Significant milestone for the BSCU project
Robert Bird Group are pleased to see the successful installation of the temporary support truss which marks a significant milestone for the Bank Station Capacity Upgrade Project. The truss which supports 4 levels of basement slab within the 18.5m deep piled basement structure, enables construction of a new 8 level deep Bank Station entrance. This innovative approach eliminates the detrimental programme and H&S impacts of the plunge column alternative within the low level 20m deep SCL shaft. The shaft houses the lift and stairs, and is adjacent to an inclined escalator barrel, both of which are subsequently constructed from the base of the piled box.
The use of a truss, which was conceived in collaboration with Dragados, integrates the design of permanent and temporary works with construction methodology and programme. RBG are responsible for its design from feasibility and concept through to detailed design, construction, and the on-going monitoring and jacking. Byrne Bros are responsible for its fabrication and installation as part of their overall concrete station box package.
The truss and the 4 suspended slabs that it supports in the temporary condition are subject to a detailed instrumentation and monitoring regime which has been developed in conjunction with Dragados and Geocisa. This ensures design assumptions can be validated, further reducing project risk and ensuring slabs remain parallel and end in the correct final position.
The truss includes approximately 100 tonnes of steelwork and a jacking system which is used to negate the complex response from increments in load as the slabs are progressively constructed and excavation advances below during the staged top down construction sequence. The truss has been designed to resist 1800 tonnes at Ultimate Limit State. The image shows the first of 4 slabs has been constructed.
RBG are the project Structural Engineer and have delivered the compliance and detailed designs for construction of the new Cannon Street entrance to the station, tunnel internal structures, existing station works and elements of the Arthur Street shaft. RBG are currently supporting Dragados in the delivery of the station entrance box and tunnel internal structures.