Design of the new extra-dosed bridge over the Kelani River

Abstract: An extra-dosed post-tensioned pre-stressed concrete box girder bridge over the Kelani River is scheduled to be built as part of an elevated roadway project in Colombo, Sri Lanka. This three-span structure will be 380m long, with a 180m main span. The box-girder will be 5.6m high at the pylon locations and 3.3m at mid-span and the ends. The two U-shaped pylon structures with a twin tower configuration will support a fan-type stay-cable arrangement with 24 stay-cables emanating from each tower. The towers which are 29m high, rise from the piers starting at the level of the under-side of the pot-bearings supporting the box girder. The stay-cables are attached to the 30.4m wide bridge deck at the sides and are proposed to be ECF cables. The detailed design of the bridge was carried out taking into consideration the in-situ balanced cantilever method of construction, which will be used for this bridge, through a staged analysis. The design was carried out in conformance with BS5400. Structural modelling and analysis was carried out using the CSiBridge2015 software. This paper presents and discusses the detailed design procedure of the main bridge elements, the load-cases considered, key results and the planned construction procedure of the proposed bridg