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The required life of civil engineering infrastructure is long, typically at least 100 years for bridges, tunnels and major public buildings and many thousands of years for nuclear waste repositories. Over these time-scales the uncertainties associated with change are substantial and difficult to handle. A key to progress in handling uncertainty is the integration of probabilistic and deterministic modelling, drawing on techniques like real option analysis with a wider more practically realistic definition of reliability.

The engineering of sustainable built environments must consider the whole life impacts from design, construction and commissioning, through use and asset management, to decommissioning. The EPSRC review of UK academic research in ground and structural engineering identified whole life approaches as a key future research challenge.

New technical developments inevitably lack a track record and assessing any aspect of their whole life performance requires predictions of performance over decades if not centuries. Hence predictive modelling, and in some cases accelerated ageing technologies, need to be an element of the whole life approach across the full range of civil engineering disciplines.

Before replacing existing infrastructure careful consideration needs to be given to achieving more from what is presently available. This may mean embarking upon a life-extension programme, implementing a more efficient use or re-purposing to achieve an alternative use.

With the application of increasingly stringent design criteria, producing desired improvements in both safety and reliability, the re-assessment of an existing structure must be based upon state-of-the-art analysis procedures, capitalising on previous design conservatisms. This is necessary to accommodate any material degradation; achieving life extension without having to compromise safety.

Assessments of this type will inevitably require a probabilistic approach, both in terms of the strength and the demand, coupled with performance monitoring and advanced surveying techniques.

There is great scope for creative thinking and rigorous analysis around developing multi-purpose infrastructure systems, for example ground works combined with geothermal energy systems, coastal defences with integrated marine renewables, flood prevention with water storage and building design with enhancement of the urban environment via integrated flow modelling both within and outside buildings.

A key requirement during this century will be to move from a predominantly linear economy, based on manufacturing and use, followed by the production of wastes requiring disposal with loss of resources, to a circular economy in which both biological and technical nutrients are continually and repeatedly exploited in order to foster prosperity in a world of finite resources.

The traditional linear pattern on consumption will become increasingly problematic due to uncertainties associated with resource availability, increased costs and inefficiencies. The circular economy will involve the development of innovative new business models, new designs incorporating bio-mimicry and new approaches to how civil engineering infrastructure is designed, constructed and deconstructed.

The way civil engineering responds to the challenges associated with the circular economy will require fundamental changes with potential to deliver significant economic and environmental benefits.

Civil engineering and particularly construction are major contributors to greenhouse gas (GHG) emissions, although the management of carbon remains relatively unregulated. Sustainable civil engineering must increasingly involve assessing development options in terms of through- life carbon emissions with potential to deliver major environmental benefits with impacts across the whole of the civil engineering supply chain.