Hassan II Bridge On Site Review Report. by Hanif Kara. Rabat, Morocco 4035.MOR. Architect Marc Mimran

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1 2013 On Site Review Report by Hanif Kara 4035.MOR Hassan II Bridge Rabat, Morocco Architect Marc Mimran Client Agence pour l Aménagement de la Vallée du Bouregreg Design 2007 Completed 2011

2 Hassan II Bridge Rabat, Morocco I. Introduction Divided into 16 regions and with a population of around 38 million, Morocco lies on the north-west corner of the African continent, boasting 2,400 scenic kilometres of Atlantic and Mediterranean shoreline. On the western side of the country the Bouregreg River creates a 6000-hectare valley more than 15 kilometres wide, stretching from the Atlantic to the boundaries of Sidi Mohamed Ben Abdella; the Hassan II Bridge is borne out of a vision to regenerate this area, close to the city of Rabat. His Majesty King Mohammed VI took a personal interest in this region by encouraging national policies and legislation to enable its large-scale redevelopment. Since His Highness the King is the highest authority in the country, his personal commitment is important, as morally this guarantees that the project cannot fail. One could argue that it also continues the tradition of the king as builder, demonstrating a well-governed state. In 2003 a special commission was formed to study the area and identify key projects and processes that would kick-start improvements in the areas of socio-economic, political, agricultural, governance and urban planning. The commission included representatives of His Majesty, the sovereign government of the region, leaders of the municipality, and experts from the fields of architecture, geography, geology, hydrology, transportation, engineering, history, archaeology, finance, agriculture and construction. The commission published its findings in 2003 in a comprehensive report entitled Projet d Aménagement de la vallée du Bouregreg (Development Project of Bouregreg Valley). Its farreaching conclusions signalled a new stage in the history of the valley, socially, economically and urbanistically. The Parti d Aménagement Global (PAG) suggested a number of interventions of different scales for the improvement of Bouregreg Valley; in particular, 13 key ideas emerged: Embouchure et Chenal Port Atlantique Tunnel Promenade El Alou Place Souk El Ghzel Rive Gauche Pont Moulay Hassan Bridge Port de Plaisance Cité des Arts et Métiers Esplanade Rive Droite Plage de Salé Front de Salé Cimetière 1

3 The findings concluded that improved transportation should be prioritised and would be a key component of the larger urban plan, generating the specific infrastructure projects that would have the most significant and immediate impact on the populations of Rabat-Salé: Hassan II Bridge The Rabat-Salé tram line The tunnel of Udaya II. Contextual Information A. Brief historical background The responsibility for delivering this vision and the individual projects was entrusted to the Agence pour l Aménagement de la Vallée du Bouregreg (AAVB; Agency for the Development of the Valley of Bouregreg), a public cooperation endowed with the status of a legal entity, given financial authority and reporting directly to the sovereign state. The AAVB, using a legal manoeuvre known as Eminent Domain, gained control of about 6000 hectares of land covering the areas around the medinas (ancient cities) of Rabat and Salé, and took into account a number of observations made by the commission, which can be summarised as follows: the region is of historical and religious interest including the ancient site of Chellah, which contains the ruins of a Roman town, and has numerous historic buildings, such as the Hassan Tower and several medinas; the valley is home to some exceptional landscapes, including a natural estuary and the plain of Oujda; due to the lack of a comprehensive strategic urban-planning framework the valley is under threat from the contaminated water quality of the River Bouregreg, which suffers from tidal saltwater intrusion, mercury contaminants, and a proliferation of wasteland and slums causing pesticide and mineral contamination of the river; it is necessary to protect against a predicted four-metre rise in water levels inundating the banks of the river and the flood plains beyond, threatening communities and agriculture. These points became the key driving forces for the urban plan, identifying several new projects that would not only transform the valley but also gradually change the identity of Rabat-Salé into a resilient, sustainable and modern city with a robust transportation network. Many of these projects are now underway. B. Local architectural character, including prevalent forms and materials The River Bouregreg has its source in the Middle Atlas mountains, is 240 kilometres in length and discharges into the ocean via a tidal estuary extending 24 kilometres upriver at a rate of around 23 m 3 /s. A number of bridges for rail and cars were built during the second half of the last century to connect both sides of the river. 2

4 In developing the design of the new Hassan II Bridge, both the character of the river and its banks (including existing bridges, marinas and so on), together with the urban forms of nearby Salé and Rabat needed to be considered as the new bridge had to extend some distance beyond the immediate banks of the river. The existing bridges (Pont Moulay Youssef, Pont Al-Fida, Pont Mohammed V) over the river are a mixture of short-span steel decks with close-centred reinforced-concrete piers that obstruct the natural flow of the river and restrict navigation. Including the existing Moulay Hassan Bridge, which was to be replaced by the new structure, these are uniformly utilitarian, with little character or concern for aesthetics, and generally follow the singular traditions of engineering economy. C. Climatic conditions Rabat-Salé has a temperate climate and is known to be quite humid, influenced both by the Atlantic Ocean and the nearby river throughout the year. The mean annual temperature is 17 o C with temperatures peaking at 30 o C, night-time lows of 8 o C and hours of sunshine throughout the year. Annual rainfall is in the order of 550 millimetres. Snow and ice, which can have a significant impact on bridge design, are not a concern here. D. Immediate surroundings of the site, including architectural character, access, and landscaping As mentioned, the new bridge extends a long way into the historic cities of Rabat and Salé, located on the plateaus that flank the banks either side of the River Bouregreg; in fact, almost 95% of its 1,200-metre length is dedicated to its transition into the two cities. These urbanised areas are situated either side of the agricultural valley of Bouregreg, with Rabat covering an area of approximately 9,528 hectares and Salé 15,075 hectares. A green belt of 1,200 hectares is prescribed in the wider plan to prevent urbanisation of the south of Rabat and separate it from Temara. North of Salé, an agricultural zone is supposed to ensure continuity between the forest of Marama and the coast. Each bank has prestigious historical sites, which include: on the Rabat bank, the Esplanade and Hassan Tower; the Mohammed V Mausoleum; Kasbah des Oudayas; the cemetery; the ruins of Chellah; on the Salé bank, the tomb of Sidi Ben Archer; the aqueduct and Salé medina (with ruins dating back to Phoenician times and still to be excavated). The mouth of the river descends down to the Atlantic and forms a beautiful natural frontier of lowland between the cities. E. Topography of the project site From the banks it can be seen that both cities meet the river at different levels. On the south-western side, Rabat s medina hangs over the cliff, while the Kasbah des Oudayas district rises up and then descends to meet the seashore at its tip. The cliff is about 60 metres above the level of the river bank, and the ribbon between the cliff and the river is used by fishermen. 3

5 To the north-east, the Salé medina is much closer to the river bank and rises to about 10 metres above the river bank level, though other districts further inland are higher. As part of the regeneration plan, the new Bouregreg Marina at the mouth of the river on the bank of Salé has been constructed, and has been operational since March It is important at this point to consider this and the other projects planned, since they were conceived as part of the grand vision and formed part of the brief for the new Hassan II Bridge, tram and tunnel projects. A mixed-use real estate project of 512,000 square metres called Bab al-bahr, designed by the architects Foster + Partners, has also been partly constructed. This development started in 2009 and comprises a range of residential units, hotels and commercial units for high-end offices. In the long term, the adjacent marina will also support this massive development, which lies in the shadows of Hassan II Bridge. It will provide catering and leisure facilities as part of the area s developing cultural sector, which includes a striking 2,500-seat theatre to be built by Zaha Hadid Architects. III. Programme A. History of the inception of the project; how the project was initiated The studies showed that Rabat and Salé (total population in the order of three million) had both suffered increased ghettoisation and fragmentation to varying degrees. It was also clear that unification of the two cities is essential for the purposes of future development, and that locally four key components are relevant and unite the cities: the new Hassan II Bridge; two tramway lines connecting the cities; a marina; the Bab al-barh district redevelopment. The city of Rabat is believed to have been formed in the 12 th century and around the 17 th century it served as a base for corsairs who waged war against the Christians from Spain and Portugal. During these times Rabat could hardly be evoked without mention of its ancient rival and neighbour Salé, recognised for its religious knowledge and mystics. Under French occupation, in 1913 Rabat was declared the civic/administrative capital (reinforced after independence, 1956) of Morocco, alongside Casablanca as its economic capital. From that time until the late 20 th century the growth of Rabat, as the centre of the kingdom, was evident in its new ministries, luxury hotels and residences for civil servants. Today 75% of Rabat s population is employed in government administration and support functions, and its economic activity therefore depends disproportionately on public departments. Salé, on the other hand, serves as a dormitory town, with the vast majority of its population commuting to Rabat and the remainder working in tourism. The river and paucity of transport links between the two cities form physical and socio-economic boundaries. Furthermore, assessments indicated that of the 400,000 people who travel daily between 4

6 the two cities, over 50% of them were using the old Moulay Hassan Bridge, which was reaching the end of its design life, causing massive traffic jams. The initiation of the tramway between the cities would relieve this congestion, and the most viable connection point for the tramlines would be in the location of the Moulay Hassan Bridge (and eventually its replacement the Hassan II Bridge). B. How were the architects and specialists chosen? The AAVB chose to organise a limited design competition for the replacement of the Moulay Hassan Bridge. The final teams that competed were: SETC and Marc Barani Marc Mimran Architecture & Engineering Schlaigh Bergman and Partners and Dietmar Feichtinger Architects Thomas Lavigne and Michel Virlogeux After two rounds of presentations the design team of Marc Mimram was selected. C. General programme objectives, functional requirements and architect s brief Though I asked for the original briefing document for the competition, to date the architects and clients have not been able to provide it. The client has, however, provided impressions of the four competition entries, and from those one can deduce that the key functional and technical objectives were: to design a structure that accommodates tramway ramps on both the Salé and Rabat sides, plus a two-lane tram route over the river; for an elevated highway to enter Salé descending approximately 9.36 metres from the bridge to Carrefour de Cardonna; to orientate the bridge axis to NE/SW over the waterway, parallel to the adjacent Moulay Hassan Bridge, which would remain in service during the construction of the new bridge; to provide a transition on plan on the Rabat side that curves (parallel to the river) and rises to Place Sidi Makhlouf by up to 20 metres; to cater for tidal changes of up to four metres (from -2.0 m to +2.0 m); to create a clear navigable channel (at the water) level of 76 metres width without intermediate supports and bridge underside approximately 11 metres clear at the centre; to provide a 46-metre bridge width that incorporates a tramway, three lanes of traffic, pedestrian routes and a cycleway; to produce a design of high architectural quality that would serve as a symbol for the modernism of the capital while rooted in the place, respecting the historical, urbanistic, topographical and economical constraints identified above; for particular consideration to be given to maintaining views of the Hassan Tower, the Chellah ruins and the Mausoleum. 5

7 IV. Description A. Bridge data: volumetry, massing, number of units, surface area in square metres The design proposed by Marc Mimram separates the bridge into three systems: the main bridge (spanning the waterway); a viaduct on the Salé side (instead of an elevated highway); and a nautical base bridge on the Rabat side, comprising 1,200 linear metres in total. Hassan II Bridge: global length: 330 m arch spans: 21 m 26 m 31 m 36 m 76 m* 36 m 31 m 26 m 21 m 21 m width: 46 m three decks of 14.5 m, 11 m and 14.5 m, separated with two rifts of 3 m about 16,000 m 2 clearance for navigation: max 33*10, min 16*9 material: 10,000 m 3 superstructure concrete 11,000 m 3 foundation concrete 3,000 tons reinforcement 360 tons of prestressing cables foundation piles up to 38 m 76 m clear span over the water Nautical Base Bridge: length: 100 m (curved on plan) arch spans: 35 m 35 m width: variable on two 14.5 m decks up to 35 m material: 4,900 m 2 surface 2,500 m 3 superstructure concrete 6,500 m 3 abutment and foundation concrete 120 tons prestressing cables Salé Viaduct: global length: 600 m arch spans: regular 21 m spans between twin columns width: 20 m material: 0,000 m 2 (including abutments and access on each side) 6,750 m 3 superstructure concrete 5,500 m 3 foundation concrete 3,300 tons reinforcement 6

8 B. Evolution of design concepts, including 1. Response to physical constraints, user requirements, spatial organisation siting, climate The designers commented that they were struck by the polarity of the flat plateaus, and were keen to preserve the views that celebrate the magnificence of the Hassan Tower. Accordingly, they reduced the level of the bridge by about two metres to ensure it was a project in touch with the landscape. Their most significant deviation from the original brief was to extend the bridge beyond the banks to reach Place Sidi Makhlouf on the Rabat side and Carrefour de Cardona in Salé; although this stretched the budget, the increase in length was deemed crucial to the success of the design. The jury supported the designers proposal that the space under the bridge could be used as a new public place for the citizens of Rabat-Salé. In order to enable this, the 600-metre-long space under the Salé Viaduct would be opened and power and water provided for future use by markets and retailers, while the underside of the 100-metre-long nautical bridge could be used to provide secure storage for yachts and market stallholders. Marc Mimram also commented that in general terms they wanted to create a well-detailed bridge that would be read as something growing out of the ground ; and that there had been no deliberate attempts to add any particular Islamic references in the proposal. 2. Landscaping Though the landscape design falls outside the scope of Marc Mimram s work, AAVB did appoint separate consultants. Given the three dimensional complexities of the bridge, tramway and tunnel it was essential to use the landscape to define and unite the project. The regenerated riverbanks of Rabat were completed in 2007 with their frontage accessible by working boats. The water quality has improved as a result of extensive dredging, and signs of flora and fauna are returning. Under the bridge itself, hard landscaping has been completed, though it is not currently in full use. On the Salé side new hard landscaping has been completed, installed up to the entrance of the historic medina and spreading onto the Bab al-bahr development. The exposed cliffs of Rabat highlight the influences of both man and nature on the ancient site, comprising a mixture of stone, historical walls and new flora and fauna. C. Structure, materials, technology 1. Structural systems The design requires three different structural systems to respond to the specifics of the site and brief: Hassan II Bridge with the longest free span, the Salé Viaduct with its repetitive span, and the nautical bridge on the Rabat bank that curves on plan while descending. 7

9 Hassan II Bridge The central portion requires a 76-metre-clear span over the waterway and is formed by a traditional arch section that supports the deck. Arches work primarily in compression and historically are used for medium spans with steep sided ravines, which provide good support laterally for arch thrust. In this case, the arches begin at column or springing points; half arches span on either side of the central span, forming a total length of 330 metres for this system. On plan, gaps are introduced between the carriageways and also to separate the tramway from the rest of the bridge; in section, three separate arches, each supporting its own deck, are formed. This enables an elegant cross section of hollow T beams with wide, thin arch sections. The half arches are not geometrically pure but asymmetric, thus inducing forces into the deck. Nautical Bridge On plan this portion of the structure curves significantly and the gaps on the deck are removed to reunite the bridge into a single-width deck. The primary structural system comprises two 40-metrespan arches that are raised to give clearance with a vertical post in the middle, while the two ends terminate in diagonal abutments that resist thrusts and uplifts. Salé Viaduct The 600-metre length was halved into two separate 300-metre lengths for ease of load transfer. Transverse portal frames were then provided to support the deck at approximately 21-metre cross centres. The portals span about 30 metres and on plan a gap is maintained for the full viaduct up to Carrefour de Cardona. Slipways either side of the viaduct are independent structures, as is the tramway ramp that peels away on plan to the west. Geology The sites of the viaduct and nautical bridge comprise made ground and alluvial deposits with a rocky layer below. As one gets closer to the river, variable strata of sandy mud overlying fine sand are found, deposited as layers of sediment over time. Bored piles were used to support the bridge throughout the whole system. 2. Materials Reinforced concrete was chosen as the primary material for structures. I understand that during the competition stages this decision was driven primarily by the designers view that steelwork was likely to depend on complex procurement methods, while concrete could be manufactured and constructed locally. It was also decided that white concrete would be used, as the designers wanted the changing surroundings to inform and colour the bridge s neutral materials. The strength of concrete required to 8

10 cope with the predicted forces also demanded a high-strength mix of grade C65; this combination of colour and strength had no precedent in Moroccan construction. Technical specifications: white concrete C65 strength minimum white cement CEM II 42.5N (imported from Lafarge France) white Dura sand from Kenitra (Morocco) gravel from Oued Cherrat (Morocco) light grey silica fume filler (imported) reinforcement (5,500) prestressing cables (51,860) both imported from France rendering and finishes include phonic asphalt, and stainless steel mesh for barriers and handrails 3. Construction technology The complex nature of a highway bridge requires the development of a comprehensive construction method in the initial design stages of the project. In this case, the designers felt strongly that a precast solution would give the desired quality of finish and deliver the fine details they wanted to achieve. Although this decision is usually made during the procurement stages, and often contractors find alternatives to the original design later in the process, in this case the designers had undertaken sufficient analysis to secure a precast solution, combining both post-tensioned and prestressed methods. Arches were precast on the bank and manoeuvred into position by a purpose-built crane, to be tensioned into position. The Salé Viaduct (which is a simple repetitive structure with 28-metre spans of the same geometry) was procured separately and used as a pilot to test the quality of finish and precasting. The nautical bridge portion was cast in place. 4. Building services, site utilities As this is a bridge structure, this section is covered within other parts of the report. D. Origin of 1. Origins of materials, technology and labour In terms of materials the project was able to use locally sourced concrete where in-situ concrete was specified, with formwork manufactured by local artisan furniture makers. The contractor SGTM also used local labour to construct the bridge, with up to 1,000 operatives active on site at its peak. However, the decision to prestress and post-tension the bridge (a decision which the form geometry and design forces demanded) required the contractors to source the expertise of specialist consultants Freyssinet from Europe. 9

11 2. Origin of Professionals Architects: Engineers: Contractors: Consultants: Marc Mimram Architecte, Paris, France Marc Mimram Ingénierie, Paris, France SGTM: Casablanca, Morocco SOGEA Maroc: Morrocan subsidiary of a French company (for the Salé Viaduct) Egis JMI LPEE, CID, Casablanca, Morocco Corrosion Engineering, Switzerland V. Construction Schedule and Costs A. History of project design and implementation, with dates International competition: late 2005 Project s attribution: late 2006 Project design: 2007 Building: B. Total costs and main sources of financing Approximate total: Hassan II Bridge: Salé Viaduct: Nautical Base Bridge: Abutments, platform and cliff reinforcement: Financing: 100 million EUR / 130,679, USD 45 million EUR / 58,810, USD 30 million EUR / 39,201, USD 12 million EUR / 15,680, USD 13 million EUR / 16,987, USD Government of Morocco C. Qualitative assessment of cost The costs provided by the team are as above. As is often the case, one cannot be absolutely certain, but I have seen in print that the cost may have been closer to 190 million EUR (248,314, USD). My opinion is that current costs of such structures in Africa are in the order of 4,000 to 6,000 EUR (5, to 7, USD) per square metre. Finance was provided by the state. D. Qualitative analysis of costs (per square metre, per unit, etc.) Hassan II Bridge: 2,800 EUR/m² (3, USD/m 2 ) Salé Viaduct: 2,300 EUR/m² (3, USD/m 2 ) Nautical Base Bridge: 2,400 EUR/m² ( USD/m 2 ) 10

12 E. Maintenance costs (heating, cooling, etc.) Financing: Government of Morocco VI. Technical Assessment A. Functional assessment (use) On the whole, the tramway and carriageway are functioning successfully, and the construction is of high quality in relative terms. On two mornings between 7 am and 9 am, I did, however, observe a lot of slow-moving traffic crossing the new bridge. The client has explained that the primary cause of this is due to the success of the bridge, which is attracting too much traffic as citizens bypass other crossings. I understand that this is a temporary situation as more infrastructures, including another new bridge, are being added to the system. The curvature and drop of the carriageway as it descends into the Rabat bank is severe; this is forcing traffic, and in particular buses, to slow down. It is likely that this unforgiving geometry was due to a last-minute change in levels in order to cut costs. B. Climatic performance, lighting, discharge and rainwater The design and construction were executed with great care to cope with the climatic conditions, and robust finishing that can cope with high surface temperatures together with well-detailed rainwater gutters and drainage systems have been provided. It is also very clear that the natural light to the underside has been well considered. However, the night lighting seemed to be incomplete not only in terms of usability but also in terms of maximising the potential of the structure as a focal point. C. Environmental response; adaptation to the natural environment; adaptation to native flora and fauna, seismic and climate change The combination of the form and orientation of the bridge means that natural light levels change with every hour of sunlight, providing unique reflections and colours. For such a long bridge I believe this was successfully handled by the designers. Flood levels and potential variations due to climatic change have been taken into account in the design. For a structure of this length and shape it was essential to undertake a very detailed analysis of the potential impact of seismic activity. The dual challenges presented by the nature of this complex structure and the lack of Moroccan seismic design standards led to a specific analysis. The loads and 11

13 findings of this study were provided to the designers who undertook an independent peer review and accounted for seismic loads. European codes of practice were referenced in parallel with incorporating the specific study. The response to seismicity was made more complex by the asymmetry of the structure and its use of a prestressed, post-tensioned design. The general quality of the waterway under the bridge and the immediate banks of the river appear to have improved when compared to the photographs taken prior to the construction of the bridge. D. Durability and ageing There is some confusion as to the design life of the bridge. I understand that at the outset a 100-year design life was prescribed, as is common for large infrastructure projects. However, this would have probably required stainless steel reinforcement and cables to support the structure, and potentially thicker structural sections. From the drawings it appears that stainless steel was not used in construction; I understand that this was a value engineering decision, but it leaves some uncertainty as to the structure s durability. VII. Users A. Description of those who use or benefit from the project The citizens of Rabat and Salé generally appreciate this aspect of the project, and are more critical of the Bab al-bahr district as this has increased property values around the bridge to the detriment of less affluent citizens. The tramway over the bridge appears to be extremely popular in achieving its objectives, and once regulated in the long term, the vehicular flow can only be of benefit. B. Response to project by clients, users, community, etc. It seems that the project is regarded as a success overall, as confirmed by everyone I managed to speak to, and that the initial concept of high quality has been delivered. My understanding is that the client and administration are also very satisfied with the outcome. The project has been published widely as an exemplar, both in a number of technical journals and in more general media. Comments include: unique, eye catching, good for Morocco and Africa; well blended with the surrounding landscape and medinas; modern, spacious, fast and efficient; gives Rabat-Salé a new symbol and reinforces the identity of the capital; some critical remarks, particularly from citizens on the Salé side, point out that traffic jams still occur. 12

14 VIII. Persons involved A. Identification of project personnel and their roles in the project Client: Project Manager: Engineers: Architects: Associate Project Manager: Construction: Detailed design: Nautical Base Bridge: Detailed design: Agence pour l Aménagement de la Vallée du Bouregreg Lemghari Essakl Saïd Zarrou Nada El Kasmi Marc Mimram Ingénierie SA Marc Mimram Jacques Durst Razvan Ionica Arnaud Delugeard Laurent Becker Nathalie Kreib Aldo Turchetti Sergio Pauletto Nicolas Videgrain Fabien Mauduit CID (Conseil Ingénierie Développement) SGTM (main bridge, nautical base bridge, abutments, cliff reinforcement, tram access) Ahmed Kabbaj, Director Serge Bisson, Project Director Youssef Kriem, Project Director Assistant Hassan II Bridge: Egis JMI (Michel Duviard) T-Ingénierie (Jean-François Klein) Freyssinet International (Jean Pierre Buys) SOGEA (Salé Viaduct and tram platform under Rabat s cliff) François Panafieu Arnaud Warcholak SECOA (Bertrand Lenoir) B. Contact Client: Project Manager: Nada El Kasmi (elkasminada@gmail.com) Marc Mimram Jacques Durst (jacques.durst@mimram.com) Valérie Barry (valerie.barry@mimram.com) 13

15 IX. Bibliography List of Publications Mimram, Marc, Un toit urbain dans l horizon paysager Le pont Hassan II entre Rabat et Salé dans la vallée du Bouregreg. Paris: Archibooks, L Agence pour l Aménagement de la vallée du Bouregreg, Plus qu un pont, un trait d union Pont Hassan II. Royaume du Maroc, summary report, Project l Aménagement de la vallée du Bouregreg, Dahir de Creation de l Agence pour l Aménagement de la vallée du Bouregreg, Decree d Application. Royaume du Maroc, summary report, Projet d Aménagement de la vallée du Bouregreg, March Picon, Antoine, Marc Mimram Architect-Engineer: Hybrid. Gallion: Infolio, Bargach, Jamila, A Human Rights Perspective for Dealing with Urban Marginalisation, research project, National School of Architecture in Morocco. Bargach, Jamila, From Capital to Global Metropolis, in The Evolving Arab City, Yasser Elsheshtawy (ed.). Taylor and Francis, Reuters-ITN, Big Development Projects to Ease Movement, Adaptation to a Changing Climate in the Arab Countries. A Case for Adaptation Governance and Leadership in Building Climate Resilience (MENA Development Report), Dorte Verner (ed.). World Bank Publications, Duviard, Michel, Lusk, Benjamin and Ledan, Arnold, Pont Hassan II sur l oued Bouregreg à Rabat, Travaux, no. 888, May 2012, pp Desveaux, Delphine, Une dentelle minérale pour un ouvrage royal, Construction Moderne/Annuel Ouvrage d Art, 2011, pp Hanif Kara April

16

17 Site plan. Road plan and bridge elevation

18 The Salé Viaduct is a simple repetitive structure with 28-metre spans of the same geometry. Slipways either side of the viaduct are independent structures.

19 Reinforced concrete was chosen as the primary material for structures. The central portion requires a 76-metreclear span over the waterway and is formed by a traditional arch section that supports the deck.

20 Nautical base bridge, on the Rabat bank, curves on plan while descending. This portion of the nautical bridge structure curves significantly and the gaps on the deck are removed to reunite the bridge into a single-width deck

21 Two tramway lines connect the cities of Rabat and Salé. Each bank has prestigious historical sites, which include: on the Rabat bank, the Esplanade and Hassan Tower.

22 4035.MOR Document B Le Prix Aga Khan d'architecture Formulaire de l'architecte Cycle IDENTIFICATION [Nom du projet. Si le projet est connu sous un nom différent, merci de l'indiquer entre parenthèses. L'adresse indique la localisation physique du projet, même si l'adresse postale est différente. La latitude et la longitude sont requis pour localiser le projet sur Googlle Map] Titre du projet : LE PONT HASSAN II ET SES OUVRAGES D'ACCES Adresse : Ville : RABAT/SALE Pays : MAROC Longitude: Latitude: II. PERSONNES RESPONSABLES : A. Architecte / Maitre d'oeuvre [Nom et adresse de l'architecte, du bureau d'architecture ou de toute autre personne en charge du projet ; pour les projets en collaboration, merci d'indiquer le nom de l'architecte responsable du projet à la fin de cette section. (Les autres membres de l'équipe seront listés comme affiliés au projet dans la section C. Affiliés/Consultants du formulaire.)] Nom : MARC MIMRAM Adresse : 21 RUE DE LA FONTAINE AU ROI Ville : PARIS Pays : FRANCE Facsimile : Principal Architecte : Marc Mimram Code Postal : Téléphone : +33(0) valerie.barry@mimram.com B. Client [Nom du particulier, de l'entreprise ou de l'institution commissionnaire du projet. Si le propriétaire du projet n'est pas le client, ou si les usagers actuels ne sont pas les clients, merci de les indiquer dans la section C. Affiliés/ Consultants du formulaire. Si le client principal est un gouvernement local, régional ou national, merci d'en spécifier le ministère ou le département, et éventuellement le nom de la personne en charge.] Nom : Adresse : Ville : AGENCE POUR L'AMENAGEMENT DE LA VALLEE DU BOUREGREG 1, ANGLE RUES GHAFSA ET PATICE LUMUMBA HASSAN RABAT Pays : MAROC Facsimile : (+212) C. Affiliés / Consultants [Merci de lister toute autre personne liée de manière significative au projet en indiquant leur rôle, i.e. ingénieur, consultant, artisan, paysagiste, technicien, autre architecte, client etc. Merci d'indiquer leur adresse, et téléphone sur une feuille séparée.] Code Postal : Téléphone : (+212) Nom AGENCE MARC MIMRAM : Nathalie Kreib, Nicolas Videgrain, Sergio Pauletto, Aldo Turchetti, Fabien Mauduit AGENCE MARC MIMRAM INGENIERIE S.A. : Marc Mimram, Razvan Ionica, Jacques Durst, Laurent Becker, Arnaud Delugeard AGENCE POUR L'AMENAGEMENT DE LA VALLEE DU BOUREGREG : Lemghari Essakl, Said Zarrou, Nada El Kasmi CID (Conseil Ingénierie Developpement) / EGIS JMI / T INGENIERIE / SECOA / TEAM MAROC / CORROSION ENGINEERING / FREYSSINET SGTM / SOGEA / Rôle Architectes Ingénieurs Client : Directeurs Bureau d'etudes Entreprises 1

23 4035.MOR III. HISTORIQUE DU PROJET [Merci d'indiquer le mois et l'année de début et de fin pour chacune des étapes de création et construction. Pour les projets à grande échelle ou achevés en plusieurs phases, indiquer les dates de la première phase et de toutes les suivantes, en notant clairement quelles sont celles achevées.] A.Commission Décembre 2006 B.Design Début 2007 Fin C.Construction Début 2008 Fin D.Livraison Remarques Avril 2011 Inauguration en présence de sa Majesté Mohammed VI, Roi du Maroc le??? mai 2011 IV. SUPERFICIES ET SURFACES [Merci d'indiquer les surfaces en mètres carrés. La superficie totale des planchers inclut les sous-sols, rez-dechaussée et tout autre étage supérieur. Si vous souhaitez fournir de plus amples informations, merci de les joindre sur une feuille séparée.] A. Superficie du site B. Surface au sol / / L'ensemble des ouvrages d'art reliant les deux villes de Rabat et Salé : mètres C. Surface totale (Inclut les sous-sols, rez-de-chaussée et tout autre étage supérieur Remarques: Détail : Le pont Hassan II : longueur 330 m 10 travées variables portée centrale 76 m Le viaduc de Salé : longueur 600 m Le pont base nautique : longueur 100 m 2 portées de 35 m La culée creuse et la rampe de Tramway V. BILAN ECONOMIQUE Montant en monnaie locale Montant en dollars US A. Budget initial total B. Prix du terrain C. Coût total actuel (Sans le terrain) , ,1717 / / / / D. Coût total du m 2 Remarques 2

24 4035.MOR VI. DESCRIPTION DU PROJET [Décrire la nature et la fonction du projet. Par exemple, qui est à l'initiative du projet, quelle était la demande initiale du client, quelle est l'idée maîtresse qui a guidé l'élaboration du projet, quelles ont été les contraintes majeures, comment peut-on évoluer dans le projet et quels sont ses liens avec son environnement.] L'Agence pour l'aménagement de la Vallée du Bouregreg a été chargée par Sa Majesté le Roi Mohammed VI de développer la Vallée du Bouregreg afin qu'elle devienne un véritable pôle urbain. L'agence Marc Mimram se voit confier la mission d'études architecturales et techniques du nouveau pont Hassan II et de ses ouvrages d'accès et voies de raccordement entre les rives de Rabat et Salé en Décembre Le pont Hassan II permet de fluidifier la circulation urbaine entre Rabat et Salé, tout en protégeant les sites historiques et les populations de l'ancienne médina de la pollution atmosphérique et sonore. Le pont Hassan II a été inauguré par Sa Majesté le Roi Mohammed VI et mis en service le 18 mai Les travaux avaient démarré en décembre 2007, pour un montant d investissement de 1,2 Milliards de Dirhams HT. Extrait de la note d'intention architecturale de Marc Mimram : S INSCRIRE DANS L HORIZON PAYSAGE Tout ici est tendu, beau et fragile. L esplanade du mausolée Mohamed V marque un plateau, la médina et les Oudayas forment au loin une fine texture entre le ciel et l embouchure du fleuve préparant la découverte d un autre horizon : la mer. Au nord, la citadelle de Salé s installe dans cet ancrage au sol, en fortifiant la minéralité de la transformation construite. Tout est sol, tout est issu de cette terre pour façonner dans la douceur de la végétation, un horizon construit, mince et délicat, animé, variable, ciselé et fragile. à l est, dans le méandre, la topographie prépare les mouvements géographiques de la vallée. Le nouveau pont doit dialoguer avec cette horizontalité construite, préserver les vues, offrir des regards, laisser filtrer sans obérer, cadrer les ouvertures sans masquer et surtout laisser le ciel. Car de cette minéralité ciselée, seule émerge de l horizon la tour Hassan ; qui souhaiterait s y confronter? Notre projet propose de dialoguer avec cet état de l horizon construit, tout ici est sensible à cette faible variation des échelles bâties dans le dialogue des rives du Bouregreg. En mettant nos pas dans ceux de cette histoire, il nous faut entrer en résonance avec cette géographie construite, sans heurt, sans gesticulation, mais dans l attention aux qualités du site : une modernité généreuse et sensible. UNE STRUCTURE ÉVOLUTIVE ET ORIENTÉE Entre le pied de la tour Hassan et Salé, le pont franchit différentes séquences : - la route qui longe les contreforts du mausolée, - l ouverture sur le Bouregreg, - l entrée sur Salé. Pour autant, l infrastructure s élevant à 10 mètres du sol doit former un projet unitaire variant continûment d une ville à l autre, d un sol à l autre. Il ne s agit pas ici de créer un viaduc solitaire mais de s inscrire en continuité, en urbanité. C est pourquoi nous projetons ici un système structurel évoluant linéairement depuis les viaducs d accès posés sur leurs appuis simples jusqu au fleuve pour former l arc central. La structure toujours évolutive s adapte aux conditions pour croître vers le Bouregreg. Les travées latérales sont composées de structures de demi-portiques qui vont croissant, orientés vers le centre du fleuve, face à face... pour former la voûte centrale. Il s agit de créer ici un ouvrage unique qui s adresse au fleuve, déterminé qu il est par le gabarit central, celui de la navigation vers le port de plaisance, marqué par la longue arche très tendue, celle du lit central qui distingue le fleuve navigable de la partie à l ouest découverte avec la marée et où s installeraient les jetées des clubs et des restaurants. Ces mouvements de la marée s inscrivent dans la géométrie de l ouvrage. Puis les demi-arcs prennent leur autonomie de part et d autre du fleuve, pour marquer les quais, border le boulevard côté Rabat, construire un toit pour le marché des pêcheurs côté Salé, et pour évoluer et se redresser de manière continue jusqu aux piles latérales des travées d accès. Cette évolution continue se fait le long d une grande courbe virtuelle ouverte sur le ciel et centrée sur le fleuve. 3

25 4035.MOR VIII. IMPORTANCE DU PROJET [Décrire le projet tel qu'il est aujourd'hui, quels en sont les usagers, quels sont les spécificités de ce projet (i.e. techniques, économiques, sociales, culturelles, environnementales, etc.] Le projet pour le nouveau pont Hassan II franchit la Vallée du Bouregreg entre Rabat et Salé. Cette infrastructure est exceptionnelle par la préciosité du site qui l'accueille, par l'attention porté à son environnement fragile et sensible. Il l'est par l'innovation technologique unique développée à cette occasion, tant par la finesse de sa structure précontrainte, que par l'expression d'une très grande habileté constructive au service d'une forme architecturale unique. Mais ce projet tendu entre les rives du fleuve est avant tout un service urbain, l'expression d'un engagement social entre la ville laborieuse de Salé et la ville administrative de Rabat. Ici, l'expression du service public prend toute sa dimension ; le tramway désenclave la ville et assemble ville centre et banlieue, ville dense et cité, populations mixtes et mélangées autour du lieu de transport unique. Mais nous avons voulu que le point soit aussi un toit offert à tous, un lieu protégé qui accueille un véritable espace public. Un lien urbain autant qu'un lieu partagé. Le projet d ouvrage d art est un service public situé, projeté à partir du paysage qui l accueille. Ici, dans la vallée du Bouregreg, le pont et ses aménagements permettent de coudre les rives dissociées des villes, celle de Rabat et celle de Salé, pour favoriser le développement urbain autour du fleuve. Le projet s ancre dans le territoire à partir de deux fondements : les qualités du paysage et les valeurs d usage de l espace public. La fine dentelle de béton s ancre dans le territoire pour construire un véritable équipement public, un toit urbain ancré dans le paysage. Le paysage est ici délicat et précieux. Le fleuve est la matrice du développement historique de la ville. APPARTENIR A L HORIZON PAYSAGER Le paysage s ancre sur l horizon finement bâti dans le ciel immense, par la ligne des constructions blanches de petites échelles, formant une texture délicate sur les strates de la topographie, celle de la falaise rouge et ocre sur Rabat, celle de la plaine alluvionnaire et du viaduc ferroviaire sur Salé. C est dans cette stratification fragile que s inscrit l ouvrage. Il appartient au sol pour laisser libre le ciel en limitant l émergence construite à la tour Hassan. C est dans cet horizon que le pont trouve son origine, son ancrage gravitaire pour s ordonner vers le centre du fleuve. Nous n avons pas voulu d un pont générique, indifférent à son environnement paysager, mais plutôt d un ouvrage issu des lectures du site, un ouvrage à l échelle territoriale qui parle du lieu en façonnant le lien, un ouvrage séquencé. OFFRIR UN TOIT URBAIN Le pont est un espace public, mais il devient ici un équipement public. D abord par le service public du transport en commun, par la multiplicité des parcours, des modes de liaisons qu il organise. Le tramway crée du lien social, le pont est son support. Il montre par la délicatesse de sa fine structure, par la générosité de son attention au site, la place de l ouvrage dans l espace public : le pont devient équipement public au service de la collectivité. Nous avons voulu qu il offre davantage, qu il façonne un espace offert, à l abri, à l ombre, qu il construise un véritable toit urbain. Sur 800 mètres de long, le tablier du pont parfaitement horizontal construit un toit au-dessus de la douce pente de la plaine alluviale vers le fleuve. La structure du tablier protège un espace public accueillant, une promenade, il se transforme en toit protecteur, celui d un marché, ou de toute autre occupation publique éphémère. Le pont prend ici tout son sens, il appartient à l horizon paysager, il en émerge même pour devenir le lieu public au service de tous, le toit urbain protecteur qui s offre à la ville : un équipement public ancré dans le territoire, une dentelle de béton fine et délicate au service d un espace généreux offert à la ville et à son fleuve. Sur ce projet, c est l aventure humaine qui résonne. Celle des ouvriers, des hommes au travail, du labeur. Ces métiers sont durs mais ils rendent fiers. Le projet fait la part du travail de construction et de celui de conception. Ici se mêlent très haute technicité de calcul, de mise en œuvre et savoir-faire artisanaux. Cette complémentarité est la marque du projet. Le paysage mais aussi cette mise en œuvre en font un projet situé. Le projet, maintenant réalisé, en est la mémoire construite. 4

26 4035.MOR VII. MATERIAUX, STRUCTURES ET TECHNOLOGIES [Décrire les principaux matériaux et technologies employées dans la construction du projet, ainsi que les éventuelles innovations mises en œuvre.] La construction d'un ouvrage d'art donne souvent l'occasion d'être l'expression des conditions constructives d'une époque. Il en va de ainsi du pont Hassan II sur le Bouregreg. Le Maroc montre ici son attention aux marques de l'époque, à la capacité technologique la plus avancée du béton précontraint de très haute résistance à partir de ciment blanc : UNE PREMIERE MONDIALE!! Le pays montre ici son attachement à la modernité, à partir d'un ouvrage unique par la finesse des ses composants structuraux, attentif à l'environnement par la frugalité et l'économie de matière dans sa mise en oeuvre, attentif à son environnement dans une relation douce et généreuse entre la géographie qui accueille le pont et la forme unique de sa délicate structure constructive. La modernité s'exprime ici à travers les compétences appliquées, sensibles et raffinées des ouvriers qui ont construit cet ouvrage en prolongeant l'histoire des savoirs faire locaux. UNE DENTELLE MINÉRALE Les arcs évolutifs sont composés à partir d un motif unique qui va croissant, permettant de rationaliser le mode constructif tout en autorisant ses variations. Au droit des appuis, les bras laissent filtrer les vues lointaines. Le pont est composé de trois tabliers juxtaposés indépendants pour offrir les lumières entre les voûtes qui varient au gré des mouvements du soleil. Par son orientation nord-sud, le pont accueille le parcours du soleil pour transformer sa structure en un capteur de lumières et d ombres, tout en évitant la noire profondeur sous son large tablier. Les trois parties du tablier sont prises en encorbellement sur la structure centrale pour ordonner et hiérarchiser les éléments constructifs. A l ouest, le spectacle de la médina et des Oudayas est offert aux piétons, aux promeneurs, grâce à une large passerelle en balcon sur le fleuve et le spectacle de l horizon construit. Ce premier pont qui accueille également le tramway peut ainsi aisément trouver une autonomie géométrique vers le sol, sur les rives de Salé et de Rabat. Les deux autres tabliers sont réservés aux véhicules automobiles, bordés par le trottoir à l est. Cette structure est délicate et sophistiquée. Sculptée dans le béton clair, elle varie continûment le long de ses membrures adaptées au schéma statique. Nous voudrions ici utiliser des bétons de haute performance pour réduire les équarrissages de ces éléments, les affiner, les tendre pour construire une dentelle légère et ouverte sur l horizon, variant au gré des lumières qui la pénètrent et la font vibrer. Ce pont est projeté pour ici et nulle part ailleurs, il est issu de cette attention aux conditions de ce paysage unique ciselé de blanc et d ocre sur l horizon. Cette ligne tendue entre Rabat et Salé dialogue avec le fleuve pour y puiser son rythme, sa géométrie, sa structure dans les lumières changeantes de l oued. Nous voulons ici que l ouvrage d art construise un lien généreux pour l espace public qu il façonne, un ouvrage dont la prouesse technique serait au service d une modernité attentive au délicat paysage du Bouregreg. La rampe tramway est un ouvrage en dalle épaisse qui prolonge le tablier supérieur du pont Hassan II jusqu à son ancrage au sol sur la culée située à Salé. Le rythme des piles prolonge par des portées égales de 21 mètres la dernière travée du pont en prolongeant de manière constante le rythme décroissant que celui-ci organise à partir de l axe du fleuve. La structure des grandes palmes de béton s affine sur les rives et l âme centrale à inertie variable est très largement ajourée sur la pile centrale pour maintenir une grande transparence à l ouvrage dans l ouverture visuelle qu il doit préserver sur le fleuve. Au-delà du pont principal sur le Bouregreg, il nous paraissait important de maintenir la vision de la géographie du fleuve. C est pourquoi nous avons prolongé l assise de la falaise jusqu à la culée du pont. Celle-ci forme un horizon construit qui limite l ouvrage d art à son assise géographique et permet artificiellement de poursuivre la ligne de la falaise. Concernant le viaduc d accès, le projet initial portait sur le pont principal dont on ne peut comprendre la logique territoriale sans son ancrage sur Salé entre le fleuve et le carrefour de Cardona à l extrémité nord. Nous avons projeté ici tout à la fois un ouvrage de liaison et un toit qui donne sens à l espace public qu il protège. Le viaduc est horizontal, c est le sol qui exprime sa topographie. Cette horizontale crée une ligne de référence et un développement modulaire de l ouvrage autour de portiques bi articulés liaisonnés par de fines palmes de béton distinguant les ancrages verticaux, façonnant la sous-face de ce toit protecteur, ordonnant longitudinalement le tablier. Ici, le système constructif, dans la répétition de ses éléments préfabriqués, autorise une délicate attention à l espace public qu il protège. La massivité du béton, l ancrage gravitaire sont ici mis en dialogue avec la finesse des composants structuraux, le jeu des courbes, des engravures, de l ombre des fines saillies : un béton distingué dans la minéralité de ses composants Les échelles se combinent ; celle du rapport tactile, de l œil dans l assemblage des composants structuraux, du béton blanc et de ses variations entre ombres et lumières, celle du schéma statique, du toit infrastructurel porté entre les portiques offrant un dispositif lisible, ordonné, hiérarchisé entre lesquels se glissent le soleil et l échelle de la ville, celle de l espace public dès l appropriation à venir afin de partager ce que la ville offre ainsi, un toit, une déambulation entre Salé et le fleuve, dans l axe de la tour Hassan. 5