only Near the Ocean Surface - Assembling components/parts made elsewhere ( inexpensively on land ). Assembly deep underwater would cost 10 X as much. ( So limit how much 'deep assembly' is done. )
Concrete Made At Rapture ? - Not made IN the Ocean - Materials sourced on land ( Most raw materials just won't be available 'locally' ). Much Concrete would be used as Prefab components shipped to Raptures build site. Some is used below to affix the buildings to the seabed. ( Aggregate to add Cement to might be obtained locally. )
Secrecy Issue ? - Building a city the size of Rapture, even in prefab building form, on the coast, would have been noticed by the government. Getting all the prefab buildings out to the Ocean Build Site on barges in good weather, sink them and finish them underwater ( a whole city ) without being noticed would be highly unlikely. Available Transport ships (used to transport thousands of miles) had limited size. 
Barges/Freighters ? - Not large enough. Simply towing such large building structures on the Open Ocean would be near impossible. The cost and effort involved in moving 'a city' from the land to the seabed, hundreds (thousands) of miles away would also be counter-productive/impractical. Multi-floor building chunks for even small buildings ( think 50 ft x 50 ft ) are too large to ship. 
How Then Was It Built ? - The realistic way to build an underwater city would be to make one or more large prefab component making factories on land (in America). ( As inexpensive as it gets. ) These Smaller Parts and Components then would be transported via Freighter, and would be assembled at Rapture's location.
Assembled on the Ocean Floor ? - Far easier to do it near the Ocean surface, where workers are above-water ( with some via Scuba/Diving gear at shallow depths ). Then these assembled Building Shells ( or large chunks of buildings ) are lowering down to be installed in their seabed Foundation.
Foundations ? - Start in Solid seabed rock locations, dug out, to fit the lower edge of the lowered buildings. Building Cemented into place afterwards. Deep Depth Work is done largely using semi-automated/remote-controlled machinery ( MOST is NOT done by diving-suited workers ). Addition anchors and piles embedded if required ( ex- for taller/more-stressed buildings ).
The Assembled Building Shells, growing upward, then are Joined where the building is placed.
More Work Below ? - There is still ALOT of work to do down below. The mentioned Prefab and Assembly is just the structural shells of the buildings, and those have to be joined to the foundation and made water tight and pressure resistant. There are the interiors to be installed once they are pumped out and dry and cleaned. There then are many miles of pipes/conduits/venting/cabling to be installed and connected. Lots and lots of machinery (ex - utility systems) need to be installed in the buildings. All the carpentry/plastering work has to be done to the inside. Note - these are skilled specialist jobs.
Riveting ? - There was That Picture ... ? - Riveting metal was largely replaced by Welding between the two World Wars.
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How Rapture Was Built So Fast 1946-1951 :
Majority of Rapture would be built of Standard Construction Parts/Components :
* Required to bring the costs down - structural components and construction parts were mass production on The Surface.
* Common parts allowed an effective stockpile of spare parts, simplifying organization and distribution. A massive well planned and executed undertaking.
* Those 'parts'/components could be recombined many ways to produce very different structures. The reinforced-concrete method used throughout Rapture could be very fluid in the structures produced, as long as its bulk was not a problem. Unitized wall sections made of Ryanium ( or Ryanium-Steel composite ? ) were a bit less flexible, but also could be recombined may ways. Combining the two methods helped overcome each's limitations.
* The Cosmetic effects put on over the basic structural form were not much restricted. Structurally non-critical decorative additions could be applied freely.
* The functional utility systems would be built to common standards and parts and applied in standard ways.
* Rich people could afford more customized designs. If they had more specialized requirements the building could be fabricated specifically with many more customized components.
* Building Decorations ( towers ontop, etc ... ) do not have to be Pressure Sealed, and thus can be built much less strongly ( strong enough to only hold up their weight and resist water currents ). If you look at the Fontaine Futuristic building, you can see about half the height of that building is actually decorative towers built to be impressive, but not to contain habitable area. Many of the other 'Skyscrapers' similarly have a big chunk at the top that does NOT have to be built as sturdily as the living (interior) spaces below.
* Add the basements sunk into the thick concrete Foundations or solid rock. They also don't require ultra strong building walls to keep the ocean's pressure out. Later, many more tunnels and caverns were built that needed no 'building' at all to expand the City's living space ( Ryan saw the need for more open space after the initial complaints about the City's "closed in" feeling. )
* During the so-called %27civil war%27, while the city 'went downhill' in its organizational cohesion, things would be repaired in a more cobbled together/irregular/inconsistent manner. That would be what we saw in BS1 (and years later in BS2).
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Sizing Rapture ( How Big Would/Could it Be ??? ) :
Placing my extended level maps onto my map of Rapture ( derived from the BS1 Austen Bathysphere map ), it looks like some of the game's outside views might not be too inaccurate, distance-wise at the scale I arbitrarily chose. The game levels are largely spread (sprawl) horizontally, and take up good chunks of the seabed. We really don't go up/down more than a handful of floors anywhere. The Skybox views do show alot of buildings/skyscrapers with dozens of floors (some 40+). Unfortunately some Skyboxes in the window views are REUSED on different level maps, and are even REPEATED if viewed out opposite sides of the same building, all giving the impression of more tall buildings than should actually be there.
The only reason to build "tall" Real World was to be impressive (adopted for the game). Some window scenes are quite Manhattan-like, but the 20000 population would have trouble filling that many large expensive buildings. Some of the building seen are 'tall and thin', and THAT would severely limit the usefulness of the interior spaces ( Some towers may be empty space or utility system space and not be habitation levels like was done in the Real World where cities had restrictive height regulations web search "Height Restriction Laws"). Decorative towers and such often may be a third of the height of the building -- the Fontaine Futuristic 'tower' is an example ... 
Rapture (City) may be about 3 miles by 2 miles, but it has empty areas in the middle which may be because of unusable seabed/seafloor conditions - not stable/solid enough to place buildings on.
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Consistency of Construction in Rapture :
Issues of engineering such a place as Rapture is to have things built to some Minimum Standards, which are still more than enough for it to hold together for decades in the hazardous environment. Since a 'break' in one place could flood a large area, sub-standard construction would NOT be allowed, and proper containment mechanisms would be Standard to protect extended areas ( and the people in them ) from any break/failure.
There would be regular maintenance, but none that is particularly costly - more of identifying unexpected problems before they happen/get-worse.
And sorry, some tinfoil-like plane sections floating down thru water into the structure ( even a glass viaduct ) would NOT be enough to do any significant damage. There is that 280 psi pressure pressing in on these structures already, and they are built like military bunkers to withstand significant forces.
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Metal : Facing Plastic Deformation and Strain Hardening and Buckling ? 
One hopes that most of Rapture was placed largely out of direct ocean currents - protected by the undersea volcanoes crater side, though you still get some turbulence eddies with some pockets in the terrain contours that would amplify those. Surging water puts a further strain on the buildings. Water is like 800 times denser than air, and a few miles per hour (mph) current's force then is multiplied by that factor. All those tall and thin buildings the game artists liked showing are problematic, with the leverage along that length to multiply the bend forces at the buildings base ( the tall spires/towers with their minimal interior space possible, might be decorative ( Art Deco did that alot ) and top 1/3rd of the structure more like a 'wiffle ball' to let alot of the moving water pass through with less resistance.
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This Property Is Condemned - Enter At Your Own Risk ! :
How many early buildings in Rapture had to be abandoned in the first few years because the construction was insufficient ( The Wales Brothers designs leaked - requiring costly/extensive retrofitting of pumps/drains ).
"Let the Buyer Beware" ('Caveat EmptorCaveat Emptor - The principle that the buyer alone is responsible for checking the quality and suitability of goods before a purchase is made) isn't too good when hundred of people can die because of one catastrophic defect, so some building standards had to be used/enforced ( and if you routed City Utilities through the building it had to meet a number of minimum requirements ). More companies than just Ryan's constructed the buildings. So he could not, in those cases, self-enforce the standards. Eventually better/improved designs were created and used ( largely before any majority of Rapture's building were built ). Some of the 'ruined' buildings we saw from a distance in BS1/BS2 may have been that way (derelict/condemned) for a very long time - back to the 1940's.
Such buildings might have other ( less safety restricted ) uses - where the sound structural elements could still be useful, despite other defects. [Sinclair]] bought more than a few for pennies on the dollar for such alternate uses - One a fish farm where being open to the sea made a leaky structure irrelevant ( and he 'made back his costs' just salvaging building components first ).
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Rapture's Construction History : 
* Rapture 'founded' 1946 (work started) to 1952 ( city 'finished', shortly after with most population in place ).
* Construction did not stop around 1952, as additional buildings were added for companies and industrial sites were developed.
* Atlantic Express was started immediately in 1946 and hauled a great deal of construction material and personnel to most of the main city locations. It kept getting extended to each new city section as Rapture grew.
* The Metro Transportation system along with the Street structures ( containing their Trolley lines ) were planned early ( when the city was in planning stage ) also. The Bathysphere system ( one of the biggest being Austen Co ) was added a little later. Consolidating the Trolley companies and interconnecting them ( and expanding into newly built sections ) finally made them much more useful than the Atlantic Express ( and stole alot of AE business ).
* Jet Postal (Pneumo) added/completed 1956 ( system presented operational on Rapture's 10th anniversary )
* The tunnel boring machines, once finished with primary projects ( ~ 1951 ), were available for expanding the farming districts and industrial sites ( and were 'for hire' for many other uses ). Additional housing space would later be built in Tunnel Systems.
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Early Rapture, First Construction :
Light House - Not just that big tower, but all the machinery/infrastructure used for construction and transferring all the materials from ships downward. Artificial Island built up at that point of the old volcano's old crater edge.
The Work Domes used to initially house the construction worker population. Tram system tunnels interconnecting domes and worksites. 
Location of phase 1 Project Organization at Welcome Center
"Hotel Monsenor" - first real accommodations - important for staff operations - better accommodations for workers ( months in dank barracks doesn't help with morale ). Expanded transportation allowed workers from all over to use this facility.
Geothermal power - Once Hephaestus Core #1 came online then construction moved into full swing ( no longer dependent on limited power generators running off barges on the surface or on Lighthouse Island ). Expansion of the 'grid' -- was mainlined first to Welcome center.
Atlantic Express lines hauling massive amounts of construction materials and workers efficiently ( city Construction actually wore out alot of the initial system ).
Quarry & Cement plant ( most of what you see of Rapture IS Concrete ) First thing Rapture was self-sufficient producing ( the huge amounts of cement would require huge numbers of additional boat shiploads across the Atlantic ). Aggregate for the concrete could be produced locally.
'The Sinker' and Pre-fabs -- Whole building sections had been constructed elsewhere ( at Ryan-owned facilities ) Much easier to build them near/at surface and join them together down below ( the structural walls you see in the extended maps ).
Submarines and Automation - more high-tech than grunt labor. Lots and lots of machines did much of the work. Guys in diving suits only did some of the trickier construction situations.
Resource production needed creating/building before any large number of people could arrive. The air systems were the first priority ( not just for people to breath, but also for all the industry systems ).
Initial manpower for all the support systems preceded the primary population, who had to have a working/stable 'City' environment ( They don't mention enough about the preparations for all this - It could NOT just be something thrown together ).
The MMORPG can have Flashback sequences for the Players to experience those early days while Rapture was being established.
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Rapture Founding : "Established" on November 5, 1946 :
"Established", that is what ? Laying the keystone of the first real building ?? Or when the first viable section was ready to start accepting immigrants ? ( It is probably NOT the construction start because the Novel has preparation work starting immediately after the A-Bomb use in Aug 1945, and possibly the survey being finalized upon the locations found previously. ) Sufficient infrastructure and accommodations to handle a normal existence is actually fairly substantial.
All kinds of preparations would have had to be made before occupation to make it livable, much more than just for housing work crews who are finishing interiors.
The Novel story indicates that Ryan gave the 'Green Light' within days after the A-bombs dropped on Japan (Aug '45) (( I prefer the story to allow as much time as possible for things to be accomplished, and not be like Infinite BS or its DLC where things get developed ( Wave of the hand ) far too quickly. ))
The City site's geothermal formation would have been critical, so the location survey results would have been achieved from long before ( when Ryan already had started advancing his dream ), and the concept was being proven technologically to provide the city's power ( Perhaps done on Iceland which has many Geo-Thermal sites ). Interesting that it would have to been done during WW2, or even before that. ( We Can have more backstory on this in the MMORPG. )
Enough construction was completed ( probably the area around the Welcome Center, and Hephaestus was operational ) to hold a ceremony declaring the city ready to start accepting the in-flood of its intended population.
Construction seems to have been underway most of that year, and the initial stages were already started in 1945 ( VJ-day August 15 after the A-bombs fell, was when Ryan made his decision to build Rapture ) with the Surveys for a location and start of marshaling the resources/technologies it would need.
One of the commemorative displays would be moved to the New Rapture City Center as part of the 'back to the old days' efforts.
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How To Build A Rapture-like City :
Not as 'Big' Chunks'. Building a city the size of Rapture, even in prefab building form, on the coast, would have been too noticeable to the government/public. Getting prefab buildings/large sections towed/floated out to the Ocean site in good weather, sinking them and finishing construction underwater without being noticed would be highly unlikely. The cost and effort involved in moving a city ( hundreds/thousands of miles through stormy waters ) constructed on land and down to the seabed, and anchored, would be counter-productive.
A realistic way to build an underwater city would be to use distributed prefab factories on land to make small (generic looking) components, which could be easily transported by railroad, then freighter. Mass production techniques could be fully utilized, and the components deceptively appearing usable anywhere for the (1946) post-war building boom.
Rapture would start as a construction camp, still largely connected up on the Ocean surface (Lighthouse) for power, and the materials being transported down to the building site. Prefabrication of building modules is easiest at (and above) the surface. This construction would be located in the shallowest area near the Lighthouse, where surface workers/machinery and conventional divers could operate with the least complications. The prefab building sections would then be sent down to position onto the prepared city foundation to be assembled ( built using maximal automation and the fewest possible men in high-pressure suits ). Once sealed and dry, the insides would be added by workers in the normal atmospheric pressure, the workers housed in the earliest finished buildings ( like 'Hotel Monsenor' ).
Post 1952, the later expansion additions could use prefabrication from facilities in Rapture ( no surface facilities used ), with airlocks large enough for components and some reasonable sized building modules. Elsewhere, I've elaborated about tunnel building being used (cheaper) for this second city building phase, which minimized use of 'buildings'. The Hephaestus complex would be one of the first things built up, as its power facilitated further construction, powered the new city, and eliminated the need for power sources up on the Ocean surface.
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If Ryan had (to make his fortune) an Industrial business building Oil Drilling Rigs ( or something similar like Maritime/Port Construction ) that would help ( definitely, with the 'knowhow' to construct Rapture ). But he could also just have the 'parts' built for land 'building construction' in one city redirected and shipped by water ( many parts too big for Railroad Train transport ), and just have them keep going out to sea using his fleet of freighters.
It depends how large the prefabricated building sections are. Sections of wall panels, the huge compression struts which cross between external walls to oppose the water pressure, etc... They are still only 'pieces' and can look fairly generic ( so with not 'too many questions asked' ... ).
Now THOSE sections can be pre-assembled into larger assemblies on-site at Rapture ( That Lighthouse means there IS a shallow zone where IT is possible to do alot of work at/near the surface or partially on land ). You could then either lower those down to assemble into the City's buildings, or smaller buildings structures could be almost entirely assembled at the Surface. Work at less than 100 feet depth can allow use of normal diving/scuba equipment, while at "City Depth" (600 feet ?) the same work requires really complex diving hardsuits - and ADAM doesn't exist at this point to bypass that need). It is much more efficient to largely build at/near the ocean surface.
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City Growth Display :
Evolving Diagram of the City ( on View in City Hall - '3D' ) showing the phases of Rapture's growth, damage done during the Civil War and afterward and now ( the reason for the display ) its rebuilding/restoration progress.
The Citizens are encouraged to move the new 'Chain of Progress' forward ... Not only to Rebuild, but to Exceed ...
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How to Build Rapture (Really) :
One hopes that Rapture was largely out of the path of direct ocean currents - protected by the undersea volcano's sides, though you would still get some turbulence eddies amplified by pockets/contours in the terrain. Water is something like 800 times denser than air, and the force of a few mile-an-hour current's force then is multiplied by that amount ( physically, a 1 mph current is equivalent to an 800 mph wind ). All those tall and thin buildings ( the game artists liked showing ) are problematic, with the leverage along that length multiplying the forces trying to bend them at the buildings base ( There is a reason why deep oil drilling rigs are spindly and have numerous guy-wired anchors ). Some Tall spires/towers with minimal interior space possibly might be decorative ( Art Deco did that alot ) and the top 1/3rd of the structure may be constructed more like a 'wiffle ball' to let alot of the moving water pass through with less surface force.
So then, sturdy and squat is the rule -- unless you want something which has to be expensively overbuilt to withstand ocean currents. In any case, the Tall building in Rapture could/should have alot less floors than the pictures/views indicated ( many images look like 40-60 floors ). Next to squat ordinary buildings, ones with 20 Stories could still look impressive. Too tall and you get the tops scraped off by icebergs or the foundations needing to be too deep for practicality to withstand water surges.
Cement structures don't bend much ( cement/concrete itself has little tensile or shear strength ). Because of the pressure, Rapture's buildings cannot be like the steel girdered modern Surface buildings which can sway yards in a high wind (and earthquakes). Plastic Deformation and Strain Hardening and Buckling aren't so much an issue with solid/rigid structures which just don't flex much (vertically at least). Compression support with the distribution of outside forces would be the long term solution for the city's building mean to last for many decades. Horizontal geological movement can be handled by semi-flexible connections BETWEEN buildings and by safeguards in the connecting structures.
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Building on the Surface - Not Quite So Many 'Construction Workers' ... :
Logical to do prefabrication where it is easier at the ocean surface, or even back on land, and not at some deep sea depth where complications (and costs) multiply many-fold and special equipment is needed for everything - deep diving hard suits are NOT used by 'Joe-Blow' workers.
Less and less writer excuse for so many ordinary 'construction workers' to be allowed into Rapture. They are used in the plot as the excuse for all the 'poor' 'downtrodden' 'out of work' people who cause so many issues ( self-destructive ADAM_Addled druggies didn't fit that narrative ). If they largely worked the Construction on the surface/on land, then any such really never had to see Rapture ( and could be prevented really from knowing where/what it was, 'So they wouldn't reveal the secret' ), and also did NOT have to be required to live there. Most of the 'Construction Workers' who worked below then would be more likely to be machine operators and technical people - versus low-skill manhandling grunts/gophers. The ones let into Rapture would also be told that construction would eventually end, and they had better be ready to take up new professions ( City Maintenance doing similar type jobs could absorb more than a few ).
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Competition - Rapture Has It ... :
Was there only one construction company ( Ryan Industries/Seaworthy Construction ) in Rapture, or would it be more likely there were competing ones, set up by various Rich investors ( which Ryan likely would want so that he didn't get 'stuck with the bill' for everything and would have more funds freed for all the other things Ryan wanted done ).
* Rich people would understand the advantages of 'ownership'.
* It is likely that several times as much money as Ryan possessed was used to build Rapture.
* Ryan still would have coordinated the know-how/personnel/equipment/materials, but others would be landlords and owners besides him.
* A program could also have been organized for workers to have deductions from pay to go towards residential ownership in the completed City and manufacturers would pay 'up front' for their facilities to be built.
The 'Vanishing' would have been matched with a large selloff of worldly assets of the various people going to Rapture. They came over an interval of years, so had time to divest themselves without resorting to 'fire sales'. Many would invest in goods and equipment and materials to bring with them as well as possessions appropriate to their lifestyles.
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Steel (and other Stuff) Is Hard To Make At The Bottom Of The Sea :
SORRY, NO underwater Steelworks - there is no workable iron ore. For such, you also need large amounts of coal to turn into coke (purified carbon), and the right kind of limestone. Those materials for steel would have to come from the surface. Ditto for most other metals that would be used. A cement works might be possible, but only for the later self-sustained self-sufficient period. Before that it would still be far cheaper to get the huge quantity of the required materials from The Surface.
Blast furnaces/foundry/rolling mills just adds to Raptures overhead/costs - anything used to produce the building materials on the Ocean floor ITSELF has to be constructed first. You would have to ship all the ship Iron Ore/Limestone/Fuel/Etc ... from the surface, as most raw materials just wont be available 'locally' ( there is far less bulk to the finished product ).
So sorry, no big Steel-Plant -- the ores adequate to make steel ( and the limestone and coke and other fuel ) all come only from limited places on land to be able to practically make steel cheaply in large amounts ( costing 10 X to 100 X as much IS prohibitive ). So you might as well produce it Up there in a US Steel Company plant and ship it ( which BTW will take a fleet of ships and not just 'The Olympian' for all the stuff Rapture took to build ). That IS ALOT of Shipping ( and Thousands, of miles to Rapture ) ? Shipping an even larger bulk of raw material required to make Steel would be EVEN MORE expensive to get it there. Besides the difficulties of getting a steel-plant actually working down IN Rapture ( and steel-making requires ALOT of air, and the installation gets VERY hot and the process generates LOTS of very hot noxious exhaust ).
The amount of pre-made Steel/Aluminium components ( Rebar, reinforcement frames around windows ) is small compared to the amount of concrete that would be used in Rapture's construction. The aggregate ( rock/sand added to the cement ) might really be the only locally available component material. The fuel used to make cement is also one of the bulky raw materials ... you'd have to ship that in ( Hephaestus power might in time be sufficient for a smaller operation ). Cement, like the Steel, is much easier/cheaper to make at VERY efficient cement plants on land, with optimal materials/process/cost.
There still is a great deal of construction work to do down below. The building prefabrication talked about so far is just the structural shells of the buildings, and those have to be joined to the built foundations, embedded and tied together, and be made water-tight and pressure-resistant. There are the interiors to be installed once they are pumped out and dry and cleaned. There are many miles of utility pipes/conduits/venting/cabling to be installed and connected. Lots and lots of machinery that needs to be in the buildings. All the carpentry/plastering/masonry/finishing work has to be done there to create the fancy interior spaces.
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Ryan : WE MAKE IT OUT OF ALUMINUM ( Ahhh .... NO ) :
* Aluminium is Stronger than Steel by weight, but weight really is not an issue ( for airplanes it is )
* Aluminium did cost far more than Steel ( quite a bit more ) .
The huge quantities would be needed to build Rapture and that would probably get far more Government Attention than Steel being used.
Only part of the structures is of metal ( we saw most building sides that are NOT metal ), and the bulk would likely be Concrete ( A good material as you need Compression Strength to withstand the water pressure ).
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Steel and cement/concrete would be more easily missed/hidden within America's economy than Aluminum ( and materials could be transshipped from around the globe, too ). Aluminum also costs a whole LOT more. Aluminum, as per that BaS told Audio Diary blurbage, was really just pointless/illogical/ignorance.
The game story of Rapture being prefabrication with Aluminum ( and as complete buildings ), even with some cover story for 'ahead of its time' tech supposedly used by Ryan for deep-sea drilling rigs and such - That metal is not really practical/safe/secret. With the skyscraper-like multitudes of windows typically shown in the window view skyboxes, it would not be fooling anybody.
Those Windows just for show ? Many I suppose could be lighted fake/faux windows, added just for looks ( and lower cost/complications ) as small windows ARE problematic to have in the ~8 foot thick concrete walls. But that is wasteful and has too many problems. The MMORPG will simply just show them as they 'would have to be' ( windows fewer and further apart, and many fewer floors on less tall buildings ).
The Rapture book author mentioned Ryanium ( Star Trek's Scotty's Transparent Aluminum ?? ) which probably would be needed ( in its transparent form of course ) for anything even close to the big (ridiculously huge) windows ...
Maybe windows could also be made of something like 'earlier-than-real-world' Polycarbonate (a plastic). Materials exhibit their best support strength when curved/arched, which few of the windows were shown to have in-game (the MMORPG can fix that -- Smaller round windows, maybe of thick Pyrex, or some equivalent of later 'Gorilla Glass'.)
The game's setting might Use fictional technologies, explaining parts of Ryan's billionaire wealth might be based upon ( high-energy electrical/plasma processing /whatever ). But the game should have nothing too far advanced/futuristic ( no carbon-nano-tubes, etc ... )
See Melted Basalt ...
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Structure Idea - Ratture To Have MORE Arched Roofs :
Curves for arches who's physical design structurally transmits external surface water pressure via Compression down into the ground(seabed) or into/within the rest of the structure. Walls would/could also employ the same for sideways 'force transmission' ( It is why you see the 'fillets' in my level map wall corner angles ). 
Many of all the squat buildings ( versus the tall thin ones we rarely are inside of, in-game ) that I've done maps of could have their roofs be of a curved shape ( and the insides can still have flat looking false ceilings - you need space up there for venting and such anyway ... ). Many buildings can have a honeycomb of walls to supply this same support of the buildings exterior. Larger open areas need to have their ceiling ( with all that water pressing on it ) supported, and the wider the space is, the greater the problem of leverage increasing the forces applied against the structure, and thus the more massive the support has to be.
A Stadium I theorize for Rapture ( where else can you play Football ?? GO SEA BULLS !!! A poster in BS1 about there being a football league and games.) would have a massive open interior, and probably the thickest walls of any building. It would require huge external buttressing to help hold itself up while having the huge open interior space.
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Rapture NOT Quite Not New York City ( Where Things are Wedged Together ) :
In cities, the Base of a Skyscraper is often irregular, matching the existing city street frontage ( ex- Chrysler building, NYC ), and then have multiple floors that shape-transition into the tower which is rectolinear/squared. Rapture had lots of space, so this really shouldn't have been require as much ( would even retroactively added buildings not simply be placed a little further out from a 'prime' location because of the short distances and low density in Rapture ).
Another reason for most buildings 5-6 stories high in Rapture - You can cast them in one piece and not have to stack-joint pieces - the higher they are (10+ floors) the higher ratio of interior is used for transport/utilities and the more substantial/complex the foundation.
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Columbia (in Infinite BS) was a glombed together MESS - giving credence to my (REDO-appropriate) theory that it was transdimensionally 'Merged' to exist that way ...
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HumanConstructionDiver.jpg
Stairdesign.jpg
AEdoors2.jpg
AEdoors.jpg
Rebarr.jpg
Rebar4.jpg
Modernskyscraper.jpg
File:Streetq.png|Streets of Rapture
Internationalstyle.jpg
1952equipment_imagine600ftunderwater.jpg|On the surface you could use this
File:HooverWaterSide.jpg|Huge Concrete Project
Designnn.jpg|Looks Rapture-ish - More Tubular structures makes sense
Concretearch.jpg|idea for proper support of all the viaducts
THISisaViaduct.jpg|A real world 'viaduct' between buildings
Mercurysuites.jpg|Tall buildings being advertised
Con1911.jpg|Concrete fabrication was a mature technology by Raptures start
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Real Skyscrapers Construction - Differences :
Terrestrial buildings (ones on 'The Surface') have I/L beams (steel girders) used as the support skeleton, originally riveted, then welded and pinned together. The primary structure supports itself mostly against gravity - holding up the building's own weigh (and its contents), and keeping from toppling over in the wind/earthquakes. The walls are simply fastened to the steel skeleton, and only need to block the weather and hold the windows.
Rapture buildings are more like a submarine's hull. They need to hold out the significant the water pressure ( from all sides, every opening ). If you've seen a WW2 movie of a submarine being depth-charged and diving deep and the pressure starts crushing the hull - that depth condition is what's facing Rapture's buildings.
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A Process for Rapture building construction includes graduated pressure/Immersion Testing ( to prove there are no defects/weak points ), and to allow corrections BEFORE anything further is risked. Rapture Construction processes were improved over time ( and other early city buildings would be retrofitted for various discovered weaknesses ).
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Many of the Real World building designs, which Rapture buildings mimicked, were shaped by City Zoning Laws and Ordinances which limited height and building shape profiles. They eventually had exceptions for 'Towers' which were a fraction of the area of the building layout and often made allowances for higher unoccupied (decorative) extensions. To prevent blocking out sunlight the buildings had 'setbacks', with the sides stepping inwards as the height increased. In cities, Buildings were built higher to maximize their capacity upon very expensive city real estate. The added high cost of those tall buildings meant few of great height were built.
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Metal Buildings in Rapture ? NO. :
needs a diagram showing opposing forces in compression
A Thin skin/wall of metal ( a couple of inches thick ) with that much pressure HAS to be closely/systematically supported behind its shell surface. That support eventually has to be conducted all the way to the opposite side of the building to provide the needed counterforce ( at 600 feet depth that's 280 psi - ~20 tons of force on EVERY square foot ON ITS surface ). Floor plates would be used to transmit all that force consistently across the building. Ceilings/Floors of the shell require similar support.
You shouldn't think it is the same as your conventional Surface skyscraper girder construction. Those only need to hold the building up against gravity ( most forces in just one direction (vertical), with minor support diagonally and horizontally ). These undersea buildings have the water pressure massively pushing from ALL angles simultaneously, and it all has to be supported completely. 
Thick spidery girders would intrude into interior spaces, no matter what, with any kind of all-METAL support. Steel might be stronger (in tensile strength) and require less material, but it has to be immediately supported AND transfer/transmit the force of the water pressure into the fabric of the building. With metal struts, that means a complex web of supports in all directions, through and across the structure, obstructing much of the interior space ( A bad thing when you like big cavernous interiors ).
That also is ALOT of steel, which is more complicated/expensive($$$) to connect/build than mass reinforced concrete would be. (Consider - that they did NOT build Hoover Dam ( nor almost all dams ) out of steel girders).
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Blocky is It (Rapture Construction) :
Why Are My Rapture Buildings (layout diagrammed in my Amended_Game_Level_Maps ) so Block-like and Well Anchored to (and into) the Seabed ? ( Look at those maps with their 'basement' and 'foundation' levels ... )
I've drawn the buildings with Monolithic shapes because their structures are mostly walled with thick Reinforced Concrete. ( Any bits that stick out, if they include inhabited space, NEED a similarly thick structure to hold OUT all that water pressure - making them typically blocky ).
Many buildings would thus be shaped fairly SQUAT to maximize internal living space, in ratio to the external walls. Buildings would also be sturdy/solid because you don't want them to sway, shake and shimmy in ocean currents (( Like Columbia would have been while floating in the air - Booker would be vomiting in no time, and throughout the city you would find Barfbags for sale in every vending machine. Watch the early scenes were you walk past buildings bobbing up and down. )). Less height also means less force leverage, from Ocean currents bearing upon building surfaces, which unless strengthened could otherwise topple the structures.
You also want different building sections to stay attached to each other ( most were prefabricated in parts, assembled in whole sections up on the surface ) to maintain proper seals. Even when flexible joints are used, you don't want them shifting out of alignment and exceeding their rated sealing ability. So standard large FLAT interface surfaces are common in the design.
If you look at the ORIGINAL interior level plans, and superimpose their floors ( within the same 'level' map set ), you see too many irregular bits sticking PAST other parts of the floors above/below. The external walls NEED to encompass ALL floor's existing dimensions. Those irregularities are (on my maps) simplified (filled out) into more basic contiguous flat surfaces and boxy volumes. Simple volumes/walls/joints are also simpler to construct.
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Monolithic Building Construction ( Buildings Build Like WW2 German Submarine Pens ) :
 see https://en.wikipedia.org/wiki/Lorient
For the common exterior structural construction. Inside there can be alot more varied styles/patterns.
Face it even in the MMORPG Players don't go outside much to warrant fancy exteriors ( and the plainness of most of the buildings will highlight those that are 'built for show'. )
Maximizes interior space ( the part that makes money and where things get done ) for the amount of structural materials used ( the place is claustrophobic enough as it is ... ) Square blocks ( though may try to have a few more cylindrical designs the Solo games largely lacked ).
Simpler to construct ( without alot of twisting odd shaped walls to fit ). Easier to prefabricate regular shaped sections.
Stronger configuration to solve the problem of the sea pressing in on all sides, especially for the common concrete construction ( which the majority of Rapture was built with ).
Buildings are actually built as 3 dimensional 'cells' as the whole structure is part of the system to push back against the deep water pressure, which at 600 feet down is about 280 lb/sq in - pressing on every surface inch of the building. The force pressing on the opposite side of the building is transmitted thru the interior 'cell' structure to counter the opposite sides surface force. Concrete is quite strong when used for such 'compression' structures. It is not strong at all in tension, so that situation is avoided.
There is some flexibility, in that the much thinner Ryanium wall structures ( particularly needed for large fancy aquarium style windows ) could be mixed in with the plain concrete construction when needed ( the extra expense of the Ryanium components prevented more extensive use. ) Ryan's supply of money ( and that of the other investors ) was not infinite, and to build the size of city he wanted, plain blocky cheaper cement construction worked fine for its majority.
Manhattan skyline - here looking as it did at the end of the 1920s/early-1930s when the Crash happened. Further building was largely slowed/stopped ( The "Empire State Building" completed in 1931 was called the "Empty State Building", and was largely unoccupied throughout the Roosevelt Depression ), and then WW2 shut down most new non-war building construction.
Rapture appears built to resemble this New York City cityscape, but in 1946 it largely would be as it appears here, and NOT with all the later changes of the Post-War boom. NOTE - Most buildings there are quite short - six or less stories high, leaving the few towering Skyscrapers to stand out.
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Rapture Prefab 101 Segments and Adjustability :
Some buildings would be built up in large sections close to the Ocean surface ( preferable efficiency with sub-assemblies completely out of the water ). Modular, so as to 'join up' with the least amount of (expensive/difficult) work being required down below. 
Other more irregular sections ( connections between the largely prefab sections ) would be build in place ( largely of smaller versatile prefab parts being 'fitted' ).
Seals between the sections were critical. When the main building sections were placed and well seated, then the more adjustable segments could be placed and secured ( and tested and verified ).
Much Hydraulic concrete was use to permanently fill and affix the connections between the building segments.
A scheme for adjustable Viaducts with standard sections down to small fractions of inches of exactness were created to fill this need.
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Hidden Places, 'Out Of Sight Out Of Mind', 'Skeletons in the Closet' :
Only a fraction of the city (Rapture) was visible to you ( when you played the games ) with many over and under parts ( behind ceilings/floors/walls ). We can have all those utility spaces and access hatches leading to many new adventures in the MMORPG. The outside views showed much overdone 'arty' building views, but you never got to see those interiors.
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Visual Eye Candy :
Nazi prisoners during WW2 being transported via New York, on seeing the NY skyline (literally) thought it was some Hollywood trick ( There being virtually no skyscrapers in Europe at that time ). So Rapture with its similar skyscraper skyline views might be impressive to those whom never saw the like.
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Rapture's Standardized Construction :
Even for other 'Investors' ( rich people who ALSO paid to build Rapture ) construction - the Primary structures 
all had to meet significant safety standards and compatible interfaces/interconnections to the rest of Rapture 
(portals/passages and utilities).
Standardization helped minimize costs and ease construction difficulties ( interchangeable/modular parts at several component levels made Surface Construction more efficient/cost-effective ).
Rapture was largely built within the same period of time, and so wouldn't reflect as much eclectic differences which most cities accumulated over many decades of regrowth and rebuilding.
Internal construction/decoration could vary significantly within the primary/external structure ( which was mostly what we saw playing the games ). 
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Building Structures vs Water Pressure:
* Water depths ( like ~600-800 feet at base of buildings )
* Looking at those square Rapture buildings ( real submarines pressure hulls are built as tubes which withstand pressure in a simpler way ).
* Tall buildings would need huge interior support struts every couple of floors to support the huge forces of pressure pressing inward on those flat walls ( pressing in at 280 psi).
* Fortunately concrete can withstand alot of Compression Force.
* Add Ryanium Rebar (Reinforcement Bars) - using all the lower-than optical quality stuff generated through the production process for extra strength ( conventional Rebar materials can also suffice ).
* Some of the tall buildings have thick support columns outside alternating with the windows which could distribute the forces between the interior compression struts running crosswise between the exterior walls.
* Blank walls would be be solid reinforced concrete more than a few feet thick.
* All Large picture windows are the most problematic, as the stress in the middle of the panes has to be passed out to the windows edges and such leverage forces ( trying to bend the pane in ) increases linearly with the windows span size.
* Many of the skylight windows are barrel vaults which at least take some of the pressure forces as compression ( like an arch or tube would ). Curved glass windows might be used in various places (if small).
* Exposed metal should be brass or stainless steel to avoid corrosion ( and eventual structural failure ). Many large pipes/girders were more conventional steel but required Zinc treatment to avoid corrosion.
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 "Cut Out The Middleman" :
A project like Rapture, with known large quantities for materials and time for pre-planning, would allow for more optimal procurement prices. Maintaining close connections to suppliers also can allow better consistency of quality ( as well as deliveries ). Ryan, with his industrial-scale experiences, would certainly be able to use such methods to minimize expenses.
The specialized construction of Rapture's quantity of unique building components would call for setting up companies to develop and implement the manufacturing processes. Facilities would be fairly large as concrete casting and proper curing takes more than a month - and that for the quantities of components to build a whole city.
Locations would be chosen with the subsequent transport in mind. Additional sites would be acquired, assisted by new availability as war production largely ceased and properties came available.
Supplies for building Rapture would require diverse materials, of all quantities and qualities. Consider : That whole "Something In The Sea" Online Flash Promotional Lutwidge story contrivance could simply be considered some minor supply intermediary for secondary interior materials ( manufacturing did not seem to be part of the arrangement ). Many Rapture Construction materials would require custom techniques and significant care, not something done in a half-arsed manor by outsiders. 
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Uh, Aluminium ? ( ... These Burial At Sea Writers Really Are Ignorant ) :
This BaSx declaration stating that Ryan would build using Aluminium to build Rapture instead of using Steel ...
That game reference to Aluminum was some weird (and wrong) things to have Ryan say - 'The Steel supply will be watched so I'll use Aluminum ...'. IT IS RETARDED/IGNORANT. Aluminum was FAR more expensive, and was watched even more closely as a resource. REALITY : Millions of tons of Steel, in a postwar boom, is far easier to lose-track-of/to-obscure/sidetrack/divert ...
(( Making that DLC prattle Nonsensical Lazy-writer gorp - Something not even needed for the story - but some game 'dressup' added to try to imply tech aspect - but then being horribly botched. ))
Alleging that Aluminum was to be used instead of Steel is faulty anyway, because you couldn't really afford to build the whole City out of metal. Remember, that this dim statement is ALSO from BaSx, which is DLC. (( DLC = Generally Sloppy Writing, which has to (VERY) often be "Taken with a Grain of Salt" as to what is stated within it. Much detail is often not well Thought Out in typical DLCs )). AND the same limitation goes for using Steel, which practically would be mostly used for (Rebar) reinforcement for the Concrete - which made up the vast majority of the city construction material.
https://handymansworld.net/what-is-rebar/
Steel still would be 'it' ( for REBAR reinforcing of concrete ), if properly material-engineered. That might be somewhat advanced for that earlier city construction period though. Ryan likely would have underwater construction in his Industrial Empire -- HE BETTER ALREADY HAVE THAT, FOR HIM TO EVEN THINK OF BUILDING RAPTURE (an 'underwater' city).
Aluminium CAN work a bit better as rebar (reinforcement bars) in concrete exposed to Salt Water, than using Steel rebar. Water does seep slowly through concrete and can cause internal corrosion and structural weakening -- doubly bad if it is Salt Water. SO for the building shell, Aluminium helps a bit for the concrete rebar ( when ordinary Steel Rebar can still be used in the interior supports which are far less exposed to salt water ).
To handle the 'salt' environment factor, there are problems (anyway) requiring special concrete formulation and rebar plating/coating, whether you use Aluminum or Steel ( elsewhere I've had Basalt (rock) fiber rebar mentioned ). Ph control additives, not mixing different metals, and other types of corrosion prevention can also be done. Long-term, Aluminum does only a little better.
Aluminum has stress deformation/breakdown problems which might be less an issue for this, if for physical flexing/temperature differentials which would be minimized with massive concrete construction (8+ feet thick structural walls, and internal reinforcements which wouldn't flex). You would hope Rapture was somewhat sheltered, ie- located INSIDE a volcanic crater (but it still would get some turbulence, even when out of direct ocean currents). Better with most buildings being quite a bit shorter than those Manhattan Skyline-like views ( looking good for a window game view is that height's only reason ). The top half/third of many of those tall buildings might even just be for show (Art Deco tower ...) and might be more flexible ( not concrete/pressure-tight, and with ship metal corrosion techniques applied there ).
Concept Art pix? showed curved buildings ( resists water currents more ), but we got shown mostly squared/rectangular in the game views.
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Producing Aluminum metal takes a huge amount of electric power to refine/convert it from its source minerals (ie- Bauxite) which when mined are of a special high purity.
In WW2, Aluminum was mass produced for the military. After the war, mass consumer production was only just starting. Various entrepreneurs were LOOKING for commercial uses for the war produced production capacity.
During the Korean War (1950-1953) America was back to controlled production for this important military material. Steel was produced in incredibly huge amounts, so was not as controlled.
And Sorry NO, Ryan did not just create his own secret 'Aluminum' making plants to provide for Rapture ( small scale production is prohibitively inefficient, and proper raw materials are from only a few known practical/economically viable sources ). However much it was used in Rapture, it would be imported along with the huge quantities of Cement, and Steel used to build the City. 
So the whole "WE'LL BUILD IT OUT OF ALUMINUM" Audio Diary was just a bit of ignorant/quicky/sloppy DLC-itus supposition. 
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Concept picture which shows actual foundations below the typical building structures seen. Also there is more utility stuff down near the seabed. Generally in-game Window 'Out in Ocean' views they just extended the same visible building pattern down ridiculously far so they wouldn't need to draw anything else ( BS1 with a limited render budget looking at a space that was secondary anyway - but it can't be taken as what would need to be there, which the MMORPG would have ).
Art Deco wasn't enough, I guess. Note the rounded building corners which would be logical for the underwater construction. And notice NOT having the array of windows ( though still too tall - too many floors ).
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Tectonic plate which causes the volcanic activity that raised the Sea Mount (undersea volcano) which Rapture is built within ( at a far shallower depth than the ocean area's seabed which is more than 3000 feet deep around this point in the Atlantic Ocean ).
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Big Daddy wandering through the subterranean Foundation levels ( where various utilities existed, and the constant structure seepage was drained to for extraction -- You cannot stop the seepage, only minimize and then handle it ).
Of course the Big Daddies would use the Foundation Tunnels to get around for their maintenance activities. The tram tracks also are useful for moving all the various equipment and replacement/repaired machinery that Rapture needed.
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Viaducts made for pretty Sea Scenes, linking buildings ( better hope that Glass is REALLY strong )
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Building Shape - Geodesic Dome or Sphere:
There should be at least one 'theme' building built in this shape. The curved surface allows the whole building to be one curved pressure wall with much less internal bracing. Unfortunately the same curves limit and complicate the internal space ( reason why you don't live in one today or house with curved walls ).
Cylinder :
Cylinder shaped building would also be built. The design is not as simple as slab sided buildings, it works better for the internal compression struts that are required for ALL the buildings to not collapse in on themselves from the oceans pressure.
I could see at least one of the building cluster 'Centers' in Rapture built around a concentric circle theme ( including cylindrical buildings and curved viaducts to link them. )
If you look at various examples of Art Deco buildings, you often see the use of curved sections in the architecture.
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Use of Metal In Construction - Exceptions :
Some Areas of Buildings in Rapture needed a more 'gracile' appearance/structuring ( ex- certain areas with large/huge aesthetic windows ) where the standard THICK concrete support structure method could not be used. It was always possible to make that construction mostly out of METAL ( rather thick, but less thick that using concrete ), so to be able to maintain its required structural strength and integrity. That that could be done IF someone was willing to go to the expense to do so ( They cost more than 10 X as much as Rapture's common reinforced concrete construction ). 
Note - This metal use still is included WITH the 'smaller than huge' more realistic windows correction done on various game scenes ( IE- Neptunes Bounty ).
Windows are generally like that anyway - Metal had to directly support/surround the 'glass', and then that material transmits/transfers the inward forces of all that outside water pressure on into the primary building structure ( which generally was a huge mass of reinforced concrete ).
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Steel Rusts, Even Aluminum Corrodes, So Basalt ? :
Rebar and other concrete reinforcements can be made from heat formed Basalt (igneous rock). Basalt ( a type of volcanic rock ) is highly resistant to salt water corrosion.
The manufacture of Basalt Fiber requires the melting of the crushed and washed basalt rock at about 1,500 °C (2,730 °F). Basalt can be formed into fibers with sufficient tensile strength to serve to reinforce concrete. Note - Concrete alone has high COMPRESSION strength, but very low TENSILE strength -- a good thing to have when transmitting great forces throughout a concrete building is needed).
Basalt-based Rebar ( reinforcement bar for concrete construction ) can be made from the igneous rock 'Basalt', which happens to be a common constituent of mid-Atlantic ridge volcanoes ( a likely local material for Rapture ).
Realworld Basalt 'rebar' is made using fiber made from basalt rock, which is is melted at around 1500C and can be extruded - as seen in this picture :
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Rapture's Warranty Hasn't Run Out Yet :
Interesting to see some buildings ( in external window views ) with substantial external damage but with lights still on inside ( already mentions that leaning one you see out window in Proving Grounds ). SO the structural integrity held up ( maintaining the pressure seals - in at least sections of the building ), which shows how Rapture was properly built over-engineered --- Planned to last for 100 years -- which would be the time Ryan might expect his people to be able to emerge back into the World after it blew itself up ( and all the 'ant people' were dead ) and then was safe again to rebuild it.
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Interior Construction :
Once the watertight structure segments are locked together into the building (below at Rapture), and the inside is watertight and stable, then ALL the rest of the work takes place in the interior.
All the :
* Scaffolding/equipment/transport/forms/construction machinery
* Interior walls 
* Floors 
* Stairs/ramps
* Doors
* Windows
* Columns 
* Elevators 
* Pipes/conduits/power/wiring/lights/ventilation/pumps/communications/connections (all utilities)
* Brickwork/tiles/woodwork/stone/plaster/metal/glass/carpets surfacing 
* Paint and polish
* Decorations 
* Space Dividers/Partitions
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Assembling Rapture's Tall Buildings from Large Pre-made Sections :
Sections built on/near Surface ( where its easier and assembled from smaller pre-made components ), are made buoyant and are floated (neutral buoyancy) down to the construction sight.
To make a tall building ( like those more than 6 stories ) you must join stacked sections, matching them up with great precision to properly fasten and seal them, to become structurally sound.
The joining needs to be carefully guided and controlled, being anchored against any Ocean currents, and guided/winched into exact place and held securely while being fastened ( Rebar tied together and more concrete added to solidify the joint ).
Sealing the sections at their join points must be done completely -- when you have water pressure outside at upto 280 lb/sq in ( a hairline crack will have water spraying in and can fill any space in little time ).
A similar process is done to assemble horizontal sections of the shorter/sprawling buildings, and the 'Street' viaducts.
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Mass Replicated of standard building (exterior) sections on dry land would be most efficient/least-costly. Made using the concrete poured into forms - pre-filled with carefully positioned/tied-together Rebar ( steel reinforcement rods/bar/wires ). Care would be taken to have the concrete Set completely, for minimal defects (much easier done out of water. 
The sections would have Temporary Seals plugging all interconnecting (including utility) ways. Those temp seals would be later dismantled after the installation on the seabed. Such temporary seals might be put back ( rebuilt to close-off a building for flood repairs ( unfortunately, alot of the installed interior work/utilities/etc... still can be ruined after being flooded with sea water ).
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Footings for Buildings and Misc Other Structures ( Like Viaducts and AE track support towers ) : 
* Added to stabilize below foundations dug into into bedrock ( My Level maps show many of them ).
 
* Extensive footings are needed for tall buildings to handle the sideways forces of water currents and eddies.
* Before planning for construction even is halfway through, the location has to be checked for a solid seabed by drilling a pattern of deep exploratory holes to verify stability. ( The holes can double as footings later. )
This is a another reason why short buildings would be less expensive, as they have less strict requirements as there are for tall buildings.
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Problem With Having Too Many of Floors in Tall Buildings :
Because of the need for Rapture building's pressure withstanding structure ( with the ~600 ft depths involved ) there is a greater separation between building floors to accommodate thick floor plates ( of reinforced concrete ) which extend cross the building to support the opposite massive forces pressing inward on both sides of those exterior walls.
Thus all the stairs are a bit longer in order to climb a greater than normal floor separation.
Unfortunately the building views you see through the windows In-Game don't reflect this extra spacing - Besides they're often having at least twice the number of floors which buildings in Rapture should be limited to be less than (20-25 floors, instead of 50). Fewer Floors can still look plenty enormous, particularly when a majority of Rapture's other buildings shouldn't be much more than 5 floors.
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Sky Scrapers - Correctly :
The 'stepped-in' pattern/shape of real 1900s 'Skyscrapers' in many cities were Mandated so as to allow the Sun to reach the ground ( instead of cities of tightly-packed tall buildings with streets becoming 'dark canyons' ). But in Rapture, the decreasing upward profile would help lessen the Ocean water current forces that push against the building sides and which work against the Building Foundation's anchorage ( There is more leverage to handle a taller building ).
Unfortunately, many of the game Skyboxes show too many extremely thin tall buildings (over and over), which if anything, would exaggerate that structural problem ( Besides being impractical/more-costly because of the progressively shrinking building interior space, while having the STILL-required very thick walls to keep the water pressure out ). 
BTW, What is the point of EVERY building being impressively (and expensively) 'Monumental', when EVERY OTHER building IS THE SAME ??? So instead, like most REAL cities, Rapture would have MANY shorter buildings, with only a few ( more expensively built ) TALL towers standing out ( and those likely with the top 'thinnest' section of those towers being only decorative (with no wasteful interior). 12 Stories, likewise, is 'impressive' in a city of 5 story buildings.
(( The game designers apparently had no understanding of the Essence of what a 'Skyscraper' really is. ))
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Materials in Rapture :
Based more on what raw materials are easily available and cheap. Also based on necessary processing using abundant/cheap energy ( you can alot with alternate materials if energy is cheap and a little effort is expended ).
Aluminum/Iron for metal - conversion of the raw materials from common impure minerals requires cheap electricity. Potential salvage from wreckage ( closer to shorelines with natural hazards preferred for 'wrecks' to accumulate ). Remelting and refining scrap.
Glass and Ceramics - purified and fused under great heat(energy)
Cement and Concrete - Superior aggregate (filler material) for concrete can be made to make concrete much stronger ( which would be needed to build Rapture )
Plastics can be made from organic/inorganic materials, and it is the patterning process and the properties of the molecular patterns that is the complication. Rapture would have gotten information on plastic technology for a long time after its founding, and via officially sanctioned channels after the 'closing off' of 1952. Technology/scientific information was likely one of the more valuable 'Contraband' smuggled into Rapture along with the cigars/quality beef/crucifixes/Bibles.
Rubber (in this case Synthetic) are one of the critical materials of the machine age. Synthetics could be tailored more to specific uses - some kind of self sealing plastic ( like used for the clear yellow goop tanks in Optimized Eugenics ). 
The indestructible windows (except to Big_Sisters apparently) has to be something else ( too much water pressure - glass just isn't strong enough ). That Ryanium stuff - whatever it was.
Recycling would also be much more common than in the Surface world, with many materials being not so easily obtained from outside.
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REAL WORLD - Thousands of Wooden Water Tanks (Local Water Systems) :
Water Tanks Existed on Roofs of Most multistory city Buildings pre-1920s ( tanks were integrated into upper stories of skyscrapers later ). City water routinely was low pressure ( and pressure went down the higher the buildings became ). A building needed to have sufficient water pressure for the buildings occupants, so they pumped water to the roof into a reservoir which raise the pressure significantly. The tanks often were made of wood and raised on legs ( a small water tower ). You can still see such tanks on buildings today.
YOU didn't really fly in Infinite BS ( definitely NOT freely ), so you couldn't see so much roof detail ( Ooh, peaked roofs, Wow, How old-school ). Realistically ( assuming the gamemakers care about 'realistic' ), there could be huge amounts of possible detail in such a 'cityscape', in plain view under those bright and pretty open skies. 
The Infinite BS gamemaker/developers barely represented them, no matter how interesting such detail would be (to have it be like a REAL city, instead of one made of shiny gingerbread). Columbia's Skybox computer graphics views were more distant, and conveniently made even more indistinct by clouds/haze-effects and such. 
Rapture's narrow window views Skyboxes ( like at Hephaestus in BS1 ) were made of '2D' pictures which COULD show alot of detail. MMORPG Rapture would have no external water tanks, the water systems would be integrated into the buildings ( the height/pressure thing still comes into play ). 
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Bronze Fittings used for seawater immersion ( bronze resists saltwater corrosion )
As used on boats/ships.
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How an Automatic Sliding Door Works 
See Securis
Note - Its even less likely for any automatic opening doors to exist in Columbia.
Door is hanging (rollers & track) or surface sliding ( and is in guideways ), slide up/sideways ( down jams too much with crap falling into the works )
Sensor/activator mechanism ( floorplate or electric eye or manual button ) - single action mechanisms are fairly easy via a triggered latch and a spring/weight driven movement, but double action ( ie- reversing the movement/motion and reset automatically ) is ALOT more complicated. Engageable/disengaging mechanisms require much more complexity. 
Sliding-way surface ( slot/rollers - low friction ) door slides into recessed space adjacent to door.
Actuator (both directions) pneumatic piston, motor drive (small motors), possibly counter-weighted
Lock (if any) disengages activation as well as physically locks door closed
Crap can block the doors movement ( unless actuator is capable of huge force - hopefully with an override safety 'crush-prevention' sensors )
Rapture-depth Pressure doors extremely complicated ( very strong seals often for both directions ) and very heavy - huge motor/mechanism needed to operate it.
Diagram of the Cosmetic vs Pressure doors ( which is more like an emergency bulkhead )
Mistake that level designers make is missing doors that DON'T have enough space adjacent for the doors to slide into ( I saw some in BioShock (which slide up) actually extrude through their frames at the top because the door was not inset deep enuf in the wall ). Other places, the doors are too close to exterior walls and windows putting their mechanisms outside the structure.
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Technologies 
Remote Closed Circuit TV Camera - Use in Construction : 
This got an early start in Rapture because of its use in the City Construction ( a whole lot of remote controlled machineries, working with pre-fabricated building sections/components, in lieu of many more Suited Men grunt workers ). That at least gives the tech a long prep time for its use later in those Security Cameras seen in the games - many not necessarily being quite 'automatic'. Instead, as suggested in the Novel, having some kind of 'flasher recognition' type friend/foe mechanism could be a good/workable solution ( ignoring the game not mentioning/having any such explanation/elaboration ).
Construction Automation (also elaborated upon in the Novel), being an important factor in building Rapture, would need to SEE to direct the work going on.
Consider : when steam shovels were first being employed in the US - one shovel did the work of over a hundred laborers using pick/shovel/wheelbarrows, and were so cost effective that they paid themselves off within a year.
Consider that Deep Sea Hardsuits ( required for the depths involved at Rapture ) were very complicated and extremely expensive to use (and required highly trained men to both be in them and to maintain/operate them).
SO A work multiplier like the Remotes used with automation to build Rapture would have been one of the early achievements. NO ADAM REQUIRED
The Novel Author has this Automation aspect (in some detail).
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Elevators Stop Working and All Those Ridiculously Tall Building Are Doomed :
You try walking up and down 20 floors to do routine things. Maybe if the buildings could be self-contained ( food being the needed item, assuming the utilities stay on ).
There is a cost to 'high-rise' type building, which includes the extra maintenance. In REAL cities it was the scarcity of land space that drove tall buildings ( and if you look at a picture of NYC/Manhattan you will see that even today the vast majority of buildings are 6 or less stories tall ).
SO corrections to Rapture for the MMORPG game would reflect similar logical building practices.
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Lighting in the Murky Depths :
Rapture's Ocean Signs need to be close to the observers/viewers because of the way water absorbs light over even short distances. BIG illuminations ( bright enough to be seen any real distance ) would be VERY expensive, and would eat the profits of a small company ( even if Electric Power is relatively cheap in Rapture - it takes ALOT of Light, and there is no daylight down there, add to the original cost and maintenance as well ).
OMG you take all the fun out of the game !!!
If you wanted fantasy THAT MUCH it should have been playing a Shooter called "Land of The Killer Easter Bunny" Can be added as a Mini-game having something to do with Sander Cohen's demented mind, with sprays of candy instead of blood, and pretty colorful splodey gibs, and fanastic weird FUN weapons which make absurd/funny noises.
( Saw an interesting billboard signs of 40s and 30s - but then those to be seen in daylight )
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Those Cable Suspended Light Globe Things : 
You saw out in the Ocean near buildings in BS1.
To be of any use the would have to be very bright ( better than bright lights shone from near you that would obliterate the view (more) in the murky water 'Murky Water' was one of Rapture's most popular Blues Bands ). Of course this means that close to them you get blinded by them.
There's no reason they are just cables with warning lights - normally run along seabed for that is more likely/simpler. For that it would be a liability to submarines, and they would be red lights as well.
Actually maybe the Skyline in Columbia coulda had some fancy lights to liven things up. Imaging going along a Skyline level loop in the dark with things like that.
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So Why Wasn't Rapture Built At a Higher Internal Air Pressure to Simplify Construction ?? :
Q : WHY NOT HAVE each part of the city be adjusted in pressure to be only within a fraction of 1 atmosphere ( 14.7 psi ) difference to the immediate outside water - thus allowing much thinner construction and less strength/expense/complication being required ???
A : Rapture's depth would have to be at least deep enough for the darkness the game portrayed, and also to be far enough from the water surface to have the tall buildings (or somewhat more reasonable tall building than the ridiculous ones portrayed), and THEN have THEIR tops far enough below to not be scraped off by passing ships or icebergs. Also, weird things start happening at high pressure to things like burning/combustion, humidity, and to human physiology. Constant significant pressure changes also can be deadly ( just from moving up or down in the city between sections at different pressures ) (( google "The Bends" and "Nitrogen Narcosis" )). Consider your ears popping on airplanes - which is really only a small psi difference.
The game designers originally though about something like this in BioShock's early design time, but the environment theme fell away because of it being so alien ( and complications like the Player wearing a pressure suit ). The whole Art Deco "New York Under the Sea" thing took over.
Q : Wouldn't pressurizing up the interior a few atmospheres help some ? Make it a somewhat higher constant pressure ( like a couple of atmospheres ) as an ambient in an attempt to ease the construction requirement ?
A : It wouldn't save much as it wouldn't help when your base water pressure at the likely depth (~600 feet) is still about 19 atmospheres ( 280 psi -- it goes up about 1 Atm per 30 feet in water depth ). You would save a little, but it would still require almost as massive construction for the many additional atmospheres that STILL had to be held out. You ALSO had to build short building ( shorter as even compared to half the height those seen in the game pictures ) fairly substantially anyway -- as the sea currents/turbulence put great forces on the flat sides of large building - made all the worse by leverage against their anchorings on the seabed - growing ever greater the taller they are.
Q : SO why not build Rapture all at the same shallow depth to allow just one fairly low pressure for the whole place ?
A : That Would mean a very flat city, with virtually no vertical buildings ( none of those iconic tall skyscraper buildings ). To have a 'city' population it would then have to cover a very large area. Most of the Ocean isn't that shallow ( except NEAR the shore - even bays/lakes are hundreds of feet deep ), and THAT would make Rapture fairly easy to find, being that close to the Surface. (( Note - strangeness of that rather blatant highly visible Lighthouse existing in the face of the story's "secrecy" - still there from years before BS1 happened )).
So it was simplest to maintain a single constant Sea Level pressure environment, no matter how far up/down ( and using whatever required construction ) to have least environmental impact on all humans/plants/animals/machinery -- build the structure at all points able to handle whatever the outside pressure ( but not to deep as to be technically absurd as some of the promotional pictures have it ). 600 feet depth was doable with the technology available at the end of WW2, just that it would be expensive, and require some improvements to make it work routinely/safely. The audacity to do so would also be required.
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Lotsa Issues -- THINGS TO FIX :
* Poor Access
** Interconnects and transport are near Street level 
** Going up and down elevators alot is wasteful
** Needs more interconnecting Viaducts 
TOO MANY TOO TALL BUILDINGS
* Too tall when it is not needed ( lots of empty real estate around Rapture ) : 
** Massive foundations required to anchor
** Elevators are expensive ( and complicated by too many unneeded floors )
** 'Tall' incurs significant extra expense
* If EVERY building is tall then 'tallness' is no longer special
* Thin buildings are inefficient ( thick walls/utility space eats most of the interior spaces )
* Decorative towers barely seen in dark water 
* Rapture simply wasn't this big ( hard enough funding building for 20000-40000 people )
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Interior Wall Details :
Rapture's Structural Walls are very thick reinforced concrete. But for aesthetic needs, an inner wall is usually in place :
* Sometimes we see wood behind tile surfacing
* Other times there is bare concrete behind the wallpaper
* Wood wainscoting (3 foot tall partial wall cover)
* Some seen are false walls with space behind ( wood and metal supports ) for pipes and such
* Pipes seen exposed under the floor and behind walls and ceilings
* Ceiling/walls collapse with BIG chunks of (Rebar) reinforced concrete showing
* Metal bracing for false walls
* Metal plate/sheet walls in industrial areas like Hephaestus and Neptunes Bounty
* Glass brick walls
* Wood wall partitions with interior windows
* Decorative pillars and columns
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Height Is Decorative :
If some of the tops of the (too) tall buildings are merely decorative towers ( a frequent Art Deco feature ) then some don't even have to be solid ( rather be empty/non-waterproofed structure ). Could be just a girder tower to mount the lights ( which is about all that might be visible only a short distance away anyway ) which WAS commonly done on some buildings.
Girders have less water resistance to currents/eddies and thus would be far cheaper to construct.
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Foliage in Rapture :
If I had designed Rapture ( and this is something to change for the MMORPG ), I would have had ALOT more interior planter boxes (spaces for) to moderate the closed interior spaces ( more in affluent areas - as the light for them would have to be artificial/paid for ).
Herb garden, flowers, prestige lawns, etc...
Of course in the BS1/BS2 times, many would look all dead and ratty due to nobody tending them any more. For the MMORPG's New Rapture, nice green ones would be a common sight ( and something the Player could get/make/cultivate ).
(( Another City Job - Urban Gardener/Landscaper )) 
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Land - How exactly Was Space Allocated to Build in Rapture ? :
There obviously was central planning for the parts Ryan built ( and coordination with others who put their fortunes into building THEIR chunks of Rapture at the early times )
The terrain itself was a limitation. Solid Rock is good to build on to have structures anchored properly, while plains of unstable/loose silt and debris rock are problematic.
Connections to other buildings and transportation infrastructure would need to be made at various points.
Outside Rapture itself, there was much available space, but distance was the issue - until it became the reason for building in such places (ie - Suburbs).
"Wide Open" did result in irregular/halphazard building often following the terrain, when people built where they wanted allowing for the above limitations.
"Mining Law" which is often the accepted law system where higher organization doesn't exist, allows for staking claims ( limit per person ), but having to do some reasonable amount of development work within a limited term to maintain the 'claim'.
Common Building Standards would be imposed on buildings connected to the rest of Rapture and its Transport systems.
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OH THAT Game Roof Damage ... EASY - Just Add Some Props and Jacks ... NOT.) :
In BS2 Paupers Drop you see various props and hydraulic jacks supposedly holding up damaged sections of building ceilings. It is more likely that those are really sub-ceilings/floors, as the REAL structure 'roof' has to be incredibly (massively) thick, and the damage/breakage they presented in those scenes would have made for catastrophic leaks -- which would have disastrously flooded the area and made it uninhabitable.
No jack could hold such forces out for the large collapsed ceiling panels they show (( Example - one smaller 5x5 foot section facing the 600 foot depth 280 lb/sq in. pressure - that's 25 x 144 sq inches times 280 lb of force - that's 1008000 lb total equaling 500+ tons -- which is quite a bit more than those Jacks you see in the game can stand - even that not blocking the leak. THAT'S for a MUCH smaller bit of broken ceiling than they show them propping up in-game. ))
- 
You see huge metal piers inside Paupers Drop holding up a high ceiling Pix111. If you didn't realize : To be correct, there ALSO should be JUST AS MASSIVE sideways struts holding those large wall surfaces apart too. The sea water presses-in, with equally massive pressure in all directions ( Underwater you don't just hold up the weight of the building roof -- it is that 600+ feet of water above pressing with 280 pounds PER SQUARE INCH on EVERY bit of every external surface -- top/bottom/sides ).
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Things of Note :
How many elevators/stairs are needed for a really tall building ( and how much of the interior volume it takes up by them ).
How thin the walls are ( compared to the deep water massive thickness that would be required for Rapture buildings ). The walls were really only 2 bricks deep ( the Steel girder frame supported everything, and the walls merely hung from that framework ).
Diagram Illustrates volume usage of tall buildings. Rapture would require more as all the air has to come from elsewhere and the heating systems are more extensive. 
The exterior Building walls in Rapture are massive compared to this building.
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Rapture was 'The Art' of the Facade :
Limitations of a small population ( 20k ? 40k ? If even smaller, then that BIG cityscape is even more absurd. )
Skyline of buildings that look bigger than they are ( handy that Art Deco often had showy elements )
Stores ( downsized from BaSx Bigification for reality ) should be more typical of what you'd find in a small town. Malls - again, make more reasonably sized rather than something blatantly enlarged for an open battle venue which some game needs. Department store - ghost town - good way for Fontaine to bankrupt himself.
Most businesses in Rapture would be small - with hardly any 'assembly line type operations. Many goods were simply stuff originally made/brought from Surface. Much more prevalent would be 'repair' businesses and sellers of 'Used' items, which Rapture never could make itself ( except as a few way-too-expensive 'custom' productions ).
"Artists" who in big cities already can barely make a living - and come to Rapture which is no Welfare State. Who will 'buy' all this art ? "Don't quit you Day Job" should have been emphasized in the game ( same for Scientists actually to 'make a living', even if they are better than average. )
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Same Problem for Columbia - Except Even More Problematic (As Written) : 
The new magic SteamPunky technology would NOT have existed in the Surface world to be obtained there. Mass production doesn't work within tiny populations. Even with slave labor most modern goods couldn't be produced with any profit or sustainability ( What does it matter when the important thing was trying to denounce Laissez Faire business ? Most Players probably didn't care anyway - just that 'whatever it is' is 'bad' and needed to be shot/blown up/slaughtered. Funny thing is : that idealized 'Paris' is based on exactly the same thing - BUT that somehow didn't happen to get mentioned. )
That's IGNORING : Factories without source of raw materials ... everything else shown was absurd Fantasy, so what's it matter ??? ( Unless you think THAT historic American economy Columbia was supposed to represent was based on use of Magic Wands and Magic Spells. But remember its "Historic" and thus relevant !!! , because they told us so... OVER AND OVER. BS. )
So in reality, the "facade" was moreso a game designer's/writer's careless presentation, when 'social relevancy' was the alleged over-hyped theme.
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Fire Escapes in Rapture ???
Obviously the 'classic' type (external) fire escapes ( seen on so many real world buildings ) make little sense out deep in the ocean, but there are some multistory interior scenes where they might be possible.
Some of Rapture's interior (cavernous) spaces are 3 stories high, and fires CAN happen with the interior walls and furnishings ( even with the main structure being concrete ), and fumes/smoke being trapped in the enclosed spaces. Multiple exits would be the a typical safety measure.
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Rebuilding :
In Rapture, Various retrofitting to buildings (Re-purposing) was done over time. Its harder to do in a deep underwater environment. Exteriors would mostly stay the same ( even adding new portals through the external walls is quite hard - example - when extending the Transit ). The interiors were easier to change, as long as the structural integrity was maintained. Depressurizing to do the work was prohibitive.
Even some of the mentioned 'leaky' buildings, which were not fixable, could be reemployed as things like Fish Farms where their interior spaces might still have useful purpose.
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Big Buildings Would have Direct Access Connections to Rapture Transit Systems :
Such buildings would have alot of people going to/from them, and thus need to be well connected to city transportation for efficiency/convenience ( often such large building's First Floor is designed JUST to channel people into the elevators accessing all their many floors ).
AE, Trolley, Bathysphere Stations ( and 'Street' Connections and Submarine docks ) would be placed in the immediate vicinity of the building, who's size contains as much as dozens of the squat/shorter buildings common in the rest of Rapture. Small shops/services are usually also placed at/near such flows of people.
Consider also the Freight transport such a building requires. A Large Jet Postal station would also likely be there (or nearby). The Utility complex required to support the building's inhabitants would likewise be huge. A large building's Foundation structure would go quite deep below to anchor it securely against ocean currents and other disturbances.
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Mushroom Columns - used to guide forces from the ceiling ( and into the floor there should be (in Rapture) a similar widening hidden below a false/sub floor ). It is a way to open up space in what fundamentally has to be a support-in-all-directions 'honey-combed' concrete structure.
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Lower Manhattan during WW2. Notice the sporadic nature of the truly tall buildings and the many quite shorter ones and the irregularity of sizes and shapes. The artists who did the water scenes for BioShock Rapture got a little stuck on repeating the same patterns a bit much.
Another interesting thing : This photo taken from a plane appears to be from something like 1500 feet up, which would make Rapture far shorter ( like a 3rd of those tallest buildings ) when the depth to their base would need to be something only like 600 feet to not get too ridiculous with the water pressure ( and stopping at ~400 feet tall to avoid having the tops of the building imperiled by icebergs. )
Notice also the many shorter building interspersed with the very tall ones. Those tall ones were built for prestige, and even in the Surface World were far more expensive to build. The game makers too many times showed external (window) views of just tall buildings. What point an overly expensive 'tall' building when ALL the others are tall also ??? (( Just "looked good" ... ))
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Construction of Real Skyscrapers Circa 1930
Girder skeleton'd Skyscrapers with floors of concrete with wire mesh suspended between secondary girders ( which also served as pseudo-diagonal reinforcement for the building ). Temporary stringers as support while the cement was setting (and locked into the wiremesh/girder edges).
Rapture would have similar secondary floors set into the primary concrete - girders spanning large distances, mesh and concrete over shorter distances, standing and hanging posts inserted as reinforcements. Bare girder/metal work can be used in interior volumes ( like inside the Sinclair Deluxe in Paupers_Drop in BS2).
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There would be a BIG reason that so much of Rapture was Pre-built and Assembled at the Ocean's surface. How ANY BIT of Infinite BS's Columbia got built was even more ignored for that Pop-a-Mole game fantasyland.
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Why Are (MY) Rapture's Floors Further Apart ? :
In an underwater building, you can't have windows or vents outside to let in air. So systems that do that function have to be run somewhere, and much of that is an extra layer between floors ( false ceilings usually ).
You also have that thick concrete construction that has to prop the walls -- with all that pressure pushing inward on all external walls. So between floors are solid/massive load bearing plates or struts to perform that function -- reinforcing the external walls with massive structural concrete under compression. 
You need to use some floorspace within the external walls to connect between floors all the utility systems. Some space is also used for stairs and elevators ( a reason you don't want to have TOO thin multi-floor buildings, since the volume needed for that function is usually a constant against the height).
Since there is no outside accessible to the inhabitants, in the 'better' places the ceilings would be made higher that normal to give at least a little 'space' openness.
With greater distance between floors, now stairs take up more space -- the extra length being required without increasing their steepness ( holding to the standard slope ). pix of stair diagram
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"Quarry" :
Indicated on Rapture map http://rapturerebornmmorpg.fandom.com/wiki/File:MetroWays2X_18.jpg was location of source of useable aggregate materials (volcanic rock) - was developed well into the City's phase 1 Construction ( some time was required to find, develop and make use of it - not instantly as the game writers usually have such things). A substanial number of building constructions made use of this source ) 
A Local source of aggregate lowered expenses for foundation work done for the city's prefabricated buildings and later 'tunnel' type construction ( and more than a little interior secondary work )
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Building Raptures buildings on Solid Rock would be important. Volcanoes spew lots of ash and loose material as well as having more solid lava flows. That kind of loose material is unstable and subject to movement and fissures forming. Even assuming Mt Ryan is a dormant volcanic Sea Mount, earthquakes can still have shifting effects on the materials around Rapture.
NOTE- During the Ice ages the Ocean was as much ( or more in places ) 400 feet shallower, potentially allowing atmospheric spewing of materials as the Sea Mount broke surface.
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Sub-floors for Basement Areas :
Another Easy-Builder Component : Floor sections usually with some kind of metal grill/grid/mesh walking surface raised over a sub-floor below that will act to catch water ( to be drained to the sumps and then pumped out ).
Alot of the building basements/foundations have access tunnels with a sub-floor to collect water from all the drains from the floors above and the external walls that continually seep slowly ( and some water condensation on the cold outer walls ).
We've seen many such floors in BS1/BS2 in many of the utility/industrial related areas of Rapture. They are also often used to cover pipes ( and thus give maintenance access to them by lifting the floor panels ).
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Varieties of Building Patterns in Rapture :
* We have the High-Rises and 'SeaScrapers' that we see out of the many windows in BS1/BS2. We do go up into a few of these like to Kashmir's at Welcome Center and the Atlantic Express Depot office building - obviously the city has some clusters of some tall building (~30 story) and a few more half tall buildings (~10 story). The tall building are generally narrow, with limited floor layouts, but multiplying each floor 20-30 times can add up to significant space.
* Most of the buildings we actually move thru in the games are sprawling complexes of connected buildings ( with rocks and much taller buildings visible out the windows ). Low spread out buildings are lower density and thus would cover more area for the number of people.
* Outside at Pauper's Drop you have a large nearly empty seafloor plain, with a few industrial buildings nearby and with tall buildings off in the distance. The Fontaine Futuristics window Skybox/Skydome (exterior window views) shows it is far away from other building clusters ( high-rises off in distance about quarter mile away ). So there are largely empty spaces within 'city limits'--- more than that 'Downtown Manhattan' scene alot of the outside views show.
* In the arrival from the Lighthouse you cross alot of rocky terrain and then are looking down into the mass of buildings of the Welcome Center ( did this have another name after people no longer were arriving at Rapture ?? ) - Steep rock sided canyons are interspersed within the city, often with small building built into their sides and ontop.
* The Residential type structures are stacked floors around a 'court' ( some upto 8 stories ) - and many of the more Squat building type.
* Variously shaped industrial buildings - there would be alot of these to provide all the different kinds of goods a city's population would need. Same for the raw materials used by those industries, many of which you don't find in the middle of a city or all in the same proximity -- so there have to be many outlying centers to provide them.
* Add the infrastructure a city needs - we've seen Hephaestus, pump houses, post offices, and various transportation facilities ( AE tracks, viaducts connecting buildings ). Multiply what we've seen by what a population of 20000+ would require.
* Many of the tall buildings have tower extensions on them, that are decorative ( lights look like windows from a distance but aren't ). The floors (if any) that would fit would be too small to be human habitable, but might have other uses ( many tall buildings have all kinds of system machinery located in their roof zone and even observation 'decks' ).
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THINGS Seen In The Game - 'Artistic License' - Which Will Need Explanations in The MMORPG :
It would be sad to have to cut out half the game Rapture because it was such fantasy and abuse of Physics and Common Sense. It would be MUCH more challenging to explain all the oddness ( and modify them as little as possible ).
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Swinging Type Doors In Rapture :
Not all doors would have been automatic ( the expense alone would be one reason - not just to install, but also to maintain ). Doors which swung are harder to do in a game engine - for the character NOT to bump into them while in a hurry ( and when clearing any movable objects ), AND to not require the hand doing the animation ( within a short arms length ) --- Particularly when one arm has a weapon and the other is a big Drill. ( We did see a swinging door in the BaSx 'Tour' section - your (Booker's) hands push/shove open a a pair of swinging doors ).
Repairing derelict sliding doors might be difficult in the MMORPG's Rapture ( but worth having to show off in your residence/shop ).
Hanging curtains useful as a interior door 'alternative' ( Hmm beads ... The Cloth techniques used for graphics these days can do stuff like this - proper physics as you 'push through' ... )
"Kicking in a Door" can be regained as a 'Cliche Action'.
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More Secret/Hidden Doors/Trapdoors, Crawl-ways, crawling thru Air-ducts ( and falling thru damaged ones ) in the game:
* Template scripts to add these at appropriate positions and tie-in/add to adjacent structures ( and 'building blocks' for building sections to include many alternate locations for these when buildings Auto-generated. )
* Many in BS1/BS2 were originally to hide various environmental control machinery and other utility stuff.
* Always good places to find Caches of goodies overlooked by years of Splicer scrounging (lotsa people in Rapture kept illegal goods out-of-sight...).
* Also as hidey-holes for Splicers to use as their 'home' ( so be careful when you find one - you might get a surprise ).
* Various hazards like fans in air ducts.
* Secret door activation triggers/buttons/levers
* Manholes down to the sewers
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Rapture Underworld ... :
Mentioned before : Rapture's ( Beneath the Streets] ) Under-Areas can be more generic (and forgettable), and handy in facilitating many 'On-the-Fly' Mission scenarios. They also are less aesthetic and more irregular and varied in their contents. No matter how well planned ( for the Prefabricated structural construction ), things get added/changed/removed/adjusted/repairs to 'organically' change things significantly over time ( and Rapture had existed almost 15 years before BS1 - and with additional messy kludge mutations after that ).
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MMORPG - No Impervious Doors :
How many games you blow the hell out of countless enemies with huge pyrotechnical special effects, yet there is that miserable door you have to go clear across the map to get some stupid key to be able to open it ??
Same for interior windows which you should be able to smash and get thru ( or fire thru or whatever ). We need to have the largely invulnerable exterior windows ( or Rapture would have all drowned long ago ), but the inside ones need not be that expensive foot-thick X-technology whatever-it-is invulnerable glass. 
Bizarre Idea - all those outside windows are really just projections with no real vulnerability to outside, made that way because Ryan figured out that it is so dark out there in the deep Ocean nobody would see anything anyway ( even WITH lights - even bright sunlight can't be seen thru 490 feet of clear water. ) 
Some games now are starting to have 'deformable' scenery, where the terrain can be extensively effected by player actions. In this MMORPG there would be a location/stuff behind every door to get to. So even the most stubborn wall/door can eventually be forced open ( whether the effort will prove worthwhile is another matter ).
An even-more 'deformable' terrain will allow you to build your own walls and doors ( and there would be enough already done in this MMORPGs design/game mechanics to allow that ).
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Water Pressure and Permeability :
It may not be commonly known, but water at high pressure is an active element in movement of water penetrating through things like concrete, which are thought to be solid. Water pressure even forces gases through seemingly impermeable materials like glass (very slowly). Other chemicals which accelerate corrosion likewise are moved by such a water flow ( important factor for the embedded reinforcement bars (Rebar) that are part of the structural concrete ). The pressure also changes the nature of chemical reactions which can greatly accelerate corrosion and weaken those materials.
At my plausible Rapture's (nominal base floor) depth at around 600 feet, the outside water there generates pressure of 280 lb per square inch ( 20 Times surface atmosphere pressure ). (( compared to typical household tap water pressure is something around 60 psi ))
Steel Rebar in concrete immersed in Salt Water needs special coatings/plating to resist corrosion long term ( or be made out of some less corrosion-prone substance for the structural reinforcement - aluminum still corrodes, but does so slower ).
In the case of actual leaks, water under this much pressure will shoot out of the hole into the interiors lower pressurization. Such a hole, if of any significant size, will produce an inflood of water that can fill up the interior volume quite quickly. At 20 atmospheres, the water will collapse any air pocket into 1/20th of is original volume. Anyone caught in such compression would suffer nitrogen narcosis, and if they are rescued ( returned back into a lower pressure area ), they can instantly suffer a fatal case of "The Bends" - having the gases dissolved in their blood vaporizing (bubbling) and clogging their body's entire blood stream.
SO, measures to prevent and contain all leaks and control seepage is an VERY important component of Rapture's construction. Sumps at lower levels would exist to contain/collect the continuous SLOW seeping inflow, and pumps to remove the liquid. This would be in every building. Most external walls should have a layer of collectors and vapor barriers, protecting the interior spaces from high humidity.
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Corrosion and Structural Failure :
* 12 million gallons of zinc paint better be somewhere in Rapture.
* Some components can be made out of brass, which resists corrosion by salt water which would likely be used in places that would normally be exposed to salt water, unfortunately leaks happen everywhere.
* Many other things like machinery, pipes, structural components would be steel which eventually rusts unless you keep it painted and usually having zinc in the paint to take the corrosion before the steel does ( basically it gives you time to detect it and repaint again ). The long lack of proper maintenance in Rapture likely will be the cause of much accumulated corrosion.
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Lots of 'Secret' Tunnels/Nooks in Rapture's Foundations :
* The massive Foundations have large stone boulders filler added to build up the foundation structure that Rapture's building stands upon ( saves on concrete used and the rock is actually stronger than the concrete ).
* Many constructions did not require completely solid foundations and to not waste cement/concrete they have are a number of 'void' spaces built into them ( using tunnel-sized forms while the concrete was poured ).
* Most were sealed off. Some were later unsealed and used for storage.
* Others were 'discovered' and put to other uses (smugglers, etc...).
* A famous TV broadcast in 1960 was one such being opened as a 'big' story - It was supposed to contain Fontaine's secret Stash, and turned out to be empty - just some beer bottles from 1946 ... I actually saw the Geraldo Rivera Al Capones Secret Vault when it happened LIVE on TV --- https://en.wikipedia.org/wiki/The_Mystery_of_Al_Capone%27s_Vaults 
* A number of these Tunnels were used as extra Sumps when Rapture turned out to be more leaky than expected.
* Whole networks of the foundation tunnels exist, and many are unknown as the building plans were lost.
* Such 'tunnels' can serve as alternate (randomized) 'quest destinations' - "twisty little passages all alike"
* Yet another source of 'survey' work for the city ...
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Wall Section Repairs :
Due to the wrecked state of many parts of Rapture, significant repairs will have to be made.
* 8,10,12 foot high sections ( standard sizes for the modular aspect of city structures )
* Taking down a 'wall section' - all modular with slot inserts at bottom and lever up and secure at top ( bolts hidden under decorations or are decorative themselves ) 6 foot wide pannels (so fit on tram cars. Height depends on building ( cheaper accommodations have lower ceilings - really cheap ones no sub ceiling at all - bare concrete.)
* Repair done on floor (easier to get to) or while section is still attached to wall ( like patching/painting ) .
* Animation of taking down/putting up wall/ceiling/floor section (using ropes)
* Window repairs ( inner glazing with glass ). Structural windows are MAJOR repair ( because of the Ocean Pressure )
* Decorative/aesthetics - paint coloring, wall paper patterns.
* Any repairs done to External Structural (like windows) requires Sea Containment Safety Protocols to be inforce.
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The City Levels Vary Alot (The Seabed Varied) :
* BS1 content (look out windows) many of the building you are in sitting on bedrock ( or even as part of interiors like Arcadia ) yet you look across at same level and you are looking at 10th - 15th floor of a building whose foundation is far below you. ( I noticed a few 'mistakes' buildings just floating in the water - must be made of the same stuff Columbia was made of ).
* Would probably have elevators down to 'street level of main city street grid ( Street-ways, Trolleys and the utility Tramway system ).
* Seabed has rocky ridges with some buildings built on them. Separate transportation lines climb to them like in a city with hills ( MetroWay Bathyspheres don't care as they can cross open space on their tow cables ).
* The large rock formation ( Mount Ryan ) to the north extended up to quite shallow depths (100 ft)
* The Abyss drop-off must be an ancient collapsed volcanic vent. Ordinary Bathyspheres and subs cannot go down there.
* Don't want too many things built to close to the ocean Surface ( Iceberg Hazard ).
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Personal Safety Airlock and Containment Systems - Equivalent of a Fallout Shelter :
If you could afford it, and after a sales spiel about having Peace of Mind when living in a City 600 feet under the ocean...
The System separates your home from water that may pour in through some major leak. With automatic systems that will slam shut ( just in case it happens while you are asleep - and the Water Alarms start going off. )
Not just Securis doors (or equivalent), but seals for all the miscellaneous utilities and air systems.
System might include a self-contained air and power reserve ( for electric and heat if that gets cut off ), provisions made for some adequate period which you might have to wait.
Deluxe systems might include an emergency submarine docking port to allow rescue from the ocean side.
Less expensive options would be a 'Safe Room' -- which would be sealed and contain sufficient air and supplies for a long period before rescue. Not quite as safe as the more expensive system - it relies on the human getting to the Safe Room in time before their dwelling was inundated and they could be swallowed by a horrible watery death.
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What Type of Sealant Is Used For Leaks ? :
Alot of hairline cracks form in concrete and between concrete and metal structural elements. 
* Would have to handle the high water pressure and preferably would be used from the inside (rather than outside)
* Alot of pumps are constantly engaged handling this continuous leakeage and it would be advantageous to elimiate at least some of these leaks ( a job the Maintenance Daddies are largely not trained/equipped for ).
* Prefer to do such repairs BEFORE Citizens inhabit an area ( as one method is to hack a section out of the concrete and then replace/patch it, which will make a wet mess of the adjacent inside areas. )
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The Leaning Building - Still INTACT :
The One seen out window in the Museum training grounds in BS1 - Lights are still on - blinking/flashing :
* Seabed subsidence ( can't be Foundation failure, or it would be floodsville ) ...
* The structural integrity held, including the whole 20 story building ( which is a good commentary on how well built Rapture's structures are, and why after more than 20 years and a decade of neglect Rapture is still largely intact ).
* Would be an interesting place to visit and see how the MMORPG's Game Engine would handle the slanted 'terrain'. Game Engine normally has the 'building blocks' generically set to upright orientation to simplify the math calculations. This case would have to be handled specially like 'vehicles' are -- In a more flexible way in orientation and position.
* Bring your climbing ropes and rope ladders when you visit.
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Bunker Rapture ( Fortress Europa-ish ) :
Rapture is built much like a WW2 German bunker/fortification ( google "hitlers atlantic wall" images ), solid and bulky, it has to be.
The famous Empire State Building built in the early 1930's is built of a supporting skeleton of steel girders and walls of brick and decorative stone sheathing. It merely has to resist gravity trying to pull it earthwards and a little wind.
Rapture is Forever under assault by the pressure of hundreds of feet of water. Instead of having to resist great force (artillery shells) impacting at any one spot like a military bunker, it needs to resist great force at all its surface simultaneously and continuously. Tall thin buildings don't make much sense with this structural requirement - contrary to artsy cityscape pictures. A few maybe, to be impressive, but large numbers are impractical when the city already cost enough as it was.
Thus the thick reinforced concrete structure to distribute forces working against its structural integrity and to seal OUT that water pressure. This also requires armored doors and windows, and the same for all other openings. Massive internal struts resist the forces tying to collapse the walls inward.
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Rapture's Expansion On A Budget - Additional Construction (Phase 2) :
Population Growth for Golden Age Rapture - The problem mainly isn't digging tunnels ( for new expansions ), it is sealing them. There really isn't such a thing as truly solid rock for very far ( It could help that Rapture is sitting in the core of the undersea volcano - a more solid 'plug' of magma ). Remember, at those Ocean depths, the water pressure turns a small crack transmitted through fissures in the rock into a jet spray that will soon drown you. The Rock has to be completely and strongly sealed from that pressure.
Melting the Rock around the tunnel to a sufficient depth ( instead of expensively lining the tunnel ) would be a possible answer ( It takes lots of energy and difficulty - getting rid of the 'melt' heat the right way WITHOUT fracturing the rock ). Automation again would be a key element to doing it efficiently ( and inexpensively and safely ). Stability of the rock must be ascertained as part of the process to make sure the seal is sufficient, or to have added work done to make sure of it.
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Large networks of good-sized tunnels first made and used for Rapture's many agricultural farms would lead later to a different kind of prevalent city construction ( different from those buildings seen sitting on the sea bed ).
Simple Arithmetic : To grow stuff for each/every human's in Rapture's food intake : How big would you need to build a Building to contain all the plants and stuff to support those plants ( This is EVEN when using high efficiency hydroponics ... )??? When building it, like your house or apartment, how much would it all cost ( and that going to be for EVERY NEW inhabitant ). Now add the greater expense of undersea construction. So PREFERABLY, some cheaper construction alternative to contain that additional INTERIOR Volume is required. Hence a solution of using tunnels in solid rock ... ( Note- that farms may NOT need to be built to the SAFETY standards of the rest of Rapture ).
Oh and NO, 'fishing' can only supply a fraction of Rapture's food ( Buy a Vowel to learn what is involve in 'ocean fishing' ).
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Plasma-Fused Ceramics Used to Build Rapture - To Make It Possible In a Practical Sense :
Ryanium - is mentioned in the "Rapture" Novel as a way for that Author, familiar with Sci-Fi writing, to explain some of Rapture's structure working under deep ocean pressures. The technology's development predating Rapture ( and discovered by Ryan's industrial company ) is a product of this Plasma-Fused family of technology ( Ryan is a Howard Hughes style technologist ). All those big/huge (or even smaller) windows would otherwise be impossible in Rapture's undersea environment ( real glass just isn't that strong for anything approaching the sizes in the game ).
This technology was a result of Ryan's genius in engineering high-energy systems ( along with other resulting technologies like the Plasma Rock Cutters ). High Temperatures in Industrial processes enable new material engineering.
High strength aggregates are needed ( Concrete can only be as strong as the materials mixed into it ). Concrete can be built thick for strength - thus likely to be the major material used to construct Rapture. Building structures at the depth Rapture existed at were possible using WW2/Post-WW2 technology, but to make it CHEAP ENOUGH ( and on a grand scale ) it needs a little help.
Metal (besides Rebar) would be the minority of Construction - Used in the few places where there were the holes in the thick concrete ( doors, window frames, machinery, utilities ). Metalwork is expensive, and too much of it would doom Rapture to being much too expensive to ever get built.
Fused materials like Basalt rock can be used as corrosion resistant Rebar required for the City's huge amount of reinforced concrete. Likewise the Aggregate used can be treated and improved. Art Deco uses LOTS of tiles/panels (ceramic) which would be fundamental in the interiors. Tunnels used to expand the City might be made without added liners (expensive) by melting rock to build a sufficiently strong sealed envelope.
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Nothing Is Perfect :
Various facilities which once the arriving population started growing larger had to be enlarged to meet the needs/correct deficiencies. Examples :
* The repair facilities at Port Rapture to keep the fishing fleet operating ( a fairly new tech methodology with unexpected difficulties and maintenance issues )
* Utility systems to handle building additions, and some 'changed plans' of the 'rich people' developers
* More efficient alternatives which were discovered/developed as things got running 
* Certain things which broke down and had to be replaced ( the usual issues with systems which take a bit of 'working out the bugs' when the stuff ordered from The Surface was found to be shoddy or 'not to spec' )
* Corrections to poor workmanship ( as in the normal world - some people try to 'get away with' as much as possible ) Penalties might be given, but the problems STILL need to be reworked.
Even with substantial expert planning, there are unforeseen problems in something as complex as creating Rapture.
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Varying "Rebar" Embedded in Concrete Structure
A '3D' web of Steel or other high tensile strength metal/materials to assist the concrete in withstanding shear forces.
More can be added to 'strengthen', which is prohibitively expensive to use in general (just as is building the entire large structure out of metal - SEE TARD DLC WRITERS). 
Additional reinforcement (the 'Re' in Rebar) is particularly needed around windows where forces are greatly increased (Because of the flat window and its frame spanning a large area), and at Pressure Doors which have large hidden mechanisms requiring the concrete in the vicinity to be thinner.
Viaducts are basically a progression of framed windows, but the base portion (and any piers) can be thick reinforced concrete and THEN heavy metal framing.
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Construction Done ON THE SURFACE As Much As Possible :
Undersea work has MANY times the difficulties and thus takes many times the effort to perform. Cost is MANY TIMES MORE.
Deep undersea work takes several times the effort. DEEP - Cost is SEVERAL TIMES MORE than that.
Hardsuits and remote controlled machinery - versus - for Near-surface diving (using conventional Diving Suits - even if assuming workable Scuba Gear is developed early).
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Fire escapes - you cannot have external 'Fire Escapes' in Rapture
Tall buildings in The Surface' as air-bound world can't have them on their upper stories and have to rely on internal escape paths - multiple fireproof stairwells.
Buildings in Rapture need would need the same internal escape paths. Lower buildings can have connections to adjacent buildings.
 
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SO MANY Being Too Tall Is Wrong :
Tall building are a kind of speculation, requiring extra expense and expecting to be desired by new tenants (assumingly for the prestige). Often in business cycles, speculation in real estate and the building of new buildings creates excess space. Rapture is not a large place and its history too short for such a cycle to have significant excess building and resource limitation on its first construction.
The famous Empire State Building in New York City planned during the Roaring 20s, but finished while the Great Depression was well started. It stayed largely vacant til the start of WW2 ( and its owners failed to make a profit until the early 1950s ) - was nicknamed for a long time "The Empty State Building". It was the tallest building in NYC for several decades.
Such tall building also would be assumed to fit huge numbers of people ( The Empire State Building was designed to fit 20000 tenants ( One of the suggested total populations for Rapture 20000 Rapture Population : John Shirley Novel )
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Towers ( A typical Art Deco Feature ) :
Alot of the building towers seen in-game could be largely Decorative Towers on the buildings below them ( one advantage is you don't have to make the decorative tower section watertight, which otherwise would require substantial structural cost for a minimum interior space ). But then appearance is what counts - the gamemakers attempt to make Rapture look like the Manhattan Skyline...
The scale also isn't what it appears, as bright sunlight only goes thru about 400 feet of clear water before being completely gone ( as in the darkest dark ), and even with brighter Xenon illuminating lights (and such) being used. So that the furthest building would only be a few hundred feet away at most ( and remember : Rapture is only supposed to have ~20000 people ). 
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Artists Repetitive Architecture Seen in (game) Skyline Views :
That Spike at top of Chrysler-like Tall Buildings ( seen repeated over and over in some Rapture Skybox views )
The original Real_World building was there to push the height ( there was a competition at that time to have the highest skyscraper ). It was quite soon superseded by the Empire State building. Its top irregular interior is largely unused space. 
In Rapture such a spike couldn't be used as an 'Air Siphon' unless it went all the way to the ocean surface ( then that would be a liability subject to icebergs and Ocean surface storm disturbances/wave action ( BTW water currents are 100X ? calc density/velocity as forceful as high winds ). It also hardly can serve as a radio tower/antenna as Radio waves work piss-poor in Water.
I Understand that it was a secondary 'artistic' Asset to the game ( with little impact on Player activities ), BUT since most were backdrop Skybox texture images, it wouldn't have been much effort to make it LESS repetitive (more realistic) if the artists had wanted to.
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Consider : Too many tall buildings in Rapture makes them ordinary. Even Manhattan (NYC) had them standing out from amongst a huge majority of much shorter buildings ( most were less than 6 stories back in Rapture era ). What's the point of spending huge extra amounts of money if someone else is far higher ?
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The grand interior in a Atlantic Express station. Trying to resemble that old NYC Grand Central Station interior.
Larger solid steel beams/pillars would not have been as pretty as these unworkable lattice beams.
Such will be fixed in the BioShock MMORPG - with far thicker and more solid beams/pillars holding up the ceiling against all the ocean water pressure. Buttresses and Mushroom Columns and Arches to try to carry all that force.
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Bunker-like Construction Rapture Required :
Nearest thing to it I've seen lately : a book on The Maginot Line ( French Border Fortifications facing the Germans/Italians built between WW1 and WW2 ).
Versus "The Chrysler Building" - How it was built ( girders and brick ) - thin walls ...
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