Group 11. MSc 1st 2011. Architecture and Design Aalborg University
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Titel : I
I
Tupic : Tectonic Design & Nordic Architecture Subtupic: An Inhabited or ‘Living Bridge’ connection over Limfjorden, Aalborg Project duration : 06.10.11- 19.12.11 Project group : MSc 1, ARK 11 Architectural supervisor : Adrian Carter Technical supervisor : Dario Parigi Copies : 8 Number of pages : 102
Jibo Chen Emil L. Dornonville de la Cour Juan Antonio Marquéz
The theme for the assignment for 7th semester focuses on Nordic architecture and tectonic approaches and deals with building a living bridge across Limfjorden in Aalborg that connects the two industrial areas, Østre Havn and the area to the East of Hedegaard. The bridge contains of a horizontal hotel mixed with several other public functions such as cafes, a restaurant, conference center and fitness center. A central public path runs through the bridge and acts as a multifunctional path by means of being a continuation of the harbourfronts and service area for the hotel.
Maja Lefoli Pedersen
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Preface
This project is a proposal of a new living bridge across Limfjorden, connecting a district of Aalborg and Nørresundby. The report describes the process and design of the living bridge. Since the concept has been develop through various studies that influence each other, the presentation is not chronological but relates to different scales and parts of the project.
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INDEX Programme
8
Introduction Mapping Character of the site Potential and spaces Local vision Our vision Bridge typologies Moveable bridges Living bridges Nordic architecture Room programme
9 10 14 18 20 22 24 26 28 30 32
Designprocess
34
Presentation
62
Strategic concept Architectural concept Frames Volumes Functions Modules Landings
Conclusion Reflection References APPENDIX Loads FEM calculation
36 38 40 48 50 52 60
90 91 92 94 96 98z
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PROGRAMME
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Introduction The characterized picture of Aalborg as an industrial city is undergoing a transformation to a knowledge-based and cultural city. This transformation can be seen in the development of the harbourfront in both Aalborg and Nørresundby. In Aalborg the program of the transformation has a cultural character along with housing and offices, while in Nørresundby the program mainly consist of housing. In order to attract people, public places are being placed along the harbourfront both in Aalborg and Nørresundby. Nørrsundby functions as a suburb of Aalborg and even though the distance between the two city centres is less than 1,5 kilometres and they are connected in three places they seem unconnected and the distance between them bigger than it actually is. A reason for this could be the fact that only one of the three connections serves bikes and pedestri-
ans but also the difference in the socio-cultural activities plays a role. The intension with an additional bridge, a living bridge, is to create a better connection between the two districts for pedestrians and cyclist and a continuity of the urban space from one of the water to the other. The bridge will be an architectural landmark that horizontally defines the connection between the two previously industial harbourfronts and thus connect the cultural and commercial areas of Aalborg with the residential areas of Nørresundby. In order to get an understanding of the area, it’s context, history and future both an empirical and phenomenological based analysis has been made. The empirical consisting of a mapping of the area and the phenomenological consisting of a registration of the character of the site.
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Hede
gaard
org
sb Stig
House of Music
ge
Bryg
vn
Østre Ha
Mapping Site
The project is situated at the Limfjord in-between the harbourfront of central Aalborg and Nørresundby and the two maintrafic connections, the Limfjordsbridge and the Limfjordstunnel. Both the harbourfront in Aalborg and Nørresundby is at the moment under development and are going through a transition from industry-based economies to knowledge-based economies by means of an expansion of a campus and science parks. Additionally the development focuses on cultural activities and recreational areas in order to attract life to the harbourfronts.
Path
Transportation between Aalborg and Nørresundby is connected by three routes across the fjord, the Limfjord Bridge, the railway bridge and the highway tunnel. Since the Limfjord Bridge is the only one that serves transport for pedestrians and bikes and is located closest to the center it is an important and heavily trafficked road especially in rush hours. There has been a propose for an additional connection for pedestrians and cyclist alongside the existing railway bridge, but so far the project, Kulturbro-Aalborg, have not been realised due to economic reasons. The third connection, the highway tunnel, is an important route that connects the northern part of Jylland to the southern part but it does not have a direct impact on the city by means of leading traffic through it. The path along the harbourfront is mainly designed for pedestrian and bicycle use and creates a flow along both side of the fjord, but at the moment industry is blocking the straight path from the Limfjord Bridge to the east on Nørresundby side.
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Indu
sty h
Indu
sty
igrise
Lim
fjor d
sbr o
en
Kemia ground
Limfjorden Aalb
Utzo n Ce ntre astle
org C
House of Music Silos and stacks
Nordkraft Nyhavnsvej
Edges
Besides the industrial areas in the area, the most dominating edge is the water which creates a clearly and broad edge between Aalborg and Nørresundby. The edge is well defined along the habourfront in Aalborg, but both East and West of Nørresunby centre the harbourfront changes to a more soft edge defined by nature.
Landmarks
Besides the two bridges crossing the fjord old industrial buildings, new and future buildings are dominating along the harbourfronts. Hedegård industry and Østre Havn with its silos has for a long time been characteristic buildings along the harbourfront reminding one of Aalborg’s past as an industrial city but the development of the harbourfront on both sides means that new buildings has started dominating the outlook of both of the waterfronts.
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Bridge landing
Green areas
Jomfru Ane Park
Public parks
Utzon Centre
House of Music
Platform 4
Nordkraft
Green areas
The area along the harbourfront in Aalborg consists mainly of public parks such as Slotsparken and the two recently developed parks, Jomfruane Park and Utzon Park but further towards East there are also bigger green areas. Nørresundby consists of green areas which seems to be more dominated by the wild nature.
Nordkraft
House of Music
Nodes
A number of activities which can be defined as nodes or nodal points can be found along the path of the fjord and in the center of Aalborg. They are mainly dominating the Aalborg side where the new harbourfront attracts people throughout the year and Nytorv appears as a key intersection for public transport.
The Limfjord
Nørresundby
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N
N
25%
360
20% 15% 10% 5%
W
E
W
270
10 20 30 40 50 60 70 80 90
90
12 10
12
5
10
E
4
1,3
8 10
6
9 10
10 6
9 8
10 8
12 10
7
4 10 10
6
1,9
1,6
sundby hage 2 0,5 9 1,4
6 12
15 12 10 5
S
strong wind steady wind low wind
Wind
Because of the location on the Limfjord it is important to take the wind into consideration. The wind rose diagram shows the average wind direction and its intensity where as indicated in the diagram the area will mainly be influenced by a strong south-western wind. Since the bridge will be fully exposed to the relatively strong western wind without protection from buildings or the like, the use of shelters will be taken into consideration during the design of the bridge and its outdoor areas and paths.
180
S
summer spring & autumn winter
Depth of water
Regarding the topography of the area there are two aspects, the water level and the topography of the seabed. The height of water varies around 25 centimes according to the tide, but during a flood it can raise around 2 meters above normal water level. This will influence the minimum distance from the body of the bridge and the water. As the diagram shows the fjord is deepest closets to Aalborg and from there the depth of water decreases towards Nørresundby thus the opening of the bridge will be located closest to Aalborg in order to enable ships to pass through.
Sun
The orientation of the sun and its effective daylight time can be read from the diagram. The sun is an important factor in terms of outdoor areas and orientation of functions on the bridge. Thus the sun will have an influence on the organization of the functions on the bridge.
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Character of the site
Nørresundby The silhouette of Nørresundby is characterized by industry in the shapes of boxes that has a cold and dark expression of the industrial identity.
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Aalborg
The industry of Ă˜stre Havn takes on a variety of shapes in a more coherent and ordered structure comparable to a city skyline.
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Nørresundby Materials
A raw and rough nature characterizes the Nørreseundby site near Stigsborg Brygge. The elements show how the site has been used and changed by industry that is gone.
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Aalborg
The Aalborg site is characterized by the built. Here, the fjord meets the concrete wall that, together with brick, glass, asphalt and steel, show an industrial, fully developed site.
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Potential and spaces
Nørresundby has a lot of space but no activities or life. The area has potential of developing into an area for living and recreation, if life can emerge from the area that is now polluted and restricted.
The Nørresundby side seems dark and deserted.
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Aalborg has a lot of life but no urban space. The Aalborg site has a potential of becoming an attractive urban space because of the numerous cultural functions and the recreative potential of the water.
The Aalborg lights express the cultural transformation of the city.
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Local vision
Recreation - Green area, park, paths, beach
Nørresundby The industrial area, Hedegaard, will be the only remaining industrial area located in the center of Nørresundby and Aalborg. The local authority’s plans for Stigsborg Brygge, the old Kemira site, includes a depollution and conversion of the area, but the plans for the development of the area surrounding Stigsborg Brygge have been suspended since 2003. Preserving rough nature
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Stigsborg Brygge The future visions for the area Stigsborg Brygge, east of Hedegaard, is to transform the area into a new district with housing, smaller businesses and green areas. In front of this district the harbourfront will become a public green area along the water with spaces to stay such as a park, Nørresundby football club, pathways and a beach.
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Preserving industrial heritage
Aalborg The site surrounding the House of Music is about to undergo radical change to facilitate life in the urban space. Housing, business, knowledge and culture will be designed in existing industrial buildings as well as in new experimental architecture and the green link and Østerå will be connected to the fjord.
Experimental high rise architecture by Schmidt Hammer Lassen
Aalborg central waterfront The harbourfront in Aalborg is undergoing a transformation from an industrial area into a cultural and public area that focuses on the speed of walking and cycling. The area will consist of parks, squares, a harbor swimming pool and cultural institutions. It will become an area for visits and stays where people and culture meet and support a living city all day.
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Østre Havn In the future Østre Havn will get the character of a “mini Manhattan” with offices, cultural activities and housing and in this way keep the spatial qualities and visual experience of the area that it is known for today with its clean shapes of the industrial volumes. House of music The development of the House of Music has just been started and will be done by the beginning of 2013. This new cultural institution provides possibilities to create a new strong identity of Aalborg as a knowledge and cultural based city. It will enhance the musical life and become a place where citizens, education and culture meets.
ill. 3
Recreational area - green link and promenade by CUBO
House of Music by COOP HIMMELB(L)AU
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Utzon Centre by Jørn Utzon
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Our vision The vision for building a living bridge between Aalborg and Nørresundby is divided into three scales; an urban vision, and architectural vision and a local urban vision. Urban vision - To connect Aalborg and Nørresundby and their different qualities of recreational green park areas with cultural knowledge areas. - To experience a horizontal landmark from Limfjordsbroen.
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Local urban vision - To create a continuation of the urban spaces and habourfronts in Aal borg and Nørresundby accross the fjord. Architectural vision - To provide the bridge with a hotel, public spaces and recreational spaces. - To make a path only for pedestrians and cyclists. - To cover and protect pedestrians against weather. - To integrate functions in the structure.
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Bridge typologies Different types of bridges have been studied in order to understand their structural solutions. The study mainly focuses on their primary structure without evaluating on the potential for transforming them into living bridges since it will depend on the interplay with other parameters such as the function and experience of the bridge.
Golden Gate Bridge, San Francisco
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Traditional arch bridge The arch bridge is one of the oldest types of bridges and can only be built on a stable and solid ground. The bridge consists of vertical elements which transfer the load of the arch. Example: Rainbow bridge Niagara Falls, America Modern arch bridge The modern arch bridge is made of materials such as steel or reinforced concrete where the arch rises above the deck where cables connects the deck to the arch. Example: Sydney Harbour Bridge, Australia Beam bridge A beam bridge is a structure built of horizontal beams which are supported at each end by piers. It has a simple construction which in the beginning was made of wood planks but today they are normally made of steel. Example: Galvanized beam bridge, Pomfret
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Rainbow bridge Niagara Falls, America
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Sydney Harbour Bridge, Australia
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Cable stayed bridge Cable stayed bridges consist of one or more towers or columns where cables support the deck. The cables are often either parallel and attaching the tower in various points, called harp design, or connected all at the top of the tower in a fan design. The cables stayed bridge is optimal for long spans. Example: Kennewick cable bridge, Washington State
Cantiliver bridge A cantilever bridge is constructed of horizontal trusses, beams or girders in a structure which is only supported in one end. The cantilever bridge can be extended both above or under the deck. The advantage of a cantilever bridge is its ability to span long distances without the need of extensive and expensive support during construction. Example: The Forth Bridge over the Firth of forth, Scotland Truss bridge The truss bridge is a simple skeletal structure made of connected parts like beams that are able to support large amounts of weight and span wide distances when they are put together. Earlier they were made of wood timbers but modern truss bridges are made of iron tension membranes or reinforced concrete. The simplest type is a king post truss, a triangle, while a queen post truss consists of a horizontal part in the middle. Example: Little Belt Brigde, Denmark Suspension bridge The suspension bridge has cables suspended between towers and vertical suspender cables from where the deck is hung which allows the deck to be either straight or arc upwards. Since all the load from the bridge is transformed into tension in the main cables, these main cables must be fixed at each end of the bridge. Example: Golden Gate Bridge, San Francisco
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Galvanized beam bridge, Pomfret report p7.indd 25
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Kennewick cable bridge, Washington State
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Little Belt Brigde, Denmark
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Movable bridges To the way movable bridges operate differnt types have been studied. Several subcategories exist within each of these bridge types. The knowledge achieved within this study will be used as a reference for the design process and as a way to understand the different possibilities of the design of a movable bridge. Draw bridge The drawbridge consists of a deck which is hinged on one end and is typically seen at the entrance of a castle, but also over small spans like canals. The term is often used to describe different kind of movable bridges.
Tilt bridge This type of movable bridge rotates about fixed endpoints instead of lifting or bending as a drawbridge. The deck is curved in to open for crossing traffic. To open the bridge by lifting it the whole structure is rotated. The two curved parts of the structure counterbalance each other and in this way a minimum of energy is needed.
Gateshead Millenium Bridge, Gateshead
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Bascule bridge A bascule bridge works by means of balance with a counterweight that balances the weight throughout a upward swing. This type of movable bridges requires relatively little energy to operate and opens quickly. Several types of bascule bridges have been built both with single and double opening parts.
Skinny Bridge, Amsterdam
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Gateshead Millenium Bridge, Gateshead
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Limfjord Bridge, Aalborg
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Slauerhoff Brdige, New York
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Rolling bascule bridge The rolling bascule bridge operates as an unhinged draw bridge. The deck is lifted by rolling a large gear segment along a horizontal rack.
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Folding bridge The folding bridge is a movable bridge where sections of the bridge is folded like a bascule bridge with multiple sections. If the bridge consist of three-segments is will be folded horizontally into the shape of the letter N. ill. 19
Hรถrn Bridge, Kiel
Lifting bridge In a vertical lift bridge a span is lifted vertically over the deck by counterweighted cables fixed on towers. This type of bridge benefits from being a lowcost bridge which can provide long spans but at the same time it generates a height restriction for crossing traffic. ill. 20
Arthur Kill lift Bridge, New York
Retractable bridge A retractable bridge operates as a movable bridge by rolling or sliding the deck backwards to open for crossing traffic. The advantage of the retractable bridge design is its potential for providing a maximum horizontal open for example over a canal. It is also known as a thrust bridge. ill. 21
Kissing Bridge, Copenhagen
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Kissing Bridge, Copenhagen
Swing bridge A swing bridge has its primary structural support at a central fixed point. The bridge opens for crossing traffic by rotating the deck 90 degrees horizontally around the center. A swing bridge is a movable bridge where the deck rotates horizontally around a central fixed point. ill. 23
BNSF Bridge, Columbia River
Curling bridge The curling bridge operate as a drawbridge with multiple sections that is curled vertically by activating hydraulic pistons.
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Paddington Bridge, London 15/12/2011 17:15:23
Living bridges
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Pont Veccio, Florence 1742
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The living bridge can be defined as a bridge that besides being a link between to places also provides a value due to its integrated functions and thus makes it possible for people to inhabit the structure that otherwise merely would serve as a transit space. Living bridges can be defined as a bridge Living or inhabited bridges has been known for a long time and one of the most well-known bridges of this kind is London Bridge build in 12th century but also Ponte Vecchio build in 1742 in Florence and Ponte de Rialto from 1894 in Venice still existing living bridges that both create a sense of place and identity to the areas. In past the reason for inhabiting a bridge differs from today. Back then the reason for building on bridges was to achieve a larger amount of fresh air and sun light which made living more pleasant and healthy. Today the interest for living bridges can been seen mainly in competitions as the one in London in 2009 where architects made proposes for a reinterpretation of the living bridge that resulted in rather diverse results, but more of them with a character of a normal bridge with building added on the deck. Thus the aim for this protect is to design a living bridge where the constructions relates to the functions and becomes part of the spaces.
Proposal for London bridge competition 2009
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Proposal for London bridge competition 2009
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Proposal for London bridge competition 2009
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Nordic architecture Nordic architecture can be characterized differently in the Nordic countries due to their various traditions but seen from outside Nordic countries have several parallels in their architectural style that correspond to similarities in living standards, social values and the Nordic light which differ from the rest of the world. The Nordic light that shifts in nuances and varies in strength depending on the season has a great impact on the architecture where natural light is often used as a design parameter as can be seen in for instance works by Jørn Utzon and Alvar Aalto. Both Utzon and Aalto find inspiration in the order and growth of nature which to Utzon meant a development of an additive approach to architecture that can be seen in several of his projects. The natural connection and adaption to the climate and terrain in Nordic architecture influence the design of spaces that often appear as closed spaces with small openings placed in relation to light and views towards the surroundings. In this way outdoor space is included in the closed interior spaces but this incorporation of the environment can also appear the other way around where the interior continues out in exterior and indicates a defined outdoor space. Architects like Gunnar Asplund, Alvar Aalto and Jørn Utzon demonstrates the characteristic Nordic awareness to nature and honesty in projects that strives for quality in architecture through a simple and hornets synthesis of form, materials and function inspired by social and local values.
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Bagsværd Church, Jørn Utzon
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Town Hall, Finland, Alvar Aalto
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Room programme Function Hotel
Room reception conference meeting room lounge business area laundary room room
CafĂŠ Bar Shop Bakery - CafĂŠ Restaurent Fitness Outdoor public spaces Paths cyclist pedestrian
No. of pers. 50 100 10-30 10 20 20 2 4 30 30 10 20 100 150 -
Size Hight /m2 /m 150 3 250 4 30-70 3 50 3 70 3 30 3 46 2,5 9 2,5 80 3 70 3 70 3 70 3 400 3 600 3 50-100 1800 3000 -
Number 1 1 2-3 1-2 1 1 ? ? 2 1 4 1 1 1 6 1 1
Public/private Time in 1-10 scale function 8 24h 7 8-22 6 8-22 8 8-24 5 8-24 8 24h 2 16-10 2 16-10 6 15-24 5 17-24 5 10-18 6 7-14 6 11-15, 17-22 8 6-22 10 24h 10 24h 10 24h
View to fjord/city + + + + + + + + + + +/+/+ + + +/+/-
View to main path + +/+/+/+/+ +/+/+ + + + + + + + +
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DESIGN PROCESS
During the design process participation has been made in the Henning Larsen Architects workshop in Utzon Center. This has concerned the conceptual phase, where HLA’s method of thinking in strategies before creating a formal concept has been applied. The strategic concept and the architectural concept have after the workshop become part of the synthesis illustrated on the follow page, where studies of structure, volumes, functions and the detailing of modules, rooms and landings all have mutual affects in the process of integration.
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Strategic concept Landings
Modules • • • • • • •
Additive principles Grid Module dimensions Hotel room Facades Roof Materials
Functions
Architectural concept
Frames • • • • •
Truss types Context and urban flow Supports Form evaluation Bridge opening
Volumes
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Strategic concept The initial intention of this project is to create a connection for pedestrians and cyclists that link the harbourfronts and relates to the industrial areas in the two cities. The industrial area of Ă˜stre Havn and the new district Stigsborg Brygge has potential to develop in to interesting areas that preserve the industrial image of the cities but invites citizens to visit, stay or live in the areas. The Inspiration from the industrial context can be seen in the ideas of a rough and rational fragmentation of the volumes into modules of different functions. The fragmentation and distribution of functions along the bridge will create life and lines of sight and merge activities in the urban space. Inspiration has been found in already known projects like the Ruhr District, where industrial areas have been closed down and transformed to cultural institutions or in other ways inhabited by humans and in the surroundings. This concept differs in the sense that there is no existing industrial structure spanning the fjord. Instead of transforming an industrial structure to be inhabitable, the qualities of the industrial identity should be the inspiration for an architecture of a new construction.
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Architectural concept Architectural and urban concept The architectural strategy of the bridge is to eliminate the mental and physical barrier that the water generates between Aalborg and Nørresundby by allowing pedestrians and bikes to cross along a public main path which runs through a hotel. The hotel is a horizontal hotel where service areas are a part of the central public path. Thus the traditional vertical hotel is reorganized into an open typology where the hotel is distributed along a public path as small apartments. In this way life is concentrated along the public main path that protects users from wind and rain and provides different sizes of recreational spaces spread along the path from where the view of the two banks can be enjoyed. Mixed functions such as a restaurant, conference centre, fitness centre and cafes will ensure a constant flow of users throughout the day and highlight the “livingâ€? quality of the bridge.
Structural concept
The steel truss structure of the bridge is module based. The intention of the structure is to create an open facade that is dynamic and expressive and in which different functions can be placed. The frames mark the boundaries of the horizontal hotel and indicate with a simple form the transtional and directional qualities of the bridge. A structure is wanted that can mediate conceptually the transition from one side to another while being interpretative of the industrial identity of the cities.
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Frames Studies on truss types
Different types of truss structures have been studied in regards of both architectural and structural advantages and afterwards placed in relation to the context. Static analysis of the structure has defined the span of the elements. Also the meeting between elements and the support have been studied and analysed.
Conclusion
Even though the truss structure with diagonal connections in the structure is stronger seen from a structural point of view the vierendeel structure is chosen for the construction of the bridge. The vierendeel structure provides flexibility in regards of placing volumes inside the structure without it disturbing the facade of the volumes and the flexibility of the facades. Besides in perspective the vierendeel makes a clear sense of defined space and direction through the space. In relation to the concept of the horizontal hotel the vierendeel structure will act as the open facade of the hotel and in some places protect users of the bridge against wind and weather while at other places being an open facade where the structure defines the space and one still is able to sense and enjoy the weather.
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Frames tilted
Truss structure
•Tilted frames connect to each other •Still create sense of direction •Still, sense of open space •No structural effect at this point
•Sense of rigidity •Clearly defined space and direction •Structure defines space instead of perspective •Like a cage, enclosed space •Feeling of a safe structure and closed structure
Dynamic truss
Vierendeel
•Sense of movement and dynamics •Diagonal direction
•Static expression •Well defined framed space •Less cage-like
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Context and urban flow
Straight run with elements relating to the direction of the landings - Creates a long view and a straight path along the whole brigde
Displaced elements relating to the banks - Creates many and complex elements
Connecting the industrial areas the bridge is placed between House of Music and Østre Havn in Aalborg and to the East of the industrial area Hedegaard in Nørresundby. Apart from the clear industrial connection, this is a functional way in an urban scale to connect the two cities, as the bridge would link main streets of both Aalborg and Nørresundby, effectively connecting East Aalborg and Nørresundby. To provide an easy access for pedestrians and cyclists the bridge will be a low bridge, but still high enough to let speedboats and other small boats pass under without the need to open the movable part of the bridge. The low bridge brings the users closer to the water which enhance the experience of being above water but still able to sense it. Two types of runs have been studied in relation to the banks and the runs they create. A straight run and a run with displaced elements. The solution for the displacement of the elements is box shaped elements. The number and dimensions of the box-elements will be defined in the following evaluation of the form and is described in the “Modules” section.
Solution to displacing elements - Relates to box-shaped industry, a horizontal interpretation - Length and number of elements determined from possible span - Scale of elements and frame dimensions determines span - Functions determine scale - Length and number determines functions
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Nørresundby industry
Ă˜stre havn industry
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Method of form evaluation
For the additive concept to be realistic, quick FEM calculation has been used in the process. The calculations have been motivators for making compromises thus finding the greatest values of the concept and making it more clear, how the concept fulfills the architectural strategy. This section will explain the way FEM calculation has been included as a tool in the process of giving form to the architectural concept. An in-depth calculation proving the stability of a final element is in the appendix showing the method and background for the calculation. A two-dimensional static system has been used in the studies. The frame represent the longitudinal direction of one side of a Vierendeel truss module. Parameters concerning the geometry, bar profiles, supports and loads have been continously changed and the effects noted as to get an overall impression of the relative effect as a consequence of the changes.
Process of form evaluation
Initially a lot of parameters were set to the desired levels with a realistic but optimistic starting point, but it comes clear that compromises have to be made. Conflicting parameters such as an elegant bar profile versus the length of the span of the module are valued and estimated along the process so that the features that strengthen the concept stand out. The initial investigations with quick FEM calculations changing the parameters of loads and dimensions etc. have given an idea of the benefits of changing each parameter:
• Bar profile. HEA, HEB, and HEM profiles have different strength •
• • • • •
•
compared to their external dimensions, HEM being the strongest but also the heaviest. Bar height. The decrease of stress in the construction is almost proportional with the increase of the bar height. If the bar becomes too high compared to the proportions of the truss, an unwanted heavy expression is obtained. Truss height. Increasing the truss height decreases stress in the construction. Span length. Decreasing the length of the span drastically decreases stress in the construction and is thus the most beneficial tool. The longer the span, the greater the relative stress decrease. Distance between vertical truss bars. Decreasing the distance by adding more bars has relatively little effect on stress in this case. Ends cantilever. Has a very small effect in balancing the construction and reducing stress. Decrease loads. The use of lightweight materials should be optimized and the floor area of on which to apply live loads minimized as loads are directly proportional with the level of stress that occurs in the construction. Steel type. Choosing a strong steel type is a compromise that can be made on the basis of the importance of other aspects in relation to the concept.
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Distance between vertical bars Truss height
Cantilever
Bar height
Span
Since the expression of the frames of the structure and the horizontality are of great importance to the concept a reasonable bar height is set as to be 1 meter compared to the height of the truss of 5-10 meters from an aesthetical point of view. The bar should be dominant but not excessive. The selection of building materials is determined by the loads. Initially a mix of steel and concrete is envisioned to express the roughness of the industrial context but concrete construction is heavy and increases stress in the steel construction drastically. Wood construction is chosen as a Nordic approach to lightweight building construction and an opportunity to create a more humane contrast in the industrial urban space as well as a reference to maritime constructions.
The distance between vertical bars of the truss is of relatively little structural importance and is set at 14 meters to fit with both steel standard lengths and the dimensions of a pair of hotel rooms. Since shortening the span is an effective method of reducing steel stress and the span is of small significance to the concept, it is here that the largest compromises are made. And as the smaller the span, the higher the number of elements and the clearer the additive aspect of the concept. Still the number of supports is wanted at a minimum, and an opening of some width integrated to the structure should be realizable. Some specific additive module lengths are found and module dimensions take shape. The HEM bar profile is chosen as to be a strong profile compared to its height and width.
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Supports
A solid concrete pier system was chosen as base for the vierendeel truss structure; it matches the abutments of the bridge (landings) in materiality, use, and intention; generating cohesion with the newly modified landscape. Supports are placed every time two modules join.
Bridge opening
Different types of movable bridges have been studiet ealier and two types, the rotating and sliding bridge, seemed to fit to the concept of a truss structure and at the same time provide an opening with no limits in regards of the hight of the ships that pass through. Following pros and cons are listsed for the two types. ‘In order to keep every elements as a vierendeel structure the sliding opening is choosen. It fits into the concept of displacement of the elements and provides a witdh opening without making the element much bigger than the openening.
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Rotating + +
Ships can pass both ways Passage can happen in a straight line (advantage?)
- - -
Elements meet in rounded shape, which is unfamiliar to the concept of truss frames The rotating movement is not integral to the orthogonal rigidity of the truss elements Symmetric shape required means that length of opening element divides in two 16 meters modules, that is 32 meters, which again means low flexibility. It is a problem in this case, as the approx. 30 meters opening is not wide enough for cruise ships to pass through. Adding two more modules to the element makes it unnecessarily large
Sliding
+ Width of the opening can divide into a single 16 meter module + Orthogonal meetings of elements are integral to the concept + The sliding movement relates to the shape of the element sliding along its own axis + The sliding movement connects parts of the bridge, that were not connected before opening occurs. Potential of conceiving the opening as an experience for the user - -
Ships can pass in only one direction at a time Flow is obstructed (disadvantage?)
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Volumes Access to hotel rooms
Intimate urban space
Pedestrians
Access to hotel rooms
Main path
Cyclists Pedestrians
The displacement of the elements that is explained earlier under meeting between elements prevents the main path from being a straight run that has a long perspective. By dividing the run into smaller runs the distance from one bank to another becomes less exhausting and more interesting since the full length is not visible. Thus the actual distance is longer than the experienced distance because one is simulated due to the displacement of the run and a variation in the functions along it. (Gehl)
The distribution of the volumes in cross section is done in relation to accessibility to the hotel rooms and the experience of spaces. To enhance the idea of mixing the service areas of the hotel with the path that runs through the bridge access to the hotel rooms on first floor is established by making the volumes in the ground floor wider than the volumes on first floor and use the extra wide as gallery. The main path is separated into pedestrian areas along each side of the volumes and a cycle path in the middle. The width of the main path corresponds to
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the space needed for pedestrians and cyclist to pass each other. The cycle path is 3 meter wide which makes it possible for ambulances or other emergency vehicle to use it if necessary. The total width of the main path on 7 meter means that pedestrians are able to see what happens on the other side of the path. At some places a volume is removed in order to open to the view of the fjord and make place for an intimate urban space that is protected by the surrounding volumes. In these kind of well-defined areas the view becomes the attraction and invites to stop or stay in the area. Distances, speed, number of levels and orientation of views influence the life in a street. To enhance life along the main path public functions and functions related to the hotel is placed on ground level. When someone starts using the urban space there is a tendency that other follows. Since the main path is a multifunctional area that includes necessary, optional and social activities and due to the fact that life generates life, people using the path for necessary activities will generate life and thus invite more activities and life. Still optional and social activities will only take place if the quality of the urban space invites to it. Thus the urban spaces vary in size and amount of protection from the climate. (Gehl) Because of the relatively small width of the open space wind will not reach the path but be lead over the volumes. As can be seen in the wind study wind will only be a problem in places where the faรงade is open. To make spaces that invite to stay even on windy days the urban spaces will be protected against the wind at some places but open at other in order to make it possible to enjoy the good weather. In order to maintain the view towards the facade that an opening creates a transparent material will be used as windscreen in the smaller intimate urban spaces.
Wind flow across the bridge with one opening in the ground floor + The opening makes it possible to have a view towards the fjord + The opening makes a variation in the faรงade by means of a combination of open and closed areas -No protection from wind -The opening means that there will be a wind flow across the central street and at first floor opposite to the opening
Wind flow across bridge without openings. + Protection from wind form west and east + When there is no opening in the building volume the central street becomes a windless street -There are no views towards the fjord -the facade easily becomes monotonous
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Functions First floor Feeling of privacy - mainly hotel rooms Ground floor Part of public path - mainly public functions and outdoor spaces
The concept of making the hotel’s service areas a part of the main path means that the main path becomes multifunctional and that functions are mixed along the path. This will enhance life on the bridge and especially in the main path since it will be used of both hotel guests and people living in Aalborg and Nørresundby. People living nearby are invited to use and stay on the bridge because of the public functions like cafes, restaurants and fitness centre. The functions are distributed along the bridge and mixed so that the functions placed closed to each are used at different times of the day. In this way life will not be con-
centrated in one part of the bridge but spread out to prevent dead areas. Also there is a relation between the functions and the outdoor spaces so that functions like cafes and connected to urban spaces to make it possible to serve outside when the weather is good. The fact that there are two levels at some parts of the bridge means that the area at first floor becomes more private in relation to the ground floor since the vertical division of the space makes it harder to follow what happen in the higher level.
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Hotel room Meeting room Shop Meeting Bar room Transition Opening Reception Café Café Aalborg
Shop Lounge
Hotel rooms Meeting room Shop Restaurent Conference room Transition Fitness centre Café Hotel rooms
Nørresundby
Business centre Hotel rooms
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Modules Additive principles
The essence of the additive system is the repetition of elements to form spaces and all the advantages this has in terms of economy, sustainability, functionality, expandability and this repetition results in a distinct architectural expression. Utzon explains: “Such a pure addition principle results in a new architectural form, a new architectural expression with the same attributes and the same effects that are obtained, e.g., from adding more trees to a forest” (Holm 2004: 92). The additive principle can easily and effectively result in a form and composition that does not necessarily pursue a specific formal composition or image. The system takes account for various functional and contextual requirements and demands because of the inherent freedom, This freedom is integral to the architecture and the expression because the architecture is the additive principle: “This is just because the architecture – or perhaps rather the character – of the building is that of the sum total of the components, and not that of a composition or that dictated by the facades” (ibid.) By adding building components the additive architecture becomes not only functional and practical but also expressional of the principle as the addition of components result in an addition of architectural spaces. The expression becomes analogous to natural principles of growth and the resulting composition almost automatically expresses the additive idea. This adds to the architectural and tectonic potential of the additive principle: it can integrate effectively into the functional, constructional and aesthetical aspects of a building. Utzon has created systems and buildings that prove this point. In the Utzon Center this synthesis between the additive in construction, function and aesthetics happen. Identical spaces are added to each
other forming flexible exhibition halls. The rules for the placement of components are copied throughout the exhibition hall and walls and windows can be put according to those rules to form a functional space. As a basis for the modular system is a 2,53m grid that dictate the placement of a column for every third line defining additive spaces of 7,59 meters squared. Columns are placed so that the grid lines become center lines. In between the columns a 0,5 meter wide space can be used for inserting a wall or serve as an indicator of the transition from one additive space to another. To integrate the wall thickness into the additive system is important for realizing the additive concept. In relation to the living bridge concept, the structural steel frames can be assigned their own space in a way similar to the walls of the Utzon Center, still allowing indoor spaces to continue across module lines.
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Functional requirements set the specific widths of the modules as seen in the cross section. A basic measure is chosen to form a grid of 7 meters, which correspond to a reasonably broad main path, the approximate depth of a hotel room as well as steel standard sizes of 14 meters. Where grid lines intersect, center points of vertical steel bars are placed, which ensures that spaces of 7 meter width can always be placed in between. As with the Utzon Center columns, the bars have considerable dimensions of 1 times 0,3 meters which is taken account for by creating a similar double line grid. The additive system in this project differs fundamentally from the Utzon Center because of the external steel structure of the bridge, which cannot intersect with the indoor spaces because of thermal conduction. Therefore the steel bar grid is conceived in only the longitudinal direction, so that building mass stay in between bars running parallel to the direction of the bridge making long building volumes possible. Is the building height lower than the steel bar height, bars and volumes do not intersect.
Volume placement Column placement
Longitudinal direction
Grid
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10m
28m 21m
10m 7m 42m
28m 21m
Two modules
The structural calculations and the compromises made as a consequence of the calculations set rules for the length of the span of the module as shown on the figure. The structural frame makes it possible not only to span a distance but also allows different ways of thinking the volume placement. Hotel rooms are suspended from the top bars of the frame, where an open 7m urban space is wanted below. 42m The experimentation with structural calculation has resulted in two types of inhabited modules that expose the steel to largely the same
14m
amount of stress but with different prerequisites. In the two story module, the main street is protected from both sides by the building volumes. The load from the two story buildings and the width of 21 meters makes it possible to span 28 meters. Adding the first floor also adds to the height of the structure making the structure stronger. Remove one third of the width of the bridge, and it is possible to add 14 meters to the span resulting in the two typologies that can be combined. The two story module has the advantages of a large inhabitable area and high level of enclosure, whilst the one story module has the advantages of a large span and more exposure to views.
14m
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The hotel room
The hotel room has its own space programme, which accommodates the necessary functions of a bed, a desk, a wardrobe and bathroom. Life should be moved out of the room into the urban spaces of the bridge in relation to the concept of a “living� main street, where functions are mixed giving inhabitants and visitors reason to go through the urban space. Therefore the functions of the room are kept to a minimum. The necessary functions should on the other hand reflect the experience of being on a bridge.
The room is conceived in a rectangular shape that fits to the modules to make the most use of the space. Two rooms can share an element of two bath rooms conceived as a box pulled out from the facade. A niche with a bath tub is created from which to experience the cantilever over the fjord by being able to look both directly downwards and upwards through the glass box. The bath tub is lifted three steps from the ground floor so that the extruded window box can function both as a cantilevered bathing niche and as a window providing a view in eye height when standing in the bath room.
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Similar elements
Subdivision in thirds
Open
Closed
Open
Facades
This section concerns the form of the facade without making decisions on materials yet. The outward faรงade is parting the faรงade in three vertical areas as a consequence of the double bathroom box extruding from the volume. Functions placed on the ground floor will have toilet and kitchen facilities placed under the hotel bathroom boxes so that glass facades are placed on both sides of this faรงade area. Window dimensions correspond to the hotel room windows with a possibility for adjustment of the window area in three levels as shown on the figure, corresponding to the functions within.
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Roof
The simple sloping roof is added to it a function, when a glass roff is attached covering the pedestrian areas of the main street and corridor spaces. The roof is shaped, so that wind moves over the the urban space in between the buildings. Sunlight is transmitted through the glass roof. At the one story modules, the roof can be used for recreational purposes allowing people to access the roof through gaps inherent to the shape of the roof.
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Materials
To combine the span and the Vierendeel truss a lightweight wood construction is made. In order to use a simple and honest approach to expressing the construction method aesthetically, wood cladding is chosen. This lightweight, organic and warm material will contrast the cold, industrial steel frame thus expressing the contrast in inhabiting a rough industrial structure. Towards the fjord, the wood is stained black for weather protection and to be consistent with the rough expression. Towards the main street, the wood will keep its warm unpainted color to contrast the cold outward faรงade and express the lively, warm mood wanted in the main street. The steel bars will be paint protected in order to keep a stainless grey color to contrast the black and warm tones of the wood. The wood cladding is a traditional Nordic approach and it is visible in some of the work of Vandkunsten. At the Kvistgรฅrd housing stainless steel and dark stained wood is paired with untreated wood window frames. The result is a play of contrasts among the materials. The contrast of dark wood and stainless steel is also created at Fjordparken in Aalborg. Here the effect of having a warm colored, protected and more welcoming faรงade is obtained by using untreated wood at the entrance faรงade.
ill. 31
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Along the main path materials are used to separate pedestrian area from the cycling path without creating a barrier. Wood is chosen as a lightweight material that is tactile and inviting as a walking street with a reference to being on a simple bridge. The cycling path is plated with steel mesh gratings to make a contrast to the footpaths. Roof is coated with asphalt roofing to be relatively neutral and light. Window frames are aluminum to withstand the conditions of the microclimate, and railings along the open parts of the bridge and the inside corridors are steel mesh railings.
ill. 32
ill. 33
ill. 34
ill. 35
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Landings The concept behind the landings design consists in three concrete platforms placed along the harbor-front and a ramp resembling concrete abutments and piers of a traditional truss bridge. The steps along the landing provide a reinterpretation of those seen in the actual harbor front, providing at the same time, sitting places.
Aalborg side
The first platform receives the metallic bridge structure serving as a solid abutment; the second platform serves as a transition between the bridge and the harbor, a space to stop and observe, to sit, lay, or pass by. The third platform contains a ramp that allows the user to walk trough the concrete structure instead of under or above it, in direct contact with the structure and material. A fourth and last element is the 20 meters-long ramp for cyclists, handicaps, service and emergency vehicles, generating with its walls, an intimate space in front of the fjord.
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Nørresundby side
The landing part of the bridge with contact to Nørresundby follows the same design criteria, placing a concrete abutment as the main acces, with two ramps to follow the natural flow of the harbor front. The landing extends its limits into the fjord allowing interaction with the structure in a linear plaza. Low height walls generate intimate spaces protected from the wind.
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PRESENTATION Master plan 1:2000
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N
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The main street
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Ground floor plan 1:200
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B
N
B'
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First floor plan 1:200
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B
N
B'
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N
Hotel room plan 1:50
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Bath room
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Cross section 1:100
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Two story module outward facade 1:100
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Two story module inward facade 1:100
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One story module outward facade 1:100
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One story module inward facade 1:100
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Bridge facades 1:1500
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Bridge opening
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Landing section
Nørresundby
Aalborg
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Landing Nørresundby 1:200
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N 87 report p7.indd 87
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Landing Aalborg 1:200
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Conclusion Aalborg has a need for a pedestrian and bicycle path crossing the fjord to break the barrier more effectively than the existing Limfjord bridge. The connection is created as an urban space conceived in additive modules. The additive aspects are visible both constructionally, as the same building elements are repeated and functionally as the additive system provides the rules for the placement of functional space. Aesthetically the additive is expressed through the identical modules repeated and the frames acting as a series of gates leading across the fjord. The gates become the indication of the hotel faรงade, which is open and expressive of the concept of a horizontal hotel merged into an urban space. Crossing the bridge at pedestrian speed, different sensations happen along the way. Openings for views over the fjord and the banks emerge regularly along the path and a differentiation between open and closed urban spaces adds to the crossing some moments of sensory experience of the rough and windy nature of this site. This space has a contrast to the spaces covered on both sides by building mass and the roof keeping strong wind out of the urban space in order to create spaces that merge slow traffic, necessary functions and optional functions to encourage people to stay, underlining the living aspect of the bridge.
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Reflection This project is fictive to a higher degree than most projects because of the initial lack of rational arguments for placing an inhabited bridge in Aalborg. Many approaches can be taken to rationalize the project: the context can be changed by building at another site, the bridging part of the assignment can be conceived as an abstract, nonphysical connection, or the weight of the arguments can be put on the necessity of doing such a project as this once in a while so that not to obstruct one’s own imaginations and dreams of building on the water. This project has taken a more rational approach in some aspects but solves the actual hotel being part of a bridge crossing Limfjorden. The additive principle can in this case be applied to make large and complex configurations such as this more rational and realizable without necessarily compromising the architectural experience of crossing the bridge. Sacrfices have been made along the process in order to make a structurally realistic project. Here the additive principle can be seen as an obstacle, but in this case it not only solves the construction and forming of the spaces, it also help provide clarity on the concept by setting specific limits. The additive can be a type of boundary that turns out to provide more possibilities itself be part of the essence of the architectural concept. Had other sacrifices been made along the process such as replacing the vierendeel truss with a more traditional triangular truss system a higher degree of efficiency could be obtained, longer span achieved etc. But by adding to the concept the boundaries of both the additive principle and the vierendeel truss, decision making was accelerated giving reason to choices of lightweight materials that, when put against the dominant bar profiles, add a contrast to the expression of the rough industrial nature of the site.
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References Litterature
Holm, M. J. et.al. 2004. Jørn Utzon – The Architect’s Universe. Louisiana Museum of Modern Art. Lund, N. O. 2008. Nordic Architecture. The Danish Architectural Press Gehl, J. 2003. Livet mellem husene. Arkitektens forlag.
Illustrations
ill. 1 (http://www.aalborgkommune.dk/Om_kommunen/Byplanlaegning/Havnefront/Noerresundby-havnefront/Stigsborgkvarteret/Documents/stigsborg. pdf) ill. 2 Cubo, Nord A/S in ”Ideoplæg fra workshop 17. April 2007” (http://www. aalborgkommune.dk/Om_kommunen/Byplanlaegning/Arkitektur/ArkitekturForum/Documents/samletpdf.pdf) ill. 3 Schmidt Hammer Lassen in ”Ideoplæg fra workshop 17. April 2007” (http://www.aalborgkommune.dk/Om_kommunen/Byplanlaegning/Arkitektur/ArkitekturForum/Documents/samletpdf.pdf) ill. 4 Coop Himmelb(l)au and Aalborg Kommune (http://www.aalborgkommune.dk/Om_kommunen/Byplanlaegning/Havnefront/Aalborg-havnefront/PublishingImages/P_0701_R19.jpg) ill. 5 Own photo ill. 6 http://mychinaconnection.com/wp-content/uploads/2010/07/Golden-GateBridge.jpg ill. 7 http://www.garywallace.net/wp-content/uploads/800px-Forth_bridge_histo_2.jpg ill. 8 http://upload.wikimedia.org/wikipedia/commons/a/a5/Rainbow_Bridge_ Niagara_Falls_2.jpg ill. 9 http://funingallery.com/world-most-amazing-bridges/
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ill. 10 http://www.bridgestogo.com/ct_PomfretCT_WolfDen_P.html ill. 11 http://www.bridgemeister.com/pic.php?pid=1774 ill. 12 http://upload.wikimedia.org/wikipedia/en/b/b1/The_Little_Belt_ Bridge_%281935%29.jpeg ill. 13 http://media.photobucket.com/image/Draw+bridge+Magere_ Brug%2C+Amsterdam+/rb10_98/Kings%20and%20Queens/DrawbridgeMagereBrugSkinnyBridgeAm.jpg
ill. 23 http://en.wikipedia.org/wiki/File:BNSF_Bridge_9.6_swing_span_turned.jpg ill. 24 http://architecturelinked.com/profiles/blogs/rolling-bridge ill. 25 http://alliestark.blogspot.com/ ill. 26 - 28 http://www.architecture.com/UseAnArchitect/FindAnArchitect/Competitions/Results/London%20Bridge/Rocker-LangeArchitects.aspx ill. 29 Own photo
ill. 14 http://en.wikipedia.org/wiki/File:Gateshead_millennium_bridge_open.jpg
ill. 30 http://www.danda.be/gallery/saynatsalo_town_hall/4/
ill. 15 http://en.wikipedia.org/wiki/File:Gateshead_Millennium_Bridge_close.jpg
ill. 31 http://www.wood-supply.dk/product/view/25807/bambus_bordplader_keflico_as
ill. 16 Own photo ill. 17 http://en.wikipedia.org/wiki/File:BNSF_Bridge_9.6_swing_span_turned.jpg ill. 18 http://surferjerry.com/machines/amazing-slauerhoff-bridge/ ill. 19 http://www.gmp-architekten.de/en/projects/bridge-across-the-river-hoern. html ill. 20 http://en.wikipedia.org/wiki/File:Arthur_Kill_Lift_Bridge_by_Dave_Frieder. jpg
ill. 34 http://www.vandkunsten.com/public_site/webroot/cache/project/fjordparken_06.jpg ill. 33 http://www.schoeller.dk/skraberiste.htm ill. 34 http://reclaimedwoodmaterials.com/resourceconservationgroup_blog/tag/ azobe/ ill. 35 http://www.vandkunsten.com/public_site/webroot/cache/project/bbb_ billede_05.jpg
ill. 21 -22 http://sozuslu.blogspot.com/2009/11/new-bicycle-bridges-over-copenhagen.html
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APPENDIX
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Loads Loads are calculated to be used as data for a FEM calculation in Autodesk Robot. Loads are based on the worst case: a two-story module with maximum number of buildings. The FEM calculation is performed on one of two frames supporting the total mass of an element. Since the bridge is an additive construction of identical elements, only the worst situations should be calculated and repeated. The table shows the loads on the elements that occur in the construction used for the development of the module dimensions. Below, the method of load calculation for the 21 meter wide two story element is described, which is similar for all element types.
Fd = 6,6kN/m + 10,1kN/m + 7,7kN/m + 2,5kN/m +0,5kN/m + 0,7kN/m = 28,1kN/m
Live load
Dead load
Dead loads include buildings on the bridge, steel frame elements that are not included in the two-dimensional FEM model and elements of the urban space. The weight of all elements are added up based on the weight added on to one frame of the 21 times 28 meter two story module. This means that half the module is considered.
Load type (kN/m) Dead load Live load Snow load Wind load
In addition to the construction elements calculated above, all steel bars going across the bridge should be added, which adds 7,7kN/m. 2,5kN/m is added because of four HEA400 bars running along the length of the bridge carrying both buildings and the main street. The main street is partly constructed by wood adding 0,5kN/m and steel mesh adding 0,7kN/m the total dead load becomes
21m wide two story
Live loads are applied to one structural frame element according to Eurocodes. The red area marks the public space functioning as an access path to all other functions. The yellow area marks the indoor area intended to be used for office space and shops. On the first floor the blue area marks the private hotel room living area as well as the cor-
14m wide one story 27,7 55,9 7,6 7,0
5m wide no buildings 12,9 31,7 5,0 5,1
2,6 12,5 1,8 1,6
7m wide no buildings 3,6 17,5 2,5 2,0
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ridor spaces leading to it. The areas are uniform along the bridge direction so loads can be calculated per meter based on the width of the area to obtain an evenly distributed load, which is halved to consider a single frame. For the two-story element, live load is
Load combinations
Fl = (5kN/m2 7,6m + 2 * 4kN/m2 * 6,7m + 2 *1,5kN/m2 *6,7m) / 2 = 55,9kN/m
Live load dominating: 1,1 * Fd + * 1,1 * Fw Snow load dominating: 1,1 * Fd + * 1,1 * Fw Wind load dominating: 1,1 * Fd + Live load only: 1,1 * Fd +
Snow load
Snow load is calculated on the basis of the formula S = ci * ce * ct * sk = 0,8 * 1 * 1 * 0,9kN/m2 = 0,72kN/m2 when ci = 0,8 is the form factor for slopes < 15ď&#x201A;°, ce =1 is the location factor for a flat landscape, ct = 1 is a thermal factor and 0,9kN/m2 is the characteristic terrain value according to Eurocodes. For the two-story element frame snow load is
For the Ultimate limit state, four different load combinations are applied to the structure in Robot. Since spans are 42 meter where buildings are supported, the bridge is placed in consequence class CC3 and ULS load combinations will be as below. 1,5 * 1,1 * Fl + 0,45 * 1,1 * Fs + 0,45 0,9 * 1,1 * Fl + 1,5 * 1,1 * Fs + 0,45 0,9 * 1,1 * Fl + 1,5 * 1,1 * Fw 1,5 * 1,1 * Fl
For the Service limit state the following load combinations are applied: Live load dominating: 1 * Fd + 1 * Fl + 0,3 * Fs + 0,3 * Fw Snow load dominating: 1 * Fd + 0,5 * Fl + 1 * Fs + 0,3 * Fw Wind load dominating: 1 * Fd + 0,5 * Fl + 0 * Fs + 1,5 * Fw
Fs = (0,72kN/m * 21m) / 2 = 7,6kN/m
Wind load
Wind load is determined from Teknisk StĂĽbi according to Eurocodes. The landscape is considered open and since the building mass is averagely 8 meters above water level, the wind force can be determined at 1kN/m2. For this calculation the affected area is 140m2 and the height of the truss is 10m. The vertically distributed wind load on one frame is Fw = ((1kN/m2 * 140m2) / 10m) / 2 = 7kN/m
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FEM calculation This calculation proves that the module with the dimensions 21x28x9m is stable in the longitudinal direction. A two-dimensional static system represents one of two frames in the longitudinal direction of the vierendeel truss module. The joints are to be conceived as rigid towards moment forces unlike a triangular truss, in which forces are non-eccentric to the joints. Load combinations are according to Eurocodes and consequence class CC3 is chosen as in this case inhabited buildings are placed on spans of 42 meters.
Data
Profile: HEM1000 Material: Steel S450 For the chosen profile, S450 has a characteristic value of fy = 430MPa. Applying the partial coefficient = 1,10 the design value is fyd = 430MPa/1,1 = 391MPa.
Loads
Loads and load combinations are calculated and described in the “Loads” appendix on the previous pages.
Load type Dead load Live load Snow load Wind load
Load kN/m 27,7 55,9 7,6 7,0
Ultimate limit state load combinations: Live load dominating: 1,1 * Fd + 1,5 * 1,1 * Fl + 0,45 * 1,1 * Fs + 0,45 * 1,1 * Fw Snow load dominating: 1,1 * Fd + 0,9 * 1,1 * Fl + 1,5 * 1,1 * Fs + 0,45 * 1,1 * Fw Wind load dominating: 1,1 * Fd + 0,9 * 1,1 * Fl + 1,5 * 1,1 * Fw Live load only: 1,1 * Fd + 1,5 * 1,1 * Fl For the Service limit state the following load combinations are applied: Live load dominating: 1 * Fd + 1 * Fl + 0,3 * Fs + 0,3 * Fw Snow load dominating: 1 * Fd + 0,5 * Fl + 1 * Fs + 0,3 * Fw Wind load dominating: 1 * Fd + 0,5 * Fl + 0 * Fs + 1,5 * Fw
Fw Fd + Fl + Fs
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Ultimate limit state
In the ultimate limit state, ULS load combinations are applied to the structure to prove that the material does not fail. The stress calculated must be below 391MPa.
Using the live load dominant combination 324MPa occurs near the bottom corner of the construction.
Using the snow load dominant load combination 257MPa occurs.
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The wind load dominant calculation shows 230MPa,
and the live load only combination has 314MPa. The highest stress recorded is under the live load dominant load combination at 324MPa < 391MPa which is acceptable. Added to the dead loads come details such as ventilation that have not been further specified during this project. The figures show the weak points of the Vierendeel truss as the largest stress occurs near nodes and corners. It is worth remarking that joints should be stiff enough as to absorb the moment forces, which is the way the Vierendeel truss transmits forces. Since the live load is the dimensioning load in this case, it can also be concluded, that a beneficial way of making the structure more efficient can be by further minimizing the size of the floor areas of the bridge thus decreasing live loads.
Load combination Live load dominant Snow load dominant Wind load dominant Live load only
Maximum stress/MPa
Yield Stress/ MPa
Acceptance
324
391 OK
257
391 OK
230
391 OK
314
391 OK
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Serviceability limit state
At the service limit state the deflection is considered and must be less than L / 300 = 28000mm / 300 = 93mm
Applying the live load dominant combination, maximum deflection is 78mm.
Applying the snow load dominant combination, maximum deflection is 59mm.
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Applying the wind load dominant combination, maximum deflection is 53mm. The maximum deflection U = 78mm < 93mm is acceptable. Load combination Live load dominant Snow load dominant Wind load dominant
Maximum de- Deflection flection/mm criteria/mm
Acceptance
78
93 OK
59
93 OK
53
93 OK
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