12 jun 2017

High tech concrete: Where technology and engineering meet

The next Fib Symposium “High-tech concrete: Where technology and engineering meet!” will take place at the MECC in Maastricht, Netherlands from 12 to 14 June 2017. Royal HaskoningDHV will be presenting three papers.

The event is being jointly organized by the Dutch Concrete Association (Betonvereniging) and the Belgian Concrete Association (Belgische Betongroepering). Germany is represented by Prof. Josef Hegger from Aachen University.

During the event Royal HaskoningDHV will present the following papers:

  • Monday 12 June 13.45-14.00 hrs (0.9 Athens): Structural Assessment of an Existing Concrete Box-girder bridge by Rob Vergoossen and Rik Cederhout
  • Tuesday 13 June 10.15-10.30 hrs (0.5 Paris): Advances in Non-Linear Time History and Modal Response Spectrum Analyses by Maurice Hermens, Harm Kraaijenbrink and Sander Meijers
  • Tuesday 13 June 14.45-15.00 hrs (0.2 Berlin): Shear Capacity – Crossing Borders by Marcel ’t Hart and Piet Barten (TEC).

Structural Assessment of an Existing Concrete Box-girder bridge

The majority of the road bridges in Western Europe were built between the post war period and the 1980s. Most of these bridges were made from concrete and many are pre-stressed. As populations increase, there are more vehicles on the roads using these bridges and their structural condition begins to deteriorate The increase in traffic wasn’t initially factored in when these bridges were first built. It must also be taken into consideration that the knowledge of structural engineering has evolved, which has resulted in more reliable design and verification rules. Based on this, the actual structural safety of most existing bridges isn’t known and there is a need to perform structural assessments of existing road bridges. The Netherlands (RWS 2013; NNI 2011) and Germany (BMVI 2011) have drawn up their own standards, complementary to the Eurocode for existing structures. These standards determine how existing structures can be recalculated. 

To emphasize the similarities and differences between the standards, Royal HaskoningDHV performed a pilot project in which a post-tensioned box-girder bridge in Germany was structurally assessed. In this assessment, both the German and Dutch standards for existing structures were taken into account. The similarities and striking differences between the German and Dutch regulations will be presented and discussed during the Fib Symposium. 

Shear Capacity – Crossing Borders

In order for the Eurocodes to be accepted, it was necessary to allow national choices with regard to parameters where no agreement between the countries involved could be reached. For the determination of the shear capacity, EN1992-1-1 defines eight parameters subject to national choices (and EN1992-2 even introduces two more). In addition, for the determination of the design load, several parameters subject to national choices were included. As a result, despite the introduction of the Eurocode, there were still considerable differences between individual countries in shear design. This was a reason to take a closer look at what is really happening in the structures. The basis underlying the Eurocode can be found in the Model Code. In the Model Code 2010, three different approaches are described to validate the safety of structures in the Ultimate Limit States by numerical simulations using non-linear models. EN 1992-1-1, clause 5.7 allows for the use of such non-linear models. A FEA package validation has been executed based on experiments, to specifically demonstrate that FE models are appropriate. The validation demonstrated the available constitutive material models are adequate to describe the behaviour of concrete and results are similar to the experimental results. After the successful validation, the same approach has been applied for a tunnel structure. From the non-linear simulations for this tunnel structure, the important conclusion can be drawn that the Model Code 2010 methods give comfortable factors of safety and that the Eurocode design based on recommended parameters will give conservative, lower bound design capacities. 

Using sophisticated models for the tunnel structure a considerable reduction of the required shear reinforcement compared to a straight forward application of the Eurocode could be justified.