Anzac MemorialCentenary Project

Commercial ProjectConcrete Institute Awards 2019

1. Description of the projectThe Anzac War Memorial is a landmark building located at the southern endof Hyde Park, Sydney. The original building completed in 1934, is a concretestructure, clad in stone, designed by Charles Bruce Dellit.

As part of the NSW Centenary of Anzac, the redevelopment intent was toconstruct new education and interpretation facilities, including a water cascadethat completes the original 1930’s vision for the Memorial. The redevelopmentenhances the Memorial serving as a focal point for future generations to learnabout our Anzac legacy and Australia’s war history.

The new underground facilities include education and exhibition areasorganized around a new central chamber, the “Hall of Service”, visuallyconnected to the Memorial through an open oculus. A new stair flanked byinclined lifts connects the new underground spaces with the existing groundfloor.

The structure is the column free space in the new Central Chamber Hall ofService, with a visual connection to the Memorial through the Oculus.The structure within the Hall of Service features dramatic precast cantileverstowards the central oculus, leaving the space free of columns.

Project CreditClientThe Trustees of the Anzac Memorial

ArchitectJPW

Structural, Civil & Facade EngineerTTW

BuilderBuilt.

Concrete SupplierPrecast Concrete Products

Project Value$40M

2. Description Materials & Concrete Technology A significant aspect of this project is how close collaboration between the Architect, Engineer, Builder and Precaster resulted in a stunning example of the marriage between structural and architectural precast concrete elements.

The concrete technology utilised new generation polycarboxylic plasiticisers in combination with off white cement to produce a consistent concrete mix with a spread of 700mm.

Paramount to this project was the combination of the smart finish in off white coloured concrete with the structural requirement for prestressing. Colour matching concretes with completely different slump characteristics and strength grades was made possible with numerous samples and casting trials before manufacture commenced.

Depending on the shape of the precast units and orientation of the pour, some of the elements were cast using self-compacting concrete, which had to be carefully colour matched to the original Memorial elements.

Advancements in concrete technology, attention to detail in the moulds and a high level of quality assurance throughout the manufacture process have enabled the striking finished product, which excels equally from an aesthetic and a structural perspective.

Additionally, to assist with the economy of the project, in parts of the structure where the soffits were not exposed, Precast’s efficient prestressed hollowcore flooring was utilised in lieu of traditional wet cast slabs.

3. Description Design & Engineering Structure of the Service and Oculus

The Structural elements are expressed directly and organised along the major north south axis of the building. Dramatic cantilevers towards the centre of the chamber draw the visitor’s gaze towards the central oculus and the Memorial beyond.

■ The structure over the Hall of Service and Foyer offers a 15 by 21.5 metres clear space featuring a 6 metres diameter open oculus. Beams and columns supporting the cantilevering beams are organized in the galleries adjacent the Hall of Service.

■ The off-form fnish for all structural elements is obtained through careful sampling of off-white cement and titanium oxide considered against different pouring methodologies for different structural elements.

■ Custom 8.5 metres precast planks infill the central section of the Hall of Service soffit between the cantilevering T-beams. In situ post tensioned beams, as long as 20.5 metres, were poured above the planks to distribute loads towards the east and west structural supports.

Proposed structural scheme

Oculus Void

Precast Structure

Underground stair link to existing Memorial

The new underground facility required access to the existing podium level from the southern side of the Memorial with allowances for excavation and shoring under and adjacent to the existing Memorial structure were made.

The existing podium stair of the Memorial was temporary supported by a series of steel beam above the stair spanning between existing walls. Once secured, the demolition / excavation and underpinning process were carried out. Movement and vibration monitoring were carried out regularly to ensure no impact.

Demolition of the stairs

Underground stairs complete

Central stair and ramp

4. Description Construction & Construction Practices Being in central Sydney CBD, the prefabrication system had constraints to consider such as transportation from Queensland yard to site, limitation on the working hours and truck access to site. Size of the precast T-beam was carefully considered to achieve ease of transportation and delivery. Additional joint to the T-beam was proposed to fit in a regular articulated truck during construction in conjunction with the architect and the Client’s approval which improved the delivery and access time through the CBD areas.The project site was constrained with mature trees, paving and access paths radiating in every direction and the Pool of Reflection to the North. Thereby the construction sequence and staging were considered to minimise major disruption to existing public use and keep the Memorial operational throughout the works.Over the Hall of Service and around the Oculus, a hybrid precast and in situ post-tensioned system were used to minimise the weight of the precast plank for transportation and erection. Each precast panel was constructed with a built-in pre-camber to ensure no noticeable differential deflection between precast panels.Excavation adjacent to and under the Memorial had been a challenge for the construction team. A buildability review was organised by the Anzac Memorial Centenary Project PMO, to identify risks and mitigations to the existing Memorial due to the impact caused by potential displacement and vibration during shoring and excavation works. Innovative solutions including construction staging sequence and advanced monitoring method were developed to reduce potential impacts caused by displacement and vibration.

5. Description Architectural & Environment General considerations and feel

From Liverpool Street, the visitor walks into the underground addition through the water cascade walkway, inviting the sound of cascading water to replace the noise of the city.

Underground, The Hall of Service is visually connected to the Memorial, the park and the city beyond through the open precast Oculus void, a direct reference to the existing Well of Contemplation. Surrounding this, artwork conceived by Fiona Hall: names of 1701 New South Wales locations with a jar of earth, each representing where soldiers of the Great War enlisted from. Under the Oculus, earth from 100 significant battlefields is inlaid in the floor.

Functional spaces articulated around commemorative ones, in keeping with the tradition of a “working Memorial”, now used by staff

Architectural Considerations About Precast

Precast concrete was selected for this project to ensure a high level of finish, suitable for a civic landmark, and to meet program and site constraints.

An extensive sampling process was carried out to select the appropriate finish through different ratios of cement and admixtures. The outcome is a crisp yet warm finish that contributes to the changing natural light conditions in the Hall of Service.

The structural composition and detailing of the precast concrete elements directly contribute to the architecture of the underground spaces. The dramatic cantilevers in the Hall of Service reinforce the main North South axis of the precinct while supporting and drawing the visitor’s gaze to the central precast oculus and the Anzac Memorial beyond it.

6. Description Sustainability & Resilience The project structural works achieved sustainable outcomes through smart use of long-cycle, durable material to ensure durability and integrity of the building without large cost interventions to maintain during its life span. Offering great flexibility for the Memorial in the future.

Not only is the finish of the raw, off form coloured concrete aesthetically pleasing, it has reduced the environmental footprint of the structure as there were no artificial coatings required during construction or maintained throughout the life of the structure.

In areas where the roof structure was not visible, prestressed hollowcore flooring was utilised. These planks are extremely efficient as they hold only half of the concrete volume in comparison to more conventional flooring solutions.

In comparison to traditional in situ construction, precasting the concrete elements removed most of the structural works from the site to a controlled factory environment, with less disruption to the City Centre, more efficient use of materials and a superior finished product.

In the park, adjacent to the water cascade, a large fig tree was relocated 16 meters east following extensive research on feasibility. The relocation allowed safer construction, cleared the view to the Memorial from Liverpool street as originally designed, whilst preserving a significant tree for visitors to enjoy.

The final design has reduced the recurrent costs for staffing and operational maintenance to require on-going budget allocations which is limited and reasonable to sustain the Memorial into the future.