Classification of Tall Building Structures

When someone says ‘Wonders of the world’, what’s the first image that strikes your mind?
Taj Mahal? The Pyramids of Giza ?

There’s a reason for it. Since ancient times, human beings have been fascinated and in awe of man-made wonders. Throughout history and mythology, the imagery of tall, majestic buildings – whether it is castles, towers or palaces – has always been a part of human imagination. These majestic structures inspire us, and reflect the innate human nature to reach for the sky.

Hundreds of years from now, skyscrapers will take over as the wonders of the 21st century. These buildings that stand tall and imposing, a sign of progress, growth and prosperity, will reflect the times we live in today.

However, when it comes to building these super structures, a lot of careful thought and precision is needed. Tall buildings require specialists who are able to take into consideration a number of factors – aesthetics, safety and practicality.

This makes it important to understand and appreciate the different types of structural systems that go into tall building structures. If one were to broadly classify tall building structural systems into two broad categories, they would be :

In this type of structural system, the load resisting system is in the interior of the building structure. This skeletal load resisting system is made up of columns and beams. If this skeletal system is present in the inner core of the building, it qualifies as an interior structure.

Some examples of interior structures are:

Rigid frame systems: In this system, the load-resisting system is made by interconnecting rigid connections. This type of system was extremely popular in the first phase of tall buildings, and can hold 20 – 25 storeys.

Shear wall systems: In this system, vertical walls act as the load resisting structure, usually located in the core of the building. This system of tall buildings can hold up to 35 storeys.

Outrigger systems: In this structural system, the load-resisting core is located at the centre of the building, but has outriggers extending outward from the centre. This sort of system can hold up to 150 floors.

In this type of structural system, the load resisting system is present in the outer periphery of the building. Due to this design system, the building is provided with a strong skeletal system that acts as load resisting system, but at the same time weighs much lesser comparatively.

Like interior structures, there are variants to the exterior structures too :

Tube system: In this type of structural system, the building is designed as a hollow cantilever that is placed perpendicular to the ground. The tube system brought in a huge leap in the heights of skyscrapers around the world.

Diagrid system: A word derived by combining the words ‘diagonal’ and ‘grid’, this technique uses a framework of diagonally intersecting metal, concrete and wooden beams. This innovative structural system made it possible for engineers and architects to envision buildings that didn’t need to have columns, thus giving rise to a number of innovative and spellbinding designs.

Exoskeleton structural system: In this structural system, an ‘external skeleton’ is used to provide the building with load-resisting structure. The term exoskeleton is taken from biology, where some creatures have an external skeleton that protects the animal’s body (as against us humans, as we have internal skeletons).