The Science of Structures: Physics Behind the Buildings We Love

Ever wondered how some of the most mind-blowing buildings stay standing, even when they seem to defy gravity? From ancient monuments to modern skyscrapers, the science of architecture has been at work, quietly keeping our favourite structures from crumbling. In this post, we'll explain important physics concepts behind iconic buildings.

1. Torque (or moment of force)

Imagine you're at the park with your friends, and you hop onto a seesaw. If both of you are the same weight and sit at the same distance from the centre, the seesaw stays perfectly balanced. But what happens if one person is heavier or sits closer to the middle? The seesaw tips! What you’ve just experienced is torque in action. Torque essentially refers to the turning force about an object and is seen everywhere in day-to-day life.

An example of torque using a seesaw where two people of the same weight (70 N) stand an equal distance away from the pivot.

For an object to attain stability, the clockwise and anticlockwise forces acting on it must be equal (like in the example shown above). In architecture, torque plays a huge role, especially when structures have to withstand powerful winds or earthquakes.

The further away you apply force from the pivot, the larger the turning effect on the object. This is why door handles are placed further from the hinge.

How does torque impact buildings?

• Tall structures experience high torque because of wind forces pushing them sideways.

• Skyscrapers use internal supports, like braces and dampers, to resist twisting forces.

One of the best examples of how buildings resist torque is "The Turning Torso"* in Sweden. This futuristic skyscraper looks like it’s twisted, but every segment is perfectly engineered to handle the torque created by its shape and the wind.

2. Centre of Mass

Ever tried balancing a pencil on the tip of your finger? It’s tricky, right? That’s because the pencil’s centre of mass (the point where all its weight is perfectly balanced) needs to stay directly above your finger to keep it from tipping over. If the centre of mass shifts, even slightly, gravity acts, and the pencil falls.

The same idea applies to buildings, but on a much larger scale. Architects and engineers need to ensure that the centre of mass of a structure is balanced in a way that keeps it standing, no matter what forces act on it. If the centre of mass is too high or off-balance, the building becomes unstable, just like that wobbly pencil on your fingertip.

How does centre of mass impact buildings?

• A building's centre of mass needs to stay within its base for it to remain stable.

• Engineers use wider foundations and other techniques to keep skyscrapers balanced, just like you'd keep the pencil steady on your finger; this is the reason the Burj Khalifa has a tapered shape.

Take the "Leaning Tower of Pisa", for example. Originally designed to stand straight, the tower’s foundation settled unevenly, causing its centre of mass to shift and the building to tilt. Despite its famous lean, engineers have stabilised it over time by making sure the centre of mass remains inside the base of the structure, preventing it from toppling over entirely.

In modern architecture, maintaining balance is even more crucial, especially in skyscrapers that have to withstand wind and earthquakes. For instance, the "Shanghai Tower" has a heavy foundation and carefully placed support structures to keep its centre of mass low and steady, allowing it to stand tall despite its massive height and external forces.

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Note: This is an ongoing post and will be updated with new facts regularly. Hope to see you back soon!

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