PRESENTATION – The Ageing Infrastructure: A Challenge for Innovative Engineers.

Presentation

When – Thursday 13th October 2016 //

Abstract:

Structural engineers have been educated for decades on designing new structures. They were taught that the design should aim at functionality and structural safety. It was a historical omision to underestimate the significance of service life design. As a result the structural safety of thousands of structures is under discussion, due to deterioration on one hand and increased loads on the other. The question is often whether structural safety is still OK, and if yes, for how long. The discovery that structures no longer satify safety provisions now applies to large groups of structures.

In The Netherlands in 2010 a safety check of existing bridges led to the conclusion that the majority of the 3600 bridges inspected did not satisfy the demands for structural safety as expressed in the building codes. This was a huge problem in many respects, requiring smart solutions in a very short period of time. The inventivity of structural engineers was an indispensable component in finding solutions. Time pressure is a common characteristic of such problems. An example was the discovery that the reinforcement at the bottom of a submerged tunnel in the centre of the city of Rotterdam, designed for 18 meters of water pressure, was substantially reduced by corrosion. Also here the experts had to make smart decisions in a very short space of time, to ensure the safety of citizens, and keep the disturbance to a minimum.

Another actual large scale problem which also has to be solved under considerable time pressure is the insufficient seismic resistance of about 180,000 houses in the Northern part of The Netherlands, where it was disovered about three years ago, that the extraction of natural gas during the last decades, has led to induced earthquakes. The forces due to the peak ground acceleration are signficantly larger than the wind loads, for which the houses had been designed. The feeling of insecurtiy for the inhabitants of the Province Groningen, led to substantial political pressure from the government on structural engineers, to come up with solutions as soon as possible. A handicap was that the country had no seismic history or expertise, so that the knowledge had to be aquired first.

It became clear that knowledge and sound understanding of the behaviour of structures should be a necessary component in the tool box of structural engineers, now and in the future, given the actual building codes are not very useful in this respect.

This was one of the reasons for the writers of the fib Model Code 2010 to distinguish various Levels of Approximation for the determination of the bearing resistance of structures. Low Levels of Approximation can be used for the design of new structures. High Levels of Approximation are a good option for the determination of bearing capacity, if the best possible estimation of stuctural capacity is required because of the high consequences for both human safety and economy.

Recently a new fib Special Activity Group began work on extending the fib Model Code 2010 to include existing concrete structures. The work is scheduled to be finished in 2020.

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About the Speaker:

Joost Walraven is emeritus professor of Delft University of Technology, The Netherlands. He was president of fib 2000-2002 and was convenor of the fib Special Activity Group which produced the Model Code for Concrete Structures 2012. He carried out research on many aspects of the behavour of concrete structures and the development of concrete as a high performance material. He is involved in many national and international committees and projects in structural engineering.

Joost has received numerous awards, such as the Swedish Concrete Award 1991, the FIP Medal of Merit 1998, the TU Delft Distinghuised Teacher Award 2005, a Doctorate of Honour of TU Kassel in Germany and the fib Freyssinet Medal. He has published over 450 papers in journals and conference proceedings