S5C10: Architecture & Buildings

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a) A practical art form

For the final chapter of this fifth series, we’ll stray somewhat to the adjacent field of architecture. This is a necessary detour and we are still well and truly connected to some of the fundamental skills required in civil engineering, namely their planning and designing. In fact, architecture is not really a discipline, it is too broad for this, it is a concept bridging the idea of a structure to its construction with the notion of design at its centre. Designing is circular and iterative, it consists in drawing a plan to guide a construction project, all the way down to the specifics, but we need to appreciate the imperatives and physical or financial constraints of the world are also an input that cannot be ignored by the architect. In that sense, designing is offering a possible solution and related instructions to a specific situation.

This notion of solution calls that of function, and as we have seen with proteins back in S1 Section 4.a, the form of a structure can often be an expression of its function. Think of a staircase for example, its most distinctive feature is not whether it coils or has split levels, it is the linking of two levels on separate horizontal planes, which means a gradient separation needs to be overcome in a way humans can handle relatively easily, hence the breaking down into steps. Or the fact that walls tend to be vertical has everything to do with their role in supporting and transferring compressive forces, as we have seen the pillars of bridges do in S5 Section 7.d.

This doesn’t mean aesthetical considerations are absent from the equation and, as long as the primary function is taken care of, the architect can wear an artist’s hat with an engineer’s uniform. This is greatly facilitated by the presence of lines that readily invoke drawings and sketches, the symmetry and elegance of structures or the break of symmetry and the anti-conformism it may convey. Moreover, besides lines and surfaces, the architect can play with volumes and spaces, light and shadows, always cognizant that the form should help or at the very least not hamper the primary function.

Beyond buildings and infrastructure, architecture also plays a central role in putting together systems of various kinds, ensuring the user experience and interface (UX and UI) not only look attractive but facilitate the handling of the system. Think of a mobile phone: the shape matters, as does the position of the camera lenses and sensors, etc. and all these need to be considered as a package, trade-offs need to be made and a final form is drawn up.

b) Storied lines

As one dwells into the topic of architecture, the pull of history is unavoidable. It is not simply a matter of trivial pursuit of knowledge and browsing drawings and pictures of structures across time and space. There is something more primordial in architecture, as there is in art. It reflects the beliefs and priorities of the time and it traces our arc from the primitive to our contemporary era, starting with the house as a basic shelter from the elements and predators, then looking for more efficient techniques and materials and now, having achieved all this, focusing on the pleasurable aspects.

When we look back upon the architecture of the Mediterranean civilization during the antiquity, or Mesopotamia, or the early Chinese Empires, one of the most striking aspects is the primacy of kingly or imperial power and their blending in the psyche and buildings of the time. During those days, buildings were either small and quite undistinguishable from the one next to them, with the exception of some rich officials, or they were monumental. I use this word not only because of the substantial dimensions, but also because they were meant to convey the grandeur of the sacred. This could be the Palace of the divinely-appointed ruler, or even divine ruler outright, its resting place, a gateway to beyond our earthly life, or a tribute, a visual reminder of a sacred being.

During the time of the Pharaohs, the necropolis of the current ruler was thus a focal point of financial and religious investment and the tomb monuments of previous rulers could be either worshipped or left to decay (or worst) depending on the political forces at play. The architectural peak of this Nile valley civilization was the building of pyramids, an expansion on the mastaba, first at Saqqara near Memphis with a step profile, then at Dahshur and eventually at Giza where the Great Pyramid housing the remains of Khufu was constructed about 4600 years ago. I include a link to the Wikipedia entry for Egyptian pyramids at the end of this chapter, should you wish to read more about this topic.

Perhaps less vibrant in the popular imagination, the pyramids found in Central America and all the way to Peru also had clear religious purpose. They were used as temples, for worshipping, burials and sacrifices, which is nothing less than paying tribute to a god in an attempt to sway its behaviour. These were built by various Mesoamerican civilizations, including but not limited to the Mayas, Aztecs, Olmec and Incas. This time as well, I am including the link to the relevant Wikipedia entry in section g).

Fast forward a few centuries and the search for stronger structures, larger volumes and more light penetrating through windows. All these endeavours progressed through a better understanding of forces and coalesced into the building of cathedrals, the temples of Christians. One could argue this is my Western culture upbringing, but I don’t think so. There were temples and grand structures in most civilizations though there is a strong case to affirm the incremental mastering of architecture was best instantiated in the evolution from somewhat plain Roman churches to the Gothic architecture and its flamboyant derivative with beautifully carved façades and flying buttresses, and finally the Renaissance architecture. The book The Pillars of the Earth by Ken Follett is a very atmospheric and non-technical way to appreciate this ground-breaking architectural developments during the European Middle Ages. Later trends such as the Baroque and Neoclassical would further expand and refine some of these principles, yet a line had been crossed in those centuries and would not be materially shifted until the advent of new construction materials such as cast iron and steel. What would change during these later centuries would be the artistic taste of the day, hitting their most strident exuberance in the over-the-top Rococo. In stark contrast, modern and contemporary architecture often does away with ornamentation and prefers playing with lines, surfaces and spaces.

The creeping overemphasis on form over function was best highlighted when it was explicitly rejected as part of bourgeois and capitalist values in the classless utopia of communism. This yielded the plain “Stalinist” architecture of concrete and straight lines with no room for art and the emotions it generates. Surely, this has inspired the uninspiring post-WW2 brutalist architecture and the greatest merit of this movement was to make us realize the need to construct buildings one enjoys living in rather than ones devoid of charm and elegance.

In contrast, contemporary architecture doesn’t always favour function over style but it certainly seeks to differentiate itself and make each building unique, a monument of sort. This plays in the hands of the wealthy whose objective is to build a trophy house or some other building. That said, there is no arguing that when done well, such a building can be art unto itself. Take the Guggenheim Museum of Bilbao designed by Frank Gehry, it certainly is more interesting that most of the pieces exhibited within and draws thousands of visitors to the city just for its own sake. Likewise for the outlandish lines and spaces of the Heydar Aliyev Centre in Baku drawn by Zaha Hadid, or for the magnificent, pure lines of the Millau Viaduct, courtesy of Norman Foster and Michel Virlogeux (the structural engineer).

As our globalized world supposedly celebrates differences but rewards standardization, only those who can afford a private architect can hope to have a truly unique place to live. Some will go the bling way, ignoring their environments, and others will seek to integrate with their surroundings, turning natural constraints into architectural opportunity to create genuinely exceptional buildings and living spaces. Taste and context do matter.

c) Tools and materials

Now, design in hand, what does it take to build a house? Well, biology points the way; there needs to be nutrients and molecules, those are the building materials, and there needs to be tools and manpower such as proteins. In residential building construction, the most sizeable equipment is required for the digging and laying of foundations and then the erecting of the superstructure, being the walls and the roof, those elements absorbing, supporting and transferring various physical forces, including compression and bending.

Before foundations can be laid, earth movers such as bulldozers need to excavate the soil and graders may be required to flatten the surface surrounding the building, though it is also possible to retain slopes. Then a concrete mixer will pour its content and the surface will be smoothed by hand with trowels before it is left to cure. As for the walls, they can be built entirely by hand with scaffoldings to reach the upper sections or with the assistance of various lifting devices – in the case of tall buildings these would likely be cranes.

Regarding the materials, no list could be exhaustive so I picked six I thought can be considered central to the building of most houses across the world.

Wood is one of the oldest building materials, although it presupposes the presence of trees in the area. It is comparatively easy to harvest, including by felling trees, and to transport. In can also withstand significant compressive and tensile forces but, even though it can bend, it doesn’t have the shear strength of some modern artificial materials. In general, provided the adequate species is used, it is more than adequate for a standard house and, being natural, it is much more energy efficient to produce and it is biodegradable. Provided trees are being replaced through replanting, wood can be considered a sustainable construction material.
Stone is more energy intensive to cut, however it is also natural so, provided it is not transported across long distances, it is a good option in terms of green credentials. The properties of stone vary widely and limestone would exhibit different density and strength compared to granite for instance but overall they are extremely resistant and durable. Stone also works extremely well as a thermal regulator due to its thermal mass.
Steel has mostly replaced iron (even the ridged corrugated iron sheets are actually made of steel) and is used as reinforcing element in foundations and walls made of concrete or as beams in roof construction and to build intermediate floors (above the ground floor). It is also widely used in the manufacturing of pipelines with the main alternatives being thermoplastics such as PVC. Steel can have some allure, especially the stainless variety, so in modern architecture it may be adopted as an integral part of the building aesthetics and, visually, it marries well with stone and glass.
Earth or clay is still used widely in the form of bricks, generally after undergoing some thermal treatment such as firing to improve their strength and durability in the face of weather. Typically bricks would not be completely filled in, so they are lighter and work well as an insulator, and they would be bond together with cement during the construction process.
Concrete, which also makes use of cement (we already took a quick look at both these materials in S5 Section 7.b on road surface and foundation), is quite versatile and is the natural choice for foundations as well as walls and indoor load-bearing structures such as columns. Like stone, concrete is not a great insulator, yet its thermal mass provides temperature regulation capabilities.
Glass is used for lightweight partitions where transparency is a sought-after quality, or at least not an issue from a privacy standpoint. It is not a good sound and temperature insulator unless double glazing technology is used, where air is the insulator. Unfortunately, glass yields easily to shear and even compression. Furthermore, glass manufacturing is an energy-intensive process since it requires high-temperature melting of raw materials such as silica. I include a link to the Wikipedia entry for glass at the end of the chapter if you wish to know more about this type of solid form.

d) The modern house

The building of a house starts from the bottom, with the foundations. Those are likely to be shallow, in opposition to the deep foundations of a multi-storey building, and their purpose is to ensure the structural load from columns and walls within the house will be spread to a level inferior to the soil’s bearing capacity. A 1-to-1 ratio would often not meet this criteria but increasing the width and therefore overall surface of the foundation does decrease the pressure density. A wall may rest on a wall footing and a column on an isolated footing or a combined one alongside other columns. Alternatively, when the load-bearing capacity of the soil is really low, a continuous slab of concrete called raft foundation may be appropriate.

Then comes the structural part, the framing. This may rely on timber or steel columns or on the load-bearing capabilities of the wall themselves, or a combination of both. The choice has to do with climate and the required level of temperature isolation, the cost, and the availability of materials. It should be noted that not all walls are load-bearing and those sections located within the house may instead serve the purpose of partitioning the interior space, in which case much lighter and cheaper materials would be used.

With the exception of homes located in areas seeing very little precipitations, and in particular no snowfall, houses are crowned by a roof rather than a flat cover. The purpose of the roof, besides covering the top floor (or only floor), is to allow the snow or rain to slide down and away from the structure. This explains the sloping surface and, the higher the snowfall level, the steeper the angle to avoid too much accumulation and the stress caused by such additional weight. A roof-supporting structure is often made of either timber or steel and the external envelope covers a broad range of materials, including banana leaves, corrugated iron, thatches, slate, and ceramic tiles. This choice must take into account the ability to face the elements, avoid water penetration and also provide some degree of thermal isolation.

This is a good segue to mention the other aspects of thermal control provided by the building envelope and equipment. This includes the choice of windows’ material with double glazing providing the best isolation, the optional sheathing of the walls with cement, gypsum board, roughcast or even wood (a choice also driven by aesthetic considerations) and the heating, ventilation and air conditioning system (HVAC). HVAC is not only about temperature control, it also helps attain a desirable air quality by removing particles, controlling the humidity level and allowing fresh air to replace stale one. If you wish to understand a bit more about heating and the differences between transfer of heat by convection, conduction or radiation, you may refer to S1 Sections 9.c and 9.d.

Talking about radiation, windows are the part of the house designed to let light in and illuminate the interior without the assistance of electrical lighting. They also provide the ability to look outside the house whilst being sheltered within, they are thus the primary interface with the external environment as far as our visual system goes. Nonetheless, windows are essentially a cut out within a protective envelope and they weaken the thermal isolation of the building. With light comes heat, which might be a sought-after quality in colder climates but not in warmer ones. Except that windows are agnostic as to which way heat is being transferred and it can also escape out of windows. Thus, there is a trade-off to be made when it comes to the number, size and orientation of openings.

Then we need to think about connectivity, the wiring and piping required for bringing in data via copper wires back in the days or optical fibre nowadays (S4 Section 4.e), wires connecting to the nearest grid for electricity, and water pipes. As for cooking and heating, depending on the technology used, this may require natural gas pipes while the ad-hoc supply of LPG cylinders doesn’t call for any particular infrastructure but larger outdoor tanks may be used in isolated locations where gas is also used for heating. As we have seen in the previous Chapter 9, the piping of water might be differentiated between drinking and non-drinking water and, after being used, it should be collected and directed towards the municipal sewage or undergo a first phase of treatment in a septic tank before collection.

And finally, we are left with the interior arrangement and aesthetic, the domain of interior design. Some spaces are designed to have only one purpose and consist of built-in hard-to-move fixtures but, for the most part, the rooms within are a series of blank canvas with fixed shapes that offer much freedom of expression and individualization. Perhaps as importantly, interior design need not be set in stone, it can be altered at the margins or even completely overhauled. A car analogy would be that the architect delivers a chassis, engine, transmission system and sensors and it is for the owner or tenant to decide on the colour of the paint, the fabric of the seats and the type of tyres. The playing with furniture can create spaces within spaces, all the while providing functionality and pleasure for the eyes. In many ways, interior design is the expression of the genetic materials of the inhabitants of the house, a phenotypic trait – you may want to refer to S1 Section 3.c if you are unfamiliar with this term.

e) Reaching for the skies

As cities grew over the centuries, their centre has increasingly been dedicated to mercantile activities such as trading in and around a marketplace with residential buildings moving at the periphery and, with the advent of the car, further out to what became suburbs. In parallel, the growth in the size of businesses and the rise of the white-collar service industry meant a growing pool of employees working in offices located in proximity of transport hubs, government buildings, and other businesses with all the benefits this brings in terms of transmission of information and more broadly doing business.

Consequently, real estate became very valuable if you owned it, or pricey if you needed it, and one way to increase the density of the number of desks, besides packing them closer together, is to stack them over vertical floors. This not only results in less land space being required but also can decrease the construction cost per floor up to a certain extent, as well as keep employees of one company together in the same building – risky but efficient in terms of internal communication. A side-effect, or opportunity, depending on one’s perspective, is the branding aspect tied to having a very tall building in a city – ideally the tallest in the world to make the headlines which, in our social networks era, unfailingly draws swathes of tourists.

Unlike a house, those tall buildings we call skyscrapers have deep foundations with piling reaching down to more stable layers of soil with superior load-bearing capabilities. To establish this, geotechnical engineers are roped in as early as the site selection stage and will work with the structural engineer and the overall architect to establish what can and cannot be done, and how the whole structure must be anchored. This is a heavy-duty undertaking with earth excavation and pillars being driven into the ground with perhaps the addition of cement or other binding agents to further strengthen the soil.

Shear forces from the wind and potential lateral movement of the soil created by earthquakes also need to be catered for. The former can be mitigated through aerodynamics and more specifically by designing a building with a twisting or rounded shape, interrupting long vertical surfaces with blow-through floors, by suspending mass dampers within the building that oscillate in the direction opposite to the swaying (Taipei 101 has a good example of this on display for visitors), and by spreading the forces laterally to avoid concentrated stress points.

For earthquakes, the mass damper and lateral diffusion of forces are also relied on in the above-ground part of the building and can be supplemented by other types of dampers set up to dissipate the energy originating from seismic waves. In addition, this type of damping can also be placed at the interface between the superstructure of the building and the ground, at the level of the foundations. This technique is called base isolation and involves elements such as rubber bearings or spring systems to effectively de-couple the superstructure from the substructure resting on the ground.

But, how do we go from a five or ten storey building to hundred stories? The answer is two-fold: use strong materials such as steel and lose weight. If you have read S3 Section 10.f on launching a space shuttle, you would recall an issue with rockets is the fact that the more fuel they need to bring a payload into orbit or to outer space, the more fuel they require to lift off that fuel. It is the same with buildings, the heavier the walls being built, the higher their combined compressive forces. The solution is simple: do away with load-bearing walls and use steel columns and beams instead, and from there hang the lightest possible envelope that does a correct job of thermal isolation. This explains why we have strong structural cores around the lift lobbies and thin walls mostly made of glass – the technical term is curtain walls. Design-wise, to avoid bringing the centre of mass of the entire structure too high up where it becomes problematic to manage, the horizontal footprint can be decreased whilst continuing to progress vertically; this explains the step-like shape of some iconic buildings (these are called setbacks in the jargon).

As for utilities, considering the total volume that needs to be temperature-controlled and the number of occupants who may require access to water and other commodities, utilities can occupy several basement floors or side buildings and require full-time management. Yet, the main difference between a normal house and a skyscraper is not the piping and wiring but the flow of people. From mostly horizontal, across two dimensions, there needs to be an efficient way to move vertically and stairs quickly prove impractical except as a back-up route. Enters the elevator, colloquially called lift. For low rise, hydraulic pistons pushing up the platform is a possibility but, as the height increases, the only viable option is for the cage to be pulled from above via a cable and be guided via rails. To avoid too much tension in the cable, having to deploy a lot of energy to pull the lift up, and see a lot of this potential energy wasted when it goes back down, lifts work in pairs with a counterweight and the mass of this counterweight is set at the expected average total weight of the lift plus the people inside. This means the gravity experienced by the counterweight offsets most of the energy required to increase the potential energy of the elevator as it moves away from the ground and, on the way down, the loss in potential energy is in great part transferred back to the counterweight. Elevator systems in large buildings are a complex affairs and a lot of maths go into optimizing the set-up, which often involves the splitting across different lobbies so that each elevator only serves a certain range of floors. This may require transferring to another lift to get where you want but, on average and across all people using the building, this should reduce the overall waiting and shuttling time.

And finally, we will end with a very quick history of sky-scraping, which is not completely independent from the progress of elevator technology. There isn’t a strict set of criteria to define a skyscraper and “10 floors and above” could be considered the general threshold. Outside of monuments, the first commercial building to have reached that level was the Home Insurance Building in Chicago in the mid-1880s and the weight of the walls was already supported by the streel frame. The iconic triangular 22-story Flatiron Building was completed in New York in 1902 and the famed Empire State Building in 1931; its roof ends 380m and 102 floors above the ground. Then came the Chrysler Building, the now defunct World Trade Centre towers, the Sears Towers (now Willis Tower), and with the Petronas Towers the baton passed to Asia before being handed over to the Middle East: Taipei 101 held the title for 6 years and Burj Khalifa in Dubai is the current holder at 828m with 224m of this being “vanity height” above the highest usable floor.

f) Trivia – Cave dwelling

Well before we sought to build ever higher with ever deeper foundations, man sought refuge and shelter in the ground itself. Whether it is in natural caves or by digging into the soil and rock, it is possible to find or fashion habitable and storage spaces providing safety away from animal predators and other aggressive tribes, and isolation from rain, cold and heat.

By happenstance, this lack of direct exposure has also ensured the survival or primordial art forms, what we call parietal art or cave paintings. Perhaps the most famous of these is the Lascaux cave in France with art dating from around 15,000 BCE. And in the district of Göreme, in Cappadocia, natural rock formations were also instrumental in the spreading of early Christianism by hosting churches and sacred art out of sight to avoid repression.

Cave dwelling is mostly a thing of the past, even though there are still inhabited houses partially built into rock faces. Nonetheless, the heat regulating properties of underground storage and the cool conditions they offer are ideal for at least two businesses: maturing cellars for cheese and wine storage. I know, this probably reflects my French cultural background.