Replacement of Sitra Bridges: a Mega- Project for Bahrain

Proceedings of ICE Civil Engineering 162 November 2009 Pages 34–41 Paper 09-00024 doi: 10.1680/cien.2009.162.6.34 Keywords bridges; geotechnical engineering; project management Replacement of Sitra bridges: a mega- project for Bahrain Mostafa Hassanain PhD, PEng, PMP The Sitra bridges are part of a busy 3.2 km causeway linking is head of bridge and flyover projects at the Ministry of Works, Manama, the main island of Bahrain to the island of Sitra, one of the most Bahrain strategic road links in the kingdom. However, after just 30 years the structures have succumbed to the aggressive marine environment and are being replaced at cost of US$280 million, along with construction of a new causeway alongside the old one and a major new grade-separated intersection. This paper describes the design, construction and management challenges of delivering the country’s biggest ever road project in a sensitive marine environment and highly congested urban area. The Sitra bridges project in Bahrain involves 1976, the structural condition of its two marine the replacement of a 3.2 km causeway linking bridges has deteriorated so significantly that it the main island of Bahrain to the island of Sitra is no longer economically feasible to maintain across the environmentally and politically sensi- or repair them. In addition, the causeway can- tive Tubli Bay (Figure 1). The causeway is one not accommodate the ever-increasing traffic of the most strategic road links in the kingdom’s volumes it must carry. This has led to long highway network. traffic queues that are frustrating to road users Since the causeway opened to traffic in and have a negative impact on the movement Figure 1. Sitra causeway in February 2007 (looking north) CIVIL ENGINEERING REplacEMENT OF SITRA BRIDGES: A MEGA-PROJECT FOR BAHRAIN of goods and services, and consequently a detri- in length. The northern bridge has four spans mental effect on the local economy. The cause- (45.4, 54.6, 54.6 and 45.4 m), while the south- way is currently being replaced. ern bridge has seven spans (50, 60, 60, 60, The project, which commenced in November 60, 60 and 50 m). Each bridge consists of two 2006, also involves the transformation of the separate and similar structures carrying one northern approach to the causeway from an direction of traffic. The superstructures consist at-grade, signalised junction into a three-level, of cast-in-place, post-tensioned, voided concrete grade-separated interchange. This will be box girders with a maximum depth of 3 m the first such interchange in Bahrain. Umm (Figure 3). The substructures consist of cast-in- Al-Hassam junction is the main road junc- place, reinforced concrete piers (Figure 4) car- tion leading to the causeway from the capital, ried on reinforced concrete pile cap crosshead Manama, and is one of the most traffic-congest- beams over bored, steel-encased reinforced ed junctions in Bahrain. concrete piles embedded in bedrock. The abut- The approximately US$280 million project ments comprise cast-in-place reinforced con- Figure 2. Existing marine bridges have 12 m spans is the largest and most complex single road crete bank seats on similar piled foundations. and only 1.9 m navigational headroom project ever undertaken in Bahrain. The kingdom is investing heavily in this road segment because most of the passenger and heavy traffic to and from Saudi Arabia passes through it. In addition, following completion of the proposed Qatar–Bahrain causeway, this segment of the road network will be the main access to Manama from Qatar. Enhancement will bring significant benefits to the economy of the kingdom by easing the movement of people, goods and services not only on a local scale but also a regional one. The client is the Ministry of Works of the Kingdom of Bahrain, the designer and construction supervision engineer is Cowi of Denmark and the main contractor is Gamuda Berhad of Malaysia. Sitra causeway The existing Sitra causeway is a dual, two- lane carriageway with two marine bridges – a Figure 3. New marine bridges span 45–50m and provide navigational clearance of 5.2 m northern bridge 216 m in length and a southern bridge 576 m in length. The remainder is on embankments. The existing bridges are charac- terised by simply-supported spans of 12 m each (Figure 2). They carry several utility lines includ- ing high- and low-voltage cables, water pipe- lines, telecommunications cables and a natural gas pipeline. These are located beneath the deck and in the central median on an independent service deck. Some of the utility lines provide vital links in the overall services grid of the whole country. The existing bridges have low navigational headroom of 1.9 m above mean high-water level. Due to the strategic importance of the causeway to the overall roads network, traffic movement and the utilities had to be maintained during its replacement. The new crossing is currently being constructed approximately 50 m to the west of the existing one and mostly parallel to it. The new causeway will be a dual, three- lane carriageway. In addition, in each direction there will be a hard shoulder that could be converted into a fourth lane in the future when increased traffic volumes require it. Figure 4. Piers of the northern bridge at various stages of construction – three temporary piled access platforms allow tidal flows to continue around the works The two new bridges are 200 and 400 m ISSN 0965 089 X PROCEEDINGS OF THE INSTITUTION OF CIVIL ENGINEERS – CIVIL ENGINEERING, 2009, 162, No. CE6 35 HASSANAIN Figure 5. Gridlocked Umm Al-Hassam junction in December 2005 Figure 6. Rendering of the proposed grade-separated interchange The new bridges have navigational headroom of Following the opening of the new causeway The junction is located at the intersection of 5.2 m above mean high-water level. to traffic, the two old bridge structures will be Shaikh Isa Bin Salman highway – the main road Aesthetics of the marine bridges was a demolished, while the existing causeway will be artery from Saudi Arabia to the new Shaikh major criterion set out by the client. This has retained and converted into a landscaped public Khalifa Bin Salman port in the east–west direc- resulted in a decision to eliminate the cluttered recreational area. tion – and Kuwait Avenue to the north and appearance of utilities on and beneath the Shaikh Jaber Al Ahmed Al Sabah (which is bridge deck and to provide instead chambers Umm Al-Hassam junction carried by the Sitra causeway) to the south. It for the numerous existing and future utilities is physically constrained due to severe space inside the cross-section of the superstructures For years, the signalised Umm Al-Hassam limitations in the surrounding areas and the of the marine bridges. road junction has held the undesirable distinc- presence of a large number of significant under- The causeway embankment comprises a bund tion as one of the most traffic gridlocked areas ground utilities. constructed out of quarry run protected by rock in Bahrain (Figure 5). It was determined that The solution adopted was to transform the armour towards the sea. The bund serves as most of the traffic capacity benefits which would junction from an at-grade, signalised junction retainer of the dredged-sand filling forming the accrue from replacement of the causeway would into a three-level, grade-separated interchange final embankment and also acts as temporary not be realised if the junction was not completely (Figure 6). This involved the construction of a access road during construction. overhauled. 560 m long underpass for east–west traffic, a 26 m long at-grade bridge for north–south traffic over the underpass, a 379 m long flyover for east–south traffic and a 183 m long ramp for east–north traffic. The underpass consists of a watertight open- trough structure with a reinforced concrete bottom slab of thickness 0.5–1.2 m tied down with 942 vertical ground anchors to resist buoyancy. The side walls comprise permanent steel sheet piles tied back in the ground with inclined ground anchors to resist horizontal forces, and covered by cast-in-place, reinforced concrete cladding on the traffic side (Figure 7). The total width of the underpass is approximately 26 m and it carries three lanes plus a verge in each direction. The at-grade north–south bridge comprises a two-span, continuous, reinforced concrete deck slab that is supported at each end by the top of the underpass walls and by a central reinforced concrete wall. The central wall, in turn, is supported by bored, steel-encased reinforced concrete piles. The bridge has an overall length of approximately 26 m and a total width of about Figure 7. Underpass trough during reinforcement placement for bottom slab – showing vertical anchor 73 m. It accommodates eight traffic lanes in a sleeves, under-slab waterproofing and permanent sheet piling variety of through and turning movements, in 36 PROCEEDINGS OF THE INSTITUTION OF CIVIL ENGINEERS – CIVIL ENGINEERING, 2009, 162, No. CE6 ISSN 0965 089 X REplacEMENT OF SITRA BRIDGES: A MEGA-PROJECT FOR BAHRAIN addition to a built-up reinforced concrete serv- It is worth noting that, according to the ment steel is specified as 80 mm, except ices corridor having a width of approximately literature, the Sitra causeway is the first for piles where it is 100 mm. This may be 10 m to accommodate several utilities. project where such extensive use of stainless reduced to 45 mm in locations where stain- The east–south flyover has six spans (49, steel reinforcement has been adopted.

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