Commerzbank Tower - Mike Benkert`s Website

Transcription

John Arend, Mike Benkert, Audrey deFilippis, Saretta Tillmaand
Commerzbank Tower
-Overview-
-Integrated Strategies-
-Structure-
-Environment-
-Construction-
Overview
Commerzbank Tower Program
Architectural Intent
Construction Ethic
01
02
03
Integrated Strategies
Structure, Environment, and Construction - Exterior Office Glazing
Structure and Construction - Mega-Column
Structure and Environment - Sky Garden Glazing System
01
02
03
Structure
Primary Structural Members
Conjecture and Structural Diagrams
Structural Strategy
Hypothesis
01
02
03
04
Environment
Climate Data
Climate Data
Climate Data
Climate Data
Climate Data
Climate Data
Climate Data: Responses
Environmental Responses:
Envionrmental Responses:
01
02
03
04
05
06
07
08
09
10
11
Daylighting and Views
Ventilation
Ventilation
Sky Gardens
Construction
How the Building Meets the Ground - Foundation
How the Building Meets the Ground - Foundation
How the Building Meets the Sky
How the Building Meets the Sky - Cladding
How the Building Meets the Sky - Cladding
Social Responsibility
The Corner
The Corner - Mega-Column and Vierendeel Frame
The Corner - Cladding
Response to Water - Exterior Office Glazing
Response to Water - Exterior Office Glazing
Response to Water - Mega-Column
01
02
03
04
05
06
07
08
09
10
11
12
Works Cited
Table of Contents
-Overview-
-Environment-
-Construction-
Commerzbank Tower
FosterArend,
& Partners,
Arup andAudrey
Krebs &
(SE),
J. Roger
Preston w/ P&A Petterson Ahrens (ME), Schad & Hölzel (EE)
John
Mike Benkert,
deKiefer
Filippis,
Saretta
Tillmaand
Site
Project
Building Facts
HVAC
Passive
Systems
Envelope
While Commerzbank Tower has a distinctive presence on the Frankfurt skyline, it is also
anchored into the lower-scale city fabric, with restoration and rebuilding of perimeter
structures reinforcing the original scale of the block. The developments at street level provide
shops, carparking, apartments and a banking hall, and forge links between the Commerzbank
and the broader community. At the heart of the scheme is a public galleria with restaurants,
cafes and spaces for social and cultural events. [fosterandpartners.com}
-Structure-
Building Facts
Structure
When construction wrapped up on the 53-story Commerzbank Headquarters in 1997 it stood
as the tallest building in Europe, but what made it revolutionary, was its combination of form,
inventiveness, and technical expertise to create an entirely new building type: the humane
and socially responsible skyscraper. Breaking away from the American model of
deep-planned, air conditioned structures with a central service core and identical, spatially
separated floors; Commerzbank tower is flooded with daylight and naturally ventilated, has a
full-height atrium, and four-storey landscaped gardens evenly distributed over the height of
the building. Working in conjunction, these architectural elements unlock the internal space
of Commerzbank, transforming the entire work environment. {Davies 9}
Overview 01
Floor Area sq.ft/floor
1.3 mill total (≈23,000 per floor)
Occupant load
2,100 workers
Cost
Program
$300,000,000 US
53-story high-rise office building
Site Description (acres?)
approximately 3 acres; site shared with old Commerzbank building
Site Type urban, rural, etc
urban
Parking spaces #
multi-story parking garage holds 300 cars and 200 bikes
Foundation type
pile raft foundation
Gravity force systems type
perforated tube structure (corner columns with link frames)
Lateral force systems type
vierendeel truss system
secondary structure/backup
continuous floors at every fourth floor act as a stiffening diaphragm
Glazing type, identify
double-glazed operable window w/ outer skin of fixed glass & ventilated cavity
Skylights
full-height atrium with glass decks every twelve floors
Cladding type, identify
double-skinned aluminum framed curtain wall
Roof
glazed roof over plaza & atrium, high albedo concrete above remaining program
Daylighting
sky gardens, atrium, & floor-to-floor glazing
Heating
passive solar gain, heat generated from office machinery & building occupants
Cooling
natural ventilation, stack effect
Equipment list
cooling towers, absorption chillers, central building management system (BMS)
Cooling system type
water-cooled, chilled-panel ceiling system
Heating system type
thermostatically controlled radiant heating system
Duct
yes/no yes
Vertical Chases
yes/no no
Sources
1. http://www.skyscraperpicture.com/commerzbank_tower.htm
2. Commerzbank Frankfurt: Prototype for an Ecological High-Rise
(Davies 51)
(Davies 46,47)
Sources: “Commerzbank Frankfurt: Prototype for an Ecological High-Rise” (Davies), www.fosterandpartners.com
Commerzbank Tower Program
-Overview-
-Structure-
-Environment-
Overview 02
-Construction-
Architectural Intent
Although Norman Fosterʼs Commerzbank design was the tallest building in Europe at the time of its completion, its
height was an after-thought to the true intentions driving its creation. Commerzbank is a social, economic, and
ecological statement in architecture. Foster considered the lives of the users, clients, and neighbors of the building when
formulating his design. Fosterʼs social, economic, and ecological goals often overlapped. Foster could have designed a
cheaper building than what Commerzbank is today, but he asked his clients to consider additional investments to realize
long-term gains. The buildingʼs program enhances its users lives and because of this increases their productivity. The
ecologically friendly design lessens the energy costs required to maintain the building over time. Even the decision to
build in the urban core of Frankfurt rather than on cheaper land in the suburbs, continued the growth of Frankfurtʼs
development and contributed to the strength of the city as a whole.
Structure
The structure of Norman Fosterʼs Commerzbank Headquarters is essentially a perforated tube in the shape of an
equilateral triangle. The structural components work together to form this shape and to resist both gravitational and
lateral forces. The three corners of this triangle are made up of 2 H-section columns connected with large steel “link
frames” covered with reinforced concrete. These columns carry the load of the building and transfer it into 101
telescoping piles that bear on the porous limestone below. Supporting the winter gardens that are cut out of the tube
are eight storey Vierendeel trusses. These trusses, made up of eight horizontal and four vertical members, also form the
eight floors between gardens. Because of the tube form, the structure of the Commerzbank Headquarters is made up of
a very few standardized pieces. All of the Vierendeel frames support the same load, and therefore are made of the same
members. The corner columns are also the same from the bottom floor to the very top, with their strength changing
depending on the amount of reinforcing in the concrete encasing them. The core columns, Vierendeel frames, and link
frames work together to form a structure of great stiffness and stability.
Environmental Response
Considered to be the worldʼs first ecological office tower, Commerzbank Headquarters relies heavily on passive
strategies to create a pleasant work environment for its occupants. These strategies include a triangular (doughnut) floor
plan, ʻskyʼ gardens, and a full-height atrium that allows for every office in the tower to have operable windows for views,
natural ventilation, and daylight. The four-storey ʻskyʼ gardens (which spiral up the sides of the tower) provide fresh air
and allow for passive solar gain, while the central atrium space acts like a natural ventilation chimney for the
inward-facing offices. Despite the effectiveness of passive systems in Frankfurtʼs temperate climate zone, Foster
recognizes the potential for technical (active) systems to maximize the buildingʼs efficiency. A computer controlled
building management system decides whether passive or active systems are most appropriate for use at a given time and
adjusts openings and shading devices accordingly. Commerzbank tower also uses water, instead of air, to condition the
building, which saves a tremendous amount of energy over the life of the building.
(http://inciarco.com)
Sources: Lambot, Ian. Commerzbank Frankfurt: Prototype for an Ecological High-Rise. Boston : Watermark Birkhauser. 1997.
Overview
-Overview-
-Structure-
-Environment-
Overview 03
-Construction-
Construction Ethic
Foster deemed the social and environmental responsibility of the building as the driving force behind the structure
and construction assembly. The Commerzbank defied traditional construction methods used for high-rise buildings in
Germany. Typical construction involved the use of a reinforced concrete structure, while the Commerzbank is made of a
simple all steel structure. Even though the use of concrete had been the original intent Foster deemed that the
lightweight form of the building outweighed the importance of traditional construction methods. The use of concrete
would have required the floor slabs of the building to be far deeper than that a simple steel frame construction. The
depth of these floors would decrease the transparency of the building, reducing its connection to the exterior
environment and its interaction with surrounding buildings. The use of a simple all-steel structure and Vierendeel
trusses allows for a repetitive lightweight construction assembly. This in turn increased the use of curtain wall glazing,
leading the overall transparency of the building. The expression of form as a twisted perforated tube, in which natural
light and ventilation can penetrate, emphasizes the lightweight structure and transparent materials, which create a
relationship with the natural world. The Commerzbank building receives continuous praise for being the tallest building
in Europe, and also distinguishably one of the most environmentally responsive office buildings. Yet in the context of
Frankfurt, Germany, the Commerzbank building is social responsive by both creating a distinctive presence in the skyline
while also assimilating itself into the city fabric.
(Davies)
Overview
Integrated Strategies 01
-Overview-
-Structure-
-Environment-
-Construction-
Exterior Office Glazing Panels
The exterior glazing to the office spaces integrates structural, environmental and
construction strategies. The extruded aluminum Aerofoil sections are included in the
glass panels in order to increase the lateral stability of the panels, allow air ventilation
within the double glazed window panel system, and to avoid rainwater penetration within
the interior of the panel systems.
Air Intake Transom
During the design of the glazing panels the deflection and thermal movement of the
structural frame had to be taken into account. Projecting from the glazing panels the
bracing provides a tolerance of up to 20mm of vertical movement (Lambot 168).
Aerofoil provides
structural bracing that
increases lateral
stabilty during
thermal expansion
Ventilation slots are included allowing air to enter through the bottom sill of the
insulated glass and exit at the head. These slots have been designed slightly below the
opening casement of the glass in order to avoid rainwater penetration. The fixed exterior
glass within the operable window system slows the flow of air avoiding the creation of a
draught or the entry of water when the interior portion of the window is opened.
Air Exit Transom
Water is shed away from
the glazing due to the
Aerofoil sections
Aerofoil provides
structural bracing that
increases lateral
stabilty during
thermal expansion
(Lambot 160)
Air Intake Transom
Water is shed away from
the glazing due to the
Aerofoil sections
Air Exit Transom
Glazing
Vented Cavity
Water is shed away from glazing to to
Aerofoil sections and the location of
the operable glazing
Ventilation allows air intake at the
bottom sill and exits at the head of the
window
Structural bracing provides lateral
stability
(Davues 28)
Glazing Panel Axon
Exterior Office Glazing Panels
Sources: Lambot, Ian. Commerzbank Frankfurt: Prototype for an Ecological High-Rise. Davies, Colin ed. Birkhauser and Jenkins, David ed. Norman Foster Works Vol. 4. Munich ; New York : Prestel, c2002
-Overview-
-Structure-
-Environment-
-Construction-
Mega-Column
The “mega-columns” of the Commerzbank tower encompass a response to structural, environmental, and
construction ideas.
Even though the buildingʼs foundation consists of piles bearing on fairly stable limestone, it has to be
as light as possible. The “mega-columns” of the building consist of two vertical steel ʻHʼ-section members
that rise from the foundation to the top of the building. The members are stabilized by beams and diagonal
bracing and encased in reinforced concrete. This creates a very light but strong structure to carry the
gravitational loads of the tower. Consequently, the concrete also acts as a damper to reduce vibration in the
steel from wind.
The concrete and steel approach to the structure also has roots in the construction of the building.
Since the steel members are erected before being encased in concrete, the equipment used to construct the
building can continue to build the structure while finished portions below are being encased in concrete.
This is a much quicker process than if the building were completely reinforced concrete ensuring a shorter
construction time. Also, the concrete acts both as fire protection for the steel and as a water barrio to protect
it from corrosion.
Diagram of how concrete can be poured while steel frame is still being constructed
above it.
Diagram of wind vibration in structure with or without concrete encasement
Mega-Column
-Overview-
-Structure-
-Environment-
-Construction-
Sky Garden Glazing System
The glazing system of the sky gardens was designed to be both a structural and
environmental response.
Structurally, the system consists of a series of vertical bowstring trusses that are connected to
the steel of the floor levels with slip joints that allow the structure above to deflect and still
provide lateral restraint. The bowstring trusses also integrate the hollow vertical mullions of the
glazing grid.
Environmentally, the hollow trusses are filled with water and connected to the buildingʼs
heating system. This transforms them into large radiators for the gardens and ensures that
condensation and down drafts do not occur in the atrium during winter months.
Diagram of truss used in radiant heating.
Diagram of heat loss if trusses arenʼt used as
radiators.
Detail of slip-joint
Sky Gardens Glazing System
-Overview-
-Structure-
-Environment-
Structures 01
-Construction-
Perforated Tube Structure
GRAVITY LOADS
The perforated tube structure of the Commerzbank is made
up of two primary structural elements: the eight-storey
Vierendeel trusses, and the corner columns. These two
elements provide the primary gravity and lateral load
resisting members of the building. To add stiffness and
stability to the structure, every fourth floor is continuous
throughout the building.
LATERAL LOADS
(Below): Plan diagram of gravity and lateral load resisting members
Base image: Davies, 44
Vierendeel trusses
resist lateral wind
loads
(Above): Exploded axon of major
structural members:
red corner columns
blue Vierendeel frames
green floor structure
Vierendeel trusses that
support gravity loads from
winter gardens and floors
Corner columns carry
concentrated gravity
load to ground
(Above): Diagram of gravity resisting members and gravity load paths
Base image: Davies
Continuous floors
provide stiffness and
stability
Horizontal floor
structure creates
stiffness and helps
resist lateral wind loads
(Above): Diagram of lateral load resisting members
Base image: Davies
Primary Structural Members
Sources: Davies, Colin ed. Birkhauser and Jenkins, David ed. Norman Foster Works Vol. 4. Munich; New York: Prestel, 2002. ; Fischer, Volker. Sir Norman Foster and Partners: Commerzbank, Frankfurt am Main. Stuttgart: Axel Menges, 1997.
Structures 02
-Overview-
-Structure-
-Environment-
-Construction-
Structural Conjecture
The structure of the Commerzbank works as a tube to resist
lateral wind loads. This tube functions like a cantilever out
of the ground. When resisting gravitational loads, the
structure pushed loads to the perimeter. It is basically
supported by the three corner columns and the Vierendeel
frames. As “frame” assumes fixed connections, the structure
works as a very large column/beam structure with fixed
connections.
(Above): Diagram of moment in a Vierendeel Frame
(Below): The gravity resisting structure functions as a
column/beam structure (with Vierendeel frames
functioning as beams between corner columns) with fixed
connections.
(Above): The lateral load resisting
structure functions like a cantilever
rising out of the ground. Shear and
moment diagrams for cantilever.
(Above): Floor structure showing steel floor beams that connect
Vierendeel frame to courtyard structure as well as providing
lateral stability.
Wise, 117
(Above): The perimeter tube formed
by Vierendeel frames and corner
columns, thus forming tube.
Wise, 114
Conjecture and Structural Diagrams
Sources: Fischer, Volker. Sir Norman Foster and Partners: Commerzbank, Frankfurt am Main. Stuttgart: Axel Menges, 1997. Wise, C. M. et al. "The new Commerzbank headquarters, Frankfurt, Germany." The Structural Engineer 74.7
(1996): 111-22.
Structures 03
-Overview-
-Structure-
-Environment-
-Construction-
Conjecture
Vierendeel Frame
Atrium Structure
The structure of the
Commerzbank is essentially a
perforated tube made up of
corner columns and Vierendeel
frames. These members work
together in a combination of
compression and tension. In
order to increase stiffness and
stability, the vertical loads are
concentrates at the perimeter
to create a large footprint
instead of a structural center
with floors moving outward.
The four story gardens are
supported by eight story
Vierendeel frames. These
twelve story structural sections
are located so that the garden
space spirals around the
building, leaving the floor
plane intact every four stories.
This intact floor plane
contributes to the overall
stiffness of the building.
The Vierendeel frames are made up of eight horizontal and
four vertical elements. These horizontal and vertical
elements work together to distribute loads equally and
absorb lateral forces in rigid moment joints.
The atrium is defined by a secondary structure
that supports the inside edges of the floors. A
vertical member links the eight end beams at the
center of the span so that they can share the
loads on each of the floors. This vertical
member allows the end beams to have less
depth without losing resistance to deflection.
The horizontal elements correspond with the floor levels,
supporting the outside edge and allowing an open plan
inside. These horizontal elements, in conjunction with the
floor structure behind them, add depth and stiffness to the
frame system, creating more resistance to wind loads.
The vertical elements could be arranged in two different
ways. To most effectively counteract wind loads, they should
be equally spread out on the face of the building. To
effectively support gravity loads, these members should be
concentrated at the corners. The final design supports a
combination of both strategies. The vertical elements are
distributed across the face of the building, but are slightly
shifted toward the corner columns. This way the Vierendeel
frame is able to support both gravity loads and wind loads.
Edge beams
(Above) Looking up through atrium, diagram of edge
beams and vertical load-sharing members
Lambot
(Above): Commerzbank from the
street
Corner Columns
Vertical
members
Fischer, 31
The three corners of the Commerzbank contain two columns
each. These columns are made up of two H-section vertical
steel pieces that are connected by beams and diagonal
bracing. The two columns that make up each corner are
connected by a link frame and enclosed in reinforced
concrete. While the structure of most tall buildings tapers
toward the top, the steel in the Commerzbank remains the
same throughout. There is a variation in strength of the
column, however, but this variation is caused by a change in
the amount of reinforcement used in the concrete.
Foundation
The foundation consists of 111 telescoping piles
that are concentrated at the corners, where the
load of the building above is concentrated.
These piles bear on a porous layer of limestone
located beneath the clay that supports most
buildings in Frankfurt.
(Above): Optimum vertical element (Above): Actual vertical element
spacing for Vierendeel frames
spacing for Vierendeel frames
Davies, 45
Fischer, 34
Structural Strategy
Sources: Davies, Colin ed. Birkhauser and Jenkins, David ed. Norman Foster Works Vol. 4. Munich; New York: Prestel, 2002. ; Fischer, Volker. Sir Norman Foster and Partners: Commerzbank, Frankfurt am Main. Stuttgart: Axel Menges,
1997.; Lambot, Ian. Commerzbank Frankfurt: Prototype for an Ecological High-Rise. Boston: Watermark Birkhauser, 1997.
Structures 04
-Overview-
-Structure-
-Environment-
-Construction-
Designer’s Strategy
The designer’s strategy was to create a structure that would
support the four-story-tall winter gardens without the space
being infiltrated by columns, as well as creating an open
floor plan, also without interruption by columns. The
designer also wanted to utilize as much of the envelope of
the building for natural daylight and ventilation as well. The
use of the Vierendeel frame allows all of these strategies to
be feasible. By spiraling the winter gardens around the
building and creating twelve story “villages,” the designer is
able to realize all the project goals.
A Vierendeel frame is engineered in such a way that the
members of the frame can be space far enough apart that
they can encompass an entire floor. In essence, the support
structure under the winter garden (the Vierendeel frame)
contains eight individual floors of office space.
(Above): Drawing of open floor plan office spaces
Fischer, 25
The corner columns serve as circulation space between floors
also allowing the interior spans between corner columns to
be free of secondary support columns.
Structural expression appears to be an important element.
When looking at the building, the structure and the load
paths are apparent. The Vierendeel frame is clearly visible in
both the articulated floors and the vertical elements. This is
partially due to the placement of glazing in the envelope:
glazing is used wherever possible, which coordinates with
the structural elements of the Vierendeel frame.
(Above): A twelve-floor village, showing Vierendeel frame elements spaced to
support floors and the rotation of Winter gardens. Fischer, 24
(Above) The structural members can be seen clearly in this
elevation
Fischer, 32
Hypothesis
Sources: Davies, Colin ed. Birkhauser and Jenkins, David ed. Norman Foster Works Vol. 4. Munich; New York: Prestel, 2002. ; Fischer, Volker. Sir Norman Foster and Partners: Commerzbank, Frankfurt am Main. Stuttgart: Axel Menges, 1997.
-Overview-
Climate Facts
Commerzbank Tower
Days Observed
Wind
Sky
H u m i d i ty
Temperature
Project
FosterArend,
& Partners,
Arup andAudrey
Krebs de
& Kiefer
(SE),
J. Roger
Preston w/ P&A Petterson Ahrens (ME), Schad & Hölzel (EE)
John
Mike Benkert,
Filippis,
Saretta
Tillmaand
Building Name
Commerzbank Tower (or Commerzbank Headquarters)
Construction Period
1994 to 1997
Client
Commerzbank
City
Frankfurt, Germany
Latitude
50.07 N
Longitude
08.41 E
Elevation
367 ft
Normal Climate Data
Heating Degree Days
Cooling Degree Days
Extreme High
Normal High
Normal Average
Normal Low
Extreme Low
Dew Point
Max %RH
Min %RH
% Days with Rain
Rain Inches
% Overcast Sky
% Clear Days
Prevailing Direction
Speed, mph
Percent Calm
Rain
Fog
Haze
Snow
Hail
Freezing Rain
Jan
588
0
56 F
38 F
34 F
30 F
-4 F
30 F
90
80
32
1.7
67
33
SW
9
6
10
19
12
-
Feb
508
0
63 F
41 F
36 F
30 F
-1 F
29 F
88
69
25
1.5
61
39
NE
8
9
7
18
8
-
Mar
427
0
75 F
50 F
43 F
36 F
9F
34 F
87
60
30
1.9
60
40
SW
9
6
9
16
5
-
Apr
317
0
77 F
56 F
48 F
39 F
20 F
37 F
84
53
28
1.7
57
43
NE
9
8
9
12
2
-
May
185
0
88 F
66 F
57 F
47 F
28 F
45 F
83
53
32
2.4
56
44
NE
8
12
10
14
0
-
Jun
110
7
93 F
71 F
62 F
53 F
34 F
51 F
83
54
34
2.4
57
43
SW
9
11
10
13
0
-
Jul
51
32
97 F
75 F
66 F
57 F
38 F
54 F
83
51
30
2.6
56
44
SW
9
11
9
12
0
-
Aug
48
31
96 F
75 F
66 F
56 F
37 F
54 F
87
51
25
2.1
54
46
SW
8
14
8
15
0
-
Sep
130
2
90 F
68 F
59 F
51 F
32 F
51 F
91
59
27
2
60
40
SW
8
12
8
18
0
-
Oct
271
0
82 F
57 F
50 F
43 F
25 F
45 F
93
70
30
2.1
66
34
SW
8
11
9
21
0
-
Nov
457
0
63 F
45 F
41 F
36 F
16 F
37 F
91
78
32
2
71
29
SW
9
6
10
19
4
-
Dec
558
0
61 F
40 F
37 F
32 F
3F
33 F
90
82
32
2.2
70
30
SW
9
6
10
20
9
-
Year
3650
72
97 F
57 F
50 F
43 F
-4 F
42 F
88
63
30
24.6
61
39
SW
9
9
109
197
40
-
-Structure-
Environment 01
-Environment-
Germany's climate is relatively constant. The summers
are generally warm with frequent rainshowers and
winters are generally cold. The amount of snowfall and
average temperatures are typically influenced by altitude
moreso than by climatic region. The weather is
continental in that it varies from year to year, meaning a
chilly spring and rainy summer one year can be followed
by a warm spring and sunny summer the next.
Therefore, it is recommended that environmental
building systems in the region be versitile in response to
the constantly changing conditions.
-Construction-
Frankfurt
The city of Frankfurt has a temperate continental climate
characterised by warm summers with occasional wet
days, and cold winters. Temperatures are not extreme
and never severe, but winters can bring occasional
violent storms.
(www.earth.google.com)
Sources
1. http://www.myforecast.com/
2. http://www.worldweather.org/
3. http://www.gaisma.com
4. http://www.eosweb.larc.nasa.gov/
Sources: www.about-germany.org, (see tables above for additional sources)
Climate Data: Frankfurt, Germany
-Overview-
Temperature
average high in Frankfurt, Germany
-Structure-
Environment 02
-Environment-
-Construction-
average low in Frankfurt, Germany
source: http://www.myforecast.com
Death Valley, CA (high)
Fargo, ND (low)
High
Avg
Low
38˚F
34˚F
30˚F
41˚F
36˚F
30˚F
50˚F
43˚F
36˚F
56˚F
48˚F
39˚F
66˚F
57˚F
47˚F
71˚F
62˚F
53˚F
75˚F
66˚F
57˚F
75˚F
66˚F
56˚F
68˚F
59˚F
51˚F
57˚F
50˚F
43˚F
45˚F
41˚F
36˚F
40˚F
37˚F
32˚F
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
110
100
90
80
70
60
50
40
30
20
10
0
Indoor and outdoor air temperature can be modified through a combination of “passive” or active design strategies. Daily average temperatures remain pleasant in Frankfurt, Germany for a good portion of the year,
However, temperature is only part of the equation when considering occupancy comfort as relative humidity is also a contributing factor.
Relative Humidity
average morning high
average afternoon low
source: http://www.myforecast.com
100
New Orleans, LA (high)
80
60
Death Valley, CA (low)
40
20
Morning
90%
88%
87%
84%
83%
83%
83%
87%
91%
93%
91%
90%
Afternoon
80%
69%
60%
53%
53%
54%
51%
51%
59%
70%
78%
82%
Jan.
Feb.
Mar.
Apr.
May
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
Jun.
0
Frankfurt, Germany is a rather humid climate when compared to those in the USA. Fortunately, the relative humidity levels are highest during the cool fall and winter months when it’s more desirable, and
considerably lower in the warm spring and summer months when it causes the most discomfort. For further explanation, please refer to the psychometric chart that follows.
Sources: http://www.myforecast.com
Images: www.corbis.com
-Overview-
-Structure-
Environment 03
-Environment-
-Construction-
Heating Degree Days
Fargo, ND (high)
1000
800
600
400
200
Miami, FL (low)
degree days
588
508
427
317
185
110
51
48
130
271
457
558
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
0
A Heating Degree Day (HDD) is defined as 65 degrees Fahrenheit minus the mean daily temperature. In Frankfurt, Germany heating is required throughout the year, even in the summer months. Annually there are
3,650 HDD. (For comparison: Miami, Florida has 40 HDD, and Fargo, North Dakota has 5,550 HDD)
Cooling Degree Days
500
400
300
200
Miami, FL (high)
100
Fargo, ND (low)
degree days
0
0
0
0
0
7
32
31
2
0
0
0
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
0
A Cooling Degree Day (CDD) is defined as the mean daily temperature minus 65 degrees Fahrenheit. In Frankfurt, Germany very little cooling is required, even during the summer months. Annually there are 72 CDD.
(For comparison: Miami, Florida has 2,451 CDD, and Fargo, North Dakota has 82 CDD)
Sources: http://eosweb.larc.nasa.gov/sse
images: www.corbis.com
-Overview-
Wind Potential
Average Speed and Direction at 50m Above Earth Surface
-Structure-
Environment 04
-Environment-
-Construction-
7.8 knots is recommended speed for effective use of wind energy
14
12
10
8
6
4
2
Knots
m/s
Direction
13.5
6.96
SW
11.4
5.85
SW
13.4
6.88
SW
11.6
5.96
SW
10.3
5.31
SW
10.2
5.27
SW
10.8
5.54
SW
10
5.16
SW
9.9
5.11
SW
10.4
5.35
SW
12.2
6.27
SW
12.7
6.53
SW
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
0
The average annual wind speed in Frankfurt, Germany is 11.4 knots with the breezes typically coming from the southwest. The velocity is strong enough in the region for wind energy to serve as an effective means of
power generation and passive cooling via cross-ventillation and stack effect. Southwestern winds from the Mediterranean keep the region relatively mild throughout the year.
Average Rainfall
Monthly Averaged Precipitation (mm/day)
7
6
5
Birmingham, AL (high)
4
3
2
Las Vegas, NV (low)
mm/day
1
3.5
2.88
2.84
2.22
2.49
3.28
2.65
2.25
2.94
2.49
3.34
3.67
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
0
Frankfurt, Germany receives a relatively high amount of precipitation throughout the year. The rainfall is fairly consistent from month to month and allows for the implementation of rainwater capture systems
throughout the region. Unfortunately, the massive program and limited roof area makes such a system somewhat impractical for Commerzbank Tower.
Sources: http://www.eosweb.larc.nasa.gov/, http://www.iht.com/
Images: http://www.corbis.com
-Overview-
Solar Potential
-Structure-
Environment 05
-Environment-
-Construction-
Monthly Averaged Insolation Incident On a Horizontal Surface
7
6
5
Miami, FL
4
3
2
Seattle, WA
1
kWh/m2/day 0.8
1.55
2.42
3.69
4.73
4.62
4.95
4.15
2.87
1.72
0.92
0.61
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
0
Statistics for average insolation (the combination of clear
sky insolation and average daylight cloud amount) indicate
that the use of photovoltaics in Frankfurt, Germany is not
an effective means of power generation. Frankfurt only
receives an average annual insolation of 2.75
kWh/m2/day. By comparison Seattle, WA receives 3.77
kWh/m2/day, while Miami, FL receives 5.18 kWh/m2/day.
Commerzbank Tower utilizes the low solar insolation in
the region as a means to effectively daylight the entire
building with minimal glare and overheating from direct
gain. At the same time, the orientation of the building
allows for passive solar heating for the majority of the
year, as well as the growth of sky gardens, which spiral up
the interior of the structure.
The sky gardens themselves are a direct response to solar
orientation with the warmer south facing gardens
containing plants and trees which are prevalent in the
temperate Mediterranean, the western gardens containing
species from North America, and the cooler east facing sky
gardens containing plants more native to the Frankfurt
region.
Commerzbank tower has no overhanging sun shades to
protect the building from the hot summer sun, but rather
utilizes shading devices sandwiched between the
double-glazed glass curtain wall.
(Quantril 165)
Sources: http://www.eosweb.larc.nasa.gov/, “Commerzbank Frankfurt: Prototype for Ecological High-Rise”
(www.earth.google.com, Lechner)
Images: www.corbis.com
-Overview-
50
%
60
%
%
70
%
%
30
K
20%
H
F
10%
D
C
G
B
I
J
40ºF
50ºF
60ºF
70ºF
80ºF
90ºF
100ºF
110ºF
Winter: December
Spring: March
Summer: June
Fall: September
am:
am:
am:
am:
pm:
32º F
90% relative humidity
40º F
A B
pm:
B
Sources: Lechner, http://www.myforecast.com
36º F
50º F
pm:
C
C
Images: Lechner
D. Internal Gains: Conditions are close enough to the
comfort zone that internal loads (heat provided by
electrical and human sources) will provide the heat
needed for comfort.
53º F
71º F
D E
H
F. Ventilation: Though temperatures and humidity levels
are high, comfort may be obtained through the direct
evaporation of perspiration, if enough air movement is
available.
G. Thermal Mass: Radiant cooling and night-flushing of
the internal air with cool outside air will store "coolth" for
the next day.
A
30ºF
C. Passive Solar: Direct gain, indirect gain and hybrid
systems, combined with infiltration and heat-loss control,
can provide the heat required for comfort.
E. Comfort: No strategy is necessary, except to prevent
further solar heat gain in summer or loss in winter
E
20ºF
-Construction-
B. Active Solar: Heat needed to achieve comfortable levels
in this zone can be effectively supplied by solar collectors
or any other active solar system supported by backup
high efficiency conventional heating systems.
40
By plotting the temperature and humidity ranges of Frankfurt,
Germany over the course of a year on the chart, one can
determine which passive and/or active heating and cooling
strategies are most effective for Commerzbank tower when it
comes to creating a comfortable work environment for its
occupants. Frankfurtʼs temperature and humidity ranges are
represented on this chart by the dashed green polygons.
10ºF
-Environment-
A. Conventional Heating: Conditions occurring in this
zone are too cold to rely on passive and active solar
heating; high efficiency conventional heating systems are
required.
%
80
90
%
10
Psychrometric charts graphically represent the relationship
between temperature and humidity, the two factors that
determine human comfort. On the chart, the "comfort zone'
indicates conditions in which most people will be thermally
comfortable. The boundaries of the zones are not absolute, as
human comfort will vary by season, metabolic rate and culture.
-Structure-
Strategies:
0%
The Psychometric Chart:
Environment 06
pm:
C
51º F
68º F
D E
H
H. Thermal Mass plus Ventilation: Some passive or active
internal ventilation is required to extract heat, in addition
to night flushing and radiant cooling.
I. Evaporative Cooling
J. Humidification: Moisture must be added to the air for
comfort.
K. Air Conditioning: Humidity levels are too high to
achieve comfort levels without the use of high-efficiency
conventional systems.
-Overview-
-Structure-
Environment 07
-Environment-
-Construction-
Commensurate Tower: Thermal Strategies
(Please refer to previous page for clarification of psychometric chart and corresponding letters)
A. Conventional Heating: Conditions in Frankfurt, Germany are sometimes too cold for a building to rely solely on passive heating
strategies as a means for creating thermal comfort: Commensurate tower utilizes high efficiency heating systems throughout the
majority of cold winter months.
C. Passive Solar: Direct gain, Indirect gain and hybrid systems inherent in the buildingʼs massive glass facades, combine with
infiltration and heat-loss controls to meet a majority of Commensurate's heating requirements for the spring, fall, and portions of
the summer season as well.
D. Internal Gains: Conditions in Frankfurt, are oftentimes close enough to the comfort zone that internal loads (heat provided by
electrical and human sources) will provide all the heat necessary for comfort.
H. Thermal Mass plus Ventilation: When conditions call for a level of cooling in Commensurate tower, passive and active internal
ventilation is utilized to extract heat along with night flushing and radiant cooling.
A. Conventional Heating: When conditions are too cold for passive
strategies to be an effective means for creating thermal comfort, heating
is provided by ordinary, thermostatically controlled panel radiators below
the windows. (Davies 204)
C. Passive Solar: Large glass facades surrounding the sky gardens and
offices allow for direct and indirect solar gain throughout Commensurate
for the majority of the year when heating is desired. Shading devices and
ventilation systems are utilized to counter overheating. (Davies 287)
Sources and Images: “Commensurate Frankfurt: Prototype for an Ecological High-Rise”
(Lechner)
H. Thermal Mass plus Ventilation: Natural ventilation as a means for
aiding in thermal comfort in Commensurate is possible for roughly 60%
of the year. This is a result, thanks in large part to four twelve-story
atrium spaces in which windward and leeward sky gardens take in and
exhaust fresh air using cross ventilation and stack effect. (Davies 196)
Climate Data: Responses
-Overview-
-Structure-
Environment 08
-Environment-
-Construction-
When analyzing the environmental systems within Commerzbank Tower, itʼs worth noting that the number one goal of Fosterʼs design is to create a
pleasant work environment for the buildingʼs 2,000+ occupants as a means of increasing worker productivity. While this significantly increases up-front
building costs of the skyscraper, in the grand scheme of Commerzbankʼs expenses, worker salaries significantly outweigh any construction costs over a
prolonged period of time. Therefore, it can be assumed that the documented increases in worker productivity from abundant daylighting and views to the
outside makes Fosterʼs scheme financially justifiable.
Commerzbankʼs use of the doughnut plan in conjunction with the four-story sky gardens allows for every office in the building to be daylit with an
unobstructed view to the outdoors. Full height windows and shallow floor plates ensure that the amount of natural light penetrating into the building is
sufficient enough to substitute for artificial lighting through the majority of the workday.
Frankfurt, Germanyʼs low solar insolation and diffuse lighting conditions make daylighting an incredibly effective environmental response in that glare
and unwanted direct solar gain in the region is minimal.
Daylit sky gardens with views to the outdoors
Daylit offices with views to outdoors
(Above) Daylight/Views Floor Plan (Davies 248)
(Left) Daylight/Views Section (Davies 46,47)
Sources and Images: “Commerzbank Frankfurt: Prototype for an Ecological High-Rise” (Davies)
Daylight/Views Perspective Sketch (Davies 15)
Environmental Responses: Daylighting and Views
-Overview-
-Structure-
Environment 09
-Environment-
-Construction-
While the majority of modern skyscrapers rely heavily on the use of massive mechanical systems to heat, cool, and
circulate air within the building, Commerzbank Tower utilizes natural ventilation as a primary means for creating
year-round thermal comfort. Natural ventilation in Commerzbank occurs at multiple scales ranging from individual
rooms to several building stories, all of which vary based on climatic conditions.
When looking at the building section as a whole, it appears as though the entire central atrium space acts like a
giant chimney with air being exhausted out the top of the building by way of stack effect. While this was Fosterʼs
original intention when designing the building, the incredible scale of the space would have resulted in a powerful
updraft of air that would have been undesirable for the building patrons. Consequently, in the final design, the
atrium is segmented by glass decks into four twelve-story spaces, each consisting of three deliberately positioned
sky gardens. In this particular scheme, fresh air enters the building through windward gardens at the bottom of
every twelve-story segment, and exhausted out of leeward gardens at the top of them. The glass decks are
completely sealed off from the atrium space below, divorcing them from the towerʼs natural ventilation process,
which includes both cross-ventillation and a limited amount of stack effect.
The means by which natural ventilation occurs in the tower section varies for the cold winter and warm summer
months. In cold winter conditions, sky garden windows are closed to store heat, but are reopened to let in desirable
breezes when conditions warm up. In both circumstances, warm air rises up and out of the building to naturally
ventilate the interior.
Central Atrium Ventilation (Quantril 165)
Winter Sky Garden Ventilation (www.architectureweek.com)
Summer Sky Garden Ventilation (www.architectureweek.com)
Environmental Responses: Ventilation
-Overview-
-Structure-
Environment 10
-Environment-
-Construction-
One of the main reasons as to why Commerzbank Tower is considered to be the first “ecological skyscraper” is that
passive strategies are utilized at all scales ranging from window detailing to the full-height atrium. Typically, modern
office buildings full of heat-producing machinery have a higher demand for cooling, but Frankfurt winters typically
require heating as well.
Foster responds to this dichotomy of needs in the cladding system by utilizing double skin glazing with ventilated
cavity spaces, operable casements, and Venitian blinds. Whenever heating is desired, exterior vents are closed to allow
heat to build up in the cavity spaces, which protects against cold winds while improving the thermal insulating
properties of the windows by as much as 20%. When cooling is required, the cavity vents and operable casements are
opened to allow for natural ventilation with cool air entering low and warm air exiting high after circulating through
the office.
While passive strategies for heating, cooling, and ventilation are effectively implemented in Commerzbank office
spaces for the majority of the year, Frankfurtʼs cold winter months and hot summer period require active systems as a
means to create thermal comfort within the tower. When in active modes (as determined by the central building
management system), Commerzbank offices utilize radiant floor heating to effectively warm objects instead of air, and
chilled (water) panel ceilings to cool the space in a more energy efficient manner than the forced-air alternatives.
Glazing
Vented Cavity
Building Skin Ventilation Detail (Davies 160)
Passive Heating/Cooling/Ventilation Systems (Davies 201)
Active Heating/Cooling/Ventilation Systems (Davies 200)
Environmental Responses: Ventilation
-Overview-
-Structure-
Environment 11
-Environment-
-Construction-
Spiraling up the sides of the building,
Commerzbank towerʼs nine four-story sky
gardens occupy three different faces, which all
have distinct solar orientations. With gardens
oriented to the south, east, and west, the design
team recognized early on that plantings from
different climates would be required to respond
to the varying levels of solar exposure.
The south facing gardens, which receive the most
amount of solar gain throughout the year consist
primarily of Mediterranean plantings including
olive trees, cypresses, and a ground cover of
thyme.
The west facing gardens, which receive a
significant amount of afternoon sun throughout
the year are filled with north American plants
including acarias, evergreen oaks and ornamental
grasses.
(Davies 248)
The northeast facing gardens, which receive very
little to no sun over the course of the year are
composed of various Asian plantings that thrive
in shaded environments such as bamboo.
To ensure that all of the plant life stays alive, the
sky gardens are always naturally ventilated, even
when the office interiors are being air
conditioned. As a result, these environments act
more as sheltered exterior spaces than interiors,
meaning that there are times in the year when
they may be too cool for people in indoor
clothing. This is somewhat supplemented with
underfloor heating, but is an adjustment that
would probably not be as widely accepted in
America as it is in western Europe.
West facing gardens filled with North American plant life. (Davies 278)
South Facing Gardens filled with Mediterranean plant life. (Davies 279)
Environmental Responses: Sky Gardens
Construction 01
-Overview-
Construction: The Foundation
-Structure-
-Environment-
-Construction-
Due to Frankfurt’s location on a soil mostly made up of clay, with a layer of sand and
gravel above, Foster and Partners along with the foundation engineers,
Ingenieursozietat katzenbach und Quick, had to consider in depth the possibility of
settling and its effects on surrounding buildings. They had found that other high-rise
buildings of the area had settled between 100mm to 300mm. The engineers predicted
that a settlement of 150mm might have been drastic enough to cause the existing
Commerzbank building, due to its proximity to the new tower, to tilt.
The solution arose when determining the size of the pile-raft foundation. It was
decided that the piles would be drilled into the ground about 45 meters deep, in order
to pass through the clay soil and embed themselves in the limestone “inflata” layer
located below.
Piled raft foundations traditionally evenly spread the piles around the footprint of the
building. The new Commerzbank tower, due to its distribution of loads to the six
mega-columns at the corners of the building, led to the 111 piles being concentrated
at these three corners rather than evenly through the footprint (Davies 63).
Location of Piles
Sand and Gravel Layer
Clay Soil Layer
Porous Limestone Layer
Construction of the Foundation
(Lambot 71)
Construction of the Foundation
(Lambot 72)
Section Diagram of the Foundation and Soil Condition
(Lambot 70)
Meeting The Ground
Construction 02
Construction: The Foundation
-Overview-
-Structure-
-Environment-
-Construction-
The long piles led to high torsion stresses during drilling, causing restrictions on their
overall diameters. The decision was made to use telescopic piles. At the base of the slab
the piles were designed to be 1.8 meters in diameters. This would be used for the initial
20 meters. Following this the piles diameter would be reduced to 1.5 meters. The
location of the piles became a concern for in traditional construction methods piles are
evenly distributed at the footprint. The design of the Commerzbank had located the cores
of the building at the 3 corners thereby concentrating the vertical loads in these corners.
This required the unconventional distribution of 111 piles, in groups at the three corners
of the building. A 12 meters high cellular box structure is used to transfer the loads. This
structure is made up of wall 3 meters deep and a horizontal slab that ranges from 2.5 to
4.5 meters.
A second issue arose with the realization of the porosity of the limestone bed, which led
to large cavities where the piles were supposed to be imbedded. This would significantly
weaken the piles. The decision was made that liquid concrete would be injected, at a high
pressure into the subsoil of each pile strengthening the foundations connection to the
subsoil. The pile cages incorporated the pipes and valves of the concrete injection
system. The concrete was injected around the base of each pile as much as 10 meters
below and around the piles. Over 2,000 tones of concrete was injected around the piles
strengthening the foundation. The design and construction of the foundation has led to a
measured settlement of the new towers of about 2 cm and only 0.6 cm in the old tower.
This is far smaller than any of the tall buildings of Frankfurt, who have had settlements
ranging from 10 to 30 cm. The use of a deep piled foundation has led to the success of
the integration of such a large building within a tight framework of existing buildings on
unstable soil (Davies 67).
Clay Region
(Lambot 66)
Model of Foundation and Piles
Porous Limestone Region
Liquid Concrete Injected
Around the Base of the Pile
Clay
Intact Limestone
Weathered Limestone
Foundation and Structure Model
(Lambot 69)
Construction of Foundation
(Lambot 73)
Typical Pile Detail
Meeting The Ground
Construction 03
-Overview-
-Structure-
-Environment-
-Construction-
Transparency: Skylight
Spacial Composition of Frankfurt’s Skyline
Perforated Design: Sky Garden
The perforated form of the buildings, along with
the extensive use of the curtain walls allows for a
transparency, not often attainable for a building of
its size. The use of gardens within the perforations
creates the link between the exterior environment
and the building. By bringing the park inside,
Foster has allowed this office building to integrate
itself not only with the existing city fabric but also
with nature and the surrounding environment.
Initially Foster had design the Commerzbank
building by located all of the gardens on the
southern side. This he felt decreased the
connection of the building to his surroundings. He
decided to then cut the building after every four
floors and twist the level above, resulting in a
spiraling garden. This increases the amount of
light and ventilation through the building along
with increasing the overall transparency within the
skyline (Davies 69).
The overall form of the building is a simple curved triangular
monolithic tube. The different functional areas are distinguished
on the exterior façade by changes in color, texture and cladding
systems. This expression and function through the structures give
the building a human scale. Glass ‘decks’ or skylights at levels 7,
19, 31, and 43 along with the enclosing top skylight divide the
atrium. The use of multiple skylight enclosures has more than one
function. A half-hour fire and smoke barrier is created between
sections of the building along with managing and control the
fresh air ventilation in the building. The skylights divide the stack
and chimney effect leading to an increase control of air quality
management. The skylights are divided into triangular panels (1.5
meters on each side by 2.5 cm thick glass). A neoprene gasket is
used to seal the joints between the glass and steel frame. The
interior and exterior of building use glazing and reflective panels
in order to reflects views from the sky allowing the building to be
imbedded within its setting. The overall structural appearance can
be seen as light and transparent, in relation to other high-rise
buildings in the city, leading to the reduction in social scale of the
building (Lambot 176).
Perforated Tube
Design Iterations
Penetration of the Sky
Skylight in Atrium
Final Design
(Lambot 153)
Atrium Skylight Locations
(Lambot 46)
Meeting The Sky
Construction 04
-Overview-
-Structure-
-Environment-
-Construction-
Transparency: Cladding Types
The exterior cladding system for the office area is made up for repetitive individual panel units that interlock with each other. These panels are suspended from brackets fixed to the Vierendeel
beams. The typical panel has two main parts, a fixed spandrel of insulated grey glass and an operable window. Each panel is a thick double glazed system included a variety of smaller components
within the glazing, including motors and operable blinds. Ventilation slots are included allowing the air to enter through the bottom sill of the insulated glass and exit at the head. These slots have
been designed slightly below the opening casement of the glass in order to avoid rainwater penetration. The fixed exterior glass within the operable window system slows the flow of air avoiding the
creation of a draught when the interior portion of the window is opened.
A ‘tongue’ projects from the top of each panel which allows for the location of the next panel above, while also allowing for vertical movement caused by thermal expansion. The slip joints along the
vertical edge also allow for movement, while retaining a tight joint system though neoprene gaskets (Lambot 168).The cladding located between the offices and the atrium is relatively the same
system, yet is slightly simplified. These is no second skin, but the windows are still operable, creating a cross ventilation. There are also no blinds located in these panels, from direct light does not
access these spaces, only the diffused light from the skylight and exterior glazing (Lambot 156).
Vierendeel Frame I-Beam
Bolted Attachment to I-Beam
Bolted Attachment to I-Beam
Attachment Clip for Glazing
Attachment Clip for Glazing
Glazing Panels Interlock
Glazing Panels Interlock
Interior Office and Atrium Cladding
Exterior Office Cladding
Meeting The Sky
Construction 05
-Overview-
-Structure-
-Environment-
-Construction-
Transparency: Cladding Types
The core columns are first protected by a layer of intumescent paint then clad in reinforced
concrete. A layer of waterproofing is then attached, followed by frameless, story height toughened
white glass panels. These are fixed to the reinforced concrete through bolted connections.
Vierendeel Frame
The cladding used to enclose the corners of the tower is a simple frame-and-infill curtain wall. A
variety of panels are used including: transparent, clear or enamel-backed glazing, opaque
glazing, louvered, insulated and un-insulated, some ventilated and other unventilated.
As this building is more often viewed from far away the paneled differences are only moderately
perceived allowing a continual unity within the rounded corners. A vertical aluminum frame
conceals the edges of the column glass and paneled corner in order to create a continuous tower
element at all three corners of the building. The transparent and reflective cladding of these
masses increase the buildings intearction with its surrouding environment and create a
relationship between the building and human scale (Lambot 155)
Vierendeel Frame
Reinforced Concrete
Aluminum Frame
Panelized Glazing
Waterproofing Membrane
Toughened White Glass Panels
Mega Column Cladding
Building Corner Cladding
Meeting The Sky
Construction 06
-Overview-
Transparency: Construction
-Structure-
-Environment-
-Construction-
The decision to use a steel structural frame allowed the Commerzbank Tower to gain
and increase transparency. The use of Vierendeel truss system, created a standardized
structural frame, that could be prefabricated and simply assembled on site. The
efficiency of this structure along with the thinner floors increased the ability to use
curtain wall glazing, both transparent and reflective. The overall structural appearance
can be seen as light and transparent, in relation to other high rise buildings in the city,
leading to the reduction in social scale of the building. The use of these panels reflects
views from the sky allowing the building to be imbedded within its setting.
Sketch of City Fabric
Social Responsibility: The Urban Fabric
The plaza and cross through that was created at the ground
floor of the office buildings, has created an area of social
gathering that has linked the building the city
surroundings, reducing the social scale of such a building.
Commerzbank Plaza
(Lambot 34)
Commerzbank Plaza
(Lambot 31)
Sketch of City Fabric
Social Responsibility
Construction 07
-Overview-
-Structure-
-Environment-
-Construction-
Mega-Column Cladding
Column Cladding
Office Cladding Construction
Vierendeel
Frame Construction
Column Cladding
Construction
Office Cladding
Mega-Column Frame Construction
Vierendeel
Frame
Construction
Mega-Column
Cladding
Location of the Cladding Detail
(Lambot 46)
Cladding Types
Construction 08
-Overview-
-Structure-
-Environment-
-Construction-
The Corner: Mega-Columns
The decision to use a steel structural frame allowed the Commerzbank Tower to gain an
increased transparency. The use of steel allows for increased openness and speed of
erection of the frame. The use of a Vierendeel truss system, created a standardized
structural frame that could be prefabricated and simply assembled on site, as a ‘kit of
parts’.
Originally the structure was intended to be made out of reinforced concrete, as is the
building tradition of Germany, but studies showed that beams would of had to be near
two meters thick to accommodate the load. This would have drastically affected the
amount of free space for glazing. The steel structural frame was proposed, with
reinforced concrete located around the mega-columns allowing 65 percent free space to
glazing as opposed to 40 percent allowable with the use of a concrete frame (Lambot 68)
The efficiency of this structure along with the thinner floors increased the ability to use
curtain wall glazing, both transparent and reflective. The overall structural appearance
can be seen as light and transparent, in relation to other high-rise buildings in the city,
leading to the reduction in social scale of the building (Lambot 68)
Mega-Column Frame Construction
(Lambot 86)
Vierendeel
Frame
Construction
Mega-Column
Frame
Construction
(Lambot 93)
Mega-Column Frame Detail
Corner Detailing
Construction 09
-Overview-
-Structure-
-Environment-
-Construction-
The Corner: Cladding
The core columns, the heaviest mass of the building are first protected by a layer of
intumescent paint, which is applied on all parts of the structural frame. The columns are
then clad in reinforced concrete, which increases structural stability as well as protects
from weathering and corrosion. A layer of waterproofing is then attached, followed by
frameless, story height toughened white glass panels. These are fixed to the reinforced
concrete through bolted connections. A vertical aluminum frame conceals the edges of
the column glass in order to create a continuous tower element of all six columns. Every
fourth floor and wider horizontal joint is used in order to break up the mass and create
a scale and hierarchy within the buildings facade. This coincides with the location of the
interior gardens.
Vierendeel Frame
The cladding used to enclose the corners of the tower is a simple frame-and-infill
curtain wall. A variety of panels are used including: transparent, clear or enamel-backed
glazing, opaque glazing, louvered, insulated and un-insulated, some ventilated and
other unventilated. Some panels have internal lining walls, while others do not. The type
of panel used in a specific location is in direct correlation with the programmatic
function housed on the interior. As this building is more often viewed from far away the
paneled differences are only moderately perceived allowing a continual unity within the
rounded corners (Lambot 155).
Reinforced Concrete
Aluminum Frame
Panelized Glazing
Building Corner Construction
(Lambot 165)
Cladding Types
(Lambot 164)
Building Corner Cladding Detail
Corner Detailing
Construction 10
-Overview-
-Structure-
-Environment-
Exterior Office Glazing System
-Construction-
Fixed External Glazing
The extruded aluminum Aerofoil sections
are included in the glass panels in order to
increase the stability of the panels and to
avoid rainwater penetration within the
interior of the panel systems. Ventilation
slots are included allowing air to enter
through the bottom sill of the insulated
glass and exit at the head. These slots have
been designed slightly below the opening
casement of the glass in order to avoid
rainwater penetration. The fixed exterior
glass within the operable window system
slows the flow of air avoiding the creation
of a draught or the entry of water when the
interior portion of the window is opened
(Lambot 161).
Double Glazed Opening
Casements
Ventilated Cavity
Extruded Aluminum Aerofoil
Section
Slip-Joint Between Panels
6mm Toughened Glass on
Felt Underlay
80mm-Thick Thermal
Insulation
Vierendeel Frame
Water is shed away from glazing to
to Aerofoil sections
8mm Toughened Glass
40mm-Deep Ceiling Panel
Extruded Aluminum Aerofoil
Section
Venetian Blinds
Casement Motor
Office Glazing System
(Lambot 158)
Office Glazing Detail
(Lambot 161)
Exterior Office Glazing Section
(Lambot 160)
Response To Water
Construction 11
-Overview-
-Structure-
-Environment-
-Construction-
Exterior Office Glazing System
In order to avoid rainwater penetration within the interior of the panel system the air
intake transom is located slightly below the opening casement of the glass. The air exit
transom is located at the top of the exterior clear glazed portion of the panel. This allows
for the controlled movement of air within the panel system and avoids the entry of water
into the interior portions when the operable window is in use (Lambot 161).
Air Intake Transom
Structural Steel
Holorib Concrete Slab
Fire Protection
Air Exit Transom
Chilled Ceiling Panels
Movable Double-Glazed
Window Element
Fixed Outer Glass
Air Intake Transom
Convection Heater
Fixed Spandral (Low Iron Glass
with RAL Enamel Coating)
Raised Floor
Office Glazing System
(Lambot 159)
Office Glazing Detail
(Lambot 168)
Exterior Office Glazing Section
(Davues 28)
Response To Water
Construction 12
-Overview-
-Structure-
-Environment-
-Construction-
Mega-Column
The reinforced concrete surrounding the mega-columns is not only used for structural
stability but also to protect the steel column from corrosion and weathering. The initial
layer of intumescent paint, which is applied on all parts of the structural frame, provides
a layer of protection while the reinforced concrete provides another. A waterproofing
membrane is added between the reinforced concrete and the glass panels.
To protect the columns from rain, the glass panels shed, rather than absorb water, as the
reinforced concrete would. Due to the location of joints in the glass panels, rainwater is
able to infiltrate this first layer of glass. Behind this is located the waterproofing, creating
an additional barrier. The thicker layer of reinforced concrete becomes a moisture barrier
along with the last layer of intumescent paint that protects the structural steel from
corrosion (Lambot 165).
Vierendeel Frame
Reinforced Concrete
Mega-Column Waterproofing
(Lambot 164)
Mega-Column Cladding
(Lambot 159)
Mega-column Waterproofing Detail
Response To Water
-Overview-
-Structure-
-Environment-
-Construction-
Works Cited
Cramer, Ned. “Europe's Tallest Tower”. Architecture August 97, Vol. 86 Issue 8, p26.
Davey, P. “High expectations”. The Architectural Review July 97, Vol. 202 Issue 1205, 26.
Davies, Colin ed. Birkhauser and Jenkins, David ed. Norman Foster Works Vol. 4. Munich ; New York : Prestel, c2002.
Fischer, Volker. Sir Norman Foster and Partners : Commerzbank, Frankfurt am Main. Stuttgart : Axel Menges, 1997.
Lambot, Ian. Commerzbank Frankfurt: Prototype for an Ecological High-Rise. Boston : Watermark Birkhäuser, 1997.
Wigginton, Michael, and Jude Harris. Intelligent skins. Oxford : Butterworth-Heinemann, 2002.
Works Cited

Commerzbank Tower - Mike Benkert`s Website

Transcription

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