Steel, in contrast to traditional stone and brick, is durable, easy to make and lightweight.
Steel is an alloy that sits between wrought iron (very low carbon) and cast iron (low carbon). It inherits the malleability of wrought iron and the strength of cast iron.
Concrete is a mix of cement, water and aggregate (consisting of particulates of a hard material).
It is easily composed and molded to suit various construction needs. It also becomes stronger over time via curing
The most important advancement to concrete is the Portland cement.
It is strong against compression (which is good for supporting a building’s weight), but it is weak against tension. It is usually reinforced with a steel mesh (to form rebar) to add tensile strength.
Concrete and steel expand and contract at almost exactly the same rate when temperatures vary.
Glass is typically used as the skin of the skyscraper.
Large sheets of glass can be made using the float glass method of Alastair Pilkington.
Considerations for using glass in skyscrapers include making it span large distances (both lengthwise and up) with little support. Glass does not support the building, it hangs.
Other considerations involve temperature control and anti-fogging mechanisms, achieved through appropriate composition of the glass.
Dead Load - pertains to the weight of the structure itself.
Live Load - pertains to the weight of anything inside.
Buildings are built using piles of steel beams which form the foundation of the building.
As we go higher, the steel beams at the top need to be closer together, and the base needs to be wider.
Using only steel foundation is not enough for buildings that are storeys. This would require specialized structures instead.
We need to transport the materials.
Cranes could be used, however, they cannot extend very high. Instead, we use growing cranes that are built alongside the building/
For efficiency, we can consider modular designs.
We need to account for the people.
Elevators are crucial for skyscrapers as they are what make tall buildings feasible to use. We can either use hydraulics or cable.
We can speed up the elevator travel time either by using better elevator algorithms or increasing the speed of the elevator itself.
We need to account for swaying.
We need to prevent the building from swaying because of wind (via vortex shedding) or seismic activity that matches its resonant frequency.
The taller we go, the more we have to worry about the wind speed and pressure (which scales quadratically with wind speed.)
The trick for vortices is to prevent them from forming in the first place. Another way is to use a tuned mass damper to counteract the force.
Revolving doors are there to prevent the air from being sucked into or pushed out of the building. Revolving doors are always closed. This also saves energy and controls wind flowing into and out of the building.