Stability systems in high rise buildings
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Neo Bankside, Southbank, London
The Gherkin (Swiss Re Bank) 30 St Mary Axe , London
Maryam & Elisavet
Vertical Elements
 Bracing

Bracing consists of diagonal elements and acts in a similar way to a cantilevering
vertical truss, from the ground up. It is for this reason that bracing should be
present at every level of the structure down to the foundations.

In order for it to be effective bracing needs to be continuous. If bracing is
discontinuous, significant lateral forces are generated and need to be transferred
from one bracing system to another, which can exert high localized lateral loads
onto elements of structure.

Additionally, the transfer system that is adopted for this purpose needs to have
adequate stiffness. It is not uncommon to see bracing working in conjunction with
other vertical elements to achieve overall lateral stability of a structure.
Vertical Elements
 Shear Cores

Shear cores and walls are vertical elements within a structure that provide lateral
stability.

The rest of the structure is framed around them and they typically work in
conjunction with floor plates and roofs.

They can also be paired with braced based systems.

Shear cores typically act as vertical access throughout the structure via lifts and
stairs and are usually located in line with the centroid of the structure.
HORIZONTAL ELEMENTS
 Diaphragms

A diaphragm is an area of the structure that provides bracing in its plane .

Typically these are floor slabs and roof cladding, but can also be in vertical
cladding elements.

If cladding is used as a diaphragm then careful consideration must be givento
the temporary condition of the structure during erection. This is also true for the
maintenance of the structure if the cladding has a shorter design life than the
structure.

There are instances where diaphragms do not have enough strength to resist the
lateral loads that can build up within them. In such cases, either the diaphragm is
strengthened or horizontal bracing is installed to either supplement or replace the
diaphragm completely.
Case Study :
Neo bankside

What is it?

Structural bracing on the exterior of the building.

Role of the element in its environment/structure?

to provide lateral and overall stability; to reduce the requirement for shear walls allowing greater internal
flexibility and to provide lateral stability under wind load making up 75% of the overall stability.

How is your “element” supported / restrained?

The bracing is joined at every third floor by pinning nodes transferring the lateral forces applied to the
structural frame by wind loads onto the cladding and into the bracing

System/element behaviour: In structural terms, how does it work to fulfil its role?

Stability forces are transferred into the external perimeter bracing via nodes, which are arranged on a six
storey interval vertically and on a sequenced interval horizontally.
Key Features Length/Span/Height
, section shape
(profile, depth,
width, diameter,
thickness),
400mm x 200mm
Grey oval hollow
sections.
Tension
Compression
CASE STUDY:
SWISS RE- THE GHERKIN

What is it?

Structural bracing on the exterior of the building Iin the form of a diagrid.

Role of the element in its environment/structure?

Resists lateral wind loading and so allows for a lighter , more open core that affords
planning flexibility.

How is your “element” supported / restrained?

The use of steel nodes to connect bracing then attached to the ground and curtain wall
that clads the diagrid.

its role?

Stability forces are transferred into the external perimeter bracing via nodes and to with
stand wind loads.
Tension
Compression
Precoated aluminum panels encase the diagrid to mask and fireproof the steel.
Comparison
 The Neo bankside uses a
single bracing whereas the
Gherkin uses a double
interlocking bracing system
 One assumes The Gherkin is
able to with stand a greater
wind load as due to its curing
shaping with the diagrid.