2014 DFG - Research group FOR 2089
Table of contents
Permanent road pavements for future traffic loads - coupled system road-tire-vehicle
Involved Institutions
Multi-physical and multi-scale theoretical-numerical modeling of the tire-road interaction
Institute of Structural Analysis
Multiphase and multiscale observation of the pavement system
Institute of Highway Engineering
Multi-scale, multi-phase simulation of the functional properties of road surfaces
Institute for Road and Transport Science
Institute for Road and Transport Science
University of Stuttgart
Characterization of the material behavior of asphalt as a basis for multi-scale modeling
Institute of Urban and Pavement Engineering
Characterization of the generic road load collectives of current and future vehicle populations
Institute for Automotive Engineering
Contracting authority
Project period
2014 - 2020
Abstract project overall
Road traffic infrastructures are an essential prerequisite and a central component of a competitive and successful industrial society. They also represent a very high economic value. Unfortunately, in Germany and many other developed countries, the actors in politics, business and research are not clearly aware of the importance of road transport infrastructures.
While the development of new vehicles and intelligent transport concepts in Germany is mainly driven by industry, there have been few major innovations in the field of road transport infrastructure in recent decades. This deficit is due, on the one hand, to a lack of research funds, which - unlike the marketable products of automotive engineering - are not to be provided by industry but mainly from public resources and, on the other hand, to relatively rigid regulations that are hardly suitable for the creativity and innovative strength to stimulate the german industry, engineers and scientists.
These circumstances have contributed to the fact that the concepts and methodological approaches of progressive engineering disciplines are not, or only very rarely, used in the construction and maintenance of road traffic infrastructure. Therefore, inadequate and less permanent solutions are often obtained. In order to cope with this problem and to prepare the road infrastructure for the requirements of the future, a paradigm shift in dimensioning, structural implementation and maintenance is aimed for, for which the planned research group is to develop the scientific basis. The new requirements essentially result from:
- increasing traffic and higher axle loads,
- Shortages and rising prices of raw materials,
- Decrease in the financial resources available for the construction and maintenance of road transport infrastructure,
- changing climatic conditions with the effects of strong heat or cold periods and extreme rain events,
- new functions to improve the safety, driving comfort and performance of the road infrastructure and from
- new ecological constraints that must guarantee the environmentally friendly construction and operation of roads.
However, the fulfillment of the new requirements harbors - with regard to the development of building materials and the structural formation of roads - some conflicting goals, which are to be described using selected examples.
- In the past few decades, asphalts have been optimized primarily for surface layers with the aim of improving deformation resistance. The use of stiffer binders and a reduction in the proportion of binder were promoted, which in turn reduced the resistance to cracking and fatigue. As a result of this procedure, the real useful life of roads has been significantly reduced compared to the planning periods recommended in the road construction regulations. In a publication (source: SZ-online (06.06.2011)), the damage to the pavements on German autobahns prompted the ADAC to make the somewhat speculative statement that, due to the increased traffic load, “today's pavements will only last about 10 years, instead of the planned 30 years of service life".
- In heavily used traffic areas, thick asphalt packages and stiff (hydraulically bound) base courses were used to increase the resistance of the pavements, without taking into account the consequences of the significantly increased shape-changing loads in the surface and binder courses. This approach leads to a large increase in ruts and negative effects on the evenness of the roads with a great influence on the interaction between vehicle and roadway.
- In order to reduce the occurrence of rolling noises and to prevent the formation of spray mist on wet roads and aquaplaning, open-pored top layers are often used. Such layers realize the drainage of surface water and air in the tire-road contact zone via their pore space and meet the requirements for driving safety and noise reduction. However, open-pored coverings have an increased tendency to age and are less durable.
Based on the few selected examples, the future challenges and the particular difficulty of the design, development and dimensioning of permanent road pavements are already clear. Only a holistic solution, which includes the components of road paving, pneumatic tires and vehicle components, creates an understanding of the complex interaction mechanisms and allows a problem-adapted, improved design of the entire system.
The overarching goal of the research group is to provide a coupled thermo-mechanical model for the holistic physical analysis of the road-tire-vehicle system. With this model, road paving and road construction materials can be designed in such a way that the new requirements are compatible with the main objective of the durability of the structures and materials.
The scientific basis for these new and qualitatively improved approaches can only be developed if a holistic approach by coupling the theoretical-numerical and experimental approaches as well as a cross-disciplinary, closely networked work for the entire system consisting of road-tire-vehicle will be developed. Through interdisciplinary research, a deeper understanding of the physics of the overall system is achieved and progress is achieved in terms of improved and thus more permanent and sustainable structures. In the long term, systematic research in this extremely important area of engineering will help to conserve resources by using the research results to improve the quality of the products and to optimize the energy efficiency of the structures as well as the manufacturing and operating processes. New materials and construction approaches can be developed up to technologies with which the characterization of structural, material and load parameters succeeds in an intelligent and reliable way.
While individual models for simulating the behavior of the vehicle/chassis and tire subsystems have already reached a relatively high level of development, the modeling of the structural behavior of road pavements is still in its infancy. A coupled consideration of the system components described has not yet been carried out. Research tasks are therefore primarily in the areas of the theoretically well-founded description of the behavior of stratified road pavements and the interaction between vehicle/chassis, tires and road.
Abstract sub-project 4
The aim of sub-project 4 is to deepen and characterize the understanding of the behavior of asphalt based on the experimental simulation of the load conditions in asphalt pavements from the load caused by traffic and temperature, and to further develop procedures for the simulation of the load based on the previous status and to prepare the test results for the model development in cooperation with the partners of subprojects 1 and 2. Furthermore, the basis for the parameter identification for the models from sub-projects 1 and 2 should be created.
The main objectives are:
- Development of a general understanding of the behavior of asphalt under load from traffic and temperature in the different layers of a pavement through experimental characterization. In particular, the influence of the behavior of the asphalt components on the behavior of the asphalt should be examined,
- Design of model-specific analysis procedures (test procedures and evaluation procedures) as the basis for the experimental characterization of the behavior of asphalt,
- Safeguarding the relevant stress areas by iterative coordination of the test parameters with the relevant stress in road pavements with the help of the calculation results from sub-projects 1 and 2,
- Creation of experimental bases for parameter identification for the models on the micro, meso and macro level for different asphalts (surface, binder and base courses) from different components (binders of different stiffness and modification, different rocks and grain size distributions).
The main focus is initially on developing a general understanding of the behavior of asphalt and its components, as well as the fundamentals for carrying out the tests and the design of the test conditions.