Basic structural shapes

01 · Floor slabs

Composite floors that spread load

Most London offices use a composite floor: steel decking with concrete poured on top and mesh reinforcement added. The decking acts as formwork during construction, and once the concrete sets, the steel and concrete work together.

• Bending: the slab is in compression at the top and tension at the bottom.
• Imposed loads: office occupancy, partitions and equipment all press down on the floor. The slab spreads that load across its area, so it reaches the beams as a distributed load rather than a single point.

02 · Beams

Spanning between columns and the core

Main beams span between columns and the core, and smaller secondary beams sit between them to support the floor deck.

• Bending: the top of each beam is in compression and the bottom in tension.
• Shear: near the supports, forces try to slide one part of the beam past another.
• Beams are usually designed to work with the concrete slab above, so the two act as one unit.

03 · Columns

Steel columns on a regular grid

Columns run the full height of the building, usually on a grid around 9 metres apart in offices. They carry the floors above and pass the load down to the foundations, while keeping the floors open.

• Compression: the column is pushed along its length, and the load grows as you move down the building.
• Buckling: a tall, slender column can bend sideways before it crushes, so the core and bracing help keep it stable.

04 · Concrete core

The spine that keeps the tower upright

The central core houses the lifts and stairs. Lateral loads are applied directly to its walls at each floor, and the walls act as a stiff vertical spine that keeps the building stable.

• Shear and bending: wind pushes the tower sideways, and the core walls resist that push like a cantilever fixed at the ground.
• Overturning: the tower wants to tip, and the core and foundations hold it down.
• Compression: concrete handles the vertical load well, while steel reinforcement handles any tension.

05 · Lift shaft and risers

Why the core is the tower's spine

This is a side-on view through the core. Wind pushes on the façade at every floor, and those sideways forces must reach the core. The core's walls resist them, and the lift shaft is one of the walls doing that work.

• Lateral (wind) shear: sideways forces from each floor pass into the shaft walls, which act together as a vertical cantilever.
• Bending and overturning: the forces create bending in the walls that grows towards the base, and the piles resist the tipping.
• Guide rails: the moving car sends sideways forces into the rails, which pass them into the shaft walls.
• Openings: lift doors and riser openings weaken the walls, so they are sized and reinforced with care.

06 · Foundations

Piles drilled into London Clay

Much of central London sits on London Clay, which is too soft to carry a tower on shallow foundations alone. Towers typically rest on piles drilled deep into the clay, joined at the top by pile caps under each column.

• End bearing: the base of each pile carries load into firmer ground.
• Skin friction: the sides of the pile grip the surrounding clay.
• Settlement: uneven movement can crack the structure, so the piles are designed to settle evenly.

07 · Load path

The whole route, roof to ground

Loads follow one route: floors → beams → columns and core → piles and pile caps → London Clay. The glazed façade is hung from the floor edges, so its weight and the wind pressure on it pass into the floors and on through the core.

This is a simplified model. A real tower includes bracing, connections, lift shafts, plant and detailed checks against design standards.