Balancing Act: The Wonders of the Center of Gravity

Credit image: public image
Credit image: public image

Article by: Abhinav Tanksale, on 19 March 2023, at 06:34 am PDT

Through sound engineering, humanity has been able to build structures that otherwise would have been impossible. Many ancient structures in the world, make us question the physical principles at work during their construction.

Bonanno Pisano was a highly skilled medieval Italian architect and sculptor of the 12th century. Best known for his contributions to the construction of the iconic Leaning Tower of Pisa, cementing his place in history as a master of both sculpture and architecture.

The tower is a remarkable example of how the principles of physics can be used to create structures that are both aesthetically pleasing and functional.

It has been a source of fascination and wonders for over 800 years, and its ability to remain standing despite its lean has been a subject of study and speculation for just as long. However, the reason why the tower does not fall can be attributed to the careful management of its center of gravity.

A structure's center of gravity is the point at which the weight of an object is evenly balanced, and it is this balance that allows a building to stand upright. In the case of the Tower of Pisa, despite its lean, the center of gravity has been carefully kept within its base, ensuring that the weight of the structure is evenly distributed and that the tower remains stable.

Despite earthquakes, storms, and wars, the tower has been able to withstand the test of time because of this careful balance. Take a look at below Free Body Diagram to understand how this actually works.

The mass of the tower is about 14500 tons and its center of gravity sits lower than the top of its fourth floor. Today, the tower leans so much that a vertical line drawn from its outer edge meets the ground 4 meters far from the base.

Galileo took advantage of its unique geometry to conduct experiments on gravity by throwing objects down from its leaning side. A virtual demonstration of Galileo's experiment is available here.

Talking about another modern wonder which is Burj Khalifa, the tallest building in the world, has a center of gravity located near its center and its stability is ensured by its reinforced concrete core and a series of outrigger walls that extend from the core to the exterior walls.

This design helps distribute the weight of the building evenly, reducing stress on any one point and increasing its overall stability. The Burj Khalifa also has a sophisticated tuned mass damper system that helps counter any vibrations caused by strong winds or earthquakes, further enhancing its stability and ensuring the safety of its occupants.

For a more detailed treatise on the structure's architecture, check out  State-of-the-Art & Structural Design Elements | Burj Khalifa.