Rod Bligh, director and principal structural engineer at Bligh Tanner Consulting Engineers, is a founding director of the firm.

With experience in institutional and community building projects, his projects include the new Global Change Institute building at the University of Queensland.

Architecture & Design spoke to Bligh about working with heritage structures, the Global Change Institute and engineering sustainability.

Can you tell A&D about some of the projects you have worked on?

The first Bligh Tanner project in 1992 was the collaboration with Mark Ross of Dot Dash for the mounting of three maritime objects (a buoy, an anchor and a propeller) along the Kangaroo Point Cliffs boardwalk in Brisbane. Following a recent visit to Carlo Scarpa’s Castellvecchio museum in Verona and a year of studying architecture at The University of Queensland, I was determined to use the opportunity to reflect and express the nature of the objects through the support structure connectivity and geometry.

Each steel detail uses a different action of reaching, holding, pinning through and hanging with supports expressing tensile, compressive and torsion forces. It was a great pleasure to be asked 20 years later by the Cliffs Boardwalk managing architect from Queensland Project Services, Spence Jamieson, to join him in designing the Kangaroo Point Parkland, a ‘sister’ project to the river boardwalk below.

I had been very fortunate to work closely with John Simpson and Ian Mitchell as a young engineer and they had made clear their great interest in working at the interface of architecture and engineering. We had a lot of fun designing steel structures for World Expo such as the river stage and piazza. Concept design of the South East Queensland Busway stations in 1997 with Derek Trusler (who was then at Woods Bagot) was a similar opportunity to explore expressed steel structure architecture. The busway stations needed to be as transparent as possible for public safety and as they were to be located in a variety of urban and suburban locations – a minimal, human scale structure was an imperative.

You've been involved in heritage structures. From an engineering point-of-view, what is the most challenging aspect of working with heritage structures?

I initially became involved with heritage buildings through sharing an office with heritage architect Robert Riddel in Fortitude Valley and also being in close proximity to Allom Lovell Marquis-Kyle. As an engineer there has been much to learn about early construction techniques and materials, but the primary skill that we bring to bear is the ability to work from first principles of physics to determine the actual structural actions and capacity of the existing buildings.

In this sense, the work we do with heritage structures is actually very similar to the design of efficient new buildings, where we look to minimise material usage. For the recent conversion of the 1884 Sisters of Mercy Convent at Ipswich into the St Mary’s College administration centre, we upgraded the capacity of original timber framed attic, which housed sleeping quarters. Tensioned cables were attached to the underside of the original timber beams, creating barrup trusses that kept intact and utilised the strength of the existing framing.

You have been involved in the University of Queensland Global Change Institute building. Can you tell A&D about the sustainable design of the building?

With an environment-focused occupier, the Global Change Institute was a perfect opportunity for the design team and the University of Queensland to create a successful low energy building. We had learnt from visiting other buildings of the importance of the occupiers being engaged in the operation of the various passive and assisted modes of thermal control to gain the full benefit available from the technology. The Global Change Institute is designed to operate in passive mode for 88 per cent of the year.

The suspended concrete floor system demonstrates the level of integration of structure, architecture and services in the building to achieve a low energy outcome. The precast panels are formed with a barrel-vaulted soffit to improve performance of the exposed thermal mass, which incorporates hydronic cooling pipes. The panels were fabricated from cement free geopolymer concrete, which we believe to be a world first for modern geopolymer technology. Geopolymer concrete utilises 100 per cent waste flyash and slag, which is hardened by reaction with an alkali additive. The panels support an access floor, which distributes air directly to work stations.

Other integrated design elements include the courtyard triple-layer ETFE roof which utilises fretted shading patterns on the outer layer and operable middle layer to moderate light ingress; and the operable shading screens and louvres on the façade. All of these elements are linked to the building management system to control airflow and solar access. My particular interest is designing these systems with the architect (HASSELL) to look beautiful.

Do you think sustainability is taken seriously enough in engineering designs?

There are many reasons that sustainable design remains largely in the realm of special cases, not least being the level of comfort that is demanded in modern buildings and the high capital cost of systems other than conventional air-condition and insulation. However I believe that there are opportunities to do more.

We are very closely following developments in ‘massive’ timber construction ,and looking for opportunities to introduce timber constructions into buildings that would otherwise be conventional steel or concrete. Timber has the tremendous advantage of low embodied energy and its inherent storage of carbon. There are currently vast reserves of plantation forests around the world that are available for structural use.

The geopolymer panels that were developed for the GCI building evolved out of an initial scheme to use a timber-concrete composite system with the geopolymer as a structural topping on timber joists. We moved away from this system to the full concrete panel, as greater thermal mass was required in the cooling strategies. Consideration of these alternative systems requires effort on the part of engineers to keep abreast of product technology and close links with various industries involved in the supply chain.

How would you describe the relationship between architects and engineers nowadays?

I have always seen structural engineering as a specialist part of architecture so by nature we have to get along well. I started Bligh Tanner 21 years ago specifically to work with architects who expect a lot from us in the design process and that has carried through, such that we are only working with architects with whom we have enjoyable relations.

A common concern in engineering offices is the cost of dealing with design changes that emanate from the architectural design development process. Our approach is to be as involved as possible in the design and to bring our experience to bear in predicting potential areas of change and suggesting alternatives early in the process. Of course this does not always work, but I think we have managed to maintain very long relationships because of the level of mutual respect throughout the design process.

Can you tell A&D about the affordable housing work you're doing at the moment?

Our current involvement is mainly around the development of composite panel systems, with the panels providing structure, insulation and weatherproofing. We have been assisting Bondor in the development of their Insulliving system which utilises a base steel-skinned EPS core panel. We are also involved in testing and system development of an OSB timber skinned PUR core panel that is manufactured in Romania using timber waste product.

Recently we have been assisting the Hopevale community with a programme of Bush Owner Built houses, an initiative to improve access to and ownership of accommodation on traditional land. This follows on from many years of involvement with Gabriel Poole’s Takeaway Timber Houses which are prefabricated in Cairns and erected throughout the Cape and Islands.