commerz bank

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Commerzbank - Frankfurt,Germany

Architect : Sir Norman Foster and Partners

Client : Commerzbank Ag

Structural Engineer : Ove Arup & Partners

Year Completed : May,1997Occupancy Type : Office

Construction type : Mixed(reinforced concrete

foundation,steel frame with

vierendeel principle)

Height : 258.7 metres(853.71 feet);298.74metres(985.8 feet) upto the top of

Antenna

Stories : 63

Area : 120,736 sqm(1,314,815 sq ft)

Prototype for an Ecological High-Rise


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Design Analysis- general aspectsconcept - layers of transparency surrounding the workplace.

Europe's tallest office building at 60 stories and just under 300 m

stepped top of the building has a strong visual impact from a long

distance- a distinct symbol for the banking district

claims to be the greenest

has gardens in the sky

operable windows for ventilation

triangular tower incorporates passive lighting and climate control

systems, including chilled ceilings for cooling

Structural columns, staircases, elevators, and utilities are located at

the corners, leaving the building's core open as a continuous atrium

and natural ventilation shaft.



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Design Analysis- Floor Plan organization

floor plan of the tower is an equilateral triangle(each side

approximately 64 meters) with rounded corners and slightly convex

sides

floors of the building as well as the cores at the three corners areorganized around the central atrium

Each floor has three wings, two of which serve as office

villages; the third forms part of one of the 4-story-high sky

gardens

atrium is separated horizontally every 12-storeys at the village

boundaries to limit stack pressures and smoke spread

principal entrance to the new tower is from the north, up a grand

flight of stairs

The tower makes an open and transparent impression thanks to

the atrium, which is also triangular in shape


Plan - Level 1


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Plan - Level 19

Plan - Level 27

Plan - Level 11

Plans of different levelswith the garden in each

wing of the building


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Typical floor Plan

Plan - Level 51 and 52

Plan - Level 43

the total height rose to 221 m at its

western core

A penthouse for mechanical

systems and an antenna extend the

tower's total height to 300 m (984

feet).


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Construction progress in lower

floors

Two storey high link frames that

connect the main compositemegacolumns

Picture taken during construction


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Passenger lifts in each core serve a distinct group of floors

the combined service/firemens lifts in the north and westcores stop at every level

interchanges at levels 7,19 and 35 simplify travel betweenfloors for those people working in the building


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Though the basic theme isfollowed, variations in the choice

of plants and in the planting

layouts ensure no two gardens are

alike

Generous interior "sky gardens" are a

fundamental element in the architect's conception

There are nine 14m high gardens spiraling up

the atrium in plan

gardens change in design and vegetation

according to orientation: three each facing

eastwards, southwards and westwards

As each garden faces a different direction, the

microclimate of each is also different

Botanically,the vegetation reflects the

geographical orientation:-gardens facing eastward are Asian, with

bamboo, magnolias, hydrangea and oriental pines

-southward are Mediterranean, with citrus and

olive trees, thyme and lavender

-western gardens are North American, withgrasses, maple, rhododendrons and cedar


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gardens to be used by the employees for relaxation, lunch

breaks and meetings

Through the atrium and the gardens, a direct relationship is

established with the outside and natural lighting is provided

for

the atrium offices

The gardens provide the inner offices with daylight

they create a feeling of openness and space and form part

of the system of natural ventilation

Energy consumption is also minimized by the reduction in

heat transfer between the gardens and atria offices


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Natural Ventilation

The building was designed to function in the mixed mode- i.e. both

natural and artificial ventilation

Requires 160 days of of air conditioning in a year

Atrium designed as a giant chimney, using stack effect to draw in airthrough openings

The building is divided into 12-storey high sections by decks which

have gardens on each face of the triangle.

Windward gardens admit air and leeward gardens exhaust it Occupants have the power to control their environment by manually

opening windows

Offices on external facades can be naturally ventilated by openable

windows

Internal offices facing atrium naturally ventialted by the air that flows

through the atrium



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Air-conditioning:

A new system introduced for Cooling - separation of the

cooling and ventilation processes

Coolness is provided by water and not air, as water as a higher

specific capacityAlso water can be re-circulated and so the cooling medium is

not thrown away

Chilled floors are provided to act as negative radiators

Indicator lights to to notify occupants of the ventilation mode -

natural or mechanical

Heating:

Heating is provided by ordinary thermostaically controlled

panel radiators



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Structure:

Designed as a hollow tube standing on end

Two major structural elements - corner columns and eight-

storey high bridge-like steel structures

Concentration of vertical loads on the perimeter to get bestresistance for horizontal loads

Spiral configuration of gardens to maintain structural

stiffness, every fourth floor is continuous to act a stiffening

diaphragm

To have column-free gardens, further concentration of

loads on the corners of the triangle necessary.

Six main columns, two in each corner, made up of two H-

section steel members

Foundation consists of 111 piles clustered in 3 groupsresting on a relatively stable layer of porous limestone



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Section through office

cladding

Plan - Level 51 and 52

Picture shows the ventilation

cavity office cladding

Office cladding highlighting

the small aerofoil section

positioned above and below

the ventilation slots toimprove the air flow

During construction

cladding was done in all 3sides simultaneously but at

different levels


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Seismic Factors

Ct = 0.035

Rw = 9 (Special Braced Frame)

Wind Factors

Wind Speed = 70 mph

Exposure factor = C

Site Conditions

Flat


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