Southkey Megamall Highway Access Ramp
A new megamall is under construction adjacent to the Eastern Dispersal Link, one of the major highways between Malaysia and Singapore near the city of Johor Bahru. Tony Gee was engaged to provide an alternative design for a curved bridge over the main highway connecting the northbound exit slip ramp to the megamall vehicular access. While the majority of the construction for the access road is in reinforced concrete, the logistics of installation, the need for minimal traffic disruption and the curved geometry of the 130m long three span bridge favoured a steel box girder solution with a composite concrete deck.
A Malaysian consultant had produced a detailed design of such a solution but the client was keen to make savings on the weight of the steelwork. The contract with Tony Gee provided for a low basic fee associated with a significant incentive bonus linked to the savings in steelwork weight actually achieved.
The permanent works design was produced by the structures team in Esher to a very tight programme with liaison, management, temporary works design and site support provided by the Malaysia office. The twin steel box girders were fabricated near Kuala Lumpur and erected in Johor over a series of nights. A trial erection of the steelwork was also undertaken beforehand. The site team noted how useful this exercise proved to be for fine tuning the construction operation.
The alternative design yielded a 50% steel saving compared with the original design (from 800T to 400T), which significantly exceeded the client’s expectations based on Tony Gee’s initial estimates. This saving, despite the tight design programme, was largely realised through initial sizing of members based heavily on previous experience of similar structures. The team was therefore also able to propose and design a lighter substructure which contributed to further savings on the scheme. Tony Gee went on to work closely with the steel fabricator and contractor to optimise the construction sequence and temporary works, making use of permanent formwork for the concrete deck. Impact on the existing highway was minimal with limited lane closures and requirements for minimum number of running lanes open at all times adhered to. The Malaysia office used the TG Standard Conditions of Contract for Malaysia.