As one of the most important traffic links in the country’s road network, linking Sitra and Manama in Bahrain, the previous Sitra Bridges had reached the end of their service life and could no longer cope with increased traffic volumes.
The dual two-lane roads and the at-grade junctions, therefore needed to be replaced by a dual three lane highway, complete with a 3-level grade-separated intersection at Umm Al-Hassam. This new configuration was designed to provide excess capacity for the heavy morning and afternoon rush hour traffic loads, which exceed 6,000 vehicles per hour.
In order to maintain traffic flow and services, the new bridges and utility conduits were built alongside the existing ones and switched out on completion. For main contractor Berhad Gamuda, the key to achieving these goals was to ensure the formwork and shoring was up to the challenge. Following a competitive tender process, RMD Kwikform was awarded the formwork and shoring contract to assist in the construction bridges and flyover sections. Key to successful creation of the new dual three lane highway, was marrying the needs of the tight programme and budget, with the requirement for minimum disruption to the existing road network. For RMD Kwikform’s engineering team, in order to achieve these goals, practical yet safe design solutions were required.
It was the trust and interaction with main Berhad Gamuda that was so important as Shekar explains:
The scope of the project was to build a brand new dual three-lane highway, a 3-level grade-separated intersection at Umm Al-Hassam and at-grade signalised intersections at the entrance to Nabih Saleh Island and at North Sitra. What Berhad Gamuda were looking for was an equipment supplier that could support them both technically and logistically to supply formwork and shoring solutions to key parts of the project.
With East to South and North to South flyovers making up a large proportion of the new highway and underpass used in other areas, the range of equipment required was significant. Special parts and complex detailing also required specific engineering attention. With over 1,050 tonnes of equipment used over a three year period, the scale of project management and delivery required a huge amount of planning and onsite support, in the form of RMD Kwikform Site Assistance Technicians all of which helped the project programme time.
For RMD Kwikform there were various phases to the project, one was the 12m, high, 1.2m thick Umm Al-Hassam Underpass walls, which were created using a single sided climbing formwork system. This was then followed by the use of Rapidshor in a modular format as backpropping to transfer the additional loads applied to the underpass slab from the flyover deck supports.
But it was the flyovers themselves that required the most equipment and engineering support. Both the East to South and North to South flyover bridge deck falsework required the use of complex side forms in order to achieve the design requirements. With Rapidshor shoring supporting Superslim primary and GTX secondary beams used for the complex bridge deck, compete with wedge shaped side forms, the varying width of the flyover decks were achieved.
When we looked at the deck design and overall structure in layman’s terms it varied in both cross section and length. therefore in order to achieve this complex shape, we had to design special hinge connections that could cater for the various slopes of side forms and interconnect with the overall Rapidshor support system. Each hinge had to be robust enough to be reused multiple times from one structure to the next, across both of the flyovers. They also had to be flexible enough to cope with varying heights of the Rapidshor system from 4m to 14m.
With the length of the East to South flyover measuring 390 linear metres, with six spans from abutment to abutment and the length of East to North flyover measuring 185 linear metres, with 5 spans from abutment to abutment, a total of 475 linear metres of flyover had to be constructed to complete the project.
In addition to the flyover and underpass systems used, RMD Kwikform also supplied over 280 tonnes of side form formwork consisting a combination of Kwikstage, Rapidshor Support with Soldier and Special Shaped Steel Walers to Support GTX Beams and plywood to form Complex Profile for the construction of the Marine bridges. Shekhar concluded:
In all the success of the project came down to designing simple modular support systems that were complemented by specially designed parts that made the erection and dismantling process simple, safe and time efficient. Through working closely with the main contractor and our support with training and supervision onsite we were able to achieve the goals to create a modern and sustainable project with a built in life of over 120 years.