Bridges

In view of the increasing demand on reducing reliance on limited labour resources, modular construction, such as the precast deck segments, precast piers and precast pile cap shells, is increasingly being adopted as an integral part of the construction process for elevated highways, particularly when constructing the viaduct in a marine environment. The approach however requires careful design considerations such as the integral connections between the precast units and the in-situ parts of the works in order to ensure durability of the structures. As part of the strategic road network in Hong Kong, an express link will connect East Kowloon and the new town of Tseung Kwan O. Part of this link includes an elevated interchange over the sea with seven post-tensioned precast segmental bridges. The series of balanced cantilever bridges within this marine interchange run in a spaghetti junction manner around the main line viaduct, which comprises two parallel bridges connected at each pier with a cast in-situ diaphragm. The alignment of one of the interchange viaducts has a plan curvature of 44m, making it the tightest radius bridge ever erected using the precast segmental balanced cantilever method in Hong Kong. According to the contract requirements, the bridges have a design life of 120 years. This imposes challenges on the design and construction of the structural elements of the bridges, especially the pile caps which are located within the splash zones at all times. This paper presents the projectís unprecedented challenges, along with the methods used to construct the complex viaducts whilst ensuring a safe construction environment, and the key design measures established to manage the construction risks.