Final Report Summary - ARCHES (Assessment and rehabilitation of Central European highway structures)
The strategic objective of the ARCHES project was to reduce the gap in the standard of highway structures between the Central and Eastern European Countries (CEEC), including New Members States (NMS), and the rest of the EU, in a sustainable way. This was planned to be achieved by developing appropriate tools and procedures for a more efficient assessment, and faster, cost-effective, and long lasting rehabilitations (repair or strengthening) of sub-standard highway structures.
To achieve its scientific and technological objectives, this project focused on structural assessment and monitoring, strategies to prevent deterioration and optimum rehabilitation of highway structures by complementary techniques. It was organised in four technical work packages (WP), with the following conceptual approach.
- Optimise the use of existing infrastructure through better safety assessment and monitoring procedures which will avoid interventions, i.e. avoid unnecessarily replacing or rehabilitating structures that are in fact perfectly safe (WP2). The main objective of WP2 was to provide recommendations and guidance for implementation of optimised bridge assessment tools in NMS and CEEC. The recommendation will deal with monitoring, load testing of different types from soft load testing up to the proof one (experiment in Poland), dynamic impact on bridges and bridge management system development.
- Monitor and prevent corrosion of existing reinforcement and develop innovative new reinforcement materials that are highly resistant to corrosion (WP3).
- Strengthen the infrastructure of bridges by means of bonded reinforcements (WP4).
- Harden highway structures with ultra high performance fibre reinforced concretes applied in severely exposed zones to dramatically increase their durability (WP 5).
Site specific assessment of traffic loading has considerable potential to prove that bridges are safe which would otherwise have been rehabilitated or replaced. This is due to the conservatism of bridge standards that cover a wide range of possible traffic loading conditions throughout the road network. There is clearly a considerable gap between the complex mathematical modelling and experiments required for an accurate determination of dynamic allowance and the conservative values available at bridge codes. In order to reduce this gap, ARCHES proposes an intermediate solution based on the large amount of experimental tests and numerical simulations carried out during the project. The quality of the road profile plays a role that becomes more dominant as the span length decreases, but in the case of very good road profiles (ISO class A), the critical loading cases governing the maximum load effects typically produce dynamic amplification factors below 1.1. Nevertheless, the presence of a bump or a damaged expansion joint prior to the bridge may lead to higher values in short span bridges. Even so, it has been shown that exceptionally heavy vehicles representing critical loading cases such as cranes have a rigid configuration that generates smaller dynamics than typical five-axle articulated trucks. So, if the road profile of a bridge was maintained in a good condition, the dynamic amplification factor associated to the critical loading cases could be substantially reduced in relation to the values built within the Eurocode traffic load models.
Cathodic protection (CP) of reinforcing steel has been applied to concrete structures with corrosion damage for over 25 years. World wide experience shows that CP prevents further development of corrosion damage in a reliable and economical way for a long time, provided that the CP system is designed, executed and maintained properly. Based on case studies, the cost of CP over the (remaining) life of a structure has been investigated and compared to other options. Generalising, it appears that CP may be instrumental in saving considerable amounts of money over the remaining life of a structure, say over periods of 10 to 25 years.
The concept of rehabilitation of structures with UHPFRC was applied for the first time outside of Switzerland, in Slovenia with a new material designed from local components. The application was successful and fast (one month instead of three month with traditional technique) and demonstrated at an industrial scale the ability of the newly designed UHPFRC mixes to reply to the difficult challenges of the site. Applications with slopes up to 5 % at least are now possible, and by means of simple surfacing techniques it is possible to achieve uniform textured UHPFRC surfaces on which barefoot walking is possible. The newly designed recipes have a dramatically reduced cement content which makes them more economical and particularly attractive from an environmental point of view. This successful example of transfer of technology opens up very promising perspectives for the dissemination of the concepts of rehabilitation of civil infrastructures not only in NMS (which was the goal of the project ARCHES) but also in virtually any country.
To achieve its scientific and technological objectives, this project focused on structural assessment and monitoring, strategies to prevent deterioration and optimum rehabilitation of highway structures by complementary techniques. It was organised in four technical work packages (WP), with the following conceptual approach.
- Optimise the use of existing infrastructure through better safety assessment and monitoring procedures which will avoid interventions, i.e. avoid unnecessarily replacing or rehabilitating structures that are in fact perfectly safe (WP2). The main objective of WP2 was to provide recommendations and guidance for implementation of optimised bridge assessment tools in NMS and CEEC. The recommendation will deal with monitoring, load testing of different types from soft load testing up to the proof one (experiment in Poland), dynamic impact on bridges and bridge management system development.
- Monitor and prevent corrosion of existing reinforcement and develop innovative new reinforcement materials that are highly resistant to corrosion (WP3).
- Strengthen the infrastructure of bridges by means of bonded reinforcements (WP4).
- Harden highway structures with ultra high performance fibre reinforced concretes applied in severely exposed zones to dramatically increase their durability (WP 5).
Site specific assessment of traffic loading has considerable potential to prove that bridges are safe which would otherwise have been rehabilitated or replaced. This is due to the conservatism of bridge standards that cover a wide range of possible traffic loading conditions throughout the road network. There is clearly a considerable gap between the complex mathematical modelling and experiments required for an accurate determination of dynamic allowance and the conservative values available at bridge codes. In order to reduce this gap, ARCHES proposes an intermediate solution based on the large amount of experimental tests and numerical simulations carried out during the project. The quality of the road profile plays a role that becomes more dominant as the span length decreases, but in the case of very good road profiles (ISO class A), the critical loading cases governing the maximum load effects typically produce dynamic amplification factors below 1.1. Nevertheless, the presence of a bump or a damaged expansion joint prior to the bridge may lead to higher values in short span bridges. Even so, it has been shown that exceptionally heavy vehicles representing critical loading cases such as cranes have a rigid configuration that generates smaller dynamics than typical five-axle articulated trucks. So, if the road profile of a bridge was maintained in a good condition, the dynamic amplification factor associated to the critical loading cases could be substantially reduced in relation to the values built within the Eurocode traffic load models.
Cathodic protection (CP) of reinforcing steel has been applied to concrete structures with corrosion damage for over 25 years. World wide experience shows that CP prevents further development of corrosion damage in a reliable and economical way for a long time, provided that the CP system is designed, executed and maintained properly. Based on case studies, the cost of CP over the (remaining) life of a structure has been investigated and compared to other options. Generalising, it appears that CP may be instrumental in saving considerable amounts of money over the remaining life of a structure, say over periods of 10 to 25 years.
The concept of rehabilitation of structures with UHPFRC was applied for the first time outside of Switzerland, in Slovenia with a new material designed from local components. The application was successful and fast (one month instead of three month with traditional technique) and demonstrated at an industrial scale the ability of the newly designed UHPFRC mixes to reply to the difficult challenges of the site. Applications with slopes up to 5 % at least are now possible, and by means of simple surfacing techniques it is possible to achieve uniform textured UHPFRC surfaces on which barefoot walking is possible. The newly designed recipes have a dramatically reduced cement content which makes them more economical and particularly attractive from an environmental point of view. This successful example of transfer of technology opens up very promising perspectives for the dissemination of the concepts of rehabilitation of civil infrastructures not only in NMS (which was the goal of the project ARCHES) but also in virtually any country.
