Broadway Subway - Millennium Line Extension to Arbutus | U/C

[jollyburger]

Allnorth developed a novel design which allows for installation without halting traffic, while supporting both vertical traffic loads and horizontal soil pressures on station excavation.

The design of the traffic decks has two key objectives. First, the decks must support both the weight of traffic above, as well as act as struts between excavation faces, supporting earth pressure. Second, a construction sequence, installing the decks in pieces, must be developed to minimize the impact on traffic.

This construction sequence has led to the following specialty solutions to be applied to the structure:

Bolted splices on the main beam to allow for modularization
Precast foundations for easy installation
Adjustable connections to allow for quick installation of the deck on steel driven piles
Considering the loading and the construction sequence, the design has resulted in a total of 6,500 tonnes of steel to be used for temporary purposes. Each traffic deck constitutes multiple bays of a beam-girder system with deck panels consisting of maximum 12m long x 3m wide x 11 mm thick plates, supported by six W460 beams, which are in turn supported by W1100 transverse girders underpinned by W610 piles.

This project is exceptionally complicated as it takes place in an extremely busy area of Vancouver. As a result, there were continuous challenges that necessitated ongoing problem solving and the application of out of the box solutions. Several sophisticated innovative approaches were developed such as a novel and unique construction sequence solution that resolved the continuous traffic flow problem which drastically reduced the construction schedule for the traffic decks. Another major challenge was supporting the Capilano #5 watermain, a 1,800mm diameter pipe with wall thickness of 12.7mm spanning across 20m over the excavation, ensuring contingency and non-disruptive utility service throughout construction.

https://www.allnorth.com/projects/broadway-subway-project/