concrete concepts 03 CONCRETE – THE RESPONSIBLE CHOICE thermal mass impact-resistance durability strength fire-resistance flexibility fast build-times low-risk energy-efficient The Eleanor Schonell Bridge over the Brisbane River low-maintenance This new river crossing significantly benefits the non-toxic environment and the broader community, by encouraging environmentally responsible modes termite-proof of transport and reducing congestion on the CBD The Eleanor Schonell feeder roads. cost-effective The bridge is a dedicated bus corridor, with two-lanes Bridge, Brisbane each way. There are separate pedestrian and cycle lanes that link the University of Queensland (UQ) The Eleanor Schonell Bridge provides an excellent at St Lucia with the cross-river south-side suburbs. example of concrete used to provide sustainable Located approximately one kilometre from Annerley infrastructure. The new key public transport crossing Road at Dutton Park, this vital river crossing provides of the Brisbane River demonstrates a balanced a new public transport link for Brisbane’s second response across the three pillars of sustainable largest traffic generator after the Brisbane CBD. 1 development: social, environmental and economic . A key transport objective was to ease congestion For more information on sustainable development, on Coronation Drive, a major arterial road that feeds see CCAA’s publication Concrete the Responsible both the CBD and the University. The recent removal 2 Choice . of the T3 lane from Coronation Drive is a clear indication that this objective has been achieved. It A sustainable infrastructure project has been so successful that additional bus services The Eleanor Schonell Bridge represents an important were initiated to cope with the increased demand just milestone in sustainable infrastructure, being the months after opening. first bridge in Australia designed specifically for the enhancement of a public transport system (buses) and the encouragement of other green modes of transport (walking and cycling). Aesthetics The outline design aimed to create an experience rather than a journey, by complementing and not dominating the bridge’s surroundings. This is achieved through the use of slender towers and a Dedicated pedestrian and cycle paths on the bridge slender composite bridge deck. It was important to achieve continuity of the colour of the finished concrete. To meet the long-term durability requirements for the structures in the river tidal zone, the chloride Two measures were taken to ensure continuity and resistance of the precast concrete permanent consistency of colour. Firstly, the concrete supplier formwork ‘boats’ and skirt panels for the pile cap ensured that all cement, sand and aggregates were was given particular consideration. The fly ash taken from a single source over the six month period incorporated into the mix for this purpose also acts during which the towers were constructed. Secondly, as a cement replacement, reducing the carbon the concrete slump was tightly controlled through the footprint of the concrete. use of water-reducing admixtures (plasticisers) and no water was allowed to be added to the concrete to Stainless steel reinforcement was specified in adjust the slump on site. the tidal zones to further enhance the corrosion resistance. Economy Innovative use of concrete The Eleanor Schonell Bridge is recognised as providing excellent value-for-money for the Brisbane Critical to the performance of the bridge deck is its community. Through a range of value engineering ability to act, as designed, as a composite structure. initiatives, the project team achieved a total of For the best results, this meant limiting the shrinkage $17 million cost savings relative to the initial in the precast concrete panels of the bridge deck tender price. and in the insitu concrete strips between them. The designers therefore specified that the precast panels Durability be manufactured from low-shrinkage concrete, and cured for a minimum of 60 days before incorporation Judicious material selection will contribute to the into the bridge deck. The concrete supplier, Boral, longevity of the bridge. Through the use of highly conducted rigorous testing in the laboratory and on durable materials, and the implementation of a site, to ensure a high level of quality control. detailed asset management programme, it is anticipated that the bridge’s life be extended from 100 to beyond 150 years. Sustainable design The name ‘Green Bridge’ was originally adopted for the project, implying a strict adherence to environmental and sustainable principles in the design and construction. During the preliminary design, environmental and materials engineers investigated potential environmental initiatives, such as the reuse of stormwater, minimum environmental impact during construction and energy regeneration. This approach to the design resulted in some of the key features adopted in the project: n Installation of a solar roof structure for green energy generation n Minimised energy consumption for lighting n Collection, treatment, and reuse of stormwater in the university irrigation system n Use of high-durability concrete, with significant cement replacement by fly ash n Use of high-strength concrete to minimise the required volume. n Improved labour efficiency. Solar energy generation The Eleanor Schonell Bridge was designed and constructed to be energy neutral. The energy requirement of the bridge is met by a high profile solar roof, containing over a hundred 175-W panels. The solar roof feeds electricity back into the supply-authority grid, thereby offsetting the mains electricity used by the bridge at night. This roof is located at a prominent position in Dutton Park to maximise visibility and help promote renewable energy. A unique feature of the solar roof is the real-time public display of the solar generation performance, which shows just how much energy the roof generates, and how much energy is consumed by the bridge and its systems. Reduced energy consumption To minimise consumption, energy-efficient, low-wattage lights were used. Feature lighting was also minimised to reduce both power requirements and the visual impact of the bridge on the surrounding area. Cut-off timers and remote operation features were also incorporated to reduce the amount of unnecessary lighting while still maintaining a safe environment for users. Water recycling An innovative and proactive approach to rainwater harvesting was taken. Runoff from the bus-way and bridge is captured and channelled through a triple interceptor and bio-retention basin at UQ before discharging into the UQ lake system, where it is ultimately used for irrigation of the UQ grounds. top: The solar roof structure and slump testing on site centre: Installation of the precast concrete deck panels above: Construction of the towers www.ccaa.com.au/ sustainability Improved labour efficiency The bridge deck is made up of 492 precast concrete panels, from which 164 unique types were identified. Each panel was approximately 5 m x 3.5 m, weighed around 10 tonnes and was designed for a specific location on the deck. Precasting some of the key components improved the efficiency by reducing onsite labour activities and associated costs. This also ensured a high quality of finish. The development of precast ‘boats’ enabled uninterrupted construction of the pile caps in the tidal zone of the river. Each ‘boat’ consisted of six precast Construction of the pile caps units that were produced on shore before being placed in the river. To minimise the risk of thermal High-durability concrete incorporating fly ash cracking, concrete with low heat of hydration was The materials used in the construction of the bridge used for the large mass pours for the pile caps. were chosen with long-term sustainability in mind. Summary The overall volume of materials was reduced to the absolute minimum by several rounds of value The Eleanor Schonell Bridge over the Brisbane engineering. The concrete mix incorporated silica River is a good example of social, environmental fume to gain the necessary strength, as well as to and economic sustainability. Completed two provide a high level of chloride resistance in the months ahead of schedule, within budget and aggressive marine environment. In addition, fly ash with exceptional quality, it is an excellent outcome was used as a component of the overall cementitious resulting from a collaborative team with a clear content. Excellent strength results were achieved sustainability vision – an excellent example of throughout the tower construction. sustainable concrete infrastructure. High-strength concrete To deliver the desired References sleek and elegant look desired by the project 1 2007 Public Domain Awards Cement Concrete team, the tower elements were kept to a minimum & Aggregates Australia, The Eleanor Schonell cross-section by using high-strength concrete. Bridge (Bridges and Sustainable Design Categories). 2 Concrete – the Responsible Choice Cement Concrete & Aggregates Australia, 2010. 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